Determination of Antibiotic Residues in Honey by High-Performance Liquid Chromatography with Electronspray Ionization Tandem Mass Spectrometry

The aim of the present study was to develop a rapid and simple method for the detection and quantification of antibiotic and antibacterial residues in honey using liquid chromatography with electronspray ionization tandem mass spectrometry. Two different extraction methods were used. The first method uses water and 1% formic acid in acetonitrile for the determination of sulfonamides while the second uses phosphate buffer, 10% trichloroacetic acid, and acetonitrile as the extracting solvent for the determination of tetracyclines, amphenicols, fluoroquinolones, penicillin g, trimethoprim, and tiamulin. The multi-residue method was validated in a thyme honey matrix. Thirty-six different antibiotics and residues from four different families (sulfonamides, tetracyclines, amphenicols, fluoroquinolones) and some individual antibiotics (penicillin g, trimethoprim, and tiamulin) were tested in 20 honey samples originating from Cyprus and Greece. The decision limits (CCα) were from 0.1 to 9.2 μg kg^?1; the detection capabilities (CCβ) were from 0.3 to 27.6 μg kg^?1 while recoveries were from to be between 65.0 and 116.1%. The method was successfully applied to commercial samples from different types of honey from Greece and Cyprus. Among them, oxolonic acid, sulfathiazole, and sulfadimethoxine were found in three honey samples. Finally, proficiency testing was applied to the proposed method while analysis of certified samples showed good method performance characteristics.     

Implementation of the Bacillus cereus microbiological plate used for the screening of tetracyclines in raw milk samples with STAR protocol – the problem with false-negative results solved

In antibiotic residue analyses the first step of screening is just as important as the following steps. Screening methods need to be quick and inexpensive, but above all sensitive enough to detect the antibiotic residue at or below the maximum residue limit (MRL). In the case of a positive result, the next step is conducted and further methods are used for confirmation. MRLs stated in European Union Regulation 37/2010 for tetracyclines in raw milk are: 100 µg kg^–1 for tetracycline, 100 µg kg^–1 for oxytetracycline, 100 µg kg^–1 for chlortetracycline and no limit for doxycycline because it is prohibited for use in animals from which milk is produced for human consumption. The current five-plate microbiological screening method for the detection of antibiotic residues in raw milk was found to be simple and inexpensive, but not specific, sensitive and reliable enough to detect tetracycline at MRL in routine raw milk screening procedures. Spiking samples with tetracycline at the MRL level and applying them on Bacillus cereus ATCC 11778 microbiological plates often gave false-negative results, indicating that tetracyclines may have to be inactivated or masked. Tetracyclines seem to bind to a certain component in milk. Consequently, when applying samples to the B. cereus microbiological plate the antibiotic cannot inhibit the growth of B. cereus which disables the formation of inhibition zones on the test plate. After adding the appropriate amount of citric acid into the milk samples, we solved the problem of false-negative results. During the validation 79 samples of milk were spiked with tetracyclines at different concentrations: 100 µg kg^–1 for tetracycline, 100 µg kg^–1 for oxytetracycline, 80 µg kg^–1 for chlortetracycline and 30 µg kg^–1 for doxycycline. Concentrations used in the validation matched the requirements for MRLs (they were either at or below the MRLs) stated in European Union Regulation 37/2010. The sensitivity of the validation was 100%.     

Development of an ELISA and Immunochromatographic Assay for Tetracycline,Oxytetracycline, and Chlortetracycline Residues in Milk and Honey Based on the Class-Specific Monoclonal Antibody

A sensitive class-specific monoclonal antibody against tetracyclines (TCs) was generated and used to develop an enzyme-linked immunosorbent assay (ELISA) and an immunochromatographic assay for TC, oxytetracycline (OTC), and chlortetracycline (CTC) detection in milk and honey samples. The dynamic range of detection for TC in ELISA was 0.26–2.00 μg L^?1 with an IC₅₀ of 0.72 μg L^?1. The IC₅₀ value of OTC and CTC was 3.2 and 6.4 μg L^?1, respectively. The recovery of TC, OTC, and CTC in milk samples was 82–102, 91–105, and 90–101 %, respectively, and 88–101, 89–101, and 89–95 % in honey samples, respectively. In the immunochromatographic assay, the cutoff values for TC, OTC, and CTC were 15, 15, and 50 μg L^?1 in milk, respectively, and 40, 40, and 40 μg L^?1 in honey, respectively. The results revealed that ELISA and the immunochromatographic assay can be applied for the rapid and sensitive detection of TC, OTC, and CTC in milk and honey samples.     

