Dissipation and Safety Analysis of Dimethomorph Application in Lychee by High-Performance Liquid Chromatography-Tandem Mass Spectrometry with QuEChERS

This study presents a method for analyzing dimethomorph residues in lychee using QuEChERS extraction and HPLC-MS/MS. The validation parameters for this method, which include accuracy, precision, linearity, and recovery, indicate that it meets standard validation requirements. Following first-order kinetics, the dissipation dynamic of dimethomorph in lychee was determined to range from 6.4 to 9.2 days. Analysis of terminal residues revealed that residues in whole lychee were substantially greater than those in the pulp, indicating that dimethomorph residues are predominantly concentrated in the peel. When applied twice and thrice at two dosage levels with pre-harvest intervals (PHIs) of 5, 7, and 10 days, the terminal residues in whole lychee ranged from 0.092 to 1.99 mg/kg. The terminal residues of the pulp ranged from 0.01 to 0.18 mg/kg, with the residue ratio of whole lychee to pulp consistently exceeding one. The risk quotient (RQ) for dimethomorph, even at the recommended dosage, was less than one, indicating that the potential for damage was negligible. This study contributes to the establishment of maximum residue limits (MRLs) in China by providing essential information on the safe application of dimethomorph in lychee orchards.

Easy and effective analytical method of carbendazim, dimethomorph, and fenoxanil from Protaetia brevitarsis seulensis using LC-MS/MS

Traditionally in Korea, Protaetia brevitarsis seulensis (white-spotted flower chafer) has been used as a medicine, and recently has attracted increased attention due to its antithrombotic efficacy. Some of spent mushroom compost or fermented oak sawdust, a feedstock for P. brevitarsis, were contaminated with three fungicides, carbendazim, dimethomorph, and fenoxanil, which could be transferred to the insect. This study was aimed to optimize a simple extraction method combined with liquid chromatography tandem mass spectrometry and apply it to the real samples. After the pulverized samples (5 g) were extracted with acetonitrile (10 mL) and formic acid (100 μL), fat and lipids in the samples were slowly precipitated at -20°C for 24 hours. After eight different clean-up methods were investigated, the mixture of 150 mg MgSO₄/25 mg PSA/25 mg C18 was selected due to optimal recovery of the target compounds. Recovery (77.9%‒80.8% for carbendazim, 111.2%‒116.7% for dimethomorph, and 111.9%‒112.5% for fenoxanil) was achieved with reasonable relative standard deviation (<5.5%) The analytical method developed in this study was used to analyze three compounds in the 24 insect samples donated by the insect farm owners but no target compounds were detected. These results can provide important data for establishing the pesticide safety standards for P. brevitarsis before the medical applications.

Simultaneous Analysis of Fenpropimorph and Fenpropimorph Acid in Six Different Livestock Products Using a Single-Sample Preparation Method Followed by Liquid Chromatography-Tandem Mass Spectrometry

Pesticides in livestock products must be measured to ensure food safety. We developed a single-sample preparation method followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) for simultaneous determination of fenpropimorph and fenpropimorph acid in six different livestock products. The extraction method was a modification of the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and was validated according to the CODEX guidelines. The matrix-matched calibration curves for fenpropimorph and fenpropimorph acid exhibited good linearity, with coefficients of determination (R2 values) higher than 0.998. The limit of detection (LOD) and the limit of quantitation (LOQ) were 1.25 and 5.0 µg kg-1, respectively. The average recovery values ranged from 61.5% to 97.1% for samples fortified to the LOQ, 2 × LOQ, and 10 × LOQ. The method fully complied with the CODEX guidelines and was successfully applied to real samples obtained from domestic markets.

Dissipation behavior, residue distribution, and dietary risk assessment of fluopimomide and dimethomorph in taro using HPLC-MS/MS

Dimethomorph is a morpholine broad-spectrum fungicide and effectively controls taro blight, cucumber downy mildew, rice blast disease, and others. Fluopimomide is a newly developed broad-spectrum fungicide to primarily control oomycetes and rhizoctonia diseases. Taro, one of the earliest cultivated crops, is a staple food in Africa, Oceania, and Asia. Recently, a commercial suspension concentrate formulation containing 15% fluopimomide and 25% dimethomorph has been registered in China, the second largest taro producer in the world. The objective of this study was to develop a high-performance liquid chromatography tandem mass spectrometry method to detect the residues of fluopimomide and dimethomorph concurrently in taro samples. The results showed that the average recoveries of fluopimomide and dimethomorph ranged from 83 to 108%, and relative standard deviations (RSD) ranged from 1 to 11%. The limit of quantitation (LOQ) was 0.01 mg kg^-1 for the two compounds. The dissipation results demonstrated that both fluopimomide and dimethomorph in taro degraded rapidly in taro fields, and the residues of the two fungicides were below the LOQ within 14 days post-application. The final residue levels of fluopimomide and dimethomorph in taro were lower than 0.066 mg kg^-1 28 days post-application. For dietary risk assessments, the dietary structure of different genders and age of people in China exposure risk assessment and whole diet exposure risk assessment shows that the risk quotient (RQ) values were substantially lower than 100%, suggesting that the long-term risks of fluopimomide/dimethomorph mixed formulation in taro at the recommended dosage were negligible. In summary, our combined results from the dissipation behaviors, terminal residues, and dietary risk assessments provide the critical empirical data for the establishment of the maximum residue levels (MRLs) of the two broad-spectrum fungicides in taro, a traditional food for African, Oceanic, and South Asian cultures.

Discovery of SARS-CoV-2 antiviral drugs through large-scale compound repurposing

The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2019 has triggered an ongoing global pandemic of the severe pneumonia-like disease coronavirus disease 2019 (COVID-19)1. The development of a vaccine is likely to take at least 12-18 months, and the typical timeline for approval of a new antiviral therapeutic agent can exceed 10 years. Thus, repurposing of known drugs could substantially accelerate the deployment of new therapies for COVID-19. Here we profiled a library of drugs encompassing approximately 12,000 clinical-stage or Food and Drug Administration (FDA)-approved small molecules to identify candidate therapeutic drugs for COVID-19. We report the identification of 100 molecules that inhibit viral replication of SARS-CoV-2, including 21 drugs that exhibit dose-response relationships. Of these, thirteen were found to harbour effective concentrations commensurate with probable achievable therapeutic doses in patients, including the PIKfyve kinase inhibitor apilimod2-4 and the cysteine protease inhibitors MDL-28170, Z LVG CHN2, VBY-825 and ONO 5334. Notably, MDL-28170, ONO 5334 and apilimod were found to antagonize viral replication in human pneumocyte-like cells derived from induced pluripotent stem cells, and apilimod also demonstrated antiviral efficacy in a primary human lung explant model. Since most of the molecules identified in this study have already advanced into the clinic, their known pharmacological and human safety profiles will enable accelerated preclinical and clinical evaluation of these drugs for the treatment of COVID-19.

