Quick, Easy, Cheap, Effective, Rugged And Safe Approach Research Articles

Withdrawal Interval Estimation of Doxycycline in Yellow Catfish (Pelteobagrus fulvidraco) Using an LC-MS/MS Method Based upon QuEChERS Sampling Preparation.

Limited information on residue depletion of doxycycline (DC) is available in yellow catfish (Pelteobagrus fulvidraco) using the determination of LC-MS/MS based upon a rapid and simple method of sample preparation. This study collected plasma and tissue samples of yellow catfish at pre-determined time points following 3-day consecutive oral administration of DC at 20 mg/kg. The samples were prepared using a QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) approach. The limit of detection and the limit of quantitation were 2.5 and 5 µg/kg or µg/L, respectively, for DC in plasma and tissues (e.g., muscle + skin, liver, kidney, and gill). The recoveries of DC ranged from 67.2% to 86.2%. The decision limit (CCα) and the detection capability (CCβ) were from 106.2 to 127.8 μg/kg or μg/L. The withdrawal times of DC in muscle + skin were estimated to be 22 d based on the guidelines in China and Europe and 27 d based on Japan’s standard. Overall, this study not only provides an efficient method to rapidly determine the DC concentrations in fish-derived tissues but also provides important information on the safety assessment of DC in aquatic animal-derived food products.

Determination of phytochemical compounds in chicken breast by gas chromatography-tandem mass spectrometry.

A gas chromatography-tandem mass spectrometry (GC-MS/MS) method was developed for the simultaneous detection and quantification of five phytogenic compounds (carvone, menthol, thymol, carvacrol and methyl salicylate) in chicken breast. Chicken breast samples were analyzed using a QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach using acetonitrile as extraction solvent, followed by a d-SPE (dispersive-solid phase extraction) clean up step. The linearities for the 5 substances were studied in the range between 2 and 100 μg/L and the coefficients of determination (R2) were always > 0.995. Matrix effects were also assessed by comparing the slopes obtained in solvent and chicken breast matrix. The recoveries for all the substances at 3 different spike levels (5, 10 and 50 μg/kg) were in the range 80–102% with RSDs < 15%. The instrumental limits of quantification were in the range 2.7–4.8 μg/kg, while the reporting level of the method was 5 μg/kg for all the aforementioned compounds. The method was successfully applied to 10 chicken breasts samples from the local market.

Diclofenac and Ibuprofen Determination in Sewage Sludge Using a QuEChERS Approach: Occurrence and Ecological Risk Assessment in Three Nigerian Wastewater Treatment Plants.

A quick, easy, cheap, effective, rugged and safe (QuEChERS) method was optimized for the extraction of non-steroidal anti-inflammatory drugs (NSAIDs) diclofenac and ibuprofen from sewage sludge. Dispersive-solid phase extraction (d-SPE) was employed for sample clean-up. Instrumental analysis was performed by high-performance liquid chromatography. Ecological risk was assessed for four trophic levels: fish, daphnia, algae and bacteria. The method limits of quantification for diclofenac and ibuprofen were 0.43 µg g- 1 and 0.45 µg g- 1, respectively. Correlation coefficients were above 0.999. Extraction recoveries ranged from 70 to 118 % and satisfactory inter-day reproducibility (% RSD) of < 18 % was obtained. Diclofenac and ibuprofen were measured up to 1.02 µg g- 1 and 6.6 µg g- 1, respectively in sewage sludge from three Nigerian wastewater treatment plants (WWTPs). Ibuprofen posed high risk to fish, daphnia, algae and bacteria. This work presents the first report on the ecological risk assessment of diclofenac and ibuprofen in sewage sludge from Nigerian WWTPs.

