Determination of veterinary drug residues by liquid chromatography and tandem mass spectrometry

Emerging organic contaminants in the soil-plant-receptor continuum: transport, fate, health risks, and removal mechanisms

There is a lack of comprehensive reviews tracking emerging organic contaminants (EOCs) within the soil-plant continuum using the source-pathway-receptor-impact-mitigation (SPRIM) framework. Therefore, this review examines existing literature to gain insights into the occurrence, behaviour, fate, health hazards, and strategies for mitigating EOCs within the soil-plant system. EOCs identified in the soil-plant system encompass endocrine-disrupting chemicals, surfactants, pharmaceuticals, personal care products, plasticizers, gasoline additives, flame retardants, and per- and poly-fluoroalkyl substances (PFAS). Sources of EOCs in the soil-plant system include the land application of biosolids, wastewater, and solid wastes rich in EOCs. However, less-studied sources encompass plastics and atmospheric deposition. EOCs are transported from their sources to the soil-plant system and other receptors through human activities, wind-driven processes, and hydrological pathways. The behaviour, persistence, and fate of EOCs within the soil-plant system are discussed, including sorption, degradation, phase partitioning, (bio)transformation, biouptake, translocation, and bioaccumulation in plants. Factors governing the behaviour, persistence, and fate of EOCs in the soil-plant system include pH, redox potential, texture, temperature, and soil organic matter content. The review also discusses the environmental receptors of EOCs, including their exchange with other environmental compartments (aquatic and atmospheric), and interactions with soil organisms. The ecological health risks, human exposure via inhalation of particulate matter and consumption of contaminated food, and hazards associated with various EOCs in the soil-plant system are discussed. Various mitigation measures including removal technologies of EOCs in the soil are discussed. Finally, future research directions are presented.

An Update on the Use of Molecularly Imprinted Polymers in Beta-Blocker Drug Analysis as a Selective Separation Method in Biological and Environmental Analysis

Beta-blockers are antihypertensive drugs and can be abused by athletes in some sport competitions; it is therefore necessary to monitor beta-blocker levels in biological samples. In addition, beta-blocker levels in environmental samples need to be monitored to determine whether there are contaminants from the activities of the pharmaceutical industry. Several extraction methods have been developed to separate beta-blocker drugs in a sample, one of which is molecularly imprinted polymer solid-phase extraction (MIP-SPE). MIPs have some advantages, including good selectivity, high affinity, ease of synthesis, and low cost. This review provides an overview of the polymerization methods for synthesizing MIPs of beta-blocker groups. The methods that are still widely used to synthesize MIPs for beta-blockers are the bulk polymerization method and the precipitation polymerization method. MIPs for beta-blockers still need further development, especially since many types of beta-blockers have not been used as templates in the MIP synthesis process and modification of the MIP sorbent is required, to obtain high throughput analysis.

Simultaneous Quantification of Chloramphenicol, Thiamphenicol, Florfenicol, and Florfenicol Amine in Animal and Aquaculture Products Using Liquid Chromatography-Tandem Mass Spectrometry

The accumulation of antimicrobial residues in edible animal products and aquaculture products could pose health concerns to unsuspecting consumers. Hence, this study aimed to develop a validated method for simultaneous quantification of chloramphenicol (CAP), thiamphenicol (TAP), florfenicol (FF), and florfenicol amine (FFA) in beef, pork, chicken, shrimp, eel, and flatfish using a quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction method coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Primary-secondary amine (PSA) and MgSO4 were used for sample purification. The analytes were separated on a reversed-phase analytical column. The coefficients of determination for the linear matrix-matched calibration curves were ≥0.9941. Recovery rates ranged between 64.26 and 116.51% for the four analytes with relative standard deviations (RSDs) ≤ 18.05%. The calculated limits of detection (LODs) and limits of quantification (LOQs) were 0.005-3.1 and 0.02-10.4 μg/kg, respectively. The developed method was successfully applied for monitoring samples obtained from local markets in Seoul, Republic of Korea. The target residues were not detected in any tested matrix. The designed method was versatile, sensitive, and proved suitable for quantifying residues in animal-derived products.