Dissipation and residues of fluazinam and dimethomorph in potatoes, potato plants, and soil, determined by QuEChERS ultra-performance liquid chromatography tandem mass spectrometry

Fluazinam and dimethomorph 35% suspension concentrate (SC) is a new combined fungicide formulation introduced in China to improve fungicidal efficacy and decrease the risk of resistance in potatoes. Fluazinam and dimethomorph dissipation and residues in potatoes, potato plants, and soil under field conditions were determined by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Fluazinam and dimethomorph 35% SC was applied at two doses to potatoes and soil in Ningxia Autonomous Region and Anhui Province, China. Fluazinam and dimethomorph dissipation fitted first-order kinetics, and the fluazinam half-lives in potato plants and soil were 3.3-5.4 and 9.4-9.5 days, respectively. The dimethomorph half-lives in potato plants and soil were 2.1-2.6 and 5.9-8.6 days, respectively. Fluazinam and dimethomorph 35% SC was sprayed onto potato plants three or four times at application rates of 420 and 630 g a.i. ha^-1 with 7 days between applications. Potato and soil samples were collected at 3, 7, and 14 days after the last application. Potatoes and soil had fluazinam concentrations of < 0.01 and < 0.05-0.183 mg kg^-1, respectively, and dimethomorph concentrations of < 0.01 and 0.129-0.677 mg kg^-1, respectively. The final fluazinam and dimethomorph concentrations in potatoes were below the EU maximum residue limits (0.02 and 0.05 mg kg^-1, respectively) 3 days after application. Fluazinam and dimethomorph can therefore be applied to potatoes at the recommended doses.

Novel Approach for the Simultaneous Determination of Carbinoxamine Maleate, Pholcodine, and Ephedrine Hydrochloride Without Interference from Coloring Matter in an Antitussive Preparation Using Smart Spectrophotometric Methods

The presence of coloring matters in syrups usually interferes with the spectrophotometric determination of active pharmaceutical ingredients. A novel approach was introduced to eliminate the interference of sunset yellow (coloring matter) in Cyrinol syrup. Smart, simple, accurate, and selective spectrophotometric methods were developed and validated for the simultaneous determination of a ternary mixture of carbinoxamine maleate, pholcodine, and ephedrine hydrochloride in syrup. Four of the applied methods used ratio spectra: successive derivative subtraction coupled with constant multiplication, successive derivative of ratio spectra, ratio subtraction coupled with ratio difference, and ratio spectra continuous wavelet transforms zero-crossing. In addition, a method that was based on the presence of an isosbestic point, the amplitude summation method, was also established. A major advantage of the proposed methods is the simultaneous determination of the mentioned drugs without prior separation steps. These methods were successfully applied for the determination of laboratory-prepared mixtures and a commercial pharmaceutical preparation without interference from additives, thus proving the selectivity of the methods. No significant difference regarding both accuracy and precision was observed upon statistical comparison of the results obtained by the proposed methods with each other and with those of official or reported ones.

Developmental effects of the industrial cooling water additives morpholine and sodium hypochlorite on lake whitefish (Coregonus clupeaformis)

Chemicals used in the prevention of corrosion and biofouling may be released into the environment via industrial cooling water discharges. The authors assessed the impacts of 2 commonly used chemicals, morpholine and sodium hypochlorite, on development in lake whitefish (Coregonus clupeaformis). Embryos were exposed chronically, beginning at fertilization or at the eyed stage. Acute 96-h exposures were also examined at 4 development stages. Chronic morpholine resulted in median lethal concentrations (LC50s) of 219 ± 54 mg/L when exposure began at fertilization and 674 ± 12 mg/L when exposure began at the eyed stage, suggesting that embryos are more sensitive earlier in development. Chronic morpholine exposure advanced hatching by up to 30%, and the early hatching embryos were up to 10% smaller in body length. A decrease in yolk conversion efficiency was also observed in embryos exposed to chronic morpholine concentrations of 1000 mg/L. The majority of effects from morpholine exposure manifested near hatch, possibly reflecting changes in chorion permeability at the end of embryonic development. Sodium hypochlorite only impacted survival with chronic exposure from fertilization, where the total residual chlorine LC50 was 0.52 ± 0.11 mg/L. Acute exposures to both chemicals had minimal effects up to the highest tested concentrations. Overall, the results suggest that the risk during development from exposure to morpholine and sodium hypochlorite is low under normal operating conditions. Environ Toxicol Chem 2017;36:1955-1965. © 2016 SETAC.

Evaluation of multivariate calibration models with different pre-processing and processing algorithms for a novel resolution and quantitation of spectrally overlapped quaternary mixture in syrup

A novel approach for the resolution and quantitation of severely overlapped quaternary mixture of carbinoxamine maleate (CAR), pholcodine (PHL), ephedrine hydrochloride (EPH) and sunset yellow (SUN) in syrup was demonstrated utilizing different spectrophotometric assisted multivariate calibration methods. The applied methods have used different processing and pre-processing algorithms. The proposed methods were partial least squares (PLS), concentration residuals augmented classical least squares (CRACLS), and a novel method; continuous wavelet transforms coupled with partial least squares (CWT-PLS). These methods were applied to a training set in the concentration ranges of 40-100 μg/mL, 40-160 μg/mL, 100-500 μg/mL and 8-24 μg/mL for the four components, respectively. The utilized methods have not required any preliminary separation step or chemical pretreatment. The validity of the methods was evaluated by an external validation set. The selectivity of the developed methods was demonstrated by analyzing the drugs in their combined pharmaceutical formulation without any interference from additives. The obtained results were statistically compared with the official and reported methods where no significant difference was observed regarding both accuracy and precision.

Influence of adjuvants on the dissipation of fenpropimorph, pyrimethanil, chlorpyrifos and lindane on the solid/gas interface

The use of pesticides is an integral part of modern agriculture and contributes to the productivity and the quality of the cultivated crop. However, use of pesticides imposes a huge burden on the environment. Volatilisation of pesticides contaminates the environment, affects nearby crops, bystanders and residents but research to mitigate this environmental contamination remains scarce. In this study, the use of adjuvants to reduce the volatilisation and mitigate the environmental contamination was investigated. Dissipation of fenpropimorph, pyrimethanil, chlorpyrifos-ethyl and lindane as pure active ingredient, formulated by different adjuvants and in a commercial formulation were studied. An empirical model assuming exponential decay of the volatilisation rate was used to calculate the volatilisation. In 48 h, up to 90% of the pure fenpropimorph and lindane volatilised. Addition of adjuvants was shown to reduce the volatilisation of pesticides by up to 80%. Commercial formulation was able to reduce the volatilisation of pyrimethanil but the formulation of fenpropimorph had no effect on its volatilisation.

A validated high-throughput UHPLC-MS/MS assay for accurate determination of rivaroxaban in plasma sample

Rivaroxaban is a novel, selective and potent oral direct factor Xa inhibitor, therapeutically indicated in the treatment of thromboembolic diseases. Like traditional anticoagulants, routine coagulation monitoring of rivaroxaban is not necessary, but important in some clinical circumstances. In this study, a sensitive UHPLC-MS/MS assay for rapid determination of rivaroxaban in human plasma was developed and validated. Rivaroxaban and its internal standard (IS) were extracted from plasma using acetonitrile as protein precipitating agent. An isocratic mobile phase of acetonitrile: 10 mM ammonium acetate (80:20, v/v) at a flow rate of 0.3 mL/min was used for the separation of rivaroxaban and IS. Both rivaroxaban and IS was eluted within 1 min with a total run time of 1.5 min only. Electrospray ionization source in positive mode was used for the detections of rivaroxaban and IS. Precursor to product ion transition of m/z 436.00 > 144.87 for rivaroxaban and m/z 411.18 > 191.07 for IS were used in multiple reaction monitoring mode. Developed assay was fully validated in terms of selectivity, linearity, accuracy, precision, recovery, matrix effects and stability using official guideline on bioanalytical method.