Determination of glyphosate,AMPA, and glufosinate in honey by online solid-phase extraction-liquid chromatography-tandem mass spectrometry

A simple method was developed for the simultaneous determination of glyphosate, its main degradation product (aminomethylphosphonic acid), and glufosinate in honey. Aqueous honey solutions were derivatised offline prior to direct analysis of the target analytes using online solid-phase extraction coupled to liquid chromatography-tandem mass spectrometry. Using the developed procedure, accuracies ranging from 95.2% to 105.3% were observed for all analytes at fortification levels of 5, 50, and 150 μg kg^?1 with intra-day precisions ranging from 1.6% to 7.2%. The limit of quantitation (LOQ) was 1 μg kg^?1 for each analyte. Two hundred honey samples were analysed for the three analytes with AMPA and glyphosate being most frequently detected (99.0% and 98.5% of samples tested, respectively). The concentrations of glyphosate were found to range from <1 to 49.8 μg kg^?1 while those of its degradation product ranged from <1 to 50.1 μg kg^?1. The ratio of glyphosate to AMPA was found to vary significantly amongst the samples where both analytes were present above the LOQ. Glufosinate was detected in 125 of 200 samples up to a maximum concentration of 33.0 μg kg^?1.     

Simultaneous Determination of Multiclass Pesticides and Antibiotics in Honey Samples Based on Ultra-High Performance Liquid Chromatography-Tandem Mass Spectrometry

A simple, fast, and efficient method was developed for simultaneous determination of 79 pesticides and 13 antibiotics compounds of different chemical classes of pesticides and antibiotics in honey samples by ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS). The sample preparation procedure includes homogenization with McIlvaine buffer 0.1 mol L^?1 (pH 4), followed by extraction with acetonitrile and cleanup with florisil, using dispersive solid phase extraction (d-SPE). The proposed method was validated with good results, such as linearity (r ²?>?0.9901), normality, and independence of the evaluated data, as well as recoveries between 70 and 120 % with relative standard deviation (RSD) <20 % for most of the compounds spiked from 0.1 to 200 μg kg^?1. The experimental method limits of detection and quantification were from 0.03 to 1.51 μg kg^?1 and from 0.1 to 5 μg kg^?1, respectively, for the pesticides. For the antibiotics, the decision limits (0.1 to 2 μg g^?1) and the detection capacity (0.12 to 2.81 μg g^?1) were below the maximum residue limits (MRLs) established for honey by the Brazilian and European legislation. The method was successfully applied to real samples from different botanical and geographic origins. From them, 44 % presented residues from 0.12 to 10 μg kg^?1 of one or more analytes. The proposed method combines the advantages of a quick sample preparation step with the selectivity and sensitivity of the UHPLC-MS/MS and proved to be suitable for routine analyses.     

Simultaneous determination of 30 hormones illegally added to anti-ageing functional foods using UPLC-MS/MS coupled with SPE clean-up

A novel analytical method employing solid-phase extraction (SPE) coupled with ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of 30 hormones in anti-ageing functional foods (capsules, powders and tablets). The analytes were extracted with acetic acid–acetonitrile (1–99 v/v), methanol and acetone, respectively. The extract was purified using a combined column, followed by analyte detection with electrospray ionisation in positive- or negative-ion modes. The results indicated that the 30 compounds had good linear correlations in the range of 1–1000 μg kg^–1, and the correlation coefficients were above 0.99. The limits of detection (LOD) and limits of quantification (LOQ) were 0.03–2 and 0.1–5 μg kg^–1, respectively. The average recovery of 30 compounds at the three spiked levels varied from 74.7% to 124.1%, and the relative standard deviation (RSD) was 2.4–15.0%. This method was applied to the analysis of hormones in 14 real samples of which seven hormones (such as estrone, dienestrol) were detected in four samples, but the remainder of the hormones were not detected. The developed method is sensitive, efficient, reliable and applicable to real samples.     