Disperse Solid-Phase Extraction Cleanup for the Determination of 1-Deoxynojirimycin in Mulberry Leaves with Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry

A new determination method of 1-deoxynojirimycin (1-DNJ) in mulberry leaves based on ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) has been developed. Dried and crushed mulberry leaves’ sample was extracted by MeCN-water solvent, purified by graphitized carbon black (GCB) and primary secondary amine (PSA) to remove organic acids and pigments, and then analyzed after attenuation and filtration. The calibration curve showed linearity in the concentration range of 10–500 ng/mL, with the correlation coefficient of 0.998. Recoveries of spiked 1-DNJ at three fortification levels ranged from 94.6% to 96.4%, with relative standard derivation below 1.2%. Additionally, the matrix effect was assessed as negligible. Compared with methods by gas chromatography (GC) and liquid chromatography (LC) via real sample detection, the proposed method acquired better stability and detection efficiency. These results proved that this method has advantages of simple operation, complete purification, small pretreatment loss, good precision and accuracy, and high determination specificity, which is suitable for massive monitoring and precise quantitation of 1-DNJ in mulberry leaves.

Wide-scope screening for pharmaceutically active substances in a leafy vegetable cultivated under biogas slurry irrigation

The use of livestock waste for the production of biogas and the application of biogas slurry to agricultural soil can resolve livestock waste problems and reduce synthetic fertiliser use. However, the migration of veterinary drugs to land and crops resulting from biogas slurry irrigation is a potential food safety concern. This study employed an ultra-performance liquid chromatography coupled with quadrupole-time of flight high-resolution mass spectrometry system for wide-scope suspect screening of pharmaceutically active substances on crop cultivated under biogas slurry irrigation. Briefly, a total of 22 pak choi samples were obtained from a greenhouse farmed in tropical south Taiwan between March 2019 and March 2020. Molecular spectra and fragmented ions (between m/z 70 and 1100) were acquired. Ion features were searched and matched with a library consisting of 1068 compounds. The matrixes in the crop production environment including soil, livestock wastewater, biogas slurry, and groundwater were included in this study to elucidate potential sources of the pharmaceutically active substances. Results demonstrated 23 suspects were matched with high mass accuracy (mass error within ±5.0 ppm) in pak choi. The detection of both bufexamac and nandrolone were confirmed using standards, where a new system of identification points was applied. Nandrolone was detected throughout the pak choi samples as well as livestock wastewater. Tetracycline, macrolide, and sulfonamide antibiotics were presented in biogas slurry and soil but not pak choi. This is the first study to reveal the presence of multiclass pharmaceutically active substances in a crop supplied as food. Such findings suggest that anabolics and antibiotics should be closely monitored in the corps irrigated by biogas slurry in future.

Rapid simultaneous determination of 160 drugs in urine and blood of livestock and poultry by ultra-high-performance liquid chromatography-tandem mass spectrometry

