An original approach to determining traces of tetracycline antibiotics in milk and eggs by solid-phase extraction and liquid chromatography/mass spectrometry

An original and highly specific method able to identify and quantify traces of five tetracycline antibiotics (TCAs) in milk and eggs is presented. This method uses a single solid-phase extraction (SPE) cartridge for simultaneous extraction and purification of TCAs in the above matrices. After diluting 5 mL of intact whole milk or 2 g egg samples with Na(2)EDTA-containing water, samples are passed through a 0.5-g Carbograph 4 extraction cartridge. After analyte elution from the SPE cartridge, an aliquot of the final extract is injected into a liquid chromatography/mass spectrometry (LC/MS) instrument equipped with an electrospray ion source and a single quadrupole. MS data acquisition is performed in the positive-ion mode and by a time-scheduled multiple-ion selected ion-monitoring program. With methanol as organic modifier, the in-source collision-induced dissociation (CID) process generated fragment ions able to pick up one methanol molecule. In several cases, these methanol-adduct fragment ions have m/z values higher than those of the protonated molecules. This event is rarely encountered in MS, thus making the analysis of TCAs by this method extremely specific. Compared with a conventional published method, the present protocol extracted larger amounts of TCAs from both milk and egg and decreased the analysis time by a factor of 3. Recovery of TCAs in milk at the 25-ppb level ranged between 81 and 96% with relative standard deviation (RSD) no larger than 9%. Recovery of TCAs in egg at the 50-ppb level ranged between 72 and 92% with RSD no larger than 7%. Estimated limits of quantification(S/N = 10) of the method were 2-9 ppb TCAs in whole milk and 2-19 ppb TCAs in eggs.     

Determination of enrofloxacin and its metabolite ciprofloxacin in goat milk by high-performance liquid chromatography with diode-array detection. Optimization and validation

A high-performance liquid chromatography-diode array detection method (HPLC-DAD) combined with liquid chromatography-mass spectrometry was developed for the determination of enrofloxacin and its metabolite ciprofloxacin in goat milk. The HPLC-DAD method validation was compliant with the "DG SANCO 1805/2000" European regulation. The residues were extracted from milk with phosphate buffer, purified on a C18 Speedisk cartridge SPE (Baker) and then analysed using HPLC-DAD set at 277 nm. The decision limit (CCa) calculated by spiking samples at 100 microg/kg with both analytes, taking into account the maximum residue limit (MRL) of 100 microg/kg established by the European Union for the sum of enrofloxacin and its metabolite ciprofloxacin in milk, was 105.3 microg/kg for enrofloxacin and 105.5 microg/kg for ciprofloxacin. The detection capability (CCbeta) was 110.7 and 110.9 microg/kg for enrofloxacin and ciprofloxacin, respectively. The mean recoveries of the method, calculated by spiking samples at 50, 100 and 150 microg/kg were 84% for enrofloxacin and 88% for ciprofloxacin. The limit of quantification was 20 microg/kg for both analytes. The HPLC-DAD validated method was successfully applied for the first time in goats milk, and proved to be suitable for the sensitive and accurate quantification and confirmation analysis of enrofloxacin and ciprofloxacin for regulatory purposes.     

Simultaneous determination of tetracylines and quinolones antibiotics in egg by ultra-performance liquid chromatography-electrospray tandem mass spectrometry

We report here an ultra-performance liquid chromatography coupled with tandem mass spectrometric (MS/MS) method for the simultaneous quantitation of multiclass veterinary drugs in egg. The analysis of the target compounds, including 7 tetracyclines and 4 types of quinolones, may be accomplished in 15 min of total run time. The egg was extracted with ethylenediaminetetraacetic acid-Mcllvaine buffer solution and further purified using a polymer-based Oasis HLB solid-phase extraction cartridge. A C18 column was used to separate the analytes followed by MS/MS using an electrospray ion source. The overall average recoveries of the analytes based on matrix-fortified calibration ranged from 71 to 112% with acceptable relative standard deviations of <20% for 6 trials. For all of the target compounds, the limits of quantitation ranged between 0.02 and 4.29 microg/kg. The proposed method is sufficiently sensitive and highly selective.     