Determination of 16 phthalate esters in tea samples using a modified QuEChERS sample preparation method combined with GC-MS/MS

A modified QuEChERS method for the determination of 16 phthalate esters (PAEs) in tea samples using GC-MS/MS was developed and validated. The kinds and amounts of adsorbents were optimised, and the crude extracts were purified using primary secondary amine (PSA), graphitised carbon black (GCB) and anhydrous magnesium sulphate (MgSO₄). Compared with extraction without matrix hydration, the addition of water could achieve higher extraction efficiency. The recoveries for PAEs obtained against matrix-matched standards at spiking levels of 50, 200 and 500 μg kg^–1 ranged from 84.7% to 112.7% with relative standard deviations below 20% (n = 6) for all cases. Limits of detection (0.6–36.0 μg kg^–1) and quantitation (2.0–120.0 μg kg^–1) were achieved using the proposed method for all PAEs. A total of 105 tea samples were found to be contaminated with PAEs.     

Validation of a liquid chromatography-tandem mass spectrometry method for the simultaneous determination of sulfonamides,trimethoprim and dapsone in muscle,egg, milk and honey

A quantitative multi-residue method that includes 13 sulfonamides, trimethoprim and dapsone was developed and validated according to Commission Decision 2002/657/EC for muscle, milk egg and honey samples. For all matrices, the same extraction procedure was used. Samples were extracted with an acetone/dichloromethane mixture and cleaned up on aromatic sulfonic acid (SO₃H) SPE cartridges. After elution and concentration steps, analytes were identified and quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Data were acquired according to the multiple reaction-monitoring approach (MRM) and analytes were quantified both by the isotope dilution and the matrix-matched approaches calculating the response factors for the scanned product ions. The developed method shows good linearity, specificity, precision (repeatability and within-laboratory reproducibility), and trueness. Estimated CCβ for sulfonamides ranged between 5.6 and 8.2 µg kg^?1 for eggs, between 11.1 and 69.9 µg kg^?1 for milk, between 64.7 and 87.9 µg kg^?1 for muscle, and between 2.7 and 5.3 µg kg^?1 for honey. CCβ values for dapsone were 3.1, 0.6, 0.7 and 1.5 µg kg^?1 and for trimethoprim were 3.1, 6.7, 81.7 and 3.0 µg kg^?1 calculated for eggs, milk, muscle and honey, respectively. Recovery for all matrices was in the range from 89.1% and 109.7%. In matrix effect testing, no significant deviations were found between different samples of muscle and milk; however, a matrix effect was observed when testing different types of honey. The validation results demonstrate that the method is suitable for routine veterinary drug analysis and confirmation of suspect samples.     

Quantification of mycotoxins in vegetable oil by UPLC-MS/MS after magnetic solid-phase extraction

ABSTRACT

The detection of mycotoxin contamination in foodstuffs is highly significant for public health. Herein we report an analytical method based on magnetic solid-phase extraction (MSPE) and UPLC-MS/MS for the simultaneous determination of mycotoxins, including fumonisins B₁ (FB₁), zearalenone (ZON) and ochratoxin A (OTA), in vegetable oil. Magnetic nanoparticles coated with double layers of silicon dioxide were synthesised and found to be an effective MSPE adsorbent for mycotoxins. The proposed MSPE procedure serves not only for sample clean-up but also for mycotoxin enrichment that enhances greatly the assay’s sensitivity. Under the selected MSPE conditions, linear matrix-matched calibration curves were obtained for mycotoxins in a concentration range from 0.178 to 625 μg kg^–1. The limits of detection were 0.210 μg kg^–1 for FB₁, 0.0800 μg kg^–1 for OTA and 1.03 μg kg^–1 for ZON. The proposed MSPE UPLC-MS/MS method was applied for the determination of mycotoxins in vegetable oil samples, including maize oil, rapeseed oil and soybean oil. ZON was detected in a maize oil at 101 μg kg^–1, which is below the European Union limit of 200 μg kg^–1 in foodstuffs.     