In order to address the specific question of food safety in livestock and poultry, it is imperative to monitor veterinary drugs at every moment in the process of livestock and poultry breeding. Thus, multi-residue analysis of a wide variety of drugs using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) has become a tool of critical significance, especially for veterinary drug monitoring programs. A total of 160 compounds, belonging to 17 different families of veterinary drugs, were investigated in the urine and blood of livestock and poultry. Drug samples were extracted using a slightly acidic acetonitrile solution. The QuEChERS (quick, easy, cheap, effective, rugged, and safe) preparation method, combined with dispersive solid phase extraction (d-SPE) was compared with the approach of solid phase extraction (SPE). In the end, the QuEChERS extraction procedure was selected to reduce matrix effects and efficiently extract target veterinary drugs, and d-SPE was applied as a cleanup step. Electrospray ionization coupled with positive dynamic multiple reaction monitoring (dMRM) was utilized for the analysis of 160 different drugs in a single chromatographic run of 24 min. The efficiency of this method was evaluated using 7 matrices (pig blood, cattle blood, sheep blood, chicken blood, pig urine, cattle urine, and sheep urine). Good linearity was obtained for the analytes in a concentration range of 1-100 ng/mL, with correlation coefficients higher than 0.990. Most of the 160 drugs studied gave estimated limits of detection (LOQs) of 1 ng/mL, with some LOQs reaching as much as 5 ng/mL. The mean recoveries at four spike-in levels of 1, 5, 10, and 50 ng/mL, ranged from 60% to 120%. The intra-day precision measurements had coefficients of variation (n = 6) <15%, and the inter-day precision measurements were below 25%. Our method was applied in real samples and proved to be adequate for routine analysis. The proposed method proved to be simple, rapid and reliable for monitoring 160 drugs in the urine and blood of livestock and poultry, and can also be used for food safety monitoring.

Targeted Multiresidue Analysis of Veterinary Drugs in Milk-Based Powders Using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

An analytical method was developed and validated for the determination of 40 veterinary drugs in various milk-based powders. The method involves acetonitrile/water extraction, solid-phase filtration for lipid removal in fat-containing matrices, and analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The limits of quantitation (LOQ) ranged from 0.02 to 82 ng/g. Acceptable recoveries (70-120%, RSD < 20%) were reached for 40 of 52 target compounds at three fortification levels in nonfat milk powder. Similar results were obtained for whole milk powder, milk protein concentrate, whey protein concentrate, and whey protein isolate. This new method will allow for better monitoring of a wide range of veterinary drugs in milk-based powders.

Development and validation of multi-residue analysis for tetracycline antibiotics in feed by high performance liquid chromatography coupled to mass spectrometry

A new multi-residue method for the analysis of the tetracycline antibiotics oxytetracycline, tetracycline, chlortetracycline, and doxycycline was developed and validated for animal feed. After extraction with 0.1M Na₂EDTA-McIlvaine buffer (pH 4), the samples were centrifuged, purified by SPE (Strata-X-CW cartridges) and analysed by HPLC-MS. Validation of the method was performed according to the guidelines indicated in European Commission Decision 2002/657/EC. The procedure was validated by spiking feed samples at three different levels (300, 1000, and 5000 µg/kg). Average recoveries for tetracyclines were in the range 79.70-98.8%, with RSD for repeatability and reproducibility in the ranges of 5.0-9.5% and 6.5-11.0%, respectively. The method was successfully validated and proved to be efficient, precise, and useful for quantification of tetracyclines in animal feed. The validated method was successfully applied to 65 suspect feed samples collected from different regions of Poland in 2015-16 and obtained from farms and feed manufactures. Of these 65 purportedly non-medicated feeds, eight (12.3%) were positive for the presence of doxycycline or chlortetracycline.

Plant Uptake and Metabolism of Nitrofuran Antibiotics in Spring Onion Grown in Nitrofuran-Contaminated Soil

Environmental pollution caused by the discharge of mutagenic and carcinogenic nitrofurans to the aquatic and soil environment is an emerging public health concern because of the potential in producing drug-resistant microbes and being uptaken by food crops. Using liquid chromatography-tandem mass spectrometry analysis and with spring onion (Allium wakegi Araki) as the plant model, we investigated in this study the plant uptake and accumulation of nitrofuran from a contaminated environment. Our study revealed for the first time high uptake and accumulation rates of nitrofuran in the edible parts of the food crop. Furthermore, results indicated highly efficient plant metabolism of the absorbed nitrofuran within the plant, leading to the formation of genotoxic hydrazine-containing metabolites. The results from this study may disclose a previously unidentified human exposure pathway through contaminated food crops.

