Direct determination of nosiheptide residue in animal tissues by liquid chromatography-tandem mass spectrometry.

Because only very weak signals of fragment ions of nosiheptide can be obtained, nosiheptide is usually detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS) via the determination of its hydrolyzed degradation product named HMIA in previous studies. The indirect method suffers from several problems, such as complicated samplepreparation, unavailable commercial HMIA, and the risk of the false-positive result by HMIA. However, we found that nosiheptide could produce several significant fragment ions under high collision energy (CE). Therefore, we developed a method for the direct determination of nosiheptide by LC-MS/MS in animal tissues. The sample was extracted with ACN, then degreased with n-hexane, and purified by an HLB solid-phase extraction (SPE) cartridge. After being filtered through the PTFE filter, it was analyzed by LC-MS/MS in selected reaction monitoring (SRM) mode. The influencing factors, such as mobile phase, SPE cartridge, filter material, and matrix effect, were investigated. Nosiheptide showed a good linear relationship (R2 ≥ 0.999) within the concentration range from 0.3 µg/L to 20 µg/L under optimized conditions. The limit of detection (LOD) was 0.3 µg/kg, while the limit of quantification (LOQ) was 1.0 µg/kg in chicken, bovine muscle, swine muscle, and swine liver. The average recoveries at spiked levels of 1.0, 2.0, and 10 µg/kg ranged from 83% to 101%, with the relative standard deviations (RSDs) <12%. Compared with the methods previously reported, our newly developed method was more simple, convenient, and sensitive. Moreover, it was successfully applied for the determination of nosiheptide residue in medicated chicken samples.

Dummy Template-Based Molecularly Imprinted Membrane Coating for Rapid Analysis of Malachite Green and Its Metabolic Intermediates in Shrimp and Fish.

A novel malachite green molecularly imprinted membrane (MG-MIM) with specific selectivity for malachite green (MG) and leucomalachite green (LMG) was prepared using a hydrophobic glass fiber membrane as the polymer substrate, methyl violet as a template analog, 4-vinyl benzoic acid as the functional monomer, and ethyleneglycol dimethacrylate as the crosslinking agent. MG-MIM and non-imprinted membrane (NIM) were structurally characterized using scanning electron microscopy, surface area analyzer, Fourier-transform infrared spectrometer and synchronous thermal analyzer. The results showed that MG-MIM possessed a fluffier surface, porous and looser structure, and had good thermal stability. Adsorption properties of MG-MIM were investigated under optimal conditions, and adsorption equilibrium was reached in 20 min. The saturated adsorption capacities for MG and LMG were 24.25 ng·cm-2 and 13.40 ng·cm-2, and the maximum imprinting factors were 2.41 and 3.20, respectively. Issues such as "template leakage" and "embedding" were resolved. The specific recognition ability for the targets was good and the adsorption capacity was stable even after five cycles. The proposed method was successfully applied for the detection of MG and LMG in real samples, and it showed good linear correlation in the range of 0 to 10.0 µg·L-1 (R2 = 0.9991 and 0.9982), and high detection sensitivity (detection limits of MG and LMG of 0.005 µg/kg and 0.02 µg·kg-1 in shrimp, and 0.005 µg/kg and 0.02 µg/kg in fish sample). The recoveries and relative standard deviations were in the range of 76.31-93.26% and 0.73-3.72%, respectively. The proposed method provides a simple, efficient and promising alternative for monitoring MG and LMG in aquatic products.

Multivariate analysis for organic milk authentication.

To differentiate organic milk (OM) from conventional milk (CM), an orthogonal projection to latent structure-discriminant analysis (OPLS-DA) model was constructed using δ13C, δ15N, δ18O, 51 elements and 35 fatty acids (FAs) as the variables. So far, most reported studies barely use three or more types of variables, but more variables could avoid one-sidedness and get stabler models. Our multivariate model combines geographical and nutritional parameters and displays better explanatory and predictive abilities (R2X = 0.647, R2Y = 0.962 and Q2 = 0.821) than models based on fewer variables for differentiating OM and CM. In particular, δ15N, Se, δ13C, Eu, K and α-Linolenic acid (ALA) are found to be critical parameters for the discrimination of OM. These results show that the multivariate model based on stable isotopes, elements and FAs can be used to identify OM, and can potentially expand the global databases for quality and authenticity of milk.