The Modified New Two Plates Test for Detecting Tetracycline,Beta-Lactam,and Sulfonamide Antibiotic Residues in Kidney and Muscle of Cattle Slaughtered in North-East Benin

In Benin, veterinary antibiotics are widely used for cattle breeding. This livestock contributes to 57% of the locally produced meat. The aim of this study was to assess the impact of the large use of antibiotics by determining the contamination level with antibiotic residues in bovine meat, in North Benin. Kidney and muscle samples taken from 50 bovine carcasses in the 2 main slaughterhouses of Parakou were analyzed for the presence of antibiotic residues by a screening method modified from the “New Two Plates Test” (NTPT), to identify tetracyclines, sulfonamides, and beta-lactam groups of antibiotics. Thirteen kidney and muscle samples were subjected to liquid chromatography coupled to tandem mass spectrometry analysis for the confirmation of tetracycline and sulfonamide residues. After modified NTPT screening, tetracycline residues were identified in 54% of cattle carcasses while beta-lactam and sulfonamide residues were present, respectively, in 2 and 6% of sampled animals. The LC-MS/MS analysis confirmed the presence in the kidney tissue of oxytetracycline, epi-oxytetracycline, tetracycline, and epi-tetracycline at maximum levels, respectively, of 1380, 350, 190, and 230 μg kg^?1. Sulfamethazine residues were confirmed in one of cattle carcass at very high levels of 3900 μg kg^?1 in kidney and 2220 μg kg^?1 in muscle. Antibiotic residue levels were found above the maximum residue limit applied in the European legislation in 38% of the carcasses subjected to the LC-MS/MS analysis. These high levels of contamination with antibiotic residues are a potential threat for the health of consumers, and are of concern regarding the selection of antibiotic-resistant bacteria in animals and humans.     

Unravelling a vicious circle: animal feed marketed in Costa Rica contains irregular concentrations of tetracyclines and abundant oxytetracycline-resistant Gram-positive bacteria

Diverse tetracyclines are used to prevent and control bacterial infections in livestock and farmed fish. These drugs are administered through the diet, but farmers seldom check whether feed contains antibiotic-resistant bacteria that may colonise their crops or transfer their resistance traits to species of veterinary relevance. To examine whether antibiotic dosage defines the abundance of antibiotic-resistant bacteria in animal feed, we determined the concentration of parental compounds and epimers of oxytetracycline (OTC), doxycycline, tetracycline and chlortetracycline, as well as the abundance and resistance level of OTC-resistant bacteria in samples of fish (n = 21), poultry (n = 21), swine (n = 21), and shrimp feed (n = 21) marketed in Costa Rica. Fish feed contained the highest amounts of tetracyclines (119–8365 mg kg^?1) and the largest proportion of bacteria resistant to 10 μg ml^?1 (1.8–92.4%) or 100 μg ml^?1 of OTC (12.5–63.8%). Poultry (78–438 mg kg^?1) and swine (41–1076 mg kg^?1) feed had intermediate concentrations of tetracyclines and OTC-resistant bacteria (0.2–66% and 0.3–49%, respectively), whereas shrimp feed showed the lowest amounts of tetracyclines (21.5–50.3 mg kg^?1), no OTC and no culturable OTC-resistant bacteria. In line with these results, the MIC₅₀ of OTC for 150 isolates from fish and poultry feed was > 256 µg ml^?1, while that of 150 bacteria isolated from swine feed was 192 µg ml^?1. Phenotypic tests, fatty acid profiles and proteotypic analyses by matrix-assisted laser desorption/ionisation-time of flight mass-spectroscopy revealed that most OTC-resistant isolates were Gram-positive bacteria of low G+C% content from the genera Staphylococcus and Bacillus. Clear correlations between OTC dosage and feed colonisation with OTC-resistant bacteria were seen in medicated feed for fish (r = 0.179–0.651). Nonetheless, some unmedicated feed for fish, swine and poultry contained large populations of OTC-resistant bacteria, suggesting that raw materials and manufacturing processes may also influence carriage of OTC-resistant bacteria in animal feed.     