Simple and suitable immunosensor for β-lactam antibiotics analysis in real matrixes: milk, serum, urine

The anti-penicillin G was conjugated to avidin-peroxidase and biotin to obtain immunogen and competitor which were then used to develop a competitive immunosensor assay for the detection of penicillin G and other β-lactam antibiotics, with Kaff values of the order of 10(8) M(-1). The new immunosensor appears to afford a number of advantages in terms of sensitivity, possibility of "in situ" analysis, but especially of simplicity and lower costs, compared with other existing devices, or different chemical instrumental methods reported in the literature and used for the analysis of β-lactam compounds. Satisfactory results were found in the analysis of real matrixes and good recoveries were obtained by applying the standard addition method to spiked milk, urine, serum and drug samples. The new device uses an amperometric electrode for hydrogen peroxide as transducer, the BSA-penicillin G immobilized on polymeric membrane overlapping the amperometric transducer and the peroxidase enzyme as marker. It proved to be highly sensitive, inexpensive and easily reproducible; LOD was of the order of 10(-11)M. Lastly, the new immunosensor displayed low selectivity versus the entire class of β-lactam antibiotics and higher selectivity toward other classes of non-β-lactam antibiotics.

Gas chromatography − mass spectral characteristics of six pharmacologically active compounds — analytical performance characteristics on a raw sewage impacted water sample

We have interrogated the characteristics of six pharmacologically active compounds in a hot gas chromatograph injector including some mass spectral characteristics in a quadrupole mass analyzer. The analytes are dimetridazole, metronidazole, chlorpromazine, trimethoprim, sulfamethazine, and dapsone. We have demonstrated the impact of the injector on the conversion efficiency of solvent to vapor in relation to analytes under investigation. The overall analytical performance of key parameters that were scrutinized and tested on a spiked raw sewer water sample using electron ionization (EI), positive chemical ionization (PCI), and negative chemical ionization (NCI) in the full and selected ion monitoring (SIM) scan modes are also presented. These parameters were the instrument detection limits (IDLs), method detection limits (MDLs), linearities, and percent recoveries. Correlation coefficients (R2) were greater than 0.9950 using all ionization and scan modes. Better MDLs were obtained using the SIM mode in all instances. The SIM mode MDLs ranged as follows: EI 0.308–0.711 and PCI 0.656–1.14 mg/L. Extremely good signals were observed in the NCI mode with dimetridazole and metronidazole where MDLs in the SIM mode were estimated to be 0.057 and 0.062 mg/L. Percent relative standard deviations (n = 3) were all less than 5% using EI employing full and SIM scan modes. Recoveries ranged from 55% to 96% in the full scan mode and from 67% to 94% in the SIM mode. Signal losses and ion population ratios in relation to the number of samples, i.e., scan speed and the mass scan range, are also interrogated.

Liquid chromatography-tandem mass spectrometry method for the determination of anthelmintics in alfalfa plants

A simple and inexpensive liquid chromatography-tandem mass spectrometric method for the determination of anthelmintics in alfalfa plants (Medicago sativa L.) was developed and validated. Anthelmintics in plant leaves and stems (green chops) were extracted with methanol/acetonitrile (7:3, v/v) followed by a concentration and clean-up step using solid-phase extraction (Strata-X, 500 mg, 6 ml cartridge). After drying with nitrogen gas, the adsorbed analytes were eluted with methanol/acetonitrile (50:50, v/v) mixture followed by 100% acetonitrile. Chromatographic separation was achieved on an Atlantis T-3 (2.1 × 100 mm × 3 µm) analytical column with a Phenomenex guard cartridge (C8, 4 × 3 mm) attached to a Waters triple quadrupole mass spectrometer operated in positive electrospray ionisation mode with selected reaction monitoring. Samples were analysed using gradient elution at a flow rate of 0.35 ml min⁻¹. The mobile phase consisted of a 10 mM ammonium formate solution in (A) water/acetonitrile (90:10, v/v) and (B) methanol/acetonitrile (50:50, v/v). The method was validated for levamisole, fenbendazole, fenbendazole sulphoxide and fenbendazole sulphone at 10, 20 and 40 µg kg⁻¹ and for eprinomectin at 20, 40 and 80 µg kg⁻¹. Limits of quantification (LOQ) were 10 µg kg⁻¹ for all analytes except eprinomectin, which had an LOQ of 20 µg kg⁻¹. The overall mean recovery in green plants was between 74.2% and 81.4% with repeatabilities ranging from 2.2% to 19.1% and reproducibilities in the range 3.8-8.7%. The validated method was applied to plant samples in a study on the behaviour of anthelmintic drugs in a soil, plant and water system.

