Comprehensive screening and quantification of veterinary drugs in milk using UPLC–ToF-MS

Ultra-performance liquid chromatography combined with time-of-flight mass spectrometry (UPLC–ToF-MS) has been used for screening and quantification of more than 100 veterinary drugs in milk. The veterinary drugs represent different classes including benzimidazoles, macrolides, penicillins, quinolones, sulphonamides, pyrimidines, tetracylines, nitroimidazoles, tranquillizers, ionophores, amphenicols and non-steroidal anti-inflammatory agents (NSAIDs). After protein precipitation, centrifugation and solid-phase extraction (SPE), the extracts were analysed by UPLC–ToF-MS. From the acquired full scan data the drug-specific ions were extracted for construction of the chromatograms and evaluation of the results. The analytical method was validated according to the EU guidelines (2002/657/EC) for a quantitative screening method. At the concentration level of interest (MRL level) the results for repeatability (%RSD < 20% for 86% of the compounds), reproducibility (%RSD < 40% for 96% of the compounds) and the accuracy (80–120% for 88% of the compounds) were satisfactory. Evaluation of the CCβ values and the linearity results demonstrates that the developed method shows adequate sensitivity and linearity to provide quantitative results. Furthermore, the method is accurate enough to differentiate between suspected and negative samples or drug concentrations below or above the MRL. A set of 100 samples of raw milk were screened for residues. No suspected (positive) results were obtained except for the included blind reference sample containing sulphamethazine (88 μg/l) that tested positive for this compound. UPLC–ToF-MS combines high resolution for both LC and MS with high mass accuracy which is very powerful for the multi-compound analysis of veterinary drugs. The technique seems to be powerful enough for the analysis of not only veterinary drugs but also organic contaminants like pesticides, mycotoxins and plant toxins in one single method.     

Multi-residue screening of veterinary drugs in egg,fish and meat using high-resolution liquid chromatography accurate mass time-of-flight mass spectrometry

The last 2 years multi-compound methods are gaining ground as screening methods. In this study a high-resolution liquid chromatography combined with time-of-flight mass spectrometry (HRLC–ToF-MS) is tested for the screening of about 100 veterinary drugs in three matrices, meat, fish and egg. While the results are satisfactory for 70–90% of the veterinary drugs, a more efficient sample preparation or extract purification is required for quantitative analysis of all analytes in more difficult matrices like egg. The average mass measurement error of the ToF-MS for the veterinary drugs spiked at concentrations ranging from 4 to 400 μg/kg, is 3.0 ppm (median 2.5 ppm) with little difference between the three matrices, but slightly decreases with increasing concentration. The SigmaFit value, a new feature for isotope pattern matching, also decreases with increasing concentration and, in addition, shows an increase with increasing matrix complexity. While the average SigmaFit value is 0.04, the median is 0.01 indicating some high individual deviations. As with the mass measurement error, the highest deviations are found in those regions of the chromatogram where most compounds elute from the column, be it analytes or matrix compounds. The median repeatability of the method ranges from 8% to 15%, decreasing with increasing concentration, while the median reproducibility ranges from 15% to 20% with little difference between matrices and concentrations. The median accuracy is in between 70% and 100% with a few compounds showing higher values due to matrix interference. The squared regression coefficient is >0.99 for 92% of the compounds showing a good overall linearity for most compounds. The detection capability, CCβ, is within 2 times the associated validation level for >90% of the compounds studied. By changing a few conditions in the analyses protocol and analysing a number of blank samples, it was determined that the method is robust as well as specific. Finally, an alternative validation strategy is proposed and tested for screening methods. While the results calculated for repeatability, within-lab reproducibility and CCβ show a good comparison for the matrices meat and fish, and a reasonable comparison for the matrix egg, only 27 analyses are required to obtain these results versus 63 analysis in the traditional, 2002/657/EC, approach. This alternative is suggested as a cost-effective validation procedure for screening methods.     

Rapid Screening and Determination of Residual Veterinary Drugs in Milk by Ultrahigh Performance Liquid Chromatography–High-Resolution Quadrupole Time-of-Flight Mass Spectrometry

A rapid screening and determination of 150 veterinary drugs of various classes in milk by UHPLC–high-resolution quadrupole time-of-flight mass spectrometry is proposed. One gram of milk was used for the analysis; the precipitation of proteins and extraction were performed with acetonitrile; the extract was analyzed without purification or preconcentration. Veterinary drugs were identified by accurate masses of analyte ions produced by electrospray ionization, their retention time, and the pattern of ion isotope distribution (mSigma). The quantitative analysis of the detected analytes was carried out by the standard addition method. The limits of detection were 0.1–0.5 ng/g; the analytical ranges were (0.1)1–500 ng/g; the duration of screening was 20–30 min; and the analysis time was 30–40 min. The relative standard deviation of the results for all analytes did not exceed 15%.     