Gas Purge Microsyringe Extraction Coupled with Dispersive Liquid-Liquid Microextraction for the Determination of Acidic Compounds in Food Packaging Materials

A green, simple and sensitive method was developed for the analysis of volatile carboxylic acids (VFAs) and perfluorocarboxylic acids (PFCAs) in food packaging materials. The acidic compounds in food packaging materials were first extracted by gas purge microsyringe extraction (GP–MSE) with 1.0 mL 0.1 mol·L^?1 NaOH solution, then the analytes were dispersive liquid-liquid microextracted (DLLME) by 50 μL chloroform as extraction solvent and 200 μL acetonitrile as dispersive solvent. The 2-(5-Benzoacridine) ethyl-p-toluenesulfonate (BAETS) with excellent fluorescence property was applied to enhance the high performance liquid chromatography (HPLC) sensitivity. The obtained recoveries for the VFAs ranged from 92.0 to 101 %. The method LODs calculated at a signal-to-noise ratio (S/N) of 3 were in the range of 0.80–3.40 μg·kg^?1, while the LOQs calculated at S/N of 10 were in the range of 2.5–10.2 μg·kg^?1. All compounds were in good linearity with concentration coefficients of higher than 0.997. Perfluorooctanoic acid (PFOA) was found in all of the 15 kinds of samples analyzed with concentrations ranging from 4.86–7.56 μg·kg^?1. Acetic acid, butyric acid, and caprylic acid were found in half of the samples analyzed. The other analytes were also found in more than 30 % samples with concentrations varied between 3.96 and 293 μg·kg^?1.     

Optimization of QuEChERS Procedure Coupled to GC-ECD for Organochlorine Pesticide Determination in Carrot Samples

An optimised version of the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method for simultaneous determination of 14 organochlorine pesticides in carrots was developed using gas chromatography coupled with electron-capture detector (GC-ECD) and confirmation by gas chromatography tandem mass spectrometry (GC-MS/MS). A citrate-buffered version of QuEChERS was applied for the extraction of the organochlorine pesticides, and for the extract clean-up, primary secondary amine, octadecyl-bonded silica (C18), magnesium sulphate (MgSO₄) and graphitized carbon black were used as sorbents. The GC-ECD determination of the target compounds was achieved in less than 20 min. The limits of detection were below the EU maximum residue limits (MRLs) for carrots, 10–50 μg kg^?1, while the limit of quantification did exceed 10 μg kg^?1 for hexachlorobenzene (HCB). The introduction of a sonication step was shown to improve the recoveries. The overall average recoveries in carrots, at the four tested levels (60, 80, 100 and 140 μg kg^?1), ranged from 66 to 111 % with relative standard deviations in the range of 2–15 % (n?=?3) for all analytes, with the exception of HCB. The method has been applied to the analysis of 21 carrot samples from different Portuguese regions, and β-HCH was the pesticide most frequently found, with concentrations oscillating between less than the limit of quantification to 14.6 μg kg^?1. Only one sample had a pesticide residue (β-HCH) above the MRL, 14.6 μg kg^?1. This methodology combines the advantages of both QuEChERS and GC-ECD, producing a very rapid, sensitive and reliable procedure which can be applied in routine analytical laboratories.     

Determination and surveillance of nine acaricides and one metabolite in honey by liquid chromatography-tandem mass spectrometry

A simple and accurate analytical method for the determination of acaricides in honey was developed and validated in accordance with Japanese validation guidelines. Analytes – amitraz, N-2,4-dimethylphenyl-N-methylformamidine (DMPF), etoxazole, fenpyroximate, fipronil, hexythiazox, propargite, pyridaben and spirodiclofen – were extracted with ethyl acetate under basic conditions and subsequently cleaned up using an InertSep^® MA-1 polymer-based anion-exchange column. The method was validated by fortified recovery tests at three different concentrations (1, 5 and 10 µg kg^?1) performed with three samples daily on five different days. The method exhibited recoveries of 77–116% and precision (relative standard deviations – RSDs) of repeatability and within-laboratory reproducibility ranged from 2% to 22% and from 3% to 23%, respectively. The sample solution was successfully cleaned up to enable quantification using external solvent calibration curves. The limits of quantification (LOQs) were estimated to be 1 µg kg^?1 for all analytes. The method was applied to honey samples commercially available in Tokyo, Japan. Analysis of 250 honey samples indicated that amitraz was present in 127 samples, and that its residual concentration was less than 20 µg kg^?1. Propargite was detected in 23 samples at concentrations less than 1 µg kg^?1.     

