Revisiting the dependence of retention factor on the content of organic component in the mobile phase in reversed-phase HPLC

In high-performance liquid chromatography, the dependence of retention factor k on volumetric fraction ϕ of organic phase is expressed by log k = F(ϕ) with F(ϕ) obtained by measuring log k at different ϕ values. From F(ϕ), a value kw is calculated by taking ϕ = 0. The equation log k = F(ϕ) is applied for predicting k, and kw is a descriptor of hydrophobic character of solutes and stationary phases. Calculated kw should not depend on the nature of organic component of mobile phase but extrapolation procedure leads to different kw for different organic components. The present study shows that the expression of F(ϕ) changes depending on the range of ϕ and the same function F(ϕ) cannot be used for the full range of ϕ from 0 to 1. Consequently, kw obtained by extrapolation of ϕ to zero is not correct because the expression of F(ϕ) was generated by fitting the data using ϕ with higher values. The present study shows the proper way to obtain the value of kw .

Occurrence and fate of Adsorbable Organic Halogens (AOX) in two WWTPs from Romania

Absorbable organic halogens (AOX) are a global parameter which refers to a group of chemical compounds that contain one or more chlorine, bromine or iodine atoms in their molecule and can easily adsorb on activated carbon. The global concern related to the occurrence of the AOX compounds in the environment is due to their toxic and mutagenic effects on aquatic organisms and their potential role as inhibitors of microorganism growth, even at AOX low concentrations. The purpose of this study was to analyze the presence, occurrence and composition of absorbable organic halogens in wastewater and sewage sludge. In addition, their genotoxicity effect on the environment was tested on a bacterial biological model. Daily mass loading, mass emission and fate of AOX parameter were investigated in two wastewater treatment plants (wastewater and sewage sludge samples) from Romania, Galati and Iasi. Their AOX daily mass loadings (151 and 55.4 g/day/1000people) and mass emissions into the environment (47.8 and 23.5 g/day/1000 people) for both locations were correlated with the concentration level of volatile organic compounds, chlorophenols, organochlorine pesticides and polychlorinated biphenyls from both wastewater and sewage sludge, respectively. Concentration levels of detected halogenated organic compounds (regulated by current standards) accounted only for a small percentage (3.70-14.5%) from the total AOX amount. An exception was observed in the case of dehydrated sludge samples where the identified compounds accounted for 80% of the AOX content from Iasi WWTP and 53% for Galati. Evaluating the genotoxic activity of AOX in sludge samples showed that genotoxicity was not induced up to 100 µg/mL dehydrated sludge.

Occurrence and Fate of Bisphenol A and its Congeners in Two Wastewater Treatment Plants and Receiving Surface Waters in Romania

The present study investigated the distribution and environmental fate of Bisphenol A (BPA), the 4-hydroxyacetophenone (4-HAP) metabolite, and 5 other bisphenol congeners in 2 municipal wastewater treatment plants (WWTPs) and their receiving rivers in Romania. Accordingly, a new, highly sensitive and accurate solid-phase extraction-liquid chromatography-electrospray ionization-tandem mass spectrometry method was developed and validated. This technique generated low limit of quantitation values: below 2.3 ng/L for surface water and less than 2.4 and 2.7 ng/L for WWTP effluent and influent water. The sum of detected analytes in wastewater was between 1337 and 16 118 ng/L for influent samples and between 15 and 96 ng/L for effluent samples. In surface water, the total of all compounds was somewhere between 34 and 240 ng/L. The highest concentration observed was for BPA in all 3 types of analyzed water (up to 9140 ng/L for influent, as high as 75 ng/L for effluent, and a maximum of 135 ng/L in surface waters). All analyzed samples were free of bisphenols B, C, and F. For all analytes detected in surface water, the concentration values were higher than those determined in the effluent samples, which may be caused by intrinsic contamination of the 2 rivers (Danube and Jiu Rivers). Values of environmental risk coefficients, calculated for both effluents and surface waters, indicated a low ecological risk or no ecological risk for 3 types of organisms (algae, daphnia, and fish). Human risk assessment calculation suggests no risk to human health as a result of the presence of BPA in either of the 2 rivers. Environ Toxicol Chem 2021;40:435-446. © 2020 SETAC.

Distribution, removal efficiencies and environmental risk assessment of benzophenone and salicylate UV filters in WWTPs and surface waters from Romania

This article presents the environmental pollution level with organic UV filters and the effect they pose on aquatic organisms in Romania.