Development of a QuEChERS-LCMS/MS method for simultaneous estimation of tebuconazole and chlormequat chloride in wheat crop

Tebuconazole (TBZ) and Chlormequat chloride (CCC) combination has been established as highly effective in reducing plant height of lodging prone wheat varieties. In this work, a novel analytical method employing the quick, easy, cheap, effective, rugged and safe (QuEChERS) cleanup technique and LC-MS/MS (liquid chromatography-tandem mass spectroscopy) was developed for simultaneous estimation of TBZ and CCC in wheat grains and harvest stage plant leaves. A total of 10 mL of acetonitrile and 50 mg of primary secondary amine (PSA) sorbent was consumed in the optimized QuEChERS process for leaves and grain samples. The LC-MS/MS analysis was performed using a C-18 column operating under electrospray ionization in positive mode. The QuEChERS approach achieved extraction recoveries in the acceptable range of 70%–120%, for both the compounds and was validated in terms of accuracy, precision, sensitivity and linearity. Persistence study was conducted using Lihocin (CCC 50% SL), Folicur (TBZ 25.9% EC) and their combination tank mix (Lihocin + Folicur-50% SL + 25.9% EC) applied as foliar spray twice in wheat crop (tester tall variety C-306). The results demonstrated that the developed QuEChERS-LCMS/MS is rapid and confirmatory for simultaneous quantification of both the test analytes in wheat crop.

Pesticide residues determination in common bean using an optimized QuEChERS approach followed by solvent exchange and GC-MS/MS analysis.

Common bean is a staple food in Latin America and Africa; however, studies about contamination of common bean with pesticides are rarely reported. So, the goals of this study were to validate a multiresidue method and apply it in monitoring of pesticides in common beans. Extraction was performed applying the QuEChERS (quick, easy, cheap, effective, rugged, and safe) approach to ground samples. Octadecylsilane and primary-secondary amine were used for clean-up, and a solvent exchange step was performed before injection for gas chromatography-tandem mass spectrometry analysis. Method validation was done analyzing blank samples spiked at 20, 30, 50, and 100 μg kg-1 (n = 5). Linearity and linear range were assessed by the analysis of standard solutions at concentrations of 5, 15, 25, 50, 75, 100, and 150 μg L-1 . The method was successfully validated for 91 (64.1%) of the 142 compounds studied (139 pesticides and three degradation products). Limits of quantification were equal to 20 μg kg-1 , 30 μg kg-1 , 50 μg kg-1 , and 100 μg kg-1 for 18 (12.7%), 17 (12.0%), 21 (14.8%) and 35 (24.6%) compounds respectively. Fifteen (10.6%) compounds were not detected at any level, and 36 (25.4%) did not fulfill the requirements for a quantitative method. Sixteen common bean samples of South of Brazil were analyzed. Two samples were positive: one for tebuconzole and a second for picoxystrobin, permethrin, and cyproconazole. Cyproconazole is not allowed for use in the common bean crop, its use being a violation. As demonstrated, the validated approach is suitable for pesticide residues determination in common bean. Results of the sample analysis show that the control of pesticide residues in common bean is necessary to ensure food safety. © 2020 Society of Chemical Industry.

Target analysis and retrospective screening of mycotoxins and pharmacologically active substances in milk using an ultra-high-performance liquid chromatography/high-resolution mass spectrometry approach

Milk is a nutritious food suitable for infants and adults, and it plays an important role in the human diet. However, it may also be a vehicle for food contaminants. In this report, we developed a method using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-Q-Exactive Orbitrap HRMS; Thermo Fisher Scientific, Waltham, MA) for simultaneous identification of target pharmacologically active substances and mycotoxins in milk. We also used the Q-Orbitrap operating in full scan mode to identify other possible drugs and microbial metabolites that occurred in samples. Fifty-six commercially available milk samples from the Italian market were analyzed. Investigated analytes were extracted using a QuEChERS (quick, easy, cheap, effective, rugged, and safe) approach. Method detection and quantification limits and performance criteria set by European regulations were fulfilled. Pharmacologically active substances were detected in 49% of samples (range 0.007-4.53 ng/mL), including nontarget mycotoxins. Retrospective analysis allowed us to identify other antibiotics and pharmacologically active substances, as well as nonregulated fungal/bacterial metabolites at a relatively high incidence. From the obtained values, the need for continuous monitoring of contaminants in the milk production chain is clear. This is the first study to assess the presence of pharmacologically active substances, mycotoxins, and other microbial metabolites in Italian milk samples using the UHPLC-Q-Orbitrap HRMS system.