Correction: Determining the geographical origin of milk by multivariate analysis based on stable isotope ratios, elements and fatty acids.

Correction for 'Determining the geographical origin of milk by multivariate analysis based on stable isotope ratios, elements and fatty acids' by Siyan Xu et al., Anal. Methods, 2021, DOI: .

Determining the geographical origin of milk by multivariate analysis based on stable isotope ratios, elements and fatty acids.

To construct a reliable discrimination model for determining milk geographical origin, stable isotope ratios including δ13C, δ15N and δ18O, 51 elements and 35 fatty acids (FAs) in milk samples from Australia, New Zealand and Austria were detected and analyzed. It is found that all of the stable isotope ratios in the milk samples of Australia are the highest, followed by those of the samples from New Zealand and Austria. In addition, 14 elements and 8 FAs show different contents in the samples of different countries at the significance level of P < 0.05. Based on these results, a multivariate model with good robustness and predictive ability for authenticating milk origin (R2X = 0.693, Q2 = 0.854) was successfully constructed. Element contents and stable isotope ratios are more reliable variables for milk origin discrimination and Rb, δ18O, Tl, Ba, Mo, Sr, δ15N, Cs, As, Eu, C20:4n6, Sc, C13:0, K, Ca and C16:1n7 are the critical markers in the multivariate model for verifying milk origin.

Microwave-assisted extraction followed by salting-out phase separation for hierarchical screening of illegal adulterants in aphrodisiac health products by multi-dimensional fingerprint profiling analysis.

A novel method for hierarchical screening of illegal adulterants in Fur seal ginseng pills (FSGP) products was developed by microwave-assisted extraction (MAE) coupled to salting-out assisted liquid-liquid extraction (SALLE) with multi-dimensional fingerprint profiling analysis. Using a homogeneous system formed by dimethyl carbonate (DMC) and water as the extractant, the MAE conditions were investigated to maximize extraction recoveries, followed by addition of ammonium sulfate to induce DMC phase separation for SALLE enrichment of 16 potentially illegal adulterants such as phosphodiesterase type-5 inhibitors, androgens, α receptor antagonists and yohimbine etc. By means of high-performance liquid chromatography (HPLC) with diode array detection (DAD) and fluorescence detection (FLD), multi-dimensional fingerprints were acquired by multi-wavelength detection to highlight the signals of the potentially illegal adulterants and reduce or remove interferences from the sample matrix. For high accuracy and reliability, a hierarchical screening strategy was designed by multi-dimensional fingerprinting profiling analysis (MDFPA). The method exhibited proper identification and quantification performance, and it was successfully applied to screening of illegal adulterants in 18 batches of the samples through the step-by-step MDFPA. Also, the results were further confirmed by ultra high-performance liquid chromatography-quadrupole-orbitrap mass spectrometry (UHPLC-Q-Orbitrap/MS). The proposed method was proved to be a green, efficient and reliable alternative to monitoring aphrodisiac health products.

Multi-dimensional fingerprint profiling analysis for screening and quantification of illegal adulterated antidiabetics in hypoglycemic health products by aqueous two-phase extraction and multi-wavelength detection.

A novel method for screening and quantification of illegal adulterated antidiabetics in hypoglycemic health products was developed by multi-dimensional fingerprint profiling analysis (MDFPA). By means of aqueous two-phase extraction (ATPE), using aqueous two-phase system (ATPS) of butanol-water as the extractant, 11 common antidiabetics could be effectively extracted to the upper and lower phases, respectively. HPLC separation conditions for the extracts from two phases were investigated by multi-wavelength detection before and after p-nitrobenzoyl chloride (p-NBC) and 2,4-dinitrofluorobenzene (DNBF) derivatizations to establish multi-dimensional fingerprints. For high accuracy and reliability, a hierarchical screening approach to screening illegal adulterated antidiabetics in samples was established by MDFPA and spectral purity examination. Meanwhile, detection limits of identification for illegal adulterants were defined by detection limits of spectra (SLOD). The proposed method exhibited good identification and quantification performances. SLODs, LODs and LOQs of 11 antidiabetics were 1.22-8.37 µg/g, 0.225-4.23 µg/g and 0.755-14.10 µg/g, respectively. They had good linearity ranged from 2.0 µg/g to 300.0 µg/g (R2 ≥ 0.9978). The recoveries and RSDs were 76.83-109.6% and 0.50-6.5%, respectively. The method was successfully applied to screening of 15 batches of samples in different forms. Among them, four samples were detected to contain 5.47 µg/g of metformin, 6.50 µg/g of phenformin, 3.69 µg/g of glibenclamide and 9.11 µg/g of glimepiride, respectively. The results proved that it was an efficient and feasible alternative to screening and detection of illegal adulterated antidiabetics in hypoglycemic health products.