Derivatization procedures and their analytical performances for HPLC determination in bioanalysis

Derivatization, or chemical structure modification, is often used in bioanalysis performed by liquid chromatography technique in order to enhance detectability or to improve the chromatographic performance for the target analytes. The derivatization process is discussed according to the analytical procedure used to achieve the reaction between the reagent and the target compounds (containing hydroxyl, thiol, amino, carbonyl and carboxyl as the main functional groups involved in derivatization). Important procedures for derivatization used in bioanalysis are in situ or based on extraction processes (liquid-liquid, solid-phase and related techniques) applied to the biomatrix. In the review, chiral, isotope-labeling, hydrophobicity-tailored and post-column derivatizations are also included, based on representative publications in the literature during the last two decades. Examples of derivatization reagents and brief reaction conditions are included, together with some bioanalytical applications and performances (chromatographic conditions, detection limit, stability and sample biomatrix).

Occurrence of Phenolic Endocrine Disruptors in Danube Delta, Romania

In the last decade, the use of chemical compounds with a molecular structure similar to that of BPA has been reported more and more as alternatives to BPA in various industrial products. This comes as a result of banning partial or total use of BPA because of its endocrine disrupting properties. However, bisphenol analogues have been shown to have similar or even greater negative properties than BPA. Thus, particular attention has been given to the risks they have for aquatic systems and human health. In this context, the present study aimed to determine the concentration level at which some of the bisphenol analogues (BPS, BPB, BPE, BPC and BPE), BPA and its major metabolite, 4-HAP, are found in surface waters. For this purpose, 11 sampling points were established in the geographical area of the Danube Delta. Among the seven targeted pollutants, only four were detected in the analyzed samples. 4-HAP metabolite was the most abundant compound in the analyzed samples, with concentrations ranging from 3.56 to 30.9 ng/L. BPA concentrations were, in most cases approximately three times lower than those determined for 4-HAP. The next bisphenol analog after 4-HAP, in the decreasing order of concentrations, was BPE, for which the concentration level ranged between LOQ and 12.4 ng/L. Lowest concentrations were detected for BPS, with a maximum level of 1.96 ng/L.

HG-ICP-OES Technique, a Useful Tool for Arsenic Determination in Soft Water

This paper presents a fast, sensitive, linear and precise method for the determination of arsenic (As) at trace levels, from different types of water (drinking, mineral, surface water and groundwater) using hydride generation and optical emission spectrometry with inductively coupled plasma (HG-ICP-OES). In order to generate the hydride, the initial pretreatment of the samples with a mixture of potassium iodide and ascorbic acid is necessary, in hydrochloric acid medium for reducing the As5+ to As3+ ions and for the subsequent formation of the hydride from As3+ ions and sodium borohydride, in a continuous-flow cell. The quantification limit of the method (LOQ = 0.43 �g/L), the precision (3.41%), the recovery yield (95%) and the measurement uncertainty of 24% frame the method within the limits imposed by the acceptance criteria of an analytical method for arsenic determination. The proposed method was tested on several types of water, the obtained results being compared to those obtained by applying two sensitive and selective alternative methods using ICP-MS, respectively ultrasonic nebulizer and ICP-OES.

Determination of Hypoglycemic Agents in Surface Water Samples Using SPE-LC-MS/MS Method

Antidiabetic compounds are a class of emerging contaminants in environment, for which there are no regulations in the world environmental legislation. These compounds are among the most widely used drugs in the world due to the large number of patients with diabetic conditions. The presence of these pollutants in the environment is insufficiently studied, so efficient analytical methods are needed to allow their detection at trace levels (ng/L). For the simultaneously quantification of the five antidiabetics (glyburide, metformin, glipizide, gliclazide, glimepiride) and one bio-degradation product (guanyl urea) in surface water samples a SPE-LC-MS/MS (solid phase extraction -liquid chromatography coupled with mass spectrometry detection) method was validated using real river water samples. The compounds were separated on C18 LC column in 9 minutes at 300C using a gradient of mobile phase of 0.1% formic acid and acetonitrile. Good performance parameters were obtained using the method: low limits of quantification (LOQs 0.1-2.4 ng/L), precision (repeatability 3.5-7.2% and reproducibility 6.5-12.7%) and determination coefficients (higher than 0.99). The most contaminated river was represented by Ialomita, which had a total concentration of antidiabetics of 112.1 ng/L in the downstream point, followed by the Siret and Dambovita rivers, which had a total concentration of antidiabetics of 66.3 ng/L and 57.3 ng/L, respectively, also in the downstream points.