Multiresidue Determination of Pesticides in Market Honey from Northern India Using QuEChERS Approach and Assessment of Potential Risks to Consumers

Honey has multiple beneficial properties but polluted environments have led to its contamination. Contaminated honey not only serves as a sentinel of environmental pollution, but can also pose potential risks to consumers’ health. In the present study, QuEChERS (quick, easy, cheap, effective, rugged and safe) method along with gas chromatography coupled to selective detectors (ECD/FTD/MS) was used for determining 24 pesticide residues and/or their metabolites in 150 honey samples collected from markets in Northern India. The method was optimized and validated according to the European Commission’s guidelines. Residues of pesticides were detected in 12% of samples, of which a majority contained organophosphate residues. Assessment of human health risks suggests that contaminated honey at current levels has minimal contribution to toxicological risks. However, precautionary measures should always be taken considering the customary honey feeding in infants and cumulative effect of these chemicals in the foreseeable future. This study highlights the importance of continuous monitoring of pesticide residues, and consumer awareness towards certified products to safeguard public health.

Development and validation of ultra high performance-liquid chromatography–tandem mass spectrometry based methods for the determination of neonicotinoid insecticides in honey

In this study, the feasibility of two sample treatments has been evaluated for the determination of seven neonicotinoid insecticides in honey from different botanical origins using ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS). A solid phase extraction with a polymeric sorbent (Strata® X) is proposed for analyzing dark honeys, while a QuEChERS (quick, easy, cheap, effective, rugged and safe) approach is recommended for light honeys. Chromatographic analysis (6 min) was performed on a core-shell column (Kinetex® EVO C18). The proposed methods were fully validated using two different MS/MS systems: quadrupole-time-of-flight and triple quadrupole. The results showed that the best overall analytical performance was achieved using triple quadrupole, mainly due to its better sensitivity and the reduced influence of the matrix onto the analyte signals. The methods developed were applied to the analysis of commercial honey samples from different regions of Spain, as well as from experimental apiaries.

Determining organochlorine pesticides in samples of green sea turtles by QuEChERS approach

Alguns Pesticidas organoclorados (OCPs) podem causar numerosos efeitos adversos na biota. As tartarugas marinhas enfrentam diversas ameaças, em especial aquelas relacionadas às atividades antropogênicas, por isso o desenvolvimento de melhorias nos métodos para monitorar compostos químicos são tarefas importantes. Neste trabalho foi desenvolvida uma metodologia baseada na extração QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) para a detecção de doze OCPs, por cromatografia gasosa com captura de elétrons, em amostras de gordura e fígado de tartarugas verdes. Os limites de quantificação ficaram abaixo de 5.3 ng g-1; com taxas de recuperação aceitáveis para a maioria de compostos; efeito matriz médio; calibração da matriz com linearidade variando de 1.0 a 200 ng g-1. Esta metodologia traz contribuições ao estudo de resíduos com efeito adverso na saúde das tartarugas marinhas, sendo importante instrumento para novas direções em temas de conservação.

Development of a method for the analysis of hormones and pharmaceuticals in earthworms by quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

The earthworm represents a kind of creature in contact with the soil surface and usually exposed to a variety of organic pollutants from human activities. Therefore, it can be considered as an organism of choice for identifying pollution or better understanding the input of contaminants in food chains in particular through the contributions of sludge. Moreover, the use of organisms such as soil invertebrates is to be developed for ecotoxicological risk assessment of pollutants. In this context, a simple, rapid and effective multi-residue method was developed for the determination of 31 compounds including 11 steroids, 14 veterinary antibiotics and 6 human contaminants (paracetamol, sulfamethoxazole, fluvoxamine, carbamazepine, ibuprofen, bisphenol A) in earthworm. The sample preparation procedure was based on a salting-out extraction with acetonitrile (QuEChERS approach) that was optimised with regard to the acetonitrile/water ratio used in the extraction step, the choice of the clean-up and the quantity of the matrix. The optimised extraction method exhibited recoveries that comprised between 44 and 98% for all the tested compounds. The limits of detection of all compounds were below 14ngg(-1) and the limits of quantification (LOQ) comprised between 1.6 and 40ngg(-1) (wet weight). The method was therefore applied to determine the levels of pharmaceuticals and hormones in six earthworm samples collected in various soils. Concentrations up to 195ngg(-1) for bisphenol A were determined, between a few nanograms per gram and 43.1ngg(-1) (estriol) for hormones and between a few nanograms per gram and 73.5ngg(-1) (florfenicol) for pharmaceuticals. Experiments were also conducted in laboratory conditions to evaluate the accumulation of the target substances by earthworm.