Phototransformation pathways of the fungicide dimethomorph ((E,Z) 4-[3-(4-chlorophenyl)-3-(3,4-dimethoxyphenyl)-1-oxo-2-propenyl]morpholine), relevant to sunlit surface waters

Dimethomorph (DMM) is a widely used fungicide that shows low toxicity for birds and mammals but can be quite toxic to aquatic organisms. The persistence of DMM in surface waters is thus of high importance, and this work modelled its water half-life time due to photochemical processes. Depending on environmental conditions (e.g. water chemistry, depth, season), DMM lifetime could vary from a few days to a few months. For lifetimes of a few weeks or shorter, photochemistry would be an important pathway for DMM attenuation in surface waters. Such conditions could be reached in summer, in shallow water bodies with low dissolved organic carbon (DOC) and high nitrate and/or nitrite. The main pathways accounting for DMM photodegradation in environmental waters would be the reactions with OH and with the triplet states of chromophoric dissolved organic matter, (3)CDOM* (under the hypothesis that (3)CDOM* reactivity is well described by the triplet state of anthraquinone-2-sulphonate), while direct photolysis would be less important. The OH pathway would be favoured in low-DOC waters, while the opposite conditions would favour (3)CDOM*. It was possible to detect and identify some intermediates formed upon reaction between DMM and (3)CDOM*, namely N-formylmorpholine, 4-chloroacetophenone and 4-chlorobenzoic acid. The transformation of DMM into the detected compounds would not increase the acute toxicity of the fungicide towards mammals, and the acute effects for freshwater organisms could be decreased significantly.

Effects of flue gas compositions on nitrosamine and nitramine formation in postcombustion CO2 capture systems

Amine-based technologies are emerging as the prime contender for postcombustion CO2 capture. However, concerns have arisen over the health impacts of amine-based CO2 capture associated with the release of nitrosamines and nitramines, which are byproducts from the reactions between flue gas NOx and solvent amines. In this study, flue gas compositions were systematically varied to evaluate their effects on the formation of nitrosamines and nitramines in a lab-scale CO2 capture reactor with morpholine as a model solvent amine. The accumulation of N-nitrosomorpholine in both the absorber and washwater increased linearly with both NO and NO2 for concentrations up to ∼20 ppmv. These correlations could be extrapolated to estimate N-nitrosomorpholine accumulation at extremely low NOx levels (0.3 ppmv NO2 and 1.5 ppmv NO). NO played a particularly important role in driving N-nitrosomorpholine formation in the washwater, likely following partial oxidation to NO2 by O2. The accumulation of N-nitromorpholine in both the absorber and washwater positively correlated with flue gas NO2 concentration, but not with NO concentration. Both N-nitrosomorpholine and N-nitromorpholine accumulated fastest in the absence of CO2. Flue gas humidity did not affect nitrosamine accumulation in either the absorber or the washwater unit. These results provide a basis for estimating the effects of flue gas composition on nitrosamine and nitramine accumulation in postcombustion CO2 capture systems.

Development and validation of a standardized method for the determination of morpholine residues in fruit commodities by liquid chromatography-mass spectrometry

An analytical method was developed for the determination of morpholine on apples and citrus. The method utilized acidified methanol extraction, centrifugation, and determination by hydrophilic interaction liquid chromatography with electrospray ionization and tandem mass spectrometry (HILIC-ESI-MS/MS). Validation of the method occurred at the Pacific Agricultural Laboratory (PAL, Portland, OR, USA) and the Trace Analytical Laboratory (TAL, UC Davis, CA, USA). Method validation recoveries from control apple, orange, lemon, and grapefruit samples ranged from 84 to 120% over three levels of fortification (0.01, 0.04, and 0.2 μg/g). The limit of quantitation (LOQ) for all commodities was 0.01 μg/g, and the calculated method detection limit (MDL) ranged from 0.0010 to 0.0040 μg/g.

An immunochromatographic assay for rapid and direct detection of 3-amino-5-morpholino-2-oxazolidone (AMOZ) in meat and feed samples

BACKGROUND

Furaltadone (FTD) is a type of nitrofuran and has been banned in many countries as a veterinary drug in food-producing animals owing to its potential carcinogenicity and mutagenicity. FTD is unstable in vivo, rapidly metabolizing to 3-amino-5-methylmorpholino-2-oxazolidinone (AMOZ); thus AMOZ can be used as an indicator for illegal usage of FTD. Usually, for the determination of nitrofurans, the analyte is often a derivative of the metabolite rather than the metabolite itself. In this study, based on the monoclonal antibody (mAb) against AMOZ, a competitive immunochromatographic assay (ICA) using a colloidal gold-mAb probe for rapid and direct detection of AMOZ without a derivatization step in meat and feed samples was developed.

RESULTS

The intensity of red color in the test line is inversely related to the analyte concentration and the visual detection limit was found to be 10 ng mL⁻¹. The performance of this assay was simple and convenient because the tedious and time-consuming derivatization step was avoided. The ICA detection was completed within 10 min. The ICA strips could be used for 7 weeks at room temperature without significant loss of activity. The AMOZ spiked samples were detected by ICA and confirmed by enzyme-linked immunosorbent assay. The results of the two methods were in good agreement.

CONCLUSION

The proposed ICA provides a feasible tool for simple, sensitive, rapid, convenient and semi-quantitative detection of AMOZ in meat and feed samples on site. To our knowledge, this is the first report of the ICA for direct detection of AMOZ.

Structural analysis of an impurity of the drug landiolol

In a course of development and preparation of landiolol (1a), a known ultra-short-acting β-blocker, process quality control by HPLC and LC-MS analysis consistently showed an impurity peak ranging from 0.05% to 0.15 % and exhibiting a molecular mass m/z 887. To identify the hitherto unknown impurity, we prepared one of the possible landiolol derivatives with the same molecular mass for proper spectral characterization (NMR and MS). Its equivalence with the unknown impurity was then confirmed by LC-MS analysis. Ultimately, using fragmentation patterns in LC-MS and selective two-dimensional NMR experiments, the structure of the impurity was assigned as [(4S)-2,2-dimethyl-1,3-dioxolan-4-yl]methyl 3-{4-[(2S)-2-hydroxy-3-(3-{4-[(2S)-2-hydroxy-3-[(2-{[(morpholin-4-yl)carbonyl]amino}ethyl)amino]propoxy]phenyl}-N-(2-{[(morpholin-4-yl)carbonyl]amino}ethyl)propanamido)propoxy]phenyl}propanoate (2). It was found that the impurity was present in two rotameric forms at room temperature. The synthesis and NMR characterization of (2) are discussed.

Analysis of sexual assault evidence by desorption electrospray ionization mass spectrometry

Desorption electrospray ionization mass spectrometry (DESI-MS) is employed in the forensic analysis of chemical components present in condoms and imaging of latent fingerprints as circumstantial evidence of sexual assault. Polymers such as nonoxynol-9, polyethylene glycol, and polydimethylsiloxane, as well as small molecules additives such as N-methylmorpholine, N-octylamine, N,N-dibutyl formamide, and isonox 132, commonly used in lubricated condom formulations, were successfully characterized by DESI. The results suggest that DESI-MS is useful for identification of this type of evidence, and it has advantages over conventional extractive techniques, in terms of speed of analysis and ease of use.

Development and validation of new spectrophotometric ratio H-point standard addition method and application to gastrointestinal acting drugs mixtures

New, simple, specific, accurate and precise spectrophotometric technique utilizing ratio spectra is developed for simultaneous determination of two different binary mixtures. The developed ratio H-point standard addition method (RHPSAM) was managed successfully to resolve the spectral overlap in itopride hydrochloride (ITO) and pantoprazole sodium (PAN) binary mixture, as well as, mosapride citrate (MOS) and PAN binary mixture. The theoretical background and advantages of the newly proposed method are presented. The calibration curves are linear over the concentration range of 5-60 μg/mL, 5-40 μg/mL and 4-24 μg/mL for ITO, MOS and PAN, respectively. Specificity of the method was investigated and relative standard deviations were less than 1.5. The accuracy, precision and repeatability were also investigated for the proposed method according to ICH guidelines.