Determination of acrylamide in food using a UPLC–MS/MS method: results of the official control and dietary exposure assessment in Cyprus

ABSTRACT

The determination of acrylamide in potato products, bakery products and coffee, and the human dietary exposure is reported. The method reported is based on a single extraction step with water, followed by the clean-up of the extract using solid phase extraction columns and finally, the determination of acrylamide using UPLC–MS/MS. The MS/MS detection was carried out using an ESI interface in positive ion mode. Internal calibration was used for the quantification of acrylamide, because of the suppression/enhancement matrix effects due to the complex nature of the samples. The method performance characteristics were determined after spiking blank samples. The mean recoveries in spiked coffee samples, potato chips, breakfast cereals and crispbread ranged from 93% to 99%, with RSDs lower than 5% for both repeatability and reproducibility conditions. The estimated limits of detection and quantification of the method were 10 and 32 μg kg^?1, respectively. The method was used for monitoring acrylamide in 406 samples. Acrylamide amounts ranged from <32 to 2450 μg kg^?1. A total of 360 samples (89%) were contaminated with acrylamide, but only 14% of the samples exceeded the benchmark levels of the EU legislation. Foods with the highest mean acrylamide amounts were potato crisps (642 μg kg^?1), French fries (383 μg kg^?1) and biscuits (353 μg kg^?1). The mean and 95th percentile acrylamide exposures of adolescents in Cyprus were 0.8 and 1.8 μg kg^?1 body weight per day, respectively. The estimated levels of dietary exposure to acrylamide are not of concern with respect to neurotoxicity. However, the margins of exposure (MOEs) indicate a concern for carcinogenicity. Potato fried products (45%), fine bakery ware (21%) and potato chips (14%) contributed the most to overall acrylamide exposure.     

Determination of Trichothecenes in Cereal Matrices Using Subcritical Water Extraction Followed by Solid-Phase Extraction and Liquid Chromatography-Tandem Mass Spectrometry

Subcritical water extraction followed by solid-phase extraction and ultra-high performance liquid chromatography coupled with tandem mass spectrometry detection is reported for the first time for the determination of 6 trichothecenes (deoxynivalenol, deoxynivalenol-3-glucoside, 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, HT-2 toxin, and T-2 toxin) from different cereals. Water with 1% formic acid was used as the extraction solvent followed by a solid-phase extraction clean-up, achieving good performance with acceptable extraction recoveries, method detection limits between 0.05 μg kg^?1 and 4.0 μg kg^?1, and method quantification limits between 0.4 μg kg^?1 and 20 μg kg^?1. The use of water as the extraction solvent allowed a selective extraction affording low matrix effect levels and the detection and quantification of natural target trichothecenes at very low concentration levels. This extraction method was applied to different cereals, a pseudocereal and an oilseed sample, of which maize, millet, and oat were contaminated by at least one trichothecene.     

Co-occurrence of aflatoxins,ochratoxin A and citrinin in “egusi” melon (Colocynthis citrullus L.) seeds consumed in Ireland and the United Kingdom

The natural co-occurrence of aflatoxins (AFs), ochratoxin A (OTA) and citrinin (CIT) in melon seed samples obtained from retailers and households in Ireland and the United Kingdom (UK) was evaluated. AFs and OTA were determined by HPLC with fluorescence detection while CIT was analysed by HPLC-MS/MS. AFB₁ was detected in all (100%) samples (mean = 9.7 μg kg^?1; range = 0.2–66.5 μg kg^?1). Mean total AFs was 12.0 μg kg^?1 (range = 0.3–82 μg kg^?1). Commercially retailed samples showed a significantly higher AFB₁ contamination (p < 0.05) than the household samples. OTA occurred in 3 (13.6%) samples, while 4 (18.2%) were contaminated with CIT at very low levels. In this study, 68% of the melon seed samples were contaminated above the 2 μg kg^?1 EU limit for AFB₁ in oilseeds. These results highlight the need for the development of strategies to reduce AF contamination in “egusi” for human consumption.     