Environmental Detection of Brilliant Blue, Sunset Yellow and Tartrazine Using Direct Injection HPLC-DAD Technique

A newly developed direct injection HPLC-DAD method for the simultaneous detection of Brilliant Blue (BB), Sunset Yellow (SY) and Tartrazine (TA) synthetic dyes was validated and applied to surface and wastewater samples. Chromatographic separation was achieved using an Acclaim Surfactant Plus column (150 x 3.0 mm, 3 um) in isocratic elution mode with a mobile phase consisting of 100 mM CH3COONH4 and ACN in the ratio 50/50 (v/v). Linear calibration curves were plotted in the range of 2-100 μg/L (BB) and 6-300 μg/L (SY, TA) respectively with correlation coefficients (R2) higher than 0.99. Low quantitation limit values (LOQ) were obtained for the direct injection HPLC-DAD method, namely: 1.0 �g/L (BB), 5.5 �g/L (SY) and 5.8 �g/L (TA), respectively. The entire sample preparation procedure consisted only in simple filtration using PTFE syringe filters (0.45 �m) without sample extraction or concentration, which improved method accuracy and precision. HPLC-DAD developed method proved to be fast (6 minutes run-time), sensitive and accurate and was succesfully applied for the analysis of the synthetic dyes in surface and wastewater samples. Considering all analyzed samples (8 surface water and 11 wastewater samples), Brilliant Blue was found in influent samples with values between 4.49 � 14.17 �g/L and effluent samples with values between 1.07 � 9.54 �g/L, whereas Sunset Yellow and Tartrazine were not detected in any of the analyzed samples.

Comparative Experimental Study on an Endocrine Disruptor Degradation by UV/H2O2 and UV/H2O2/TiO2 Systems

Bisphenol A (BPA) � an endocrine disruptor, degradation was studied using the following systems: UV/H2O2 and UV/H2O2/TiO2. Optimum operating conditions were established for both studied systems and experimental results showed that the two systems could be successfully used for advanced degradation of BPA achieving degradation efficiencies for BPA of 99.99% in optimum working conditions. The two systems were compared and both advantages and disadvantages of each system were identified. Nine degradation intermediates were identified for BPA degradation in UV/H2O2/TiO2 system and a possible degradation pathway was proposed.

Liquid Chromatography Tandem Mass Spectrometry Method for Ultra-Trace Analysis of Organic UV Filters in Environmental Water Samples

A liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) method was developed and validated for the simultaneous determination of six organic compounds (2-hydroxy benzophenone, 4-hydroxy benzophenone, 2,2�,4,4�-tetrahydroxy benzophenone, 2,4-dyhydroxy benzophenone, 4,4�-dyhydroxy benzophenone, 2,2�-dyhydroxy-4-methoxy-benzophenone) used as UV filters in personal care products used to protect against UV radiation. The major concern about this type of pollutants is due to their persistence and bioaccumulation potential in the environment and aquatic organisms and for their endocrine disruptor properties. Solid phase extraction was used for sample preparation, followed by liquid chromatography tandem mass spectrometry analysis. Benzophenone derivatives were analyzed on a Phenomenex Luna C18 column (150 x 2.0 mm, 3.0 �m) with the mobile phase run in gradient mode with a mixture of aqueous 0.1% formic acid and acetonitrile as the mobile phase components (at a flow rate of 0.2 mL/min). MS detector response was linear, on the tested concentration domain from 1 to 100 μg/L with correlation coefficient R2 ] 0.998. The recoveries of benzophenone derivatives after solid phase extraction procedure from surface water was found to be ]81% for surface water and higher than 79% for wastewater matrix. The standard deviation values for intra-day precision were situated between 7.67% and 9.88% for lower concentration and 7.27% and 8.86% for higher concentration respectively. The limits of quantitation were calculated for both environmental water matrices (1.6-4.1 ng/L for surface water and 3.3-8.2 ng/L for wastewater). This method can be applied for benzophenone derivatives detection in real environmental samples.