Determination of chloramphenicol in bovine milk by liquid chromatography/tandem mass spectrometry

A rapid confirmatory liquid chromatographic/tandem mass spectrometic method was developed for determination of chloramphenicol in bovine milk. Chloramphenicol was extracted directly from milk by solid-phase extraction on a C18 cartridge. The extract was further cleaned up on neutral aluminium oxide. Three transition products were monitored in negative ion mode after atmospheric pressure chemical ionization. The detection capability related to the transition product of lowest abundance was 0.03 microg/kg. The mean recovery was 90% at levels of 0.1-0.2 microg/kg. The relative repeatability standard deviations were 4.3, 3.8, and 2.8% at levels of 0.1, 0.2, and 1.0 microg/kg, respectively.     

Validation of a high-performance liquid chromatography method for the determination of oxytetracycline,tetracycline, chlortetracycline and doxycycline in bovine milk and muscle

High-performance liquid chromatography with diode-array detection (HPLC-DAD) was optimised and validated for the determination of tetracyclines in bovine milk and tissues. Milk and tissue samples were extracted and purified using a solid-phase extraction HLB Oasis cartridge and analysed using HPLC-DAD set at 365 nm. The analyses were carried out using the mobile phase of 0.01 M oxalic acid-acetonitrile-methanol (60:25:15, v/v/v) on a C8 column (250 x 4.6 mm I.D., 5 microm). Recoveries of tetracyclines from spiked samples at the three concentrations (0.5, 1 and 1.5) of the maximum residues limits (corresponding to 100 microg/kg for milk and the muscle) were higher than 81.1% in milk and 83.2% in muscle. The method was successfully validated for bovine milk and muscle in compliance with requirements set by draft SANCO/ 1805/ 2000 European Decision. The decision limit (CCalpha) was in the range 113.2-127.2 microg/kg and 107.7-129.9 micro/kg for all compounds in milk and muscle, respectively. The detection capability (CCbeta) was in the range 117.2-131.3 microg/kg and 114.9-133.1 microg/kg for all compounds in milk and muscle, respectively.     

固相萃取-高效液相色谱-串联质谱法同时测定牛奶和羊奶中莫奈太尔及其代谢产物残留

建立了高效液相色谱-串联质谱快速测定牛奶和羊奶中莫奈太尔及其代谢产物残留量的分析方法。样品经乙腈沉淀蛋白质,中性氧化铝固相萃取柱净化,以Inertsil C8-3（150 mm×4.6 mm,5 μm）色谱柱分离,甲醇-乙酸铵溶液为流动相进行梯度洗脱,采用电喷雾负离子监测模式检测,外标法定量。结果表明,在0.1~5.0 μg/L范围内,待测物色谱峰面积与其质量浓度间的线性关系良好（相关系数均大于0.99）,定量限为2.0 μg/kg。莫奈太尔及其代谢产物在2类基质中3个水平（2.0、50和100 μg/kg）下的加标回收率为90.1%~103.3%,相对标准偏差（RSD）为2.0%~6.2%（n=6）。该方法操作简便、快速,灵敏度高,抗干扰能力强,回收率和重复性良好,能够满足牛奶和羊奶中莫奈太尔及其代谢产物残留量的检测要求。     

超高效液相色谱-串联电喷雾四极杆质谱法同时测定牛奶中12种糖皮质激素的残留

采用超高效液相色谱-串联电喷雾四极杆质谱(负离子模式)在多反应监测(MRM)模式下测定了牛奶中12种糖皮质激素的残留。试样中加入pH 5.20的醋酸盐缓冲溶液和甲醇,超声提取,以去除部分蛋白质,然后用正己烷脱脂,依次经HLB柱、硅胶柱和氨基柱等固相萃取柱浓缩和净化后,通过Waters ACQUITY UPLCTM BEH C18色谱柱分离,以甲醇和含0.1%甲酸的水为流动相进行梯度洗脱。在超高效液相色谱-质谱分析过程中以保留时间和离子对(母离子和两个碎片离子)信息比较进行定性,以母离子和响应值高的碎片离子进行定量。该法的检出限为0.02～0.38 μg/kg,最低定量限为0.07～1.27 μg/kg。添加水平为2 μg/kg和0.4 μg/kg时,12种糖皮质激素的加标回收率为69.3%～94.3%,相对标准偏差为3.5%～16.7%。     