Bivariate versus multivariate smart spectrophotometric calibration methods for the simultaneous determination of a quaternary mixture of mosapride, pantoprazole and their degradation products

The ability of bivariate and multivariate spectrophotometric methods was demonstrated in the resolution of a quaternary mixture of mosapride, pantoprazole and their degradation products. The bivariate calibrations include bivariate spectrophotometric method (BSM) and H-point standard addition method (HPSAM), which were able to determine the two drugs, simultaneously, but not in the presence of their degradation products, the results showed that simultaneous determinations could be performed in the concentration ranges of 5.0-50.0 microg/ml for mosapride and 10.0-40.0 microg/ml for pantoprazole by bivariate spectrophotometric method and in the concentration ranges of 5.0-45.0 microg/ml for both drugs by H-point standard addition method. Moreover, the applied multivariate calibration methods were able for the determination of mosapride, pantoprazole and their degradation products using concentration residuals augmented classical least squares (CRACLS) and partial least squares (PLS). The proposed multivariate methods were applied to 17 synthetic samples in the concentration ranges of 3.0-12.0 microg/ml mosapride, 8.0-32.0 microg/ml pantoprazole, 1.5-6.0 microg/ml mosapride degradation products and 2.0-8.0 microg/ml pantoprazole degradation products. The proposed bivariate and multivariate calibration methods were successfully applied to the determination of mosapride and pantoprazole in their pharmaceutical preparations.

Simultaneous effects of two fungicides (copper and dimethomorph) on their phytoremediation using Lemna minor

Effects of two fungicides, copper and dimethomorph ((E,Z)4-[3-(4-chlorophenyl)-3-(3-4dimethoxyphenyl) acryloyl] morpholine) on Lemna minor growth and phytoremediation were evaluated. The toxicity of copper and dimethomorph alone and in combination, was assessed by growth inhibition of L. minor cultures after 96 and 168 h. Copper had a severe impact on growth (max. inhibition: 90 % at 1,000 μg L(-1)) while dimethomorph (as pure ingredient or formulated as Forum) did not (inhibition <45 % at 1,000 μg L(-1)) after 168 h of treatment. When both chemicals were combined, synergism was observed after 96 h of exposure to copper and Forum. However, this interaction was a simple additivity after 168 h. Additivity was also observed when the pure active ingredient (dimethomorph) replaced Forum in the mixture of copper and dimethomorph at 96 and 168 h. L. minor showed an excellent performance in removing copper from the medium since after 96 h, 36, 60, and 76 % removal were reached for 10, 20, and 30 μg L(-1) of Cu respectively. Copper accumulated in the plants. The removal of copper increased with Forum concentration. After 96 h copper (10 μg L(-1) initial concentration) elimination increased from 36.39 ± 5.86-60.70 ± 6.06 % when Forum concentration increased from 0 to 500 μg L(-1). Accumulation of copper in plants was also increased by Forum but not by the active ingredient alone. Depuration of Forum by L. minor varied between 10 and 40 % after 96 h and it was generally more efficient than that of the pure ingredient. This depuration decreased in the presence of copper possibly due to the metal toxicity.

Development of a monoclonal antibody-based competitive indirect enzyme-linked immunosorbent assay for furaltadone metabolite AMOZ in fish and shrimp samples

A monoclonal antibody-based competitive indirect enzyme-linked immunosorbent assay (ELISA) with improved sensitivity and specificity for the determination of furaltadone metabolite 5-methylamorpholino-3-amino-2-oxazolidone (AMOZ) was described. AMOZ was derivatized with 2-(3-formylphenoxy)acetic acid and coupled with bovine serum albumin to form a novel immunogen. BABL/c mice were immunized and monoclonal antibody specific to the nitrophenyl derivative of AMOZ (NP-AMOZ) was produced and characterized. Four other haptens with different heterology to the immunizing hapten were synthesized and coupled to ovalbumin as coating antigens to study the effect of heterologous coating on assay sensitivity. Under the optimized heterologous coating format, the competitive indirect ELISA showed very high sensitivity to NP-AMOZ, with an IC(50) of 0.14 μg/L and limit of detection of 0.01 μg/L. The assay showed high specificity toward NP-AMOZ, and negligible cross-reactivity with analogous compounds was observed. The average recoveries of AMOZ from spiked fish and shrimp samples were estimated to range from 81.0 to 104.0%, with coefficients of variation below 20%. Good correlation was obtained between the results of ELISA analysis and of standard liquid chromatography-tandem mass spectrometry analysis. These results indicated that the proposed ELISA is ideally suited as a monitoring method for AMOZ residues at trace level.

Determination of total nitrofuran metabolites in shrimp muscle using liquid chromatography/tandem mass spectrometry in the atmospheric pressure chemical ionization mode

The method of MacMahon and Lohne for analysis of nitrofuran metabolites in shrimp was optimized to streamline the extraction processes and the LC analysis. This revised method includes 16 h of mild acid hydrolysis/derivatization followed by ethyl acetate extraction and analysis by LC/MS/MS in the atmospheric pressure chemical ionization mode. This revised method was validated in shrimp for concentrations of 0.25 to 2.0 ng/g. The LOQ was 0.25 ng/g for all metabolites. The LOD was 0.052 nglg for 1-aminohydantoin (AHD), 0.206 ng/g for 3-amino-2-oxazolidinone (AOZ), 0.108 ng/g for semicarbazide (SC), and 0.062 ng/g for 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ). The spike recoveries with RSD into negative matrix at 1 ng/g were 100.2% (3.2%) for AHD, 102.5% (1.0%) for AOZ, 103.7% (2.3%) for SC, and 104.0% (3.3%) for AMOZ. The spike recoveries at 1 ng/g into unknown samples (n=108) containing varied levels of nitrofuran metabolites were 112.6% (25.7%) for AHD, 108.1% (12.1%) for AOZ, 103.0% (12.0%) for SC, and 100.3% (6.9%) for AMOZ. Interday precision with samples containing incurred AOZ concentrations of 0.92 to 17.8 ppb performed over a year was 10.4% RSD. The method is accurate and precise for determining nitrofuran concentrations in the edible tissue of shrimp.

Behavior of mixed formulation of metalaxyl and dimethomorph in grape and soil under field conditions

This study investigates the dissipation and residue of a metalaxyl and dimethomorph mixed formulation in grape and soil. A high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) analytical method was developed to determine the residue of metalaxyl and dimethomorph in grape and soil. The results showed that the average recoveries are in the range of 86.84 percent to 97.30 percent. The dissipation rate of metalaxyl in grape (with half life of 4.9 days) was faster than in soil (with half life of 8.7 days). The dissipation rates of E- and Z-isomers of dimethomorph in grape were almost the same (with half lives of 9.0 and 9.8 days, respectively). However, the dissipation rate of the E-isomer in soil was much faster than that of the Z-isomer (with half lives of 10.3 and 31.5 days, respectively). Moreover, the terminal residue of metalaxyl and dimethomorph were significantly below the available maximum residue limits (MRL). However, a difference was observed between the concentration of the Z- and E-isomers either in grape or soil. The ratio of E-isomer to Z-isomer in grape was higher than in soil, which may due to the different water solubilities and polarities of the two isomers.

Development of an enzyme-linked immunosorbent assay for determination of the furaltadone etabolite, 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ) in animal tissues

OBJECTIVE

To determine 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ) residues released from protein bound AMOZ in animal tissues.

METHODS

Polyclonal and monoclonal antibodies were produced in this study. A rapid, sensitive, and specific competitive direct enzyme-linked immunosorbent assay (cdELISA) was developed.

