Application of ion-exchange cartridge clean-up in food analysis. II. Determination of benzylpenicillin, phenoxymethylpenicillin, oxacillin, cloxacillin, nafcillin and dicloxacillin in meat using liquid chromatography with ultraviolet detection.

A multiresidue analytical method was developed for the simultaneous determination of benzylpenicillin (PCG), phenoxymethylpenicillin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcillin (NFPC) and dicloxacillin (MDIPC) in meat. The method involves the use of an ion-exchange cartridge for sample clean-up followed by ion-pair high-performance liquid chromatography with ultraviolet detection. The recoveries of PCG, PCV, MPIPC, MCIPC, NFPC and MDIPC from pork muscle spiked at levels of 0.5, 0.1 and 0.05 mg/kg were in the range of 77-90, 73-95 and 80-93% with coefficients of variation of 0.5-1.7, 1.6-4.4 and 3.2-6.6%, respectively. For beef muscle spiked at levels of 0.5, 0.1 and 0.05 mg/kg, the recoveries of these compounds were 83-92, 71-86 and 77-90% with coefficients of variation of 1.7-4.4, 2.6-7.0 and 3.9-6.4%, respectively. The detection limits for each penicillin were 0.02 mg/kg in meat.     

Application of ion-exchange cartridge clean-up in food analysis. VI. Determination of six penicillins in bovine tissues by liquid chromatography-electrospray ionization tandem mass spectrometry

A multiresidue analytical method was developed for the quantification of benzylpenicillin (PCG), phenoxymethylpenicillin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcillin (NFPC) and dicloxacillin (MDIPC) in bovine tissues using liquid chromatography- electrospray ionization tandem mass spectrometry (LC-ESI MS/MS) with a multiple reaction monitoring technique. Using the deuterated PCG and NFPC as internal standard was effective for improvement of repeatability and accuracy. We chose [M-H-141]- as a monitor ion of MRM analysis and [M-H]- as a precursor ion for each penicillin. Combination of an ion-exchange cartridge clean-up and ion-pair LC enable us to determine the residual penicillins using the standard curves made from standard solutions without the influence of sample matrix on the MS. The average recoveries of PCG, PCV, MPIPC, MCIPC, NFPC and MDIPC from bovine liver, kidney and muscle at the same concentrations as the tolerance levels of PCG (50 microg/kg) ranged from 77 to 101% with the coefficients of variation ranging from 0.7 to 4.2% (n = 5). The limits of quantification for the six penicillins were 2-10 microg/kg in bovine muscle, liver and kidney (S/N ratio >10).     

Application of ion-exchange cartridge clean-up in food analysis IV. Confirmatory assay of benzylpenicillin, phenoxymethylpenicillin, oxacillin, cloxacillin, nafcillin and dicloxacillin, in bovine tissues by liquid chromatography-electrospray ionization tandem mass spectrometry

A multiresidue analytical method was developed for the confirmation of benzylpenicillin (PCG), phenoxymethylpenicillin (PCV), oxacillin (MPIPC), cloxacillin (MCIPC), nafcillin (NFPC) and dicloxacillin (MDIPC) in bovine tissues using electrospray ionization liquid chromatography-tandem mass spectrometry (LC-ESI-MS-MS) with a product ion scan mode. All penicillins gave [M-H]-, [M-H-CO2]- and [M-H-141]- as the product ion, when [M-H]- was selected as the precursor ion. Combination of an ion-exchange cartridge clean-up and the LC-ESI-MS-MS method can reliably identify all of these penicillins fortified at a concentration of 0.05 mg/kg in bovine tissues, including liver, kidney and muscle. The limits of confirmation satisfy the maximum residue limits for each of the penicillins established by the World Health Organization, US Food and Drug Administration, European Union and Japan.     

Application of ion-exchange cartridge clean-up in food analysis I. Simultaneous determination of thiabendazole and imazalil in citrus fruit and banana using high-performance liquid chromatography with ultraviolet detection

A simple, rapid and reproducible analytical method for thiabendazole (TBZ) and imazalil (IMA) in citrus fruit and banana has been developed. The method involves the use of an ion-exchange cartridge for sample clean-up followed by ion-pair high-performance liquid chromatography with ultraviolet detection. The recoveries of TBZ and IMA from citrus fruits spiked at levels of 10 μg/g and 5 μg/g were in the range of 94–98% and 93–98% with coefficients of variation of 0.5–2.2% and 1.6–2.7%, respectively. The recoveries of TBZ and IMA from banana spiked at levels of 3 μg/g and 2 μg/g were 94% and 94% with coefficients of variation 1.1% and 4.9%, respectively. The detection limits for TBZ and IMA were 0.1 μg/g in citrus fruit and 0.05 μg/g in banana.     