Simultaneous detection of residues of 25 β₂-agonists and 23 β-blockers in animal foods by high-performance liquid chromatography coupled with linear ion trap mass spectrometry

A sensitive method has been developed for the simultaneous determination of residues of 25 β₂-agonists and 23 β-blockers in animal foods by high-performance liquid chromatography coupled with linear ion trap mass spectrometry (HPLC-LIT-MS). This method is based on a new procedure of hydrolysis and extraction by 5% trichloracetic acid, and then cleaned up by mixed strong cation exchange (MCX) cartridges coupled with a novelty cleanup step by methanol. Methanol and 0.1% formic acid were used as mobile phases for gradient elution, while a Supelco Ascentis Express Rp-Amide column was used for LC separation. ESI positive ion scan mode was used with consecutive reaction monitoring (CRM, MS³). Nine β₂-agonists labeled by the deuterium isotope were used as internal standards for quantification. The linear ranges of 48 analytes were from 5 to 200 μg/L; the coefficient of correlation was not less than 0.995. Blank pork muscle, blank liver, and blank kidney were selected as representative matrix for spiked standard recovery test. The recoveries of each compound were in the range of 46.6-118.9%, and the relative standard deviations were in the range of 1.9-28.2%. Decision limits (CCα, α = 0.01) of 48 analytes in muscles, liver, and kidney samples ranged from 0.05 to 0.49 μg/kg, and the detection capability (CCβ, β = 0.05) ranged from 0.13 to 1.64 μg/kg. This method was successfully applied to 110 real animal origin food samples including meat, liver, and kidney of pig and chicken samples.

Identification of isobaric amino-sulfonamides without prior separation

RATIONALE

Direct analysis mass spectrometry (DAMS) techniques offer increased speed of analysis without the need for sample preparation or prior separation. A feature of these techniques is that all ionisable species will typically be analysed at the same time which makes the ability to distinguish between isobaric compounds increasingly important.

METHODS

Investigations have been carried out to distinguish isomeric compounds by mass spectrometry only, without the use of any separation technique, in order to further understand the capabilities of DAMS techniques. The work focused on commercially available isomeric amino-sulfonamides, i.e. sulfalene, sulfameter, sulfamethoxypyridazine, sulfamonomethoxine, sulfadoxine, sulfadimethoxine, sulfisomidine, sulfamethazine, sulfamerazine, sulfaperine, sulfadiazine and sulfapyrazine.

RESULTS

All the isomeric compounds investigated could be distinguished from each other based on their tandem mass (MS/MS) spectrum or failing that, based on their MS(3) spectrum. Common fragmentation patterns/pathways were observed for groups of the sulfonamides and a rationale for the fragmentations observed is proposed. For the sulfonamides which contain a methoxy group on the pyrimidinyl, pyridazynil, or pyrazinyl ring, the fragmentation-directing feature is the positioning of the methoxy group in the ortho position of the ring with respect to the sulfonamide bond. The presence of an ortho substituent precludes the formation of the product ion resulting from the loss of aniline.

CONCLUSIONS

This work has demonstrated the usefulness of MS(n) fragmentation data in identifying and distinguishing isobaric structural isomers without the need for separation by high-performance liquid chromatography (HPLC), allowing the identification of compounds by DAMS techniques. This work has also highlighted patterns in the product ion data which has led to a postulation of how the protonation preference of a molecule can affect the product ions observed and how the presence of ortho substituents can affect this initial protonation preference.

