Comparison of four different multiclass, multiresidue sample preparation methods in the analysis of veterinary drugs in fish and other food matrices

Determination and Identification of Antibiotic Residues in Fruits Using Liquid Chromatography-High-Resolution Mass Spectrometry (LC-HRMS)

Antibiotic residues may be present in fruit products from trees that were treated to combat bacterial diseases such as citrus greening or blight. A liquid chromatography-high-resolution mass spectrometry (LC-HRMS) method was developed for the simultaneous determination and identification of streptomycin, kasugamycin, penicillin, and oxytetracycline residues in fruit. Samples were extracted with acidic methanol and separation was optimized for a hydrophilic interaction LC column. A Q-Exactive HRMS instrument was used to obtain product ion spectra for analyte identification. Quantitation was performed with matrix-extracted calibration curves and internal standard correction. The method was tested on many different types of fruit. In general, fortified samples demonstrated acceptable recoveries (82-116%) and reproducibility (<15% RSD). Method detection limits for these analytes were well below the established US EPA tolerance levels. It was also possible to analyze the fruit extracts prepared using this method for additional chemical contaminants using LC-HRMS.

Analysis of chemical contaminants in fish using high resolution mass spectrometry - A review

High resolution mass spectrometry (HRMS) has become an important tool in environmental and food safety analysis. This review highlights how HRMS has been used to analyze chemical contaminants in fish. Measuring and documenting chemical contaminants in fish serves not only as an indicator of environmental conditions but can also monitor the health of these animals and help protect an important source of human food. The incidence and significance of contaminants including veterinary drugs, human drugs and personal care products, pesticides, persistent organic pollutants, per- and poly fluorinated substances, and marine toxins will be reviewed. The advantage of HRMS over traditional MS is its ability to expand the number of compounds that can be detected and identified. This is true whether HRMS is used for targeted analytes, or more broadly for suspect screening and nontargeted analyses. The classes of compounds, types of fish or seafood, options for data acquisition and analysis, and reports of unexpected findings from recent HMRS methods for chemical contaminants in fish are summarized.

Improved method robustness and ruggedness in liquid chromatography-mass spectrometry by increasing the acid content of the mobile phase

A routine multiresidue method developed for the detection and quantification of veterinary drug residues in animal-based food was used to analyze sheep (ovine) liver. Unlike when working with previously validated matrices (e.g., bovine liver), some of the analytes of interest chromatographed in the form of split- or even fully baseline separated peaks. In other cases a significantly longer retention times (tR) was observed. A detailed investigation led to the elucidation of taurocholic acid as the causative agent. This compound is present in sheep liver at significantly higher concentrations than in most other animal tissues. Taurocholic acid is a zwitterionic compound and likely acts as an ion pairing agent, which modifies the selectivity of the stationary phase in a highly spatial and dynamic way. Injecting smaller volumes of matrix extract or the use of a significantly higher formic acid concentration in the mobile phase reduced or even completely eliminated the peak splitting. A more detailed examination led to the observation that the problem is not restricted to this particular matrix and extraction procedure or the used stationary phase. In fact, a higher formic acid concentration (e.g., 1.0 % versus 0.1 %) significantly improves the peak shape of many analytes present in fortified matrix samples as well as in pure standard solutions. In addition, analytical column aging was observed as being slower with a higher formic acid concentration. Finally the peak shape of analytes interacting with the metallic parts along the flow path of the liquid chromatograph was also significantly improved. Use of 0.1 % acid in mobile phases is often taken for granted in LC-MS. Regardless of the stationary phase, a higher ionic strength better stabilizes the pH and reduces unwanted interactions, which ultimately improves the method robustness. Flow injection experiments often show that 0.1 % acid concentrations produce the highest analyte signals. Yet, the use of 1 % acid in the mobile phase often leads to narrower and therefore taller chromatographic peaks, which may lead to lower detection limits for many analytes and to an improved separation efficiency.