PTV In Situ Derivatization of Several Acidic Herbicides Using a Newly Developed GC-MS/MS Method

The uses of herbicides increased during the last decades. Because acid herbicides can be identified in environmental samples, specific analytical methods are required. In this work a new GC-MS/MS method was developed in order to detect some pyridinecarboxylic acids (clopyralid, triclopyr and fluroxypyr) and a methoxybenzoic acid (dicamba) from environmental water samples. Because these polar analytes involve a derivatization step, a Programmed Temperature Vaporizing injector (PTV) was used to shape the derivatization conditions and to minimize the working time. This process is called in port derivatization (IPD), a relative new technique which encourages greener practices in analytical laboratory. MtBSTFA was chosen to be the most suitable silylation agent due to generation of specific derivatized analyte structures, which can be further fragmented in the EI ionization source to produce specific ions for the targeted analytes, easily detectable with high sensitivity.Few studies analyzed the derivatization of above-mentioned herbicides with MtBSTFA, while no other paper work was identified in studying the in port derivatization of these compounds. The results revealed that the developed method is sensitive and robust to obtain quantitation limits below 10 ng/L.

Fast and sensitive detection of acrolein in environmental water samples without derivatization using liquid chromatography tandem mass spectrometry

A fast and sensitive SPE-LC-MS/MS method for the determination of acrolein in environmental water samples using activated charcoal as SPE adsorbent was developed. The novelty of this study consists in acrolein extraction, separation and detection without the need of a derivatization process. Physicochemical properties of acrolein, such as low molecular weight and high polarity represent real challenges for extraction, separation, and detection of this pollutant using SPE-LC-MS/MS. These were addressed by choosing a suitable chromatographic column which ensures a good peak symmetry and retention for the analyte, as well as the choice of SPE adsorbent suitable for retaining very polar compounds like acrolein from the aqueous matrix. The chromatographic column was a Synergi Fusion RP (150 × 2.0 mm, 4.0 μm) with a C18 stationary phase modified with polar embedded amide groups. Activated charcoal adsorbent used as SPE extraction media was able to extract efficiently highly polar molecules such as acrolein and ¹³C₃-acrylamide (internal standard) from water samples. Using this method, the obtained extraction recovery for acrolein was 88% at a 50 ng/L concentration level. Overall method quantitation limit (LOQ) for acrolein in water was established at 3.8 ng/L. The newly developed SPE-LC-MS/MS method was successfully applied to detect acrolein occurrence in wastewater and drinking water samples. Acrolein level in these samples ranged from LOQ to 122 ng/L.

Fast and Sensitive LC-MS Detection of Bisphenol A and Butylhydroxyanisole in WWTP Sewage Sludge

In this study, a new LC-MS/MS method was developed and optimized in order to detect two omnipresent additives, Bisphenol A (BPA) and Butylhydroxyanisole (BHA), in WWTP sewage sludge. Both analytes are synthetic phenolic compounds known for their endocrine disruptive and toxic properties. BPA and BHA were isolated from sludge samples using ultrasonic assisted liquid-solid extraction followed by silicagel clean-up to remove interferences, and evaporation to dryness and extract re-dissolution with 1 mL methanol prior to LC-MS analysis. All LC-MS parameters were optimized in order to obtain high sensitivity and selectivity. MS detector response was linear in the range 1 � 200 �g/L with correlation coefficient R2 ] 0.999 for both analytes. Intra-day and inter-day precision expressed as RSD values were 4.7% and 10.3% for BPA, whereas for BHA 7.8% and 13.8% RSD values were obtained. Recovery values after ultrasonic assisted extraction were 85.5% for BPA and 79.3% BHA with internal standard correction. Overall method LOQs were established at 1.97 ng/g (BPA) and 1.86 ng/g (BHA) on dry weight. Optimized chromatographic parameters allowed separation and detection of the two additives in less than 10 minutes. Both BPA and BHA were detected in all tested sludge samples with higher levels for BPA (34.6 - 132.6 ng/g), whereas BHA was found at lower levels in the range 3.16 - 5.64 ng/g.