[Progress in analysis methods for major mycotoxins in foodstuffs].

The analysis of mycotoxins in foodstuffs is affected by the complexity of the matrix and the extremely low concentration levels. The development of sample pretreatment and analytical methods that enable highly selective enrichment as well as highly sensitive detection is of great significance for food safety. This paper reviews the recent progress in biotoxin analysis methods and summarizes the prospects and development of this field.

A hierarchical screening method for detection of illegal adulterants in Fur seal ginseng pills by profiling analysis of HPLC multi-dimensional fingerprints.

A novel method for hierarchical screening of illegal adulterants in Fur seal ginseng pills products was developed by multi-dimensional fingerprint profiling analysis. Fingerprint feature of the samples was acquired by high-performance liquid chromatography analysis of 11 batches of samples with diode array detector and fluorescence detector, and then potential illegal adulterants including phosphodiesterase type-5 inhibitors, androgens, α receptor antagonists and yohimbine, were further separated at multiple wavelengths to reduce or remove interferences from sample matrix for highlight their chromatographic characteristics. Accordingly, a hierarchical screening strategy was designed by first-order and second-order fingerprints combined with spectral examination to achieve high accuracy and reliability. The method was successfully applied to screening of illegal adulterants in real samples, and it also exhibited good quantification performance through validation tests. From 16 batches of samples, three suspected samples were confirmed to be positive, containing 9.37µg/g of testosterone, 18.8 µg/g of tadalafil, and 48.5 µg/g of sildenafil, respectively. The recoveries and relative standard deviations were in the range of 83.6-103.1% and 4.2-6.8%, respectively. The proposed method provided a simple, efficient and promising alternative to monitoring functional foods.

Rapid determination of 54 pharmaceutical and personal care products in fish samples using microwave-assisted extraction-Hollow fiber-Liquid/solid phase microextraction.

In this paper, a simple, rapid, solvent-less and environmental friendliness microextraction method, microwave-assisted extraction-hollow fiber-liquid/solid phase microextraction (MAE-HF-L/SME), was developed for simultaneous extraction and enrichment of 54 trace hydrophilic/lipophilic pharmaceutical and personal care products (PPCPs) from fish samples. A solid-phase extraction material, solid-phase microextraction (SPME) fiber, was synthesized. The SPME fiber had a homogeneous, loose structure and good mechanical properties, and they exhibited a good adsorption capacity for most PPCPs selected. The material formed the basis for the method of MAE-HF-L/SME. A method of liquid chromatography-high resolution mass spectroscopy (LC-HRMS) for analysis of 54 PPCPs. Under optimal synthesis and extraction conditions, the limits of detection (LODs, n=3) and the limits of quantitation (LOQs, n=10) for the 54 PPCPs were between 0.01-0.50µg·kg-1 and 0.052.00µg·kg-1, respectively. Percent recoveries and the relative standard deviations (RSDs) in spiked fish samples (n=6) were between 56.3%-119.9% and 0.3%-17.1%, respectively. The microextraction process of 54 PPCPs in MAE-HF-L/SME took approximately 12min. The method has a low matrix interference and high enrichment factor and may be applicable for determination of 54 different PPCPs in fish samples.

[Determination of perfluoroalkyl acids in lamb liver by high performance liquid chromatography- tandem mass spectrometry combined with dispersive solid phase extraction].