Development of multiple monolithic fiber solid‐phase microextraction and liquid chromatography–tandem mass spectrometry method for the sensitive monitoring of aminoglycosides in honey and milk samples

A simple and sensitive method for the simultaneous extraction and determination of six aminoglycosides in honey and milk samples was developed using multiple monolithic fiber solid‐phase microextraction and liquid chromatography with tandem mass spectrometry. The multiple monolithic fibers based on poly(methacrylic acid‐co‐ethylenedimethacrylate) monolith as the extraction medium was used to concentrate target analytes. Because there were abundant carboxyl groups in the monolith, the monolithic fibers could extract aminoglycosides effectively through cation‐exchange and hydrophobic interactions. To obtain optimum extraction performance, several extraction parameters including desorption solvent, adsorption and desorption time, pH value and ionic strength in sample matrix, were investigated in detail. Under the optimized extraction conditions, the limits of detection of the proposed method were 0.10–0.30 and 0.23–0.59 μg/kg for honey and milk samples, respectively. Satisfactory linearity was achieved for analytes with the coefficients of determination above 0.99. At the same time, the developed method showed acceptable method repeatability and reproducibility. Finally, the proposed method was successfully applied to the determination of aminoglycosides in real honey and milk samples. Recoveries obtained for the determination of six target analytes in spiking samples ranged from 67.9 to 110%, and the relative standard deviations were in the range of 1.2–11%.     

Development and validation of a liquid chromatographic-electrospray tandem mass spectrometric multiresidue method for anthelmintics in milk

A liquid chromatographic-tandem mass spectrometric multiresidue method for the simultaneous quantitative determination of the tetrahydroimidazole, levamisole and the benzimidazoles thiabendazole, oxfendazole, oxibendazole, albendazole, fenbendazole, febantel and triclabendazole in milk has been developed and validated. The anthelmintic residues were extracted with ethyl acetate. The liquid chromatographic separation was performed on a reversed-phase C18 column with gradient elution. The analytes were detected by tandem quadrupole mass spectrometry after positive electrospray ionisation by multiple reaction monitoring. The confirmatory method is very sensitive and each component can be detected at a residue level lower than 1 microgram/l. The method is validated according to the revised European Union requirements and all parameters were found conform the criteria. The evaluated parameters were linearity, specificity, stability, recovery, precision (repeatability and within-laboratory reproducibility) and analytical limits (detection limit, decision limit and detection capability). This analytical method is applied in the Belgian monitoring programme for classical anthelmintic veterinary drugs in raw farm cow's milk.     

Fluoroquinolone antibiotic determination in bovine,ovine and caprine milk using solid-phase extraction and high-performance liquid chromatography-fluorescence detection with ionic liquids as mobile phase additives

This paper describes the use of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIm-BF₄) as mobile phase additive for the analysis by high-performance liquid chromatography with fluorescence detection of a group of seven basic fluoroquinolone antibiotics (i.e. fleroxacin, ciprofloxacin, lomefloxacin, danofloxacin, enrofloxacin, sarafloxacin and difloxacin) in different milk samples. EMIm-BF₄ was found superior to 1-butyl-3-methylimidazolium tetrafluoroborate for the separation of the analytes from chromatographic interferences of the sample matrix. The optimized method was applied to the analysis of ovine, caprine and bovine milk, in the last case in either skimmed, semi-skimmed and full-cream milk after suitable acidic deproteination followed by a solid-phase extraction procedure. Recovery values between 73% and 113% were obtained for the three types of bovine milk samples, as well as for ovine and caprine milk (RSDs below 16% in all cases), which clearly demonstrates the applicability of the method to the three types of milk irrespective of the fat content of the samples. Limits of detection were in the range of 0.5–8.1 μg/L (approximately 0.5–25.9 μg/kg), well below the maximum residue limits established for these compounds by the current European legislation. A screening study of 24 different milk samples was also developed. In none of the samples, residues of the selected antibiotics were found.     