Development and validation of a multiclass method for the determination of veterinary drug residues in chicken by ultra high performance liquid chromatography-tandem mass spectrometry

A multiclass method has been optimized and validated for the simultaneous determination of 20 veterinary drug residues belonging to several classes, as quinolones, sulfonamides, macrolides, anthelmintics, avermectins and diamino derivatives, and benzathine, used as a marker of the presence of penicillin, in muscle chicken. It has been based on QuEChERS methodology (quick, easy, cheap, effective, rugged and safe) and ultra high performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry (UHPLC-MS/MS). Several chromatographic conditions were optimized, obtaining a running time <8.5 min. The developed method was validated on the basis of international guidelines. Mean recoveries ranged from 70 to 120%, except for benzathine (65.6% at 20 μg kg(-1)) and sulfadimidine (69.0% at 100 μg kg(-1)). Repeatability was lower than 20.0% except for sulfachlorpyridazine (22.1% at 20 μg kg(-1)) and tylosin (20.5% and 20.6% at 30 and 50 μg kg(-1), respectively), whereas reproducibility was lower than 25% except for flumequine (27.4% at 20 μg kg(-1)) and benzathine (37.8% and 27% at 20 and 50 μg kg(-1), respectively). Limits of detection (LODs) and quantification (LOQs) ranged from 3.0 to 6.0 μg kg(-1) and 10.0 to 20.0 μg kg(-1), respectively, except for tylosin that showed a LOD and LOQ of 9.0 and 30.0 μg kg(-1). Decision limit (CC(α)) and detection capability (CC(β)) were calculated and CC(β) ranged from 24.1 μg kg(-1) (mebendazole) to 423.6 μg kg(-1) (flumequine). Finally, the method was applied to real samples and traces of some compounds were found in eight samples of chicken and benzathine was detected in one sample at 29.9 μg kg(-1).

The effects of the nitrofuran furaltadone on Ulva lactuca

The use of pharmaceuticals in the food production industry as prophylatic and therapeutic agents is necessary to promote animal health, but may entail significant consequences to natural ecosystems, especially in the cases of overdosing and use of banned pharmaceuticals. The vast effects that antibiotics released into the environment have on non-target organisms are already under the scope of researchers but little attention has been given to primary producers such as macroalgae. The present study assessed furaltadone's, an antibacterial agent illegally used for veterinary purposes, uptake capacity by Ulva lactuca and its effect in the growth of this cosmopolitan macroalgae. Differences in macroalgal growth were shown when submitted to prophylactic and therapeutic concentrations of furaltadone in the water (16 and 32 μg mL⁻¹, respectively). The therapeutic concentration caused higher growth impairment than the prophylactic treatment did, with 87.5% and 58% reductions respectively. Furthermore, together with data collected from the accumulation assays, with values of internal concentrations as high as 18.84 μg g⁻¹ WW, suggest that the macroalgae U. lactuca should be included in field surveys as a biomonitor for the detection of nitrofurans.

Multiresidue analysis of antibiotics in food of animal origin using liquid chromatography-mass spectrometry

Antibiotics are the most important drugs administered in veterinary medicine. Their use in food-producing animals may result in antibiotic residues in edible tissues, which are monitored to protect human and animal health, support the enforcement of regulations, provide toxicological assessment data, and resolve international trade issues. This chapter provides basic characterization of the most important classes of antibiotics used in food-producing animals (aminoglycosides, amphenicols, β-lactams, macrolides and lincosamides, nitrofurans, quinolones, sulfonamides, and tetracyclines), along with examples of practical liquid chromatographic-(tandem) mass spectrometric methods for analysis of their residues in food matrices of animal origin. The focus is on multiresidue methods that are favored by regulatory and other food testing laboratories for their ability to analyze residues of multiple compounds in a time- and cost-effective way.