Sample preparation for residue determination of gentamicin and neomycin by liquid chromatography

The effect of sample preparation on the determination of gentamicin and neomycin residues in animal tissues was investigated. The extract was mixed with an ion-pair reagent and applied to an octadecyl cartridge. The cartridges were washed with buffer followed by water, and analytes were eluted with ion-pair buffer-acetonitrile mixture. The aminoglycosides were derivatized with 9-fluorenylmethyl chloroformate prior to liquid chromatography using a reversed-phase column and fluorescence detection. Under the conditions applied neomycin was fully separated from all the gentamicin compounds. The highest recoveries of gentamicin and neomycin from spiked tissues were obtained using trichloroacetic acid after initial extraction with phosphate-buffered saline. No interfering peaks from endogenous compounds of matrix were noted at the elution position of the analytes. An intra-laboratory validation of the whole procedure was performed. The calibration graphs were linear from 0.1 to 1.0 mg/kg for gentamicin, and from 0.2 to 1.0 mg/kg for neomycin. Limits of detection were 0.05 mg/kg and 0.10 mg/kg for gentamicin and neomycin, respectively. Limits of quantitation for gentamicin and neomycin were 0.1 and 0.20 mg/kg muscle, liver or kidney tissue, respectively. Recoveries of gentamicin spiked at levels of 0.1 mg/kg porcine tissues ranged from 76 to 86%. Recoveries of neomycin spiked at levels of 0.2 mg/kg porcine tissues ranged from 77 to 83%. The validated procedure was used to determine gentamicin concentrations in porcine tissue after dosing with gentamicin at a level of 5 mg/kg body mass.     

Studies on residual antibacterials in foods. IV. Simultaneous determination of penicillin G, penicillin V and ampicillin in milk by high-performance liquid chromatography

A rapid and simple method for the simultaneous determination of penicillin G (PCG), penicillin V (PCV) and ampicillin (ABPC) in milk is described. The retention behaviour of these beta-lactam antibiotics in reversed-phase liquid chromatography with mobile phases containing sodium alkylsulphonate was studied. Good separations were obtained with methanol-water-0.2 M phosphate buffer (pH 4.0) (5:13:2) containing 11 mM sodium 1-heptanesulphonate and a LiChrosorb RP-18 column. The sample was pre-treated with a Sep-Pak C18 cartridge. The peaks corresponding to each beta-lactam antibiotics can be confirmed with the treatment using penicillinase. The recoveries from milk fortified with sodium PCG, potassium PCV and ABCP at levels of 0.5 and 0.1 micrograms/g each were generally better than 87% and the relative standard deviations were 1.17-4.98%. The detection limits corresponded to 0.03 microgram/g of these beta-lactam antibiotics in milk.     

Determination of beta-agonists in liver and retina by liquid chromatography-tandem mass spectrometry

A liquid chromatography-tandem mass spectrometry (LC/MS/MS) method for the determination of bromobuterol, cimaterol, clenbuterol, clenpenterol, hydroxymethylclenbuterol, isoxsuprine, mabuterol, ractopamine, ritrodrine, salbutamol, terbutaline, and tulobuterol residues in bovine liver and retina is reported. This procedure uses enzymatic digestion, liquid-liquid extraction, and cleanup on Oasis HLB solid-phase extraction cartridges, followed by determination of the residues by LC-tandem quadrupole MS using atmospheric pressure chemical ionization in the positive ion mode. Overall average recoveries ranged from 23 to 76% for liver and 34 to 77% for retina. The mean values for samples fortified at levels between 0.5-2.0 microg/kg (liver) and 5-20 microg/kg (retina) agreed within 98-118% of the spiked levels, with coefficients of variation ranging from 6 to 20%. The decision limits, CCalpha, ranged from 0.1 to 0.3 microg/kg for liver, 1-3 microg/kg for retina, and detection capabilities, CCbeta, from 0.2-0.5 microg/kg for liver and 2-5 microg/kg for retina.     