Generic sample preparation combined with high-resolution liquid chromatography–time-of-flight mass spectrometry for unification of urine screening in doping-control laboratories

A unification of doping-control screening procedures of prohibited small molecule substances—including stimulants, narcotics, steroids, β2-agonists and diuretics—is highly urgent in order to free resources for new classes such as banned proteins. Conceptually this may be achieved by the use of a combination of one gas chromatography–time-of-flight mass spectrometry method and one liquid chromatography–time-of-flight mass spectrometry method. In this work a quantitative screening method using high-resolution liquid chromatography in combination with accurate-mass time-of-flight mass spectrometry was developed and validated for determination of glucocorticosteroids, β2-agonists, thiazide diuretics, and narcotics and stimulants in urine. To enable the simultaneous isolation of all the compounds of interest and the necessary purification of the resulting extracts, a generic extraction and hydrolysis procedure was combined with a solid-phase extraction modified for these groups of compounds. All 56 compounds are determined using positive electrospray ionisation with the exception of the thiazide diuretics for which the best sensitivity was obtained by using negative electrospray ionisation. The results show that, with the exception of clenhexyl, procaterol, and reproterol, all compounds can be detected below the respective minimum required performance level and the results for linearity, repeatability, within-lab reproducibility, and accuracy show that the method can be used for quantitative screening. If qualitative screening is sufficient the instrumental analysis may be limited to positive ionisation, because all analytes including the thiazides can be detected at the respective minimum required levels in the positive mode. The results show that the application of accurate-mass time-of-flight mass spectrometry in combination with generic extraction and purification procedures is suitable for unification and expansion of the window of screening methods of doping laboratories. Moreover, the full-scan accurate-mass data sets obtained still allow retrospective examination for emerging doping agents, without re-analyzing the samples.     

固相萃取-超高效液相色谱-串联质谱法同时测定动物源性食品中11种禁限兽药及代谢物

建立了固相萃取-超高效液相色谱-串联质谱(SPE-UPLC-MS/MS)同时检测鸡蛋、液态奶、鸡肉及淡水鱼中4类(氯霉素类、硝基咪唑类、林可酰胺类与大环内酯类)8种禁限兽药与3种代谢物残留的分析方法.对样品前处理及色谱条件进行优化,样品经0.1 mol/L pH 9.0的磷酸盐缓冲液水解分散,乙腈提取,提取液经乙酸乙酯...     

Determination of organochlorine pesticides in complex matrices by single-drop microextraction coupled to gas chromatography-mass spectrometry

A rapid and simple single-drop microextraction method (SDME) has been used to preconcentrate eighteen organochlorine pesticides (OCPs) from water samples with a complex matrix. Exposing two microlitre toluene drop to an aqueous sample contaminated with OCPs proved an excellent preconcentration method prior to analysis by gas chromatography-mass spectrometry (GC-MS). A Plackett-Burman design was used for screening and a central composite design for optimizing the significant variables in order to evaluate several possibly influential and/or interacting factors. The studied variables were drop volume, aqueous sample volume, agitation speed, ionic strength and extraction time. The optimum experimental conditions of the proposed SDME method were: 2 μL toluene microdrop exposed for 37 min to 10 mL of the aqueous sample containing 0% w/v NaCl and stirred at 380 rpm.The calculated calibration curves gave high-level linearity for all target analytes with correlation coefficients ranging between 0.9991 and 0.9999. The repeatability of the proposed method, expressed as relative standard deviation, varied between 5.9 and 9.9% (n = 8). The detection limits were in the range of 0.022-0.101 μg L⁻¹ using GC-MS with selective ion monitoring. The LOD values obtained are able to detect these OCPs in aqueous matrices as required by EPA Method 625. Analysis of spiked effluent wastewater samples revealed that the matrix had no effect on extraction for eleven of the analytes but exerted notable effect for the other analytes.     

Multi-residue determination of 115 veterinary drugs and pharmaceutical residues in milk powder,butter, fish tissue and eggs using liquid chromatography–tandem mass spectrometry