A method was developed for the determination of 19 perfluoroalkyl acids (PFAs) in lamb liver by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/ MS) combined with dispersive solid phase extraction. The sample was extracted with acidified acetonitrile, and then cleaned-up by a mixture of N-propylethylenediamine (PSA), C18 and graphitized carbon black (GCB) sorbents. The 19 PFAs were analyzed by HPLC-MS/MS with a C18 chromatographic column, adopting the multiple reaction monitoring (MRM) mode with negative electrospray ionization. The effects of the dosages of hydrochloric acid and the sorbents on the recoveries of the 19 PFAs were studied. For accurate quantitative analysis, the isotope internal standard method was used. The calibration curves were linear with the correlation coefficients over 0.998 in the range of 0.05-20 µg/kg for the 19 PFAs. The limits of detection were 0.004-0.111 µg/kg. The limits of quantification were 0.012-0.370 µg/kg. The mean recoveries of the 19 PFAs at spiked levels of 0.5, 1.0, 2.0 µg/kg were in the range from 80% to 128% with the relative standard deviations of 0.31%-11.1%. The developed method is rapid, simple, accurate. It is suitable for the determination of the 19 PFAs in large quantities of lamb liver samples.

[Determination of 25 quinolones in cosmetics by liquid chromatography-tandem mass spectrometry].

An analytical method was developed for the simultaneous determination of 25 quinolones, including danofloxacin mesylate, enrofloxacin, flumequine, oxloinic acid, ciprofloxacin, sarafloxacin, nalidixic acid, norfloxacin, and ofloxacin etc in cosmetics using direct extraction and liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Cosmetic sample was extracted by acidified acetonitrile, defatted by n-hexane and separated on Poroshell EC-C18 column with gradient elution program using acetonitrile and water (both containing 0. 1% formic acid) as the mobile phases and analyzed by LC-ESI-MS/MS under the positive mode using multiple reaction monitoring (MRM). The interference of matrix was reduced by the matrix-matched calibration standard curve. The method showed good linearities over the range of 1-200 mg/kg for the 25 quinolones with good linear correlation coefficients (r ≥ 0.999). The method detection limit of the 25 quinolones was 1.0 mg/kg, and the recoveries of all analytes in lotion, milky and cream cosmetics matrices ranged from 87.4% to 105% at the spiked levels of 1, 5 and 10 mg/kg with the relative standard deviations (RSD) of 4.54%-19.7% (n = 6). The results indicated that this method is simple, fast and credible, and suitable for the simultaneous determination of the quinolones in the above three types of cosmetics.

Ultrasensitive detection and rapid identification of multiple foodborne pathogens with the naked eyes.

In this study, a novel approach for ultrasensitive detection and rapid high-throughput identification of a panel of common foodborne pathogens with the naked eyes is presented. As a proof-of-concept application, a multiple pathogen analysis array is fabricated through immobilizing three specific polyT-capture probes which can respectively recognize rfbE gene (Escherichia coli O157:H7), invA gene (Salmonella enterica), inlA gene (Listeria monocytogenes) on the plastic substrates. PCR has been developed for amplification and labeling target genes of rfbE, invA, inlA with biotin. The biotinated target DNA is then captured onto the surface of plastic strips through specific DNA hybridization. The succeeding staining of biotinated DNA duplexes with avidin-horseradish peroxidise (AV-HRP) and biotinated anti-HRP antibody greatly amplifies the detectable signal through the multiple cycle signal amplification strategy, and thus realizing ultrasensitive and specific detection of the above three pathogens in food samples with the naked eyes. Results showed approximately 5 copies target pathogenic DNA could be detected with the naked eyes. This simple but very efficient colorimetric assay also show excellent anti-interference capability and good stability, and can be readily applied to point-of-care diagnosis.

QuEChERs Combined with Online Interference Trapping LC-MS/MS Method for the Simultaneous Determination of 20 Polyfluoroalkane Substances in Dietary Milk.

In this study, a highly sensitive and reliable method for the determination of 20 polyfluoroalkane substances (PFASs) in milk was established using the QuEChERS approach and an online interference trapping LC-MS/MS analysis. By a calibration with stable-isotope-labeled internal standards, we showed that the method displayed excellent linear dynamic ranges for 20 PFASs (correlation coefficients ≥0.997). The LOQs for the two types of PFASs, perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), were 0.010 and 0.050 µg/L, respectively. At the three spiking levels, the average recoveries for PFCAs ranged from 78.5 to 111% with the RSD (n = 6) within 1.20-13.1%, and those for PFSAs ranged from 72.8 to 105% with the RSD (n = 6) within 3.53-14.9%. By the developed method, 16 PFASs were found to be positive in 46 milk samples, and the levels for the PFASs with longer chains were significantly higher than those reported from other known regions.