Multiresidue determination of organochlorine pesticides and polychlorinated biphenyls in milk by gas chromatography with electron-capture detection after extraction by matrix solid-phase dispersion

A multiresidue analytical method based on matrix solid-phase dispersion was developed to analyze liquid milk for 22 organochlorine pesticides (OCPs) and 6 polychlorinated biphenyls (PCBs). Initial extraction is performed by loading 3 mL milk onto a 2.0 g octadecyl (C18)-bonded silica cartridge with n-hexane as the eluant. Neutral alumina column chromatography with sodium sulfate as the drying agent is used for further cleanup. The eluate is concentrated to 0.5 mL, and target analytes are determined by capillary gas chromatography with electron-capture detection. The optimized method was validated by determining accuracy (recovery percentages), precision (repeatability and reproducibility), and sensitivity (detection and quantitation limits) from analyses of milk samples fortified at 10 and 1 microg/L levels. Average recoveries were between 74 and 106% for all residues except beta-HCH, beta-endosulfan, and endosulfan sulfate. Both repeatability and reproducibility relative standard deviation values were < 22% for all residues. Detection limits ranged from 0.02 to 0.12 microg/L and quantitation limits were between 0.02 and 0.62 microg/L. The proposed analytical method may be used as a fast and simple procedure in routine determinations of OCPs and PCBs in milk.     

气相色谱-质谱法测定动物组织中三种1,2-二苯乙烯类药物的残留量

建立了动物组织中己烯雌酚(DES)、己二烯雌酚(DIS)和己烷雌酚(HS)残留量的气相色谱-质谱分析方法。动物组织样品在碱性条件下用乙酸乙酯提取,经碳酸钠溶液液-液分配净化,再用硅胶柱固相萃取净化,洗脱液均分成两份后经氮气吹干,分别用双三甲基硅基三氟乙酰氨(BSTFA)和七氟丁酸酐(HFBA)衍生,采用选择离子监测模式(SIM)进行测定,外标法定量。检出限为0.30 μg/kg(cis-DES),0.10 μg/kg(trans-DES和HS)和0.15 μg/kg(DIS)。在0.5~4.0 μg/kg添加水平,回收率为73.0%～86.5%,相对标准偏差(RSD)为1.0%～7.2%。衍生物的峰面积与样品浓度在10～1000 μg/L(DES和DIS) 和5～500 μg/L(HS)范围内呈良好的线性关系,线性回归系数大于0.99。     

Validated method for determination of ultra-trace closantel residues in bovine tissues and milk by solid-phase extraction and liquid chromatography-electrospray ionization-tandem mass spectrometry

A liquid chromatographic-electrospray ionisation-tandem mass spectrometry method (LC-ESI-MS/MS) with solid extraction was developed and validated for the detection and determination of closantel residues in bovine tissues and milk. An acetonitrile-acetone mixture (80:20, v/v) was used for one-stage extraction of closantel residues in bovine tissues and milk samples, and the extract was cleaned by solid phase extraction with Oasis MAX cartridges. The mass spectrometer was operated in multiple reactions monitoring mode with negative electrospray interface. The limits of detection in different matrices were in the range of 0.008-0.009 microg/kg. The overall recoveries for bovine muscle, liver, kidney and milk samples spiked at four levels including MRL were in the range of 76.0-94.3%. The overall relative standard deviations were in the range of 3.57-8.61%. The linearity is satisfactory with a correlation coefficient (r(2)) of 0.9913-0.9987 at both concentration ranges of 0.02-100 microg/kg and 200-5000 microg/kg. The method is capable of identifying closantel residues at > or =0.02 microg/kg levels and was applied in the determination of closantel residues in animal origin foods.     