The QuEChERS approach in a novel application for the identification of antifungal compounds produced by lactic acid bacteria cultures

Lactic Acid Bacteria (LAB) play an important role as natural food preservatives in many fermented food systems. To-date, characterisation of their diverse range of metabolites has been limited. Improved quantitation of low, medium and high concentration antifungal compounds is required, ensuring that both known and unknowns compounds are identified. This manuscript reports the first application of QuEChERS (quick, easy, cheap, effective, rugged and safe) for the extraction of natural antifungal metabolites in LAB cultures. The method provides improved individual recoveries (>78%) for 15 known antifungal compounds, an improvement of 26% compared to previously reported techniques (>52%). A protocol was developed that allowed LAB cultures to be easily assessed on a fully validated high performance liquid chromatography with ultra violet/diode array detection (HPLC-UV/DAD) method. Previously reported methods involving direct injection of filtered extracts and SPE clean-up, suffered from a rise in chromatographic baseline due to interfering matrix components, limiting accurate quantitation. This QuEChERS method removed these interfering matrix components to deliver clean chromatograms with greater recoveries (78.2–127.4%) and lower RSD values (2.5–10.8%) of all 15 antifungal compounds. The validated method was applied to LAB strains showing particularly strong antifungal activity and provided an increase in the number of compounds detected (both known and unknown) compared to previous techniques for the same strains, due to the improved recoveries now possible by this method. Confirmation of the compounds identified was performed by analysis on a liquid chromatography linear ion trap quadrupole Orbitrap hybrid Fourier transform mass spectrometer (LC-FTMS). This first application of QuEChERS to LAB cultures has significantly improved the analytical capabilities of antifungal compound profiling especially where the synergy of numerous compounds is suspected as producing the observed activity. LAB cultures can now be easily integrated into various food matrices, as natural food preservatives, now that a complete analyte profile is achievable.

QuEChERS sample preparation for the determination of pesticides and other organic residues in environmental matrices: a critical review.

Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) is an extraction and clean-up technique originally developed for recovering pesticide residues from fruits and vegetables. Since its introduction, and until December 2013, about 700 papers have been published using the QuEChERS technique, according to a literature overview carried out using SciFinder, Elsevier SciVerse, and Google search engines. Most of these papers were dedicated to pesticide multiresidue analysis in food matrices, and this topic has been thoroughly reviewed over recent years. The QuEChERS approach is now rapidly developing beyond its original field of application to analytes other than pesticides, and matrices other than food, such as biological fluids and non-edible plants, including Chinese medicinal plants. Recently, the QuEChERS concept has spread to environmental applications by analyzing not only pesticides but also other compounds of environmental concern in soil, sediments, and water. To the best of our knowledge, QuEChERS environmental applications have not been reviewed so far; therefore, in this contribution, after a general discussion on the evolution and changes of the original QuEChERS method, a critical survey of the literature regarding environmental applications of conventional and modified QuEChERS methodology is provided. The overall recoveries obtained with QuEChERS and other extraction approaches (e.g., accelerated solvent extraction, ultrasonic solvent extraction, liquid/solid extraction, and soxhlet extraction) were compared, providing evidence for QuEChERS higher recoveries for various classes of compounds, such as biopesticides, chloroalkanes, phenols, and perfluoroalkyl substances. The role of physicochemical properties of soil (i.e., clay and organic carbon content, as well as cation exchange capacity) and target analytes (i.e., log KOW, water solubility, and vapor pressure) were also evaluated in order to interpret recovery and matrix effect data.