Mobility of Some High Persistent Organochlorine Compounds from Soil to Mentha Piperita

The fate of organochlorine compounds in soil ecosystem is shaped by their physical-chemical properties and by environmental conditions. The high persistence of polychlorobiphenyls (PCBs) in soil is given by a slow degradation which varies from months to years (the half-life of PCB 28 is 10.9 years, and PCB 52, 11.2 years). Due to high lipophilicity, these carcinogenic compounds can be easily uptaken by plants and transferred to the food chain. The widespread use of medicinal plant, Mentha Piperita, in pharmaceutical and food industry represents a risk of contamination and pollution. Through laboratory studies, we worked to identify the chemical behavior in soil and plants of some PCB congeners: 28, 52, 138, 153 and 180). The compounds mobility from soil to the roots and then through plant was monitored for 5 weeks. By optimizing the analytical method the contaminants were determined from soil and plant with good recoveries and with reduced limit of detection, below 0.01 mg/kg. It was reported that usually are uptaken into the plant high chlorinated PCBs like PCB 153 and PCB 180 but this study shows that after 5 weeks of PCB application, the concentration of PCB 28, a trichlorobiphenyl, is increasing. Fortunately, calculating the bioconcentration factor (BCF) of the selected PCBs in roots, it was shown that is similar to BCF of other plants like poplar and zucchini. The obtained value of 0.2 is assessed as being low.

Occurrence of Neonicotinoid Residues in Danube River and Tributaries

Occurrence and fate of 6 neonicotinoid insecticides belonging to different chemical classes were investigated in the aqueous phase of surface water at 16 sampling locations along the Romanian side of the Danube River and its three main tributaries (Jiu, Olt, Arges). This is the first report on the neonicotinoid occurrence in the Danube River and three tributaries. It was observed a contamination of Danube River and its tributaries, higher in planting period than pre-or post- planting period, with the next compounds (detection frequency and the concentration range): thiamethoxam (68.7%, 0.9-3.8ng/L), clothianidin (64.6%, 0.84-9.6ng/L), nitenpyram (52.08%, 0.39-11.1ng/L), imidacloprid (31.2%, 0.5-8.2ng/L), acetamiprid (16.6%, 0.84-12.7ng/L). The four main neonicotinoids (clothianidin, thiamethoxam, imidacloprid, nitenpyram) follow the classic pattern in which concentrations and frequency increase during the planting period and that is correlated with seed crop treatment. Total neonicotinoid levels present in investigated Rivers, reaching up to 31.6 ng/L, may affect aquatic invertebrates that are most susceptible to these insecticides. For clothianidin and nitenpyram were obtained positive correlations between the percentage of the area planted with cereals and concentrations of this compound (r= 0.574, r =0.665) which indicate their use in agricultural area. For imidacloprid were obtained positive correlations between percent of permanent cultivated crop in urban land and concentrations of this compound (r =0.264, r =0.877).

Investigation on Parabens Occurrence in Romanian WWTP Sludge by LC-MS/MS Method

A sensitive and precise method for detection of five parabens in sewage sludge was developed based on ultrasonic assistedextraction, SPE clean-up and LC-MS/MS. Most of the parameters that affect the extraction step such as type of solvent and volume, extraction time were optimized. For ultrasonic extraction it was used a mixture of methanol: acetone, then the extract was centrifuged in order to obtain clean supernatant and the extract was purified on polymericSPE cartridges. The parabens were separated on C18 column in 13 min at 18�C using a gradient of mobile phase of 0.01% acetic acid and acetonitrile. Using the method, limit of quantitation (LOQ) were obtained ranging from 0.4 to 2ng/g. All recoveries ranged from 71% to 109% for all compounds. The repeatability and reproducibility between days expressed as RSD (%) were less than 7.4% and 14.5%, respectively. The sum concentrations of all parabens for each sludge sample ranged between 19 ng/g dry weight and 32.7 ng/g dry weight. The study of the profile sample composition shows that the average contribution of each compound of the total parabens concentration was as follow: methyl paraben 62.9%, ethyl paraben 18.6%, iso-propyl paraben 10.9%, propyl paraben 10.8%. This result indicate that methyl paraben is the most used paraben followed by ethyl paraben.

Possible Pathway for Ifosfamide Degradation via Fe-TiO2 Assisted Photo Catalysis

Ifosfamide (IF) degradation from aqueous system via UV-Vis Fe-TiO2 system was studied for a photo catalyst dose of 200 mg/L and an irradiation time up to 240 min. IF degradation efficiency was monitored via Liquid Chromatography-Mass Spectrometry technique (LC-MS). Experimental photocatalytic tests were performed both in the absence and presence of 2-propanol and F- radicals� scavengers and the results proved that IF degradation occurs most likely in the bulk solution. Experimental results showed that degradation efficiencies for IF varied between 39.52% in the presence of 2-propanol and 70.70% in the scavengers� absence. Six degradation intermediates were identified using the same LC-MS technique and a three stage degradation pathway was proposed based on both available literature data and evolution of degradation intermediates peaks.