Quantitative determination of five ergot alkaloids in rye flour by liquid chromatography-electrospray ionisation tandem mass spectrometry

A confirmatory method for detecting five ergot alkaloids, ergocristine, ergotamine, ergonovine, ergocornine and alpha-ergokryptine, in rye flour is described using high performance liquid chromatography coupled to tandem mass spectrometry detection by monitoring two transition reactions per analyte. The procedure entails a liquid-liquid extraction followed by a clean-up step using a C18 solid-phase extraction (SPE) cartridge. An analogue compound, methysergide hydrogen maleinate, was used to assess both repeatability sample preparation and potential MS response fluctuations. The method was fully validated according to the European Union (EU) criteria. Detection and quantification limits of all analytes were calculated ranging from 7 to 11 microg/kg and from 23 to 37 microg/kg, respectively. Fifteen rye flour samples were investigated with the newly developed method, and none of them were above the current Swiss limits of 200mg/kg for total ergot alkaloids.     

Validation of a confirmatory method for the determination of residues of four nitrofurans in egg by liquid chromatography-tandem mass spectrometry with the software InterVal

A method for the detection and determination of nitrofuran derivatives in egg by liquid chromatography-tandem mass spectrometry (LC-MS/MS) was validated with the software InterVal and can be applied for the confirmation of nitrofuran metabolites in fresh or lyophilised eggs. The validation study comprises variations in operator, storage condition, breeding, equipment and duration of sample preparation. A comprehensive overview of the robustness of the method is obtained by analysing eight samples at six concentration levels. First results of short- and medium-term investigations for stability of analytes in solution show that standard solutions of nitrofuran metabolites are stable for at least 1 year when stored at +4 degrees C in the dark. The decision limit CCalpha expressed for the underivatised metabolite is 0.05 microg kg(-1) for 3-amino-5-methyl-morpholino-2-oxazolidinone, 0.03 microg kg(-1) for 3-amino-2-oxazolidinone, 0.20 microg kg(-1) for semicarbazide and 0.22 microg kg(-1) for 1-amino-hydantoin.     

Aflatoxin M1 determination in cheese by liquid chromatography-tandem mass spectrometry

A new method for determining aflatoxin M1 (AFM1) in cheese by liquid chromatography-tandem mass spectrometry has been developed. Two methodologies were compared for sample extraction. The first one involves sample extraction with dichloromethane for hard, aged cheese or acetone for fresh cheese and includes a preliminary matrix solid-phase dispersion-extraction step before solid-phase extraction (SPE) clean-up by a Carbograph-4 cartridge. The second method uses a water/methanol solution (90:10, v/v) extraction at 150 degrees C before clean-up. The average recoveries of AFM1 from samples spiked at levels of 0.25-0.45 microg/kg, were 81-92% and the precision (RSD) ranged from 3 to 7% with the first method, whilst the average recoveries were 79-84%, and RSD ranged from 7 to 15% for the second method. Due to different matrix effect, the quantification limits were 0.019-0.025 microg/kg in the first case and 0.048-0.143 microg/kg in the second one, depending on cheese typology.     