Comparison of filter membranes in the analysis of 183 veterinary and other drugs by liquid chromatography-tandem mass spectrometry

Although filtration is one of the most common steps in sample preparation for chemical analysis, filter membrane materials can leach contaminants and/or retain some analytes in the filtered solutions. In multiclass, multiresidue analysis of veterinary drugs, it is challenging to find one type of filter membrane that does not retain at least some of the analytes before injection in ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). In this study, different filter membranes were tested for use in UHPLC-MS/MS analysis of 183 diverse drugs in bovine muscle, kidney, and liver tissues. Membranes evaluated consisted of polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), polyethersulfone, nylon, and regenerated cellulose. Drug classes represented among the analytes included β-agonists, β-lactams, anthelmintics, macrolides, tetracyclines, sulfonamides, tranquilizers, (fluoro)quinolones, anti-inflammatories, nitroimidazoles, coccidiostats, phenicols, and others. Although the presence of a matrix helped reduce the binding of analytes on surface active sites, all of the filter types partially retained at least some of the drugs in the final extracts. In testing by flow-injection analysis, all of the membrane filters were also observed to leach interfering components. Ultimately, filtration was avoided altogether in the final sample preparation approach known as the quick, easy, cheap, effective, rugged, safe, efficient, and robust (QuEChERSER) mega-method, and ultracentrifugation was chosen as an alternative.

Production and certification of BOTS-1: bovine muscle-certified reference material for incurred veterinary drug residues

A freeze-dried bovine muscle-certified reference material (CRM), known as BOTS-1 (DOI: https://doi.org/10.4224/crm.2018.bots-1 ), containing incurred residues of commonly used veterinary drugs was produced and certified for the mass fraction of eight veterinary drug residues. Value assignment was carried out using liquid chromatography tandem mass spectrometry (LC-MS/MS) methods in conjunction with isotope dilution and standard addition approaches involving stable isotope internal standards. Data from the National Research Council of Canada (NRC), Canadian Food Inspection Agency (CFIA), United States Department of Agriculture (USDA), and the Federal Office of Consumer Protection and Food Safety in Germany (BVL) were used for value assignment. Results for two drug residues were also obtained through an international inter-laboratory comparison CCQM-K141/P178 organized under the auspices of the International Bureau of Weights and Measures (BIPM). Quantitative NMR (1H-qNMR) was used to characterize primary standards of all veterinary drugs certified. The certified mass fractions of the veterinary drug residues were 490 ± 100 µg/kg for chlorpromazine, 44 ± 4.4 µg/kg for ciprofloxacin, 3.3 ± 1.4 µg/kg for clenbuterol, 9.5 ± 0.8 µg/kg for dexamethasone, 57 ± 4.8 µg/kg for enrofloxacin, 3.0 ± 0.4 µg/kg for meloxicam, 12.4 ± 1.2 µg/kg for ractopamine, and 2290 ± 120 µg/kg for sulfadiazine with expanded uncertainties quoted (95% confidence) which include the effects due to between-bottle inhomogeneity, instability during long-term storage and transportation, and characterization.

Stability study of selected veterinary drug residues spiked into extracts from different food commodities

Analyte stability is more commonly a confounding factor in analytical chemistry than many analysts recognize. In this study, we assessed the stability of 31 common veterinary drugs in water and final extracts of bovine (milk and kidney/liver) and chicken (muscle and egg) matrices. Two different sample preparation methods were evaluated for one-month storage of the final extracts at typical room, refrigerator, and freezer temperatures. Liquid chromatography - mass spectrometry (LC-MS) by triple quadrupole and high-resolution techniques was used for analysis of the extracts spiked at different relevant concentrations for general regulatory purposes (10-1000 ng/g sample equivalent). Comparison of results between two labs demonstrated that stable drugs (≤20% loss) at all tested conditions consisted of danofloxacin, enrofloxacin, florfenicol, flubendazole, hydroxy-flubendazole, flumequine, flunixin, 5-hydroxy-flunixin, lincomycin, and meloxicam. The tested drugs found to be the most unstable (>20% loss at room temperature within a matter of days) consisted of the β-lactams (ampicillin, cefalexin, cloxacillin, and penicillin G). Curiously, the following antibiotics (mostly macrolides) were apparently more stable in sample extracts than water: emamectin, erythromycin, ivermectin, lasalocid, monensin, tilmicosin, tulathromycin, and tylosin. Those and the other drug analytes (ciprofloxacin, doxycycline, florfenicol amine, 2-amino-flubendazole, oxytetracycline, sulfadiazine, sulfadimethoxine, sulfamethazine, and trimethoprim) were mostly stable for a month in refrigerated extracts, especially at higher concentrations, but not in all cases. In practice, freezer storage of extract solutions was found to be acceptable for at least a month, with a few exceptions.