A simple and sensitive multi-residue method for the determination of 115 veterinary drugs and pharmaceuticals, belonging in more than 20 different classes, in butter, milk powder, egg and fish tissue has been developed. The method involves a simple generic solid–liquid extraction step (solvent extraction, SE) with 0.1% formic acid in aqueous solution of EDTA 0.1% (w/v)–acetonitrile (ACN)–methanol (MeOH) (1:1:1, v/v) with additional ultrasonic-assisted extraction. Precipitation of lipids and proteins was promoted by subjecting the extracts at very low temperature (−23 °C) for 12 h. Further cleanup with hexane ensures fat removal from the matrix. Analysis was performed by liquid chromatography coupled with electrospray ionization and tandem mass spectrometry (LC-ESI-MS/MS). Two separate runs were performed for positive and negative ionization in multiple reaction monitoring mode (MRM). Particular attention was devoted to extraction optimization: different sample-to-extracting volume ratios, different concentrations of formic acid in the extraction solvent and different ultrasonic extraction temperatures were tested in butter, egg and milk powder samples. The method was also applied in fish tissue samples. It was validated, on the basis of international guidelines, for all four matrices. Quantitative analysis was performed by means of standard addition calibration. For over 80% of the analytes, the recoveries were between 50% and 120% in all matrices studied, with RSD values in the range of 1–18%. Limits of detection (LODs) and quantification (LOQs) ranged from 0.008 μg kg⁻¹ (oxfendazole in butter) to 3.15 μg kg⁻¹ (hydrochlorthiazide in egg). The evaluated method provides reliable screening, quantification, and identification of 115 veterinary drug and pharmaceutical residues in foods of animal origin and has been successfully applied in real samples.     

Food contaminant analysis at high resolution mass spectrometry: application for the determination of veterinary drugs in milk

Veterinary drugs (VDs) can remain in milk as a consequence of their use in livestock. In order to control the levels of VD residues in milk, screening methodologies can be applied for a rapid discrimination among negative and non-negative samples. In a second stage, non-negative samples are classified as negative or positive samples by using a confirmation method. Pre-target screening methods in low resolution MS (LRMS) are normally applied, but the number of analytes is limited, whereas the information obtained by full scan acquisition in high resolution mass spectrometry (HRMS) is improved. Here, three screening methods (running time<4 min) based on Orbitrap, quadrupole-time of flight (QqTOF) and triple quadrupole (QqQ) have been compared, using in all cases ultra-high performance liquid chromatography (UHPLC). For HRMS, the identification of the VDs was based on retention time (RT) and accurate mass measurements. Confirmation was based on the monitoring of fragments generated without precursor selection. The performance characteristics of the screening method provided reliable information regarding the presence or absence of the compounds below an established value, including uncertainty region and cut-off values. Better results in terms of cut-off values (≤ 5.0 μg kg(-1), except for spiramycin with a cut-off of 13.4 μg kg(-1) for milk samples and 43.1 μg kg(-1) for powdered milk based, emamectin with a cut-off of 42.2 μg kg(-1) for milk samples and doxycycline, with a cut-off value of 15.8 μg kg(-1) in powdered milk-based infant formulae) and uncertainty region were obtained using the Orbitrap-based screening method, which was submitted to further validation and used to analyze different real milk samples. The proposed method can be used in routine analysis, providing reliable results.     

Multiclass and multiresidue screening of veterinary drugs and pesticides in infant formula using Quadrupole‐Orbitrap MS with PRM scan mode

A multiclass and multiresidue method for screening veterinary drugs and pesticides in infant formula was developed and validated using ultrahigh‐performance liquid chromatography coupled to Quadrupole‐Orbitrap high‐resolution mass spectrometry (UHPLC‐HRMS). A total of 49 veterinary drugs and pesticides investigated belong to 11 classes including antivirals, anticoccidials, macrolides, pyrethroids, insecticides, sulfonamides, beta‐agonists, sedatives, thyreostats, nonsteroidal anti‐inflammatory drugs, and other pharmacologically active substances. A generic sample preparation and highly selective acquisition mode of parallel reaction monitoring (PRM) were deliberately incorporated to perform efficient screening analysis. As a result, the screening target concentrations of the analytes varied from 1 to 500 μg/kg with ≤5% of false compliant rate as specified in Decision 2002/657/EC for screening analysis. The average recoveries ranged from 40.7 to 124.9% as well as the relative standard deviations from 4.2 to 26.6%, respectively. The matrix effects and interferences were effectively controlled by integrated application of dispersive solid phase extraction, PRM scan mode, and matrix‐matched standard calibration. The proposed method will be helpful to provide applicable strategy for screening residues in infant formula with surveillance purpose.     