Application of a liquid chromatographic procedure for the analysis of penicillin antibiotics in biological fluids and pharmaceutical formulations using sodium dodecyl sulphate/propanol mobile phases and direct injection

A direct injection liquid chromatography procedure was developed for the simultaneous determination of four penicillin antibiotics (amoxicillin, ampicillin, cloxacillin and dicloxacillin) in pharmaceutical formulations and physiological fluids (urine) using hybrid micellar mobile phases. These antimicrobials are used to treat gastrointestinal and systemic infections. The four penicillins were analysed using a Zorbax C18 reversed-phase column and detected at 210 nm. These antibiotics were separated by an interpretive optimisation procedure based on the accurate description of the retention and shape of the chromatographic peaks. Antibiotics were eluted in less than 16 min with no interference by the urine protein band or endogenous compounds using the mobile phase 0.11 M sodium dodecyl sulphate-6% propanol-0.01 M NaH(2)PO(4) buffered at pH 3. The method was validated according to the Food and Drug Administration guideline, including analytical parameters such as linearity (R(2)>0.993), intra- and inter-day precisions (RSD, %: 0.1-4.4 and 1.2-5.9, respectively), and robustness for the four compounds. This method is sensitive enough for the routine analysis of penicillins at therapeutic urine levels, with limits of detection in the 1.5-15 ng mL(-1) range and limits of quantification of 50 ng mL(-1). Recoveries in a micellar medium and a spiked urine matrix were in the 92.4-108.2% and 96-110% ranges, respectively. Finally, the method was successfully applied to determine these antibiotics in urine samples and pharmaceutical formulations.

Metabolites from fungal laccase-catalysed transformation of sulfonamides

Soil metabolism of sulfonamides is largely unknown. Hence the sulfonamides sulfanilamide (SAA), sulfadimethoxine (SDT) and sulfapyridine (SPY) were reacted in model experiments with a fungal laccase from Trametes versicolor. Enzymatic transformation after a reaction time of 15 d ranged from 10.0% for SAA up to 95.6% for SPY and the difference was attributed to the different molecular substituents. Metabolites were first tentatively assigned after LC-ESI(+)-MS full-scan analysis. Secondly, the proposed metabolites were further confirmed employing either multiple reaction monitoring in comparison with standard substances or precursor ion scan LC-ESI(+)-MS/MS experiments striving for the precursor and two to three product ions. Aniline was confirmed as a breakdown product of SPY and further metabolites of SPY and of SDT were identified as rearranged SO(2) extrusion products. Thirdly, some of the metabolites matched those that were previously reported for sulfonamide photodegradation and degradation in soil. It was concluded that enzymatic metabolism as investigated here also occurs in soil.

Advantages of soybean peroxidase over horseradish peroxidase as the enzyme label in chemiluminescent enzyme-linked immunosorbent assay of sulfamethoxypyridazine

An indirect competitive chemiluminescent enzyme-linked immunosorbent assay (CL-ELISA) of sulfamethoxypyridazine (SMP) was developed. The conjugates of streptavidin with cationic horseradish peroxidase (HRP) and anionic soybean peroxidase (SbP) were used in CL-ELISA for the detection of biotinylated anti-SMP antibodies. For streptavidin-HRP conjugate-catalyzed chemiluminescence measured 20 s after the initiation of the enhanced chemiluminescence reaction (ECR), the limit of detection (IC(10)), the IC(50) value, and the working range in CL-ELISA of SMP are 0.3, 12.4, and 1.2-85.0 ng/mL, respectively. An increase in the time interval between the ECR initiation and the luminescence measurement results in the loss in the quality of analytical measurements because of the time-dependent quenching of chemiluminescence typical of the HRP-catalyzed ECR. In the case of SbP-based CL-ELISA of SMP, the limit of detection, the IC(50) value, and the working range (0.025, 0.17, and 0.045-0.63 ng/mL, respectively) are better than those for HRP-based CL-ELISA. Furthermore, the analytical parameters of SbP-based CL-ELISA remain unchanged during a long period of time (for at least 30 min). The recovery values from four spiked milk samples with different concentrations of SMP in SbP-based CL-ELISA vary from 70 to 130%.