Quantification of veterinary antibiotics (sulfonamides and trimethoprim) in animal manure by liquid chromatography-mass spectrometry

A fast and cost effective method was developed to extract and quantify residues of veterinary antimicrobial agents (antibiotics) in animal manure by liquid-liquid extraction and liquid chromatography-mass spectrometry. The compounds investigated include six sulfonamides, one metabolite, and trimethoprim. The method was performed without sample clean up. Recoveries from spiked manure slurry samples (spike level = 1 mg/kg) were as follows: sulfaguanidine (52%), sulfadiazine (47%), sulfathiazole (64%), sulfamethazine (89%), its metabolite N4-acetyl-sulfamethazine (88%), sulfamethoxazole (84%), sulfadimethoxine (51%), and trimethoprim (64%). Relative standard deviations of the recoveries were less than 5% within the same day and less than 20% between days. The limit of quantification was below 0.1 mg/kg liquid manure slurry for all compounds and calibration curves obtained from extracts of spiked samples were linear up to a level of 5 mg/kg liquid manure, except for trimethoprim (0.01-0.5 mg/kg). Analysis of six grab samples taken in Switzerland from manure pits on farms where medicinal feed had been applied revealed total sulfonamide concentrations of up to 20 mg/kg liquid manure.     

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.     

Bestimmung von isomeren 4-Nonylphenolen in B?den

Summary It was reported that 4-nonylphenol isomers had been found in high concentrations in sewage sludge. When this sludge is applied to fields there is a risk that soils may be contaminated with nonylphenols. Therefore, a method is described here for the determination of 4-nonylphenol isomers in soil. The steam distillation/solvent extraction technique is used. An essential part of the method is the clean-up step by column chromatography. The determination is performed on a fused silica capillary by a flame ionization or a mass selective detector. Average recoveries from soil samples spiked with 0.1 to 1 mg/kg ranged from 90 to 116%. The detection limit is 0.1–0.05 mg/kg soil (this limit corresponds to the technical mixture of the isomers).     

Evaluation of dithiocarbamates and beta-diketones as chelating agents in supercritical fluid extraction of Cd, Pb, and Hg from solid samples

The use of four dithiocarbamates and three fluorinated β-diketones as potential chelating agents for three transition metal ions (Cd²⁺, Pb²⁺, and Hg²⁺) extracted from spiked sand and filter paper samples by supercritical fluid extraction (SFE) was investigated. The extractions were performed at 45°C and 250 atm for spiked sand samples and at 60°C and 200 atm for filter paper samples using supercritical carbon dioxide modified with 5% methanol. At 250 atm and using carbon dioxide modified with 5% methanol, the recoveries of Cd²⁺, Pb²⁺, and Hg²⁺ ions from spiked sand samples were 95% with lithium bis(trifluoroethyl)dithiocarbamate (LiFDDC) as the chelating agent; they ranged from 83–97% with diethylammonium diethyldithiocarbamate and from 87–97% with sodium di-ethyldithiocarbamate as chelating agents, and from 68–96% with trifluoracetylacetone, hexafluoroacetylacetone, and thenoylfluoroacetone as chelating agents. Ammonium pyrrolidinedithiocarbamate was not effective in the chelation SFE of Cd²⁺, Pb²⁺, and Hg²⁺ ions from either spiked sand or spiked filter paper samples under the extraction conditions used. Supercritical carbon dioxide alone gave consistently lower analyte recoveries than supercritical carbon dioxide modified with 5% methanol. The results suggest that the solubility of the metal chelate in the supercritical fluid plays a more important role than the solubility of the chelating agent in the supercritical fluid, as long as sufficient chelating agent is present in the fluid phase. Fluorination of the chelating agent, as in the case of LiFDDC, increases the solubility of the metal chelate, and subsequently enhances the extraction efficiency for the metal ions.     

Simple, rapid and sensitive spectrofluorimetric determination of diflunisal in serum and urine based on its ternary complex with terbium and EDTA

A very simple, rapid and highly sensitive fluorimetric method for the determination of diflunisal in serum and urine is described. The method is based on the formation of a ternary complex between diflunisal, Tb³⁺ and EDTA in alkaline aqueous solutions. This complex exhibits very intense terbium ion luminescence with a main emission maximum at 546 nm when excited at 284 nm. Optimum conditions for the complex formation have been investigated. The detection limit for diflunisal is 2.4 μg 1⁻¹, while the range of application is 0.01–6.00 mg 1⁻¹. The method has been successfully applied for the determination of diflunisal in untreated human serum and urine samples. Analytical recoveries from serum and urine samples spiked with diflunisal were in the ranges of 96.8–101.2% and 98.0–102.0%, respectively.     