RESULTS

Rabbit polyclonal antibodies were used in the optimized cdELISA method, and exhibited negligible cross-reactivity with other compounds structurally related to AMOZ. The IC(50) of the polyclonal antibody was 0.16 ng/mL. The method limit of detection in four different types of animal and fish tissues was less than 0.06 μg/kg. Recoveries ranged from 80% to 120% for fortified samples with the coefficient of variation values less than 15%. The results of the cdELISA method were in good agreement with the results from an established liquid chromatography-tandem mass spectrometry confirmatory method used for AMOZ residues.

CONCLUSION

The cdELISA method developed in the present study is a convenient practical tool for screening large numbers of animal and fish tissue samples for the the detection of released protein bound AMOZ residues.

Simultaneous determination of triacetin, acetic ether, butyl acetate and amorolfine hydrochloride in amorolfine liniment by HPLC

A simple, rapid, specific and precise reversed-phase high-performance liquid chromatographic method was developed for simultaneous estimation of triacetin, acetic ether, butyl acetate and amorolfine in marketed pharmaceutical liniment. Chromatographic separation was performed on a Shimadzu VP-ODS C(18) column using the mixture of citric acid-hydrochloric acid-sodium hydrate buffer (pH 3.0), acetonitrile and methanol (32:30:38) as the mobile phase at a flow rate of 1.0 mL/min with UV-detection at 215 nm. The method separated the four components simultaneously in less than 10 min. The validation of the method was performed with respect to specificity, linearity, accuracy, and precision. The calibration curves were linear in the range of 35.1-81.9 μ/mL for triacetin, 431.1-1005.9 μ/mL for acetic ether, 167.0-389.7 μ/mL for butyl acetate and 151.0-352.3 μ/mL for amorolfine. The mean 100% spiked recovery for triacetin, acetic ether, butyl acetate and amorolfine is 99.43 ± 0.42, 101.5 ± 1.09, 101.4 ± 1.02 and 100.8 ± 0.69, respectively. The intra-day and inter-day relative standard deviation values were <2.0%. The limits of detection of these compounds ranged from 0.08 to 5.88 ng. The utility of the procedure was verified by its application to the commercial liniment.

Stability of [(N-morpholine)metylene]daunorubicin hydrochloride in solid state

The influence of temperature and relative air humidity on the stability of the novel derivative of daunorubicin: [(N-morpholine)metylene]daunorubicin hydrochloride was investigated. The process of degradation was studied by using high-performance liquid chromatography with ultraviolet (UV) detection. In dry air, the degradation of [(N-morpholine)metylene]daunorubicin hydrochloride was a first-order reaction depending on the substrate concentration, while at relative air humidity from 60.5 to 90.0% it was an autocatalytic reaction of the first order with respect to MMD concentration. The kinetic and thermodynamic parameters of degradation were calculated.

Dissipation and residue of dimethomorph in pepper and soil under field conditions

The dissipation and residual levels of dimethomorph in pepper and soil under field conditions were determined by gas chromatography with an electron capture detector (GC-ECD). The dissipation rates of dimethomorph were described using first-order kinetics and its half-life ranged from 1.7 to 3.8 days in pepper and 11.5-18.5 days in soil. At harvest time, the terminal residues of dimethomorph were below the EU's maximum residue limit (MRL, 0.5 mg kg⁻¹) in pepper when measured 7 days after the final application, which suggested that the use of this fungicide was safe for humans. The collected field samples were stable for up to two months when refrigerated at -20°C. The residues persistence varied among three geographically separated experimental fields, suggesting that it might be affected by climatic, soil properties and local microorganisms. These results will be helpful in setting MRL guidance for dimethomorph in pepper in China.

Residue dynamic of pyrimorph on tomatoes, cucumbers and soil under greenhouse trails

A modified QuEChERS method for analysis of pyrimorph residue in tomatoes, cucumbers and soil was developed and validated. Residue dynamics and final residues in greenhouse vegetables and soil were studied. At fortification levels of 0.05, 0.1 and 1 mg kg(-1) in tomatoes, cucumbers and soil, the method got recoveries ranged from 86.1% to 99.3% with relative standard deviations of 1.0%-7.7%, in agreement with directives for method validation in residue analysis. The limit of determination in tomatoes, cucumbers and soil was 0.05 mg kg(-1). The proposed method was successfully employed for the determination of pyrimorph residue levels and dissipation rates in vegetables and soil. At six experimental sites, pyrimorph residues in tomatoes and cucumbers showed relatively fast dissipation rates, with half-lives of 5.8-7.7 days and 5.7-7.1 days respectively. Half-lives of pyrimorph in soil were 8.5-11.0 days. The final residues of pyrimorph in tomatoes ranged from 0.19 to 3.66 mg kg(-1), 0.18 to 4.35 mg kg(-1) in cucumbers and 0.22 to 16.5 mg kg(-1) in soil with pre-harvest interval of 3-7 days. 5 mg kg(-1) was proposed as the MRL of pyrimorph in tomatoes and cucumbers.

Influence of initial pesticide concentrations and plant population density on dimethomorph toxicity and removal by two duckweed species

Aquatic plants take up, transform and sequester organic contaminants and may therefore be used in phytoremediation for the removal of pollutants from wastewaters. A better understanding of factors affecting the rate of contaminant uptake by aquatic plants is needed to improve engineered systems for removal of pollutants from wastewaters. This work focused on the influence of initial concentrations of pesticide and population density of plants on toxicity and uptake of the fungicide dimethomorph by two duckweed species. An increased sensitivity to dimethomorph was observed with increasing duckweed population density. Less light, due to crowding, may explain this higher sensitivity and reduced removal rate. A positive relationship was also found between toxicity or contaminant uptake and initial pesticide concentration with a maximal removal of 41 and 26 microg g(-1) fresh weight of dimethomorph (at 600 microg L(-1) of dimethomorph and an initial density of 0.10g E-flask(-1)) by Lemna minor and Spirodela polyrhiza, respectively. This research also indicated that these aquatic plants can efficiently eliminate organic contaminants and may ultimately serve as phytoremediation agents in the natural environment.

Fungicides and herbicide removal in Scenedesmus cell suspensions

Remediation capacities of two freshwater microalgae, Scenedesmus obliquus and Scenedesmus quadricauda, were assessed for the removal of two fungicides (dimethomorph and pyrimethanil) and one herbicide (isoproturon) from their medium. To ensure these studies were performed with healthy algae, pesticide effects where first apprehended on chlorophyll a fluorescence emission and growth rate. After a 4d-exposure to 600 microg L(-1) of dimethomorph or pyrimethanil, or to 10 microg L(-1) of isoproturon, algal growth rate and some of their photosynthetic processes were weakly affected (< 30% variation). The pesticide removal percentage of Scenedesmus cells reached a maximum of 10%, 24% and 58% for pyrimethanil, dimethomorph and isoproturon, respectively. In parallel, the maximum removal rate was 36 and 40 microg x 10(-9) cells for dimethomorph, 17 and 26 microg x 10(-9) cells for pyrimethanil, 2 and 2 microg x 10(-9) cells for isoproturon, in the presence of Sc. obliquus and Sc. quadricauda, respectively. Results showed that Sc. quadricauda was more effective in the removal of dimethomorph and pyrimethanil compared to Sc. obliquus.

Fate of vinclozolin, thiabendazole and dimethomorph during storage, handling and forcing of chicory

BACKGROUND

As part of ongoing research for a sustainable production of Belgian endives, the fate of three fungicides during storage, handling and forcing of witloof chicory roots was investigated. Storage roots are protected against Sclerotinia sp. Fuckel and Phoma exigua var. exigua Desm. by means of vinclozolin and thiabendazole respectively. During hydroponic forcing, the most imminent pathogen is Phytophthora cryptogea Pethybr. & Laff., which is controlled by the use of dimethomorph.