冷诱导液液萃取-分散固相萃取净化-超高效液相色谱-串联质谱法同时测定鸡蛋中白僵菌素和4种恩镰孢菌素残留

新型生物毒素白僵菌素(BEA)和恩镰孢菌素(ENNs)是由镰刀菌种产生的有毒代谢产物,主要污染谷物及其制品,会威胁人类健康,因此受到人们越来越多的关注。该工作建立了冷诱导液液萃取-分散固相萃取净化-超高效液相色谱-串联质谱法(CI-LLE-DSPE-UPLC-MS/MS)同时测定鸡蛋中白僵菌素和4种恩镰孢菌素残留的分析方法。以乙腈-水-乙酸(79∶20∶1, v/v/v)为提取溶剂,采用冷诱导液液萃取与分散固相萃取净化相结合的方法进行样品处理,同时,对影响待测物提取与净化效率的提取溶剂、冷冻萃取温度与时间、净化剂用量等因素和色谱条件进行了优化。样品经20 mL提取液涡旋提取20 min,放入-40 ℃冰箱静置30 min后,取2 mL上层溶液经70 mg C18粉末净化,离心,上清液于40 ℃浓缩至近干,残留物用1 mL 80%(v/v)乙腈水溶液溶解,进样分析。以乙腈与5 mmol/L甲酸铵溶液作为流动相进行梯度洗脱,经ACQUITY UPLC BEH C18色谱柱(100 mm×2.1 mm, 1.7 μm)分离,采用ESI⁺电离,在多反应监测模式下采集,白僵菌素采用稳定同位素内标法定量,4种恩镰孢菌素采用基质匹配曲线外标法定量。结果表明,5种待测物在0.1~50.0 μg/L范围内线性关系良好,相关系数(r²)为0.9983~0.9997,该方法的检出限(LOD)为0.05~0.15 μg/kg,定量限(LOQ)为0.20~0.50 μg/kg。以阴性鸡蛋样品为基质,在低、中、高3个浓度水平(0.5、5.0、25.0 μg/kg)下进行加标试验考察方法的准确度与精密度,各待测物的平均回收率为81.1%~106%,相对标准偏差(RSD)为0.27%~9.79%。采用所建立的方法对农村散养鸡蛋与市售鸡蛋进行检测,结果表明,BEA在散养鸡蛋的检出率为30.4%, 4种ENNs均未被检出。该方法灵敏度高,稳定性好,回收率高,定量准确,简单易操作,适用于禽蛋食品中白僵菌素与恩镰孢菌素的同时快速测定。     

固相萃取-高效液相色谱法同时测定牛奶中22种磺胺类兽药残留

建立了一种基于固相萃取技术同时测定牛奶中22种磺胺类兽药残留的高效液相色谱分析方法.样品经乙腈-甲酸混合溶液提取,乙腈饱和的正己烷除酯后,HLB固相萃取柱净化,以甲醇-2 mmol/L乙酸铵(含0.2％乙酸)为流动相进行梯度洗脱,XBridge C18色谱柱进行分离,采用光电二极管阵列检测器检测,外标法定量.磺胺类化合...     

Development of a rapid and sensitive method for the simultaneous determination of 1,2-dibromoethane, 1,4-dichlorobenzene and naphthalene residues in honey using HS-SPME coupled with GC-MS

A new method for the simultaneous determination of 1,4-dichlorobenzene (p-DCB), naphthalene and 1,2-dibromoethane (1,2-DBE) residues in honey has been developed. Analysis is carried out using gas chromatography-mass spectrometry (GC/MS) in selected ion monitoring mode (SIM), after extraction and preconcentration of target analytes by headspace solid-phase microextraction (HS-SPME), with a 100 microm film thickness polydimethylsiloxane (PDMS) fiber. Several parameters affecting the extension of the adsorption process (i.e., addition of salt, extraction time, extraction temperature) were studied. The optimal conditions for the determination of these analytes were established. The proposed HS-SPME method showed good sensitivity, without carryover between the samples. Linearity was studied from 5 to 2500 microg kg(-1) for p-DCB, 0.5 to 500 microg kg(-1) for naphthalene and 5 to 500 microg kg(-1) honey for 1,2-DBE with correlation coefficients (r(2)) ranging from 0.9901 to 0.9999. Precision was assessed and both intra and inter-day R.S.D.s (%) were below 6.3%. The detection limits were found to be 1, 0.1 and 2 microg kg(-1) honey for p-DCB, naphthalene and 1,2-DBE, respectively. The percentage recoveries that were evaluated with the proposed HS-SPME method and the standard addition calibration technique gave values among 72.8 and 104.3% for measurements in samples spiked with one target analyte or mixtures of the three. This method has been applied for the analysis of unknown honey samples. The results showed an excellent applicability of the proposed method for the determination of the target compounds in honey samples.     