气相色谱-串联质谱法测定食用油中两种非邻苯二甲酸酯类增塑剂

建立了气相色谱-串联质谱同时测定食用油中对苯二甲酸二（2-乙基己基）酯和偏苯三甲酸三（2-乙基己基）酯两种非邻苯二甲酸酯类增塑剂的方法。样品采用乙腈提取,于-20℃冷冻除脂净化,用气相色谱-串联质谱选择反应监测模式测定。两种化合物的检出限为0.03 mg/kg,定量限为0.1 mg/kg,线性范围为0.1~10 mg/kg。3个添加水平（0.1、0.3和1.0 mg/kg）下的回收率为81.04%~108.31%,相对标准偏差为0.70%~9.91%。该方法简便、准确,适用于食用油中对苯二甲酸二（2-乙基己基）酯和偏苯三甲酸三（2-乙基己基）酯的检测。     

Determination of microcystins in biological samples by matrix solid-phase dispersion and liquid chromatography-mass spectrometry

A method for the detection and quantification of the microcystins (MCs)-MC-LR, MC-RR and MC-YR-in biological samples by matrix solid-phase dispersion (MSPD) has been developed. The optimum extraction conditions were 500 mg of liver or kidney, C18 bonded silica as dispersant, and a mixture methanol-water (70:30) as eluent. The MCs were determined by liquid chromatography electrospray mass spectrometry (LC/ES/MS). Recoveries of biological extracts at three different spiked levels (1-10 mg kg(-1)) ranged from 40.5 to 87.0% in liver, and from 52.5 to 74.5 in kidney. R.S.D.s were < 15.6% and < 10.6%, respectively. The detection and quantification limits were 0.05 and 0.5 mg kg(-1), for all MCs. The method was applied to MCs detection in liver and kidney of rat previously injected i.p. with MC-LR. Results showed the presence of MC-LR in the liver of the animals injected with the highest dose.     

气相色谱-质谱联用法同时测定乳及乳制品中的三聚氰胺及肌酐

建立了同时测定乳制品中三聚氰胺及肌酐的气相色谱-质谱联用方法。样品经1%三氯乙酸溶液萃取,混合型阳离子交换固相萃取净化,提取液用氮气吹干后加入N,O-双(三甲基硅基)三氟乙酰胺-三甲基氯硅烷(BSTFA-TMCS)硅烷化试剂,于75 ℃下衍生60 min,最后采用选择离子模式下的气相色谱-质谱测定。三聚氰胺和肌酐的定量限分别为0.10 mg/kg和0.20 mg/kg;在0.1～50 mg/L范围内的线性相关系数均大于0.99。实际样品中,肌酐在10～100 mg/kg和三聚氰胺在0.1～5.0 mg/kg添加范围内的回收率分别为80.7%～116.8%和77.6%～107.5%,相对标准偏差分别小于9.4%和8.5%。该方法能有效除去干扰,灵敏度高,回收率较好,可用于乳制品中三聚氰胺和肌酐的同时测定。     

Development of an HPLC multi-residue method for the determination of ten quinolones in bovine liver and porcine kidney according to the European Union Decision 2002/657/EC

A sensitive multi-residue analytical method was developed for the determination of ten quinolones: enoxacin, ofloxacin, norfloxacin, ciprofloxacin, danofloxacin, enrofloxacin, sarafloxacin, oxolinic acid, nalidixic acid, and flumequine in bovine liver and porcine kidney. A simple liquid extraction step followed by a solid phase extraction clean up procedure was applied for the extraction of quinolones from liver and kidney tissues. Recoveries of the extraction varied between 82 and 88% for bovine liver and 92 and 95% for porcine kidney. Separation was performed on an ODS-3 PerfectSil Target (250 x 4 mm) 5 microm analytical column at 25 degrees C. The mobile phase consisted of a mixture of TFA 0.1%-CH(3)CN-CH(3)OH, delivered at a flow rate of 1.2 mL/min according to a gradient program. Elution of quinolones and the internal standard (caffeine, 7.5 ng/microL) was complete within 27 min. Photodiode array detection was used for monitoring the eluants at 275 and 255 nm. The method was fully validated according to the European Union Decision 2002/657/EC, determining linearity, selectivity, decision limit, detection capability, accuracy, and precision. The LODs of the specific method of quinolone determination in bovine liver varied between 3 and 7 microg/kg and in porcine kidney between 3 and 4 microg/kg.     