Determination of nonylphenol ethoxylate and octylphenol ethoxylate surfactants in beehive samples by high performance liquid chromatography coupled to mass spectrometry

Nonylphenol and octylphenol ethoxylates (NP(EO)n and OP(EO)n) are major toxicants in agrochemicals used around beehives. Here we developed a LC–MS method for analysis of NP(EO)3–13 and OP(EO)3–13 oligomers in bee hive matrices. Less than 2 g of honey, pollen or wax were extracted using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach. Recoveries for each oligomer in all matrices are between 75% and 111% at three spiked concentrations. The method proved to be rapid, precise and sensitive. Five honey, 10 pollen and 12 wax samples were collected and analysed. NP(EO)n was detected in every sample with concentrations ranging from 26ppb to 10,239ppb. Much higher NP(EO)n residues levels were found in wax followed by pollen than in honey. OP(EO)n concentrations on average were more than 10 times lower in pollen and wax. This method demonstrates a probable wide occurrence of alkylphenol ethoxylates in USA beehives.

Evaluation of a modified QuEChERS method for analysis of mycotoxins in rice

A simple and efficient QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) sample preparation method was modified to provide good analytical results for 14 mycotoxins in rice. The method involved mixing sample with acidified aqueous acetonitrile, followed by salt-out liquid partitioning using MgSO4, NaCl, and citrate buffer salts. The extract was cleaned-up by dispersive solid-phase extraction with MgSO4, PSA, C18, and alumina-neutral. The analysis was performed using ultra-high performance liquid chromatography coupled to triple-quadrupole tandem mass spectrometry (UHPLC–MS/MS). Throughout the validation experiments, 70–98% overall recoveries were achieved with RSDs ⩽7% for most analytes at concentrations 10–100μgkg−1. Limit of detections were 0.5–15μgkg−1. Inter-laboratory precision was performed by proficiency testing, |z|⩽2 was considered satisfactory. We compared our modified QuEChERS method against sample preparation using an immunoaffinity column; the recovery and specificity were comparable for the two methods, but the QuEChERS approach was more time- and cost-effective.

Development of a multi-residue method for fast screening and confirmation of 20 prohibited veterinary drugs in feedstuffs by liquid chromatography tandem mass spectrometry

A simple multiresidue method was developed for detecting and quantifying twenty analytes from 5 classes of prohibited veterinary drugs (β-agonists (9), anabolic hormones (4), quinoxalines (4), tranquilizers (1), cyproheptadine, and clonidine in animal feeds using a QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach. Feed samples were extracted by ultrasonic-assisted extraction with a mixture of methanol-acetonitrile (50:50, v/v), followed by a cleanup using a dispersive solid-phase extraction with PSA (primary secondary amine). Target compounds were separated and determined by a liquid chromatography tandem quadrupole mass spectrometer operating in positive electrospray ionization mode, using multiple reaction monitoring (MRM). The recoveries of these compounds were between 56.7% and 103% at three spiked levels. The repeatability was lower than 10%, whereas reproducibility was no more than 15% except for nandrolone (17% at 10μgkg(-1)) and diazepam (19% at 10μgkg(-1)). Decision limits (CCαs) and detection capabilities (CCβs) ranged from 0.42 to 5.74μgkg(-1) and 5.70-9.81μgkg(-1), respectively. The method was successfully applied to screening of real samples obtained from local feed markets and confirmation of the suspected target analytes.

Quantitative Determination of Trisiloxane Surfactants in Beehive Environments Based on Liquid Chromatography Coupled to Mass Spectrometry

Organosilicone surfactants are increasingly being applied to agricultural agro-ecosystems as spray adjuvants, and were recently shown to impact the learning ability of honey bees. Here we developed a method for analyzing three trisiloxane surfactants (single polyethoxylate (EO) chain and end-capped with methyl, acetyl, or hydroxyl groups; TSS-CH3, TSS-COCH3, or TSS-H) in beehive matrices based on liquid chromatography coupled to mass spectrometry (LC-MS) and the QuEChERS (quick, easy, cheap, effective, rugged, and safe) approach from less than 2 g of honey, pollen, or beeswax. Recoveries for each oligomer (2-13 EO) were between 66 and 112% in all matrices. Average method detection limits (MDL) were 0.53, 0.60, 0.56 ng/g in honey, 0.63, 0.81, 0.78 ng/g in pollen, and 0.51, 0.69, 0.63 ng/g in beeswax. Five honey, 10 pollen, and 10 beeswax samples were analyzed. Trisiloxane surfactants were detected in every beeswax and 60% of the pollen samples. Total trisiloxane surfactant concentrations were up to 390 and 39 ng/g in wax and pollen. The described method is proved suitable for analyzing trisiloxane surfactants in beehive samples. The presence of trisiloxane surfactants in North American beehives calls for renewed effort to investigate the consequence of these adjuvants to bee health and the ongoing global bee decline.