Determination of 13 endocrine disrupting chemicals in sediments by gas chromatography-mass spectrometry using subcritical water extraction coupled with dispersed liquid-liquid microextraction and derivatization.

In this study, a sample pretreatment method was developed for the determination of 13 endocrine disrupting chemicals (EDCs) in sediment samples based on the combination of subcritical water extraction (SWE) and dispersed liquid-liquid microextraction (DLLME). The subcritical water that provided by accelerated solvent extractor (ASE) was the sample solution (water) for the following DLLME and the soluble organic modifier that spiked in the subcritical water was also used as the disperser solvent for DLLME in succession. Thus, several important parameters that affected both SWE and DLLME were investigated, such as the extraction solvent for DLLME (chlorobenzene), extraction time for DLLME (30s), selection of organic modifier for SWE (acetone), volume of organic modifier (10%) and extraction temperature for SWE (150 °C). In addition, good chromatographic behavior was achieved for GC-MS after derivatisation by using N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA). As a result, proposed method sensitive and reliable with the limits of detection (LODs) ranging from 0.006 ng g(-1) (BPA) to 0.639 ng g(-1) (19-norethisterone) and the relative standard deviations (RSDs) between 1.5% (E2) and 15.0% (DES). Moreover, the proposed method was compared with direct ASE extraction that reported previously, and the results showed that SWE-DLLME was more promising with recoveries ranging from 42.3% (dienestrol) to 131.3% (4,5α-dihydrotestosterone), except for diethylstilbestrol (15.0%) and nonylphenols (29.8%). The proposed method was then successfully applied to determine 13 EDCs sediment of Humen outlet of the Pearl River, 12 of target compounds could be detected, and 10 could be quantitative analysis with the total concentration being 39.6 ng g(-1), and which indicated that the sediment of Humen outlet was heavily contaminated by EDCs.

A "three-in-one" sample preparation method for simultaneous determination of B-group water-soluble vitamins in infant formula using VitaFast(®) kits.

VitaFast(®) test kits designed for the microbiological assay in microtiter plate format can be applied to quantitative determination of B-group water-soluble vitamins such as vitamin B12, folic acid and biotin, et al. Compared to traditional microbiological methods, VitaFast(®) kits significantly reduce sample processing time and provide greater reliability, higher productivity and better accuracy. Recently, simultaneous determination of vitamin B12, folic acid and biotin in one sample is urgently required when evaluating the quality of infant formulae in our practical work. However, the present sample preparation protocols which are developed for individual test systems, are incompatible with simultaneous determination of several analytes. To solve this problem, a novel "three-in-one" sample preparation method is herein developed for simultaneous determination of B-group water-soluble vitamins using VitaFast(®) kits. The performance of this novel "three-in-one" sample preparation method was systematically evaluated through comparing with individual sample preparation protocols. The experimental results of the assays which employed "three-in-one" sample preparation method were in good agreement with those obtained from conventional VitaFast(®) extraction methods, indicating that the proposed "three-in-one" sample preparation method is applicable to the present three VitaFast(®) vitamin test systems, thus offering a promising alternative for the three independent sample preparation methods. The proposed new sample preparation method will significantly improve the efficiency of infant formulae inspection.

Coupling gold nanoparticles to silica nanoparticles through disulfide bonds for glutathione detection.

Advances in the controlled assembly of nanoscale building blocks have resulted in functional devices which can find applications in electronics, biomedical imaging, drug delivery etc. In this study, novel covalent nanohybrid materials based upon [Ru(bpy)3](2+)-doped silica nanoparticles (SiNPs) and gold nanoparticles (AuNPs), which could be conditioned as OFF-ON probes for glutathione (GSH) detection, were designed and assembled in sequence, with the disulfide bonds as the bridging elements. The structural and optical properties of the nanohybrid architectures were characterized using transmission electron microscopy, UV-vis spectroscopy and fluorescence spectroscopy, respectively. Zeta potential measurements, x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were employed to monitor the reaction processes of the SiNPs-S-S-COOH and SiNPs-S-S-AuNPs synthesis. It was found that the covalent nanohybrid architectures were fluorescently dark (OFF state), indicating that SiNPs were effectively quenched by AuNPs. The fluorescence of the OFF-ON probe was resumed (ON state) when the bridge of the disulfide bond was cleaved by reducing reagents such as GSH. This work provides a new platform and strategy for GSH detection using covalent nanohybrid materials.