加速溶剂萃取-凝胶渗透色谱净化-气相色谱快速分析动物源性食品中残留的多种有机磷农药

建立了动物源性食品猪肉、牛肉、鸡肉及鱼肉中36种有机磷农药残留的快速分析方法。以乙腈作为溶剂,对试样采用加速溶剂萃取仪萃取,自动凝胶渗透色谱仪净化预处理,N-丙基乙二胺(PSA)填料再净化,毛细管气相色谱法分离,火焰光度检测器(磷型)检测,内标法定量。该方法分离效果良好,重现性好,灵敏度、精密度高,杂质干扰少。36种有机磷农药的检测限(LOD)为0.0012 mg/kg(乙拌磷)～0.014 mg/kg(吡唑硫磷),定量限(LOQ)为0.004 mg/kg(乙拌磷)～0.047 mg/kg(吡唑硫磷)。当试样中有机磷农药的添加浓度分别为0.05,0.1,0.2 mg/kg时,回收率为58.2%～106.3%。方法的最低检测限和添加回收率均符合农药残留分析的要求。     

Analysis of DDT residues in soil by ELISA: an international interlaboratory study

An international interlaboratory study was conducted to determine the performance of a group of laboratories from developing and developed countries. The study used a commercial microwell ELISA on unknown samples spiked with different levels of DDT. The study design was based on Youden pairs and balanced replicates. Two soils, differing in particle size distributions, organic matter content, and cation-exchange capacities and thought to be DDT-free, were spiked at 5 DDT levels between 0.025 and 2 mg/kg. Nineteen laboratories in 17 countries took part in the collaborative trial; of these, the majority were modestly equipped laboratories in developing countries. Samples were analyzed without filtration or cleanup and using standards of pure DDT in methanol. Data were analyzed for repeatability and reproducibility, and average recoveries at the spike levels were calculated. Mean real recoveries for both soils were similar (103% for soil A and 100% for soil B), with values between 0.1 and 2 mg/kg DDT. Precision estimates were best in the linear working range of the assay (0.1-0.5 mg/kg DDT), with reproducibility relative standard deviations (RSDR) typically averaging about 38 and 46% near the upper and lower detection limits, respectively. Corresponding repeatability relative standard deviation (RSDr) values were 20-36% and 36-57%. Thus, even though much of the trial was performed under developing country conditions, performance statistics were similar to other reported results obtained with ELISAs on small molecules of agricultural importance, such as mycotoxins and pesticide and antibiotic residues.     

Rapid liquid chromatographic determination of residual penicillin G in milk

A simple and rapid high-performance liquid chromatographic (HPLC) method for determination of residual penicillin G (benzylpenicillin, PCG) in milk was developed. The sample preparation was performed by stirring with ethanol and reacting with 5 M 1,2,4-triazole-mercury (II) chloride solution at 65?°C for 10 min followed by an ultra centrifugation step. The HPLC separation was carried out using a Mightysil^® RP-4GP column, a mobile phase of acetonitrile and 0.1 M phosphate buffer (pH 6.5) (35:65, v/v) and a photo-diode array detector. The average recoveries from spiked PCG (0.004, 0.01, 0.05 and 0.1 μg/mL) were above 86% with coefficients of variation between 1.2 and 4.5%. The limit of detection was 0.004 μg/mL. This value corresponds to the maximum residue limit (MRL) in milk (0.004 μg/mL, EU and Japan). The total time required for the analysis of one sample was below 40 min.     

超高效液相色谱-串联质谱法同时测定牛奶和奶粉中的二氰二胺、三聚氰胺和三聚氰酸

建立了一种超高效液相色谱-串联质谱法测定牛奶和奶粉中二氰二胺(DCD)、三聚氰胺(MEL)和三聚氰酸(CY)的分析方法。样品用5%(质量分数)三氯乙酸水溶液提取,无需净化和浓缩,用Acquity UPLC HSS T3色谱柱(50 mm×2.1 mm, 1.8 μm)分离,以乙腈和乙酸铵作为流动相进行梯度洗脱,电喷雾正、负离子(ESI^±)模式同时电离,多反应监测模式进行检测。结果表明:在5.0～200.0 μg/L范围内线性关系良好(r≥0.995)。牛奶中3种化合物在0.02、0.10、0.20 mg/kg的添加回收率为60.0%～105.8%,相对标准偏差(RSD, n=6)为4.2%～13.6%;奶粉中3种化合物在0.05、0.10、0.20 mg/kg的添加回收率为78.0%～115.0%, RSD (n=6)为2.7%～7.5%。牛奶中方法的定量限(信噪比为10)为0.02 mg/kg,奶粉中方法的定量限为0.05 mg/kg。该方法简单、快速、灵敏、准确,适合于牛奶、奶粉等乳及乳制品中DCD、MEL和CY的快速、高灵敏的分析检测。