Determination of four nitroimidazoles in poultry and swine muscle and eggs by liquid chromatography/tandem mass spectrometry

A rapid method is presented for the determination of 4 nitroimidazoles in poultry and swine muscle and eggs by liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS). Samples were extracted with acetonitrile, then evaporated the organic phase. After filtration, the extract was directly injected into the LC/ESI-MS/MS system. The LC separation was made on a C8 column by applying a gradient composed of water and acetonitrile. Overall average recoveries ranged from 50-86% for egg, 66-115% for poultry muscle, and 79-111% for swine muscle. The decision limits ranged from 0.05-0.25 microg/kg for egg, 0.07-0.27 microg/kg for poultry muscle, and 0.07-0.26 microg/kg for swine muscle; and detection capabilities ranged from 0.51-0.68 microg/kg for egg, 0.41-0.75 microg/kg for poultry muscle, and 0.53-0.78 microg/kg for swine muscle.     

Analysis of linear alkylbenzenesulfonates in water samples by large-volume injection-port derivatization and gas chromatography-mass spectrometry.

This work presents a modified method to analyze linear alkylbenzenesulfonates (LASs) in water samples. The method involves extraction of samples by a graphitized carbon black (GCB) cartridge, and direct derivatization in the GC injection port using a large-volume (10-20 microl) direct sample introduction (DSI) device with tetraalkylammonium (TAA) salts. The analytes were then identified and quantitated by ion-trap GC-MS. The large-volume DSI injection-port derivatization technique provides sensitivity, fast and reproducible results for LAS residues, to quantitation at 0.1 microg/l in 200 ml of water samples. The retention effect of TAA salts in the injection port was not detected. Enhanced selected mass chromatograms of [M-55]+ ions of butylated C10-C13 LASs by electron impact ionization MS allows one to determine LAS residues at trace levels in environmental samples. Recovery of total LASs in spiked variety water samples ranged from 89 to 112% while RSDs ranged from 2 to 13%.     

Determination of alkylphenol and alkylphenolethoxylates in biota by liquid chromatography with detection by tandem mass spectrometry and fluorescence spectroscopy

A quantitative method for the simultaneous determination of octylphenol, nonylphenol and the corresponding ethoxylates (1 to 5) in biota is presented. Extraction methods were developed for egg and fish matrices based on accelerated solvent extraction followed by a solid-phase extraction cleanup, using octadecylsilica or aminopropyl cartridges. Identification and quantitation were accomplished by liquid chromatography-electrospray tandem mass spectrometry (LC-MS-MS) and compared to the traditional liquid chromatography with fluorescence spectroscopy detection. LC-MS-MS provides high sensitivity and specificity required for these complex matrices and an accurate quantitation with the use of 13C-labeled internal standards. Quantitation limits by LC-MS-MS ranged from 4 to 12 ng/g in eggs, and from 6 to 22 ng/g in fish samples. These methods were successfully applied to osprey eggs from the Chesapeake Bay and fish from the Great Lakes area. Total levels found in osprey egg samples were up to 18 ng/g wet mass and as high as 8.2 microg/g wet mass in the fish samples.     

高效液相色谱-串联质谱法测定动物源性食品中矮壮素残留

建立了高效液相色谱-串联质谱测定动物源性食品中矮壮素残留的分析方法。样品经含1%（v/v）乙酸的乙腈溶液提取、正己烷脱脂、阳离子固相萃取柱（PCX）净化,采用Venusil MP C18（2）色谱柱（150 mm×2.1 mm,3 μm）分离,以乙腈和0.1%（v/v）甲酸水溶液为流动相进行梯度洗脱,采用电喷雾电离、正离子模式扫描,多反应监测模式（MRM）检测,基质匹配标准曲线内标法定量。结果表明：矮壮素在0.200~500 μg/L范围内呈良好线性,相关系数（r²）均不低于0.9993,方法的定量限为0.500 μg/kg;以猪肉、牛肉、羊肉、鸡肉、鸡蛋、猪肾、牛肝、羊肾、鸡肝、牛奶为基质,矮壮素的平均加标回收率为93.4%~101%,相对标准偏差为2.3%~8.0%。该方法基质干扰小,灵敏度高,准确可靠,适用于动物源性食品中矮壮素残留的定量检测。