Multiresidue Screening of Veterinary Drugs in Meat,Milk, Egg,and Fish Using Liquid Chromatography Coupled with Ion Trap Time-of-Flight Mass Spectrometry

New approaches to veterinary drug screening based on liquid chromatography-mass spectrometry (LC-MS/MS) and time-of-flight mass spectrometry (ToF/MS) are rapid and have high selectivity and sensitivity. In this study, we developed a multiresidue method for screening over 100 veterinary drug residues using ion trap (IT)-ToF/MS. The screened compounds comprised major drug classes used in veterinary practice, representing the following: amphenicols, anthelmintics, benzimidazoles, β-lactams, coccidiostats, ionophores, macrolides, non-steroidal anti-inflammatory drugs, quinolones, sulfonamides, tetracyclines, and tranquilizers. The method was developed based on chromatographic retention time, specific accurate mass, isotope distribution, and fragment data. Each compound was validated at three levels, and the mass accuracy, accuracy, and repeatability were calculated. All parameters showed acceptable values and conformed to the Commission Decision 2002/657/EC criteria. This screening method can simultaneously analyze over 100 veterinary drugs in meat, milk, eggs, and fish in a single analytical run.     

Ultrasound‐assisted magnetic dispersive solid‐phase microextraction: A novel approach for the rapid and efficient microextraction of naproxen and ibuprofen employing experimental design with high‐performance liquid chromatography

A simple, rapid, and sensitive method for the determination of naproxen and ibuprofen in complex biological and water matrices (cow milk, human urine, river, and well water samples) has been developed using ultrasound‐assisted magnetic dispersive solid‐phase microextraction. Magnetic ethylendiamine‐functionalized graphene oxide nanocomposite was synthesized and used as a novel adsorbent for the microextraction process and showed great adsorptive ability toward these analytes. Different parameters affecting the microextraction were optimized with the aid of the experimental design approach. A Plackett–Burman screening design was used to study the main variables affecting the microextraction process, and the Box–Behnken optimization design was used to optimize the previously selected variables for extraction of naproxen and ibuprofen. The optimized technique provides good repeatability (relative standard deviations of the intraday precision 3.1 and 3.3, interday precision of 5.6 and 6.1%), linearity (0.1–500 and 0.3–650 ng/mL), low limits of detection (0.03 and 0.1 ng/mL), and a high enrichment factor (168 and 146) for naproxen and ibuprofen, respectively. The proposed method can be successfully applied in routine analysis for determination of naproxen and ibuprofen in cow milk, human urine, and real water samples.     

Optimization and validation of a multiclass screening and confirmation method for drug residues in milk using high-performance liquid chromatography/tandem mass spectrometry

The further optimization and validation of a multiresidue veterinary drug screening method for milk is described. The drug residues of regulatory interest in milk include beta-lactams, sulfonamides, tetracyclines, fluoroquinolones, and macrolides. A previously published procedure has been modified to incorporate new compounds and to collect both screening and confirmatory ion transitions in one acquisition method. Milk samples were extracted with an equal volume of acetonitrile. The samples were then subjected to cleanup with a bonded SPE cartridge and a MW cutoff filter. The SPE protocol was modified to effectively recover a metabolite of flunixin. Established tolerance levels are set for most of these drugs in milk; thus, the screening procedure was semiquantitative, using positive controls for comparison. The positive controls, consisting of extracts from milk fortified with the drugs at their tolerance or safe level, were used to set statistically valid minimum response criteria for unknown samples. This updated method was validated with fortified milk, as well as with milk samples from animals administered veterinary drugs.     

Ultra-performance liquid chromatography coupled to time of flight mass spectrometry (UPLC-TOF): a novel tool for multiresidue screening of veterinary drugs in urine

A multiresidue method for the screening of veterinary drugs in urine with ultra-performance liquid chromatography (UPLC) coupled to time of flight mass spectrometry (TOF) is proposed. The method covers currently more than 100 analytes belonging to different families of veterinary drugs. Urine samples are simply diluted and injected unfiltered into the UPLC-TOF. The short run time permit high-throughput of large series under a routine environment. The suggested approach includes the detection of some metabolites which are relevant to the urine matrix. The paper discusses the usefulness of metabolites as additional confirmation criteria for positive findings and suggests a revisiting of the identification point system in the light of additional resolution, as provided by the TOF and the UPLC technology. The proposed multiresidue approach was further broadened by monitoring drug group specific collision induced fragments (CID). Examples show the monitoring of generic CID fragments typical for sulfonamides and penicillins.     