RESULTS

Vinclozolin and thiabendazole concentrations on roots remained constant during storage at -1 degrees C. Dermal exposure of the workers in hydroponics was exceeded. Vinclozolin and thiabendazole residues were not detected 2 weeks after hydroponic forcing; dimethomorph was still detected at harvest. At harvest, the vinclozolin concentration in the chicory heads was below the maximum residue limit, but the chicory roots contained residues much above the thiabendazole and dimethomorph maximum residue level.

CONCLUSION

Vinclozolin and thiabendazole residues applied before storage are still present on the roots at the start of the forcing cycle. During the set-up of chicory roots, preventive measures are recommended, as effects of repeated human exposure to low doses of applied fungicides cannot be excluded. Dimethomorph applied at the start of the hydroponic forcing is the only pesticide detected in the drainage water at harvest. The chicory heads were safe for human consumption. However, more attention should be paid to the residues of fungicides in the roots used for cattle feeding.

Phytoremediation of fungicides by aquatic macrophytes: toxicity and removal rate

The rate of removal of two fungicides (dimethomorph and pyrimethanil) from water by five macrophyte species (L. minor, S. polyrhiza, C. aquatica, C. palustris and E. canadensis) was assessed in laboratory tests. In order to assure that these studies were performed with healthy plants the effects of the fungicides on chlorophyll fluorescence were studied as well. At exposure concentrations of 600microgL(-1) the effects of the fungicides on chlorophyll fluorescence were minor, so that this initial concentration level was selected for the fungicide removal rate tests. The removal yields during the 4-d test periods varied from 10% to 18% and 7% to 12% for dimethomorph and pyrimethanil, respectively. The maximum removal rate during the 4-d test period was 48microgg(-1) fresh weight (FW) for dimethomorph and 33microgg(-1) FW for pyrimethanil. L. minor and S. polyrhiza showed the highest removal efficiency for the two fungicides.

Indirect spectrofluorimetric determination of mosapride citrate in pharmaceutical formulations

New europium complexes of 3-oxo-1-hydroxy-quinoline-2-carboxylic acid amide derivatives (L1-L3), which are highly luminescent and do not require luminescence enhancers are reported. The luminescence intensity of the Eu-L1-3 complexes was enhanced by the addition of citrate ions in water solution. A sensitive luminescence enhancement system was developed for the determination of citrate ions on the base of Eu-9-fluoro-1-hydroxy-5-methyl-3-oxo-6,7-dihydro-3H,5H-pyrido[3,2,1-ij]quinoline-2-carboxylic acid (2-piperazin-1-yl-ethyl)-amide (L1) complex. This effect was applied to the determination of the drug, which is not a lanthanide luminescence sensitizer. The Eu-L1- Cit complex with a components' ratio 1:1:2 was proposed to be used as the analytical form for the luminescence determination of drug - mosapride citrate. The calibration curve is linear in the range of 1.0-25.0 microg/mL of mosapride citrate (LOD is 0.35 microg/mL). This method was applied for the determination of mosapride citrate in dosage form - tablets "Mosid MT" - 2.5 mg.

Solid-phase extraction method for preconcentration of trace amounts of some metal ions in environmental samples using silica gel modified by 2,4,6-trimorpholino-1,3,5-triazin

A method was proposed for the preconcentration of some transition elements at trace levels using a column packed with silica gel modified by a synthetic ligand. Metal ions were adsorbed on 2,4,6-trimorpholino-1,3,5-triazin modified silica gel, then analytes retained on the adsorbent were eluted by 1molL(-1) hydrochloric acid and determined by flame atomic absorption spectrometry (FAAS). The influences of some experimental parameters including pH of the sample solution, weight of adsorbent, type, concentration and volume of eluent, flow rates of the sample solution and eluent, and sample volume on the preconcentration efficiency have been investigated. The influences of some matrix elements were also examined. The method also was used for simultaneous preconcentration of these elements and the method was successfully applied to the preconcentration and determination of them. The detection limits of the method for Ni2+, Co2+, Cd2+ and Zn2+were 0.29, 0.20, 0.23 and, 0.30ngmL(-1), respectively. The application of this modified silica gel to preconcentration of investigated cation from tap water, lake water, urine and apple leaves gave high accuracy and precision (relative standard deviation (R.S.D.) <3%).

Determination of flumorph residues in vegetables, soil, and natural water by solid-phase extraction cleanup and high-performance liquid chromatography with UV detection

A method for high-performance liquid chromatographic (HPLC) determination of flumorph residues in cucumber, tomato, soil, and natural water was developed and validated. Primary secondary amine or octadecylsilyl (C18) solid-phase extraction cartridges were used for sample preparation. Reversed-phase HPLC with UV detection was used for separation and quantification of the pesticide. The combined cleanup and chromatographic method steps were sensitive and reliable for simultaneous determination of residues of the 2 isomers of flumorph in the studied samples. This method is characterized by recovery > 97.9%, coefficient of variation < 6.2%, and limit of quantification of 0.01 mg/kg, in agreement with directives for method validation in residue analysis. Flumorph residues in the samples were further confirmed by HPLC/mass spectrometry. The proposed method is fast, easy to perform, and could be used for monitoring of pesticide residues.

Identification of osteogenic purmorphamine derivatives

During embryonic and cancer development, the Hedgehog family of proteins, including Sonic Hedgehog, play an important role by relieving the inhibition of Smo by Ptc, thus activating the Smo signaling cascade. Recently, a purine compound, purmorphamine, has been reported to target the Hedgehog signaling pathway by interacting with Smo. Interestingly, both Sonic Hedgehog and purmorphamine were found to promote the osteogenic differentiation of mouse chondroprogenitor cells. However, there is insufficient information as to how the activation of this seemingly unrelated signaling pathway, either by Sonic Hedgehog or purmorphamine, contributes to osteogenesis. Using alkaline phosphatase assays, we screened 125 purmorphamine derivatives from the Korea Chemical Bank for effects on the differentiation of preosteoblast C2C12 cells. Here, we report that two purine derivatives modulate ALP activity as well as the expression of genes whose expression is known or suggested to be involved in osteogenesis.

Liquid chromatography–tandem mass spectrometric method for determination of mosapride citrate in equine tissues

A simple method for determination of mosapride citrate and its metabolite, des-p-fluorobenzyl mosapride (M-1), in equine muscle, liver, kidney, adipose tissue and intestine by liquid chromatography-tandem mass spectrometry has been developed. (+/-)-4-Amino-5-chloro-2-ethoxy-N-[[4-(2-chlorobenzyl)morpholinyl]methyl]benzamide was used as an internal standard. The analytes and internal standard were spiked and extracted from tissues by acetonitrile. The chromatographic separation was performed on a reversed-phase TSK-GEL SUPER ODS column with a mobile phase of acetonitrile-0.05% (v/v) formic acid containing 5 mmol/L nonafluoropentanoic acid (2:3, v/v). The method exhibited a large linear range from 0.0005 to 0.2 microg/mL for both mosapride citrate and M-1 (r>0.9976). In the intra-day assay (n=5), the relative standard deviations (RSDs) ranged from 1.1 to 7.8% for mosapride citrate and 1.6 to 7.2% for M-1. In the inter-day assay (n=3), the RSDs ranged from 1.0 to 13% for mosapride citrate and 0.8 to 11% for M-1. The extraction recovery at 1.28 microg/g of mosapride citrate from equine tissues ranged from 97 to 107%. The lower limit of quantification for mosapride citrate was found to be 0.004 microg/g. Stability studies were carried out at different storage conditions. The method reported is reliable, precise, and accurate and it has the capacity to be used for determination of mosapride citrate and its metabolite in tissue samples.