Development of a liquid chromatography–tandem mass spectrometry procedure for determination of endocrine disrupting compounds in fish from Mediterranean rivers

A new, sensitive and rapid method based on QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach followed by ultra high performance liquid chromatography coupled with tandem mass spectrometry (UHPLC–MS/MS) was developed for the determination of nineteen endocrine disruptors (EDCs) and related compounds belonging to different classes in various fish species. Matrix effect on the analytical performance was evaluated, and thus, internal sample calibration was chosen as the most appropriate approach when analyzing such complex matrices as biota. The procedure provided adequate recoveries in the range from 40% to 103% for most of the compounds, low method detection limits (MDLs) in the range from 0.002 to 3.09ng/g for fish homogenates and high accuracy <20%. The developed method was applied for the analysis of target compounds in homogenates of different fish species from four impacted Mediterranean rivers: Ebro, Llobregat, Júcar and Guadalquivir. Eleven out of the nineteen target EDCs were found at least once in fish homogenates. Llobregat was identified as the most polluted river, where high concentrations were measured in fish homogenates especially for bisphenol A (223.91±11.51ng/g). Tris (2-butoxyethyl) phosphate (TBEP), caffeine, and methyl and benzyl paraben were found in fish from the four river basins.

Multi-Analyst, Multi-Matrix Performance of the QuEChERS Approach for Pesticide Residues in Foods and Feeds Using HPLC/MS/MS Analysis with Different Calibration Techniques

Three different calibration approaches were applied in HPLC/MS/MS using electrospray ionization for the determination of 14 diverse pesticide residues at different levels in a variety of food matrixes. This study was conducted as part of a 4 day training course for 17 chemists to learn the "quick, easy, cheap, effective, rugged, and safe" (QuEChERS) approach to pesticide residue analysis in foods. The analysts were divided into four different teams for the analysis of 12 different matrixes (strawberries, plums, carrots, green peppers, milk, molasses, alfalfa oats, corn silage, dry pet food, soybean, almonds, and foliage). The acetate-buffered QuEChERS protocol gave excellent results in the spiked samples for all matrixes tested. The HPLC/MS/MS calibration techniques consisted of external standardization in solvent solutions, matrix-matching, and the echo-peak technique. Peak areas were normalized to an internal standard in all three approaches. Matrix effects were observed with the corn silage, carrot, and foliage extracts, but they were minimal or nonexistent in the other matrixes. Matrix-matching best compensated for matrix effects, but has logistical difficulties in real-world application and required extra sample preparation compared to the other approaches. The echo-peak technique reduced matrix effects but did not eliminate them.

The development and validation of a multiclass liquid chromatography tandem mass spectrometry (LC–MS/MS) procedure for the determination of veterinary drug residues in animal tissue using a QuEChERS (QUick, Easy, CHeap, Effective, Rugged and Safe) approach

A novel rapid multiresidue/multiclass procedure with liquid chromatography tandem mass spectrometry (LC–MS/MS) detection has been developed to screen for the presence of veterinary drug residues in animal tissues. The method uses a new sample preparation procedure loosely based on QuEChERS (QUick, Easy, CHeap, Effective, Rugged and Safe) methodology. Validation to date has been restricted to chicken muscle and has been performed according to European Commission guidelines [COMMISSION DECISION of 12 August 2002 implementing Council Directive 96/23/EC concerning the performance of analytical methods and the interpretation of results] for nitroimidazoles, sulphonamides, fluoroquinolones, quinolones, ionophores and dinitrocarbanilide. Recent work has shown that the method is also applicable to macrolide and lincosamide antibiotics, benzimidazoles, levamisole, avermectins and tranquillisers.