Multi-residual Pesticide Monitoring in Commercial Chinese Herbal Medicines by Gas Chromatography–Triple Quadrupole Tandem Mass Spectrometry

To investigate multi-residual pesticide monitoring data in commercial Chinese herbal medicines on major markets, an easy, rapid, and selective gas chromatography with mass spectrometry (GC/MS/MS) method was established for simultaneously determining multi-residual pesticides including organochlorine, pyrethroid, carbamate, and organophosphorus pesticides in Chinese herbal medicines. The analytical method was based on an efficient extraction procedure and further cleanup steps by solid-phase extraction columns, yielding recovery rates in the range of 70.0–120.0 % for the majority of pesticides, except for hexachlorobenze, diazinon, β-HCH, δ-HCH, and omethoate, with precision values expressed as relative standard deviation of 0.1–14.7 %. The limits of detection of the established GC/MS/MS method for all investigated pesticides ranged from 0.01 to 3.6 μg kg^?1 and limits of quantification from 0.03 to 11.88 μg kg^?1. With this validated method, multi-residual pesticides of 132 Chinese herbal medicine samples were analyzed. The monitoring results indicated that pesticide residue was found in 74 samples. In total, 51 pesticides were found with detection rate ranging from 0.76 to 18.94 %. An 82.3 % of positive pesticides were found in less than 6 % of samples. Hexachlorobenzene was found in 25 samples, quintozene in 15 samples, and acephate and simazine in 13 samples. Concentrations of pesticide residue from monitoring data obtained ranged from 0.5 to 203.5 μg kg^?1. The simple and rapid method can be used as routine analysis method in multi-residual pesticide monitoring of Chinese herbal medicines.     

A Modified QuEChERS Sample Preparation Method for the Analysis of 70 Pesticide Residues in Tea Using Gas Chromatography-Tandem Mass Spectrometry

A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method for the simultaneous determination of 70 pesticides in tea was developed using gas chromatography-tandem mass spectrometry. Prior to acetonitrile extraction of the target compounds from tea matrix, samples were soaked in distilled water to improve the extraction efficiency. A mixture of adsorbents containing primary–secondary amine, octadecylsilane, graphite carbon black, and multiwalled carbon nanotubes was applied for the cleanup. Additional steps of concentration and solvent exchange were performed to reduce the amount of co-extracts and to decrease the limit of detection of the method. For all pesticides, good linear calibrations with coefficients (R ²) ≥0.99 were obtained at the concentration levels of 10, or 50 to 1,000 μg ml^?1. The limits of quantifications (LOQs) were 5–25 μg ml^?1, respectively. The recovery rates of samples spiked with 20, 100, and 200 μg kg^?1 of analytes ranged from 71 % to 105 %. In addition, the relative standard deviations were lower than 20 %. A total of 331 tea samples were analyzed using this method, and the levels of five pesticide residues in nine tea samples exceeded the strictest maximum residual limits (MRLs).     

Rapid Screening and Determination of the Residues of Hormones and Sedatives in Milk Powder Using the UHPLC-MS/MS and SPE

A method based on the ultra-high-performance liquid chromatography tandem mass spectrometry for determination of the residues of sex hormones, glucocorticoids, and sedatives in milk powder was developed. The sample was extracted with the acetic acid-acetonitrile (1:99, v/v) twice, purified by the PRiME hydrophilic-lipophilic balance (HLB) cartridges and analyzed by the ultra-high-performance liquid chromatography-tandem mass spectrometry. The analytes were separated by the Waters Acquity UPLC? BEH C18 column (50 mm?×?2.1 mm, 1.7 μm) and determined using the electrospray ionization in the positive mode with the multiple reaction monitoring (MRM). The developed method was validated with the specificity, linearity and range, matrix effects, recovery, and precision. The results showed that the analytes were linear with the correlation of determinations (R²) higher than 0.991 in the corresponding ranges. The limits of detection (LODs) and limits of quantification (LOQs) were in the range of 0.1–1.1 μg kg^?1 and 0.3–3.8 μg kg^?1, respectively. The average recoveries of the analytes ranged from 78.5 to 107.0% with the relative standard deviations lower than 15%. The practical applicability was tested by analyzing real samples and the progesterone was observed in two samples.