A one-step solid-phase extraction with UHPLC-MS/MS for fast and accurate determination of multi-class veterinary drugs in animal muscles

Excessive use of veterinary drugs in livestock growth poses a threat to food safety. It is, however, challenging to quantify these multi-class veterinary drugs within animal muscles, because of their varied physicochemical properties. In this work, we presented a simple, efficient and sensitive method for the simultaneous determination of multi-class veterinary drugs with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The method involves a highly efficient extraction using a EDTA (pH 7)-ACN (30:70, v/v) solvent system, followed by a one-step solid-phase extraction cleanup approach with PRiME HLB sorbent (Reversed-phase N-vinylpyrrolidone and divinylbenzene copolymer). For all the analytes, over a wide range of polarity, satisfactory recoveries were obtained between 70% and 120%, with relative standard deviations <15%. Excellent sensitivities were achieved with the limits of quantification ranging from 0.2 μg/kg to 3.0 μg/kg. This developed method provides a new targeted strategy for the analysis of multi-class veterinary drugs in muscle matrices.

The QuEChERSER Mega-Method

Introduced in 2003, the “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) sample preparation approach has been widely adopted in many applications, particularly in chemical residue analysis of foods. Prior to QuEChERS, sample preparation generally entailed several time-consuming, labor-intensive, and reagent-excessive steps, but the commercialization at the time of powerful, cost-effective, benchtop gas chromatography–mass spectrometry (GC–MS) and liquid chromatography–tandem MS (LC–MS/MS) instruments enabled the implementation of the QuEChERS procedure. Despite analytical technologies continuing to improve over the last two decades, many laboratories are still using QuEChERS protocols developed for outdated instrumentation. Recently, QuEChERS has been updated into QuEChERSER (with “efficient and robust” being added to the portmanteau) to better take advantage of the features provided by modern sample preparation and analytical techniques. Most notably, QuEChERSER is a “mega-method” that covers a broader scope of polar and nonpolar analytes in diverse sample types. In this article, the new QuEChERSER approach and its advantages over QuEChERS are explained.

Simultaneous determination of pharmaceuticals and metabolites in fish tissue by QuEChERS extraction and UHPLC Q/Orbitrap MS analysis

In recent years, the occurrence, fate, and adverse effects of pharmaceutically active compounds (PhACs) in aquatic organisms have become a noteworthy issue. In the present study, a rapid and sensitive multiresidue analytical method was developed for the determination of 18 parent PhACs and 5 metabolites in sea bream (Sparus aurata), by combining a modified QuEChERS (quick, easy, cheap, effective, rugged and safe) procedure with ultra-high performance liquid chromatography-Orbitrap-mass spectrometry (UHPLC-Orbitrap-MS). The method development involved optimization of extraction solvent, extraction salts, clean-up sorbents, and amount of sample evaluation, while identification on Orbitrap MS was based on accurate mass and further confirmation with MS/MS fragmentation. The developed method was validated, and linearity was higher than 0.99. Recoveries in all cases ranged between 62 and 107% (at 10, 50, and 100 ng g^-1), while intra-day and inter-day precision, expressed as relative standard deviation, RSD, was lower than 4% and 7%, respectively. In addition, limits of quantification (LOQs) ranged between 0.5 and 19 ng g^-1. The compounds presented a low matrix effect, between - 13 and 4%, while the expanded uncertainty U% estimated at the three spiking levels 10, 50, and 100 ng g^-1 was found below 49% in all cases. Finally, the validated method was applied to sea bream samples from an aquaculture farm located in the Mediterranean Sea, with one positive finding for the antibiotic trimethoprim at a concentration of 26 ng g^-1, presenting negligible human health risk.