Stability studies of the metabolites of nitrofuran antibiotics during storage and cooking

Nitrofuran antibiotics cannot be used in food production within the European Union because of their potential health risks to consumers. The recent discovery of their widespread use in global food industries and the finding of semicarbazide in baby food as a result of packaging contamination have focused attention on the toxicity and stability of these drugs and their metabolites. The stability of the nitrofuran marker residues 3-amino-2-oxazolidinone (AOZ), 3-amino-5-morpholinomethyl-2-oxazolidone (AMOZ), 1-aminohydantoin (AHD) and semicarbazide (SEM) were tested. Muscle and liver of nitrofuran treated pigs were cooked by frying, grilling, roasting and microwaving. Between 67 and 100% of the residues remained after cooking, demonstrating that these metabolites are largely resistant to conventional cooking techniques and will continue to pose a health risk. The concentration of metabolites in pig muscle and liver did not drop significantly during 8 months of storage at -20 degrees C. Metabolite stock and working standard solutions in methanol were also stable for 10 months at 4 degrees C. Only a 10 ng ml(-1) solution of SEM showed a small drop in concentration over this extended storage period.

High-performance liquid chromatographic method for the determination of moclobemide and its two major metabolites in human plasma

A selective, sensitive, and simple high-performance liquid chromatographic (HPLC) method was developed for the determination of moclobemide and its two major metabolites, Ro 12-5637 and Ro 12-8095, in human plasma. Sample preparation (0.5 ml of plasma) involved solid-phase extraction (SPE) using Speedisk H(2)O-Philic DVB columns. Separations were performed on a Waters XTerra RP18 column (5 microm, 150 mm x 4.6 mm). The mobile phase consisted of 10 mM KH(2)PO(4) with 1% triethylamine (pH 3.9) and acetonitrile (83:17, v/v), and a flow-rate was 1.2 ml/min. The total run time was 13 min. UV detection was performed at 240 nm. Mean absolute recoveries were > or =90% and the limit of quantification (LOQ) for all analytes was 0.02 mg/l. Calibration curves were linear (r>0.995) over a wide range of the analyte concentrations in plasma; thus, the method is suitable for different clinical studies when large variations in the drug/metabolites concentrations are observed. During a 5-day assay validation procedure the accuracy and precision were tested and proven (relative errors (RE)< or =13%; intra-day coefficient of variation (CV)< or =7%; inter-day CV< or =13%). Many drugs frequently used in the target patient population were evaluated for potential interference in order method selectivity to be ensured. The assay has been used in a clinical pharmacokinetic study to assess steady-state pharmacokinetics of moclobemide and two metabolites in depressive patients on mono- and combined therapy.

Comparison of wind tunnel and field experiments to measure potential deposition of fenpropimorph following volatilisation from treated crops

The potential for short-range transport via air, i.e. volatilisation from the area of application and subsequent deposition on adjacent non-target areas, was investigated for the fungicide fenpropimorph in a wind tunnel system and under outdoor conditions in a higher-tier field study. Fenpropimorph 750 g L(-1) EC was applied post-emergence to cereal along with a reference standard lindane EC. Stainless steel containers of water were placed at different distances downwind of the application area to trap volatile residues during a study period of 24 h following application. Meteorological conditions in the wind tunnel as well as on the field were constantly monitored during the study period. The wind tunnel system was a partly standardised system on a semi-field scale, i.e. wind direction and wind speed (2 m s(-1)) were constant, but temperature and humidity varied according to the conditions outside. In the field experiment, the average wind speed over the 24 h study period was 3 m s(-1) and no rainfall occurred. Three different measuring lines were installed on the non-target area beside the treated field to cover potential variations in the wind direction. However, no significant differences were observed since the wind direction was generally constant. Fenpropimorph was detected in minor amounts of 0.01-0.05% of the applied material in the wind tunnel experiment. Even at a distance of 1 m beside the treated field, no significant deposition occurred (0.04% of applied material after 24 h). In the field, less than 0.1% of the applied fenpropimorph was detected at 0 m directly beside the treated field. At 5 m distance the deposition values were below 0.04%, and at 20 m distance about 0.01%. In general, the amounts of deposited fenpropimorph detected in the partly standardised wind tunnel system and the higher-tier field study were in good agreement.

Quantification of fexofenadine in human plasma by liquid chromatography coupled to electrospray tandem mass spectrometry using mosapride as internal standard

A rapid high-performance liquid chromatography/positive ion electrospray tandem mass spectrometry method was developed and validated for the quantification of fexofenadine in human plasma using mosapride as internal standard. Following solid-phase extraction, the analytes were separated using an isocratic mobile phase on a reverse-phase column and analyzed by MS/MS in the multiple reaction monitoring mode using the respective [M+H]+ ions, m/z 502/466 for fexofenadine and m/z 422/198 for the IS. The method exhibited a linear dynamic range of 1-500 ng/mL for fexofenadine in human plasma. The lower limit of quantification was 1 ng/mL with a relative standard deviation of less than 5% for fexofenadine. Acceptable precision and accuracy were obtained for concentrations over the standard curve range. The total chromatographic run time of 2 min for each sample made it possible to analyze more than 400 human plasma samples per day. The validated method has been successfully used to analyze human plasma samples for application in pharmacokinetic, bioavailability or bioequivalence studies.

Sublimation of antimycotic agents as proved by various analytical methods

Qualitative and quantitative results demonstrate that the pure substances amorolfine base, amorolfine hydrochloride, two selected morpholine derivatives and terbinafine hydrochloride are clearly able to sublimate. As amorolfine hydrochloride is also capable to sublimate from galencial forms laquer and cream in this experimental setup, a clinical relevance of sublimation phenomenon at least for topical treatment of onychomycosis has to be considered. This phenomenon could be one reason for advantageous clinical and mycological cure rates of amorolfine nail laquer to comparable topical products reported in the literature.

A selective high-performance liquid chromatography method for the determination of reboxetine in bulk drug and tablets

Reboxetine is used as a selective noradrenaline reuptake inhibitor for the treatment of major depressive disorders. It is effective in the treatment of severe depression and safer to use than traditional tricyclic antidepressants. In this study, a novel, simple, and rapid stability-indicating high-performance liquid chromatography (HPLC) method for reboxetine methansulfonate was successfully developed and validated for the assay of tablets. The method was used to quantify reboxetine in tablets; it employed a C18 column (150 x 4.6 mm id) with an isocratic mobile phase consisting of methanol-phosphate buffer (pH 7, 0.02 M; 55 + 45, v/v) at a flow rate of 1.0 mL/min. Reboxetine was detected by an ultraviolet detector at 277 nm. The retention time of reboxetine was about 4.5 min. The developed HPLC method was validated with respect to linearity, precision, sensitivity, accuracy, and selectivity. The method was linear over the concentration range 1-50 microg/mL (r = 0.9999). The limits of detection and the quantitation of reboxetine were 0.1 and 0.3 microg/mL, respectively. The relative standard deviation values for intraday and interday precision were 0.78-1.01 and 1.08-1.37%, respectively. Selectivity was validated by subjecting a stock solution of reboxetine to neutral, acid, and alkali hydrolysis, as well as oxidation, dry heat treatment, and photodegradation. The peaks of the degradation products did not interfere with the peak of reboxetine. The results indicated that the proposed method could be used in a stability assay. The proposed method was successfully applied to the determination of reboxetine in tablets. Excipients present in the tablets did not interfere with the analysis.