Development of a simple method for simultaneous determination of nine subclasses of non-steroidal anti-inflammatory drugs in milk and dairy products by ultra-performance liquid chromatography with tandem mass spectrometry.

A multi-residue analysis method for simultaneous determination of nine subclasses of non-steroidal anti-inflammatory drugs (NSAIDs) in milk and dairy products by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) has been established. The sample was initially extracted and deproteinized with ascorbic acid buffer (0.01M, pH 3) and acetonitrile-ethyl acetate mixture, followed by centrifugation and evaporation, then reconstituted with acetonitrile-0.1% formic acid (1+1, v/v). After removal of lipid material by n-hexane, the sample was analyzed by UPLC-MS/MS with electro-spray ionization (ESI) interface in Multiple Reaction Monitoring (MRM) mode. The range of limits of detection (LODs) and limits of quantification (LOQs) were 0.03-0.30µg/kg and 0.10-1.00µg/kg, respectively. The recoveries in milk, milk powder, yogurt, processed cheese and milk beverage ranged from 61.7% to 117%, and the relative standard deviations (RSDs) were less than 17.9% at three spiked levels (1, 10 and 100 times of the LOQ). Matrix effects were also investigated and it was determined the signals of the analytes were suppressed from 9.4% to 76.6% in processed cheese. The proposed method was also applied to incurred sample analysis. The results proved that this method was suitable for the simultaneous determination of nine subclasses of NSAIDs residues in milk and dairy products.

[Determination of three estrogens in animal liver and kidney tissues by liquid chromatography-tandem mass spectrometry].

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the determination of estrone, 17beta-estradiol, estriol in animal liver and kidney tissues. The sample was extracted by tert-butyl methyl ether, and the extract was evaporated by nitrogen at 45 degrees C. The residue was redissolved in hexane-dichloromethane (6:4, v/v), then purified on a silica solid-phase extraction column. The eluant was evaporated by nitrogen, dissolved in acetonitrile-water (7:3, v/v) and then analyzed by LC-MS/MS. The separation of estrogens was performed on a Poroshell 120 EC-C18 column with the mobile phases of acetonitrile and water with a gradient elution. The identification and quantification of estrogens were carried out by negative electrospray ionization in the multiple reaction monitoring mode using external standard method. The calibration curves showed good linearity in the range of 1.0-20.0 microg/kg with the correlation coefficients above 0.99. The limit of quantification was 1.0 microg/kg for each estrogen. The average recoveries of the estrogens spiked at 1.0, 2.0, 10.0 microg/kg levels in different matrices were between 70.2% and 114%, and the relative standard deviations were between 2.01% and 14.5%. The method is simple, rapid, sensitive, good in purification effect. It is suitable for the confirmation and quantification of estrogens in animal liver and kidney tissues.

Simultaneous determination of thirty non-steroidal anti-inflammatory drug residues in swine muscle by ultra-high-performance liquid chromatography with tandem mass spectrometry.

An ultra-high-performance liquid chromatography with tandem mass spectrometric detection (UHPLC-MS/MS) method was established for the simultaneous determination of residues of thirty non-steroidal anti-inflammatory drugs (NSAIDs) in swine muscle. The samples were extracted with acetonitrile and phosphoric acid. The extracts were defatted with n-hexane, and then purified by HLB solid-phase extraction cartridge. Analysis was carried out on UHPLC-ESI-MS/MS working with multiple reaction monitoring mode with polarity switching. Limits of detection were between 0.4 µg/kg and 2.0 µg/kg, and limits of quantification were between 1.0 µg/kg and 5.0 µg/kg. The recoveries of NSAIDs were between 61.7% and 125.7% at spiked levels of 1.0-500 µg/kg. The repeatability was less than 8% and the within-laboratory reproducibility was not more than 12.3%. The method was reliable, convenient and sensitive.