Parallel between Offline-SPE-LC-MS and Direct Injection LC-MS Methods for Acrylamide Detection in Drinking Water at Parts Per Trillion Level

The presence of acrylamide, a potential human carcinogen, in treated drinking water has been a long-time concern for public health agencies. Due to this, acrylamide is included among the substances to be monitored in drinking water with a stated maximum admissible level of 0.1 �g/L in Europe. The necessity for ultra-trace level detection of acrylamide has led to development of an Offline-SPE-LC-MS method that involves SPE extraction of acrylamide using a strong adsorbent like activated charcoal followed by concentration. Simultaneously, a simple and rapid large volume Direct Injection LC-MS method was optimized from the previous method to detect acrylamide without the resource and time-consuming SPE step. A comprehensive comparison between the efficiency and sensitivity of the two methods is made. Optimization of LC-MS parameters (column temperature, mobile phase composition and flow, collision energy, fragmentor voltage, capillary voltage or MRM transitions) allowed high detection sensitivity. Due to Acrylamide high polarity, a Synergi Fusion-RP column with amide polar embedded groups was chosen to achieve reasonable retention and peak shape for acrylamide with a short run-time of only 3 min. The two methods provided excellent sensitivity, with reasonably low LOQ values of 2 ng/L for the Offline-SPE-LC-MS method and 30 ng/L for the Direct Injection LC-MS method. Intra-day and inter-day precision (RSD%) were 7.3 and 10.3%, for the Offline-SPE-LC-MS method and 2.4% and 6.2%, respectively for the Direct Injection LC-MS method. The analysis of acrylamide was successfully performed in drinking water from different location consumers and water treatment plants in Romania. Acrylamide was found in drinking water samples with levels between 5.2 and 35.7 ng/L using the Offline-SPE-LC-MS method. The direct injection method can only be used for acrylamide levels higher than its LOQ value (30 ng/L).

Comparing Carbonyls Levels in Indoor Air in two Offices -Green and Old Building

The concentrations of 17 carbonyl compounds were investigated in indoor air of two offices - one located in a green building and the other in an old building, both from Bucharest. Indoor air samples were collected during normal activities of the working staff on passive samplers. Two analytical techniques were used: Ion Chromatography for carboxylic acids and High Performance Liquid Chromatography for aldehydes and ketones. A questionnaire was administrated in order to collect information about buildings characteristics, indoor furniture, decorating materials and electronical devices used during the sampling. Formaldehyde, acroleine+acetone, acetaldehyde, hexaldehyde and carboxylic acids were the most abundant compounds that accounted for more than 50% of the total carbonyls. The majority of the aldehydes showed higher concentrations in the old building office compared to the concentrations found in the green building office. Regarding the carboxylic acids: the concentration of formic acid was slightly higher in the old building office versus the green building office; in the case of acetic acid, the concentration found in the old building office was around two times higher comparing to the green building office.

New Study Concerning the Biodegradation of Dimethoate, Chlorpyrifos and Chlorfenvinphos in some Medicinal Plants

Herbal drugs are widely used in pharmaceutical industry due to their beneficial effects on human health. The current research was carried out to evaluate the organic pollutant degradation in the flower part of the plant after a foliar application of pesticides. Also, based on the fact that selected pesticides are highly toxic to bees, it is important to monitor the removal rate of the pollutant. Under laboratory conditions, the marigold and French flowers (Calendula Officinalis and Tagetes Patula) were spiked with a mix of organophosphorus insecticide, dimethoate, chlorpyrifos and chlorfenvinphos, where the first two substances are still used on Romanian territory. The samples were extracted at different time moments over 300 min after sprayed treatment in order to evaluate the concentration in flower. The analytes were quantified by using gas chromatography with flame photometric detection (GC-FPD) technique. The developed method ensures the quality and comparability of analytical results, with a good sensitivity in determining the analytes over the concentration range 5-250 �g/L.