Liquid chromatography method for quantifying D-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol (D-threo-PPMP) in mouse plasma and liver

A high-performance liquid chromatography (HPLC) method was developed to measure levels of d-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol (d-threo-PPMP) in mouse plasma and liver. d-threo-PPMP was measured by HPLC with a Luna Pheny-Hexyl column (5 microm, 250 mm x 4.6 mm) employing UV detection at 210 nm using a mobile phase of potassium phosphate buffer (20mM, pH 3.0)-acetonitrile in a 45:55 (v/v) ratio. d-threo-1-phenyl-2-pentadecanoylamino-3-morpholino-1-propanol (PC15MP) was employed as an internal standard (IS). The lower limit of quantitation (LLOQ) was 0.3 microg/ml. The assay was linear over a concentration range of 0.3-10 microg/ml, with acceptable precision and accuracy. Assayed in plasma, the intra- and inter-day validation for all coefficients of variation (R.S.D.%) were found less than 15%. The method was applied to samples from athymic (nu/nu) mice treated with d-threo-PPMP by intraperitoneal injection. d-threo-PPMP levels of approximately 10-20 microg/ml ( approximately 20-40 microM) in plasma and approximately 45 microg/g in liver were obtained. The present method can be used to quantify d-threo-PPMP in mice for bioavailability and dose-response studies.

Enantioselective determination of a gastroprokinetic drug using amylose tris-(3,5-dimethylphenylcarbamate) as a stationary phase by HPLC

An enantioselective high-performance liquid chromatographic method for determination of enantiomers of mosapride citrate in bulk drugs and pharmaceuticals using UV-vis and polarimetric detectors in series has been developed. Baseline separation with resolution >2.0 was achieved on a column containing amylose tris-(3,5-dimethylphenylcarbamate) as stationary phase using a mobile phase consisting of n-hexane:ethanol:triethylamine (80:20:0.3, v/v/v) at 40 degrees C. The detection was carried out at UV-276 nm and enantiomers were identified by polarimetric detector. The effect of ethanol, 2-propanol, TEA, temperature and mobile phase flow rate on separation of MSP enantiomers was studied and the method was validated with respect to accuracy, precision, linearity and limits of detection and quantification. The linearity of the method was studied between 6.25 and 50 microg/ml and r2 was >0.9997. The recoveries were in the range 99.63-100.22%, the method was suitable not only for process development of mosapride citrate but also for quality assurance of the individual enantiomers in bulk drugs and pharmaceuticals.

Volatilization of the pesticides chlorpyrifos and fenpropimorph from a potato crop

Volatilization of pesticides from crops in the field can be an important emission pathway. In a field experiment with characterization of meteorological conditions, the pesticides chlorpyrifos and fenpropimorph were sprayed onto a potato crop, after which concentrations in the air and on/in the plants were measured. Rates of volatilization were estimated with the aerodynamic profile (ADP), energy balance (EB), relaxed eddy accumulation (REA), and plume dispersion (PD) methods. The volatilization rates obtained with the ADP and EB methods were similar, while some rates obtained with the REA and PD methods in the initial period were lower. Cumulative volatilization of chlorpyrifos during daylight hours (ADP and EB methods) was estimated to be about 65% of the dosage. By far the majority of this volatilization occurred in the first few days. Competing processes at the plant surface had a considerable effect on the dissipation of fenpropimorph, so cumulative volatilization during daylight hours was estimated to be only 7% of the dosage. Plant surface residues were higher than would correspond with the volatilization rate, indicating that penetration into the leaves had occurred.

[The estimation of the perspectives of the 1,3,4-thiadiazine derivatives as the protectors means for the health tissues under radiation therapy of malignant tumour patients]

We generalized the results of our own researches of the mechanisms, determined the high (90% BALB-line mice were survived) radioprotection activity by 1,3,4-thiadiazine derivatives. It was determined that this preparat achieves the highest concentrations in the critical for the acute radiation influence tissues. The preparate bind with the cell's membranes, nucleus and mitochondries, blockade the development of the radial reactions on the tissues level. Small quantity passes to the brain marrow, takes part in the regulative processes, which central nervous system is produced, reduces the metabolitical processes in the organism. It doesn't possess the election accumulation in the tumour and it is perspective for the prevention of damage health tissues under irradiation cancroid's therapy.

Depletion of four nitrofuran antibiotics and their tissue-bound metabolites in porcine tissues and determination using LC-MS/MS and HPLC-UV

Depletion of the nitrofuran antibiotics furazolidone, furaltadone, nitrofurantoin and nitrofurazone and their tissue-bound metabolites AOZ, AMOZ, AHD and SEM from pig muscle, liver and kidney tissues is described. Groups of pigs were given feed medicated with one of the nitrofuran drugs at a therapeutic concentration (400?mg?kg(-1)) for ten days. Animals were slaughtered at intervals and tissue samples collected for analysis for six weeks following withdrawal of medicated feed. These samples were analysed both for parent nitrofurans (using LC-MS/MS and HPLC-UV), and for tissue-bound metabolites (using LC-MS/MS). The parent drugs were detectable only sporadically and only in pigs subjected to no withdrawal period whatsoever. This confirms the instability of the four major nitrofuran antibiotics in edible tissues. In contrast, the metabolites accumulated to high concentrations in tissues (ppm levels) and had depletion half lives of between 5.5 and 15.5 days. The metabolites of all four drugs were still readily detectable in tissues six weeks after cessation of treatment. This emphasizes the benefits of monitoring for the stable metabolites of the nitrofurans.

[Spectroscopic research on the interaction of 2-(4-dimethylaminophenyl)-5-fluoro-6-(morpholin-4-yl)-1H-benzimidazole and calf thymus DNA]

UV-Vis spectra of the aqueous solutions of 2-(4-dimethylaminophenyl)-5-fluoro-6-(morpholin-4-yl)-1H-benzimidazole (1) at different pH values revealed that compound 1 is a tertiary base, which can combine three protons. Through the non-linear least square method, the logarithm of the three accumulative protonation constants of compound 1, namely, lgbeta1, lgbeta2 and lgbeta3, were determined to be 4.96 +/- 0.03, 5.72 +/- 0.07 and 7.95 +/- 0.10, respectively. UV-Vis and the steady-state fluorescence spectra indicated that a special interaction occurs between compound 1 and calf thymus DNA at the pH value of 3.40, of which thebinding constant, Kb, is (2.30 +/- 0.10) x 10(4) mol(-1) x L. Compound 1 in the concentration range of 10(-8) to 1.2 x 10(-6) mol x L(-1) has a potential application to the quantitative determination of DNA.

Measured and computed volatilisation of the fungicide fenpropimorph from a sugar beet crop

Depending on their vapour pressure, volatilisation can be one of the main pathways of emission of pesticides into the environment. The volatilisation of fenpropimorph was studied in a field experiment in which the fungicide was sprayed onto a sugar beet crop. Volatilisation rates were calculated by measuring the concentration gradient in air, using the Aerodynamic and Bowen Ratio methods. A simplified computation model was used to simulate pesticide volatilisation, together with the concurrent processes of penetration into the plant leaves and phototransformation. Input data for the model had already been obtained by carrying out a wind-tunnel study with fenpropimorph, whereby field conditions were imitated. The computations yielded a reasonable description of the level and rate of decline of fenpropimorph volatilisation in the first 4 h after spraying. The continued volatilisation 2 and 3 days after spraying could be described by assuming that a fraction of the deposit was poorly exposed with comparatively low rates of the decline processes. In the first 3 days, penetration of fenpropimorph into the plant leaves was computed to be the main route for the pesticide (52% of the dosage), with substantial contributions from volatilisation (12%) and phototransformation (11%). The computation model can be developed further as a tool for extrapolating results on volatilisation from small-scale experiments to field conditions, but this requires more information on the effect of environmental conditions on the model parameters.