Development of a Quantitative Method for Detection of Multiclass Veterinary Drugs in Feed Using Modified QuPPe Extraction and LC–MS/MS

A method was developed for the rapid and quantitative analysis of 30 veterinary drugs belonging to 17 classes (amphenicols (1), anthelmintics (1), cephalosporins (4), coccidiostats (1), lincosamides (1), macrolide (1), nitroimidazole (1), penicillins (3), phenylhydrazines (1), polypeptides (1), pyrethrins (1), quinolones (5), sulfonamides (3), tetracycline (3), neuroleptic agents (1), triazene trypanocidal agents (1), other. (1)) in feeds. The proposed method with a modified Quick Polar Pesticides (QuPPe) sample preparation was validated for the determination of 30 veterinary drugs in feed samples by liquid chromatography triple-quadrupole mass spectrometry (LC–MS/MS). The sample was extracted with methanol containing 1% acetic acid and purified by dispersive solid-phase extraction (d-SPE) with C18. Good linearity (r² ≥ 0.98) was observed, and the LOQ values ranged from 10 to 200 µg/kg. Average recoveries ranged from 70.8 to 118.4%, and the relative standard deviation was ≤ 18.7%. This validated method was used in the determination of 30 veterinary drugs in 142 feed samples obtained from South Korea. The results show that lincomycin was present in only one of the tested feed samples, although it was detected at a value lower than the LOQ. In conclusion, this multi-residue method can be used for screening through the detection and quantitation of residual multiclass veterinary drugs in feed samples.     

Development of fast screening methods for the analysis of veterinary drug residues in milk by liquid chromatography-triple quadrupole mass spectrometry

Two rapid multi-residue screening methods for the determination of 21 veterinary drugs in milk by ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) have been developed and compared. For both methods, veterinary drugs were extracted from milk samples using a rapid extraction procedure based on the modification of the well-known QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method, and no further clean-up steps were necessary. One screening method was based on the selection of a characteristic neutral loss or product ion of the various families of compounds, whereas another one was based on the choice of a selected reaction monitoring (SRM) for each compound. These methods were compared with regards to false negatives, cut-off values and the unreliability region. The total run time for both methods was 3 min, allowing quick selection of samples that contained veterinary drugs. Non-negative samples were re-analyzed by the UHPLC-MS/MS confirmation/quantification method, which consisted in the monitoring of two SRM for each compound. The methods were validated according to international guides. The proposed analytical methods allow for the identification and confirmation of the target veterinary drugs at trace levels employing quick analysis time.     

超高效液相色谱-四极杆-飞行时间质谱法快速筛查牛奶中的农药和兽药残留

利用超高效液相色谱-四极杆-飞行时间质谱(UPLC-Q-TOF-MS)技术建立了牛奶中42种农药和兽药残留的快速检测方法。目标药物包括常用的13种农药和29种兽药,采用QuEChERS（Quick, Easy, Cheap, Effective, Rugged, and Safe）方法进行样品前处理。牛奶样品经含1%甲酸的乙腈溶液提取,同时加入无水硫酸钠和氯化钾盐析,提取液经C18填料净化后直接测定。目标药物经ACQUITY UPLCTMBEH C18柱分离,以乙腈和0.1%甲酸水溶液为流动相进行梯度洗脱,采用正离子全信息串联质谱扫描模式(MSE)进行检测。结果表明,牛奶中42种农药和兽药的定量限(LOQ, S/N=10)为1～100 μg/kg; 3个加标水平的平均回收率为68.2%～129.1%,相对标准偏差为2.8%～30.8%。该方法快速简便、灵敏度较高,可用于牛奶中42种农兽药的快速筛查。     

Determination of melamine residues in milk products by zirconia hollow fiber sorptive microextraction and gas chromatography–mass spectrometry

News stories about the contamination of milk with melamine in China emerged on Sept 11, 2008, and the situation has since become an international health scare. In this work, a novel analytical method based on enrichment and pretreatment of analytes in the milk sample, hollow fiber sorptive extraction and gas chromatography–mass spectrometry has been developed for the rapid analysis of melamine in the dairy products. In the proposed method, melamine in the fresh milk was extracted by zirconia hollow fiber, enriching on zirconia coating of the hollow fiber, and then analyzed by GC–MS. The method validations including linearity, limit of detection, limit of qualification, recoveries at three different concentrations, precision, and repeatability were investigated. It was found that the proposed method provided linear range from 0.001 to 1000 μg/mL (r² = 0.9997), low detection limit of 0.001 μg/mL, and preferable recoveries at three different concentrations. The obtained results demonstrated that zirconia hollow fiber combined with GC–MS is a simple, rapid and solvent-free method for the analysis of melamine in the dairy products.