Neonicotinoids Detection by new LC-MS/MS Method in Romanian Surface Waters

Increasing and widespread use of neonicotinoid insecticides in all world, together with their highly toxicity to invertebrates and environmental persistence mean that surface waters need to be monitored for these compounds. In the 2015, neonicotinoid insecticides have been incorporated in the watch list of substances for a European Union monitoring program (495/2015/ EU). A new method using automated solid phase extraction (SPE) with polymeric cartridges (OASIS HLB) followed by LC-MS/MS provided good separation of the most common neonicotindoid compounds. The method was developed for the determination of four neonicotinoid insecticides (nitenpyram, thiamethoxam, clothianidin, acetamiprid) in surface water with low limit of quantification (0.3-0.9 ng/L, nanograms per liter). Recoveries in surface water samples fortified at 200 ng/L for each compound ranged from 71.4 to 109.9 %; relative standard deviation ranged from 4 to 9%. The method was applied to water samples from four streams in Romania, Danube River and its tributaries (Arges River, Jiu River, and Olt River). The surface water samples were found to be contaminated clothianidin (1.08-6.4 ng/L) and by thiamethoxam (1.1-3.8ng/L). The highest concentrations were recorded in Danube River in Oltenita point (6.4ng/L) and in Gura-Vaii point (5.5ng/L). The concentration of acetamiprid and nitenpyram were situated below limit of quantification in all samples.

Simultaneous Determination of alfa-, beta- and gama-hexabromocyclododecane Diastereoisomers in Sewage Sludge using Liquid Chromatography Tandem Mass Spectrometry

Hexabromocyclododecane (HBCD) is a large-scale usage brominated flame retardant consisting of a mixture of diastereoisomers which has been reported as an ubiquitous environmental contaminant. HBCD has attracted much attention due to its toxicity and increasing levels in waste water sewage sludge. Since November 2014, HBCD was added to the Persistent Organic Pollutants list of the Stockholm Convention which generated a higher concern regarding its presence in the environment. A rapid (8 min) and accurate liquid chromatography electrospray ionization tandem mass spectrometry method (LC-ESI-MS/MS) was developed to separate and detect a-, b- and g-HBCD isomers from sewage sludge. Optimization of LC-MS parameters (column temperature, mobile phase composition and flow, collision energy, fragmentor voltage, capillary voltage and drying gas temperature) allowed complete separation of the three isomers and also very good detection sensitivity with instrumental quantitation limits (IQLs) between 0.3 and 0.6 ng/mL. The three isomers were separated on a C18 reversed-phase column, kept at 18�C, using a H2O/ACN/MeOH mobile phase mixture and detected by negative electrospray ionization using MRM mode with two transitions, one for quantitation and one for confirmation. MS detector response was linear in the range 1.0 � 100.0 ng/mL with correlation coefficients (R2) higher than 0.99 for all three isomers. A simple ultrasonic assisted liquid-solid extraction procedure using a solvent mixture was employed to extract HBCD isomers from WWTP sewage sludge. Overall method intra-day and inter-day precision (RSD%) were situated between 7.6 � 9.2% and 10.3 � 14.5%, respectively. LOQs for a-, b- and g-HBCD were 1.4, 0.7 and 1.0 ng/g, comparable and even lower to those reported by similar studies concerning HBCD presence in WWTP sewage sludge. HBCD presence was tested from several WWTP sludge samples. All three isomers were found with 100% detection frequency ranging from 3 to 76 ng/g.

Assay of free captopril in human plasma as monobromobimane derivative, using RPLC/(+)ESI/MS/MS: validation aspects and bioequivalence evaluation

A sensitive method for determination of free captopril as monobromobimane derivative in plasma samples is discussed. The internal standard (IS) was 5-methoxy-1H-benzimidazole-2-thiol. Derivatization with monobromobimane immediately after blood collection and plasma preparation prevents oxidation of captopril to the corresponding disulfide compound and enhances the ionization yield. Consequently, derivatization enhances sample stability and detection sensitivity. Addition of the internal standard was made immediately after plasma preparation. The internal standard was also derivatized by monobromobimane, as it contains a thiol functional group. Preparation of plasma samples containing captopril and IS derivatives was based upon protein precipitation through addition of acetonitrile, in a volumetric ratio 1:2. The reversed-phase liquid chromatographic separation was achieved on a rapid resolution cartridge Zorbax SB-C(18), monitored through positive electrospray ionization and tandem MS detection using the multiple-reaction monitoring mode. Transitions were 408-362 amu for the captopril derivative and 371-260 amu for the internal standard derivative. The kinetics of captopril oxidation to the corresponding disulfide compound in plasma matrix was also studied using the proposed method. A linear log-log calibration was obtained over the concentration interval 2.5-750 ng/mL. A low limit of quantitation in the 2.5 ng/mL range was obtained. The analytical method was fully validated and successfully applied in a three-way, three-period, single-dose (50 mg), block-randomized bioequivalence study for two pharmaceutical formulations (captopril LPH 25 and 50 mg) against the comparator Capoten 50 mg.

Achiral–chiral LC/LC–FLD coupling for determination of carvedilol in plasma samples for bioequivalence purposes

Bioequivalence data for two pharmaceutical formulations (solid oral dosage forms) containing carvedilol is presented for both racemic and enantiomers of the active substance. This was achieved by on-line coupling of two liquid chromatographic separations followed by fluorescence detection. The first LC dimension was used for a fast separation of racemic carvedilol from propranolol (IS) and the endogenous matrix, by means of a reversed phase mechanism. The peak of racemic carvedilol was on-line transferred to the second enantioselective LC dimension, based on a reversed phase separation on cellulose tris(3,5-dimethyl-phenylcarbamate) stationary phase. Both stages were monitored over a single run by means of a fluorescence detector operated at an excitation wavelength of 285 nm and an emission wavelength of 355 nm. Automated shortcutting of the racemic carvedilol peak to the chiral column and simultaneous detection over the two LC dimensions have been obtained by using an experimental set-up based on two six-port rotative switching valves. Linearity was demonstrated on the interval 2-150 ng/mL for racemic carvedilol and on 1-75 ng/mL intervals for enantiomers. LLOQ fits between 0.7 and 1.4 ng/mL. Recoveries of the target compounds are 87+/-4 and 81+/-4% for the IS. Precision ranged from 0.6 to 2.5% and the mean accuracy obtained on quality control samples (measured as % bias) over the whole study falls between -0.8 and 6.3%.

Fast RPLC-UV method on short sub-two microns particles packed column for the assay of tenoxicam in plasma samples

An extraction-less sample preparation technique followed by a RPLC-UV method on sub-two microns particles packed short column were used for the assay of tenoxicam in plasma samples. Protein precipitation was made by means of trichloroacetic acid addition. Supernatant was injected to the chromatographic column without any further pH adjustment. The mobile phase consisted in a mixture of acetonitrile and aqueous 0.1% phosphoric acid, at 2 mL/min flow rate and gradient elution. The Zorbax SB-C18 column (50 mm length, 4.6 mm internal diameter and 1.8 microm particle size) was thermostated at 60 degrees C. The mobile phase gradient composition program allowed separation of tenoxicam and piroxicam (internal standard), column clean-up and re-equilibration within 4 min. UV detection was achieved at 368+/-10 nm. The method is characterized by a low limit of quantitation of 25 ng/mL for tenoxicam, with a linearity interval up to 5500 ng/mL. The use of a low volume detection cell and detector high frequency data acquisition rate produced high precision and accuracy through a whole bioequivalence study of tenoxicam in two commercially available tablet formulations, after a single oral administration dose. Full method validation is presented. The high throughput characteristic of the proposed method allowed full validation and bioanalytical study completion within a 96 h period.

High-throughput liquid-chromatography method with fluorescence detection for reciprocal determination of furosemide or norfloxacin in human plasma

A simple, high-throughput, highly selective and sensitive HPLC-FLD method for isolation and determination of furosemide and/or norfloxacin in human plasma samples following a simple organic solvent deproteinization step with acetonitrile as sample 'clean-up' procedure is reported. One of the two drug substances plays the internal standard role for the determination of the other. Separation of analyte and internal standard was achieved in less than 5.3 min (injection to injection) on a Chromolith Performance RP-18e column, using an aqueous component containing 0.015 mol/L sodium heptane-sulfonate and 0.2% triethylamine brought to pH = 2.5 with H(3)PO(4). The composition of the mobile phase was: acetonitrile-methanol-aqueous component = 70:15:15 (v/v/v) and the flow-rate was set up to 3 mL/min. The chromatographic method applied to the determination of furosemide relies on fluorescent detection parameters of 235 nm for the excitation wavelength, and 402 nm for the emission wavelength. In case of norfloxacin, the excitation wavelength is set up to 268 nm and the emission wavelength is set up to 445 nm. The overall method leads to quantitation limits of about 27 ng/mL for furosemide, and 19.5 ng/mL for norfloxacin, using an injection volume of 250 microL. The method was applied to the bioequivalence study of two furosemide-containing formulations.