Deposition and depletion of maduramicin residues in eggs after oral administration to laying hens determined by LC-MS

The coccidiostat maduramicin has been approved as a feed additive for chickens and turkeys, although it is prohibited for use in laying hens. In the present study, laying hens were divided into three groups and fed for 14 days with medicated feed containing maduramicin, at three different concentrations: 50, 100 and 500 µg kg^?1. Eggs were collected during treatment and for 26 days after the end of feeding with medicated feed. Maduramicin residues were found exclusively in egg yolk, with the highest concentration in egg yolk of 459 µg kg^?1 for the highest dose. The maximum concentration of maduramicin in whole egg was 16.6 µg kg^?1 for the group receiving feed containing the maximum permitted level of maduramicin in feed (50 µg kg^?1). The half-life of elimination of maduramicin, calculated for post-treatment days 1–10, was 6.5 days. Twelve days after drug administration, the concentration of the maduramicin in egg yolk for Group 3 (fed with 500 µg kg^?1 maduramicin) still exceeded 20 µg kg^?1, while the concentrations for Groups 1 and 2 were 1.2 and 2.7 µg kg^?1, respectively.     

液相色谱-串联三重四极杆质谱测定牛奶中的氯霉素残留量

建立牛奶中氯霉素残留的高效液相色谱-串联四极杆质谱联用测定方法。该方法经乙腈提取样品,以MGⅢ-C18柱(2.1×150 mm,1.8μm)分离,流动相为水溶液和乙腈(体积比为65∶35),电喷雾负离子MRM模式检测。该方法的检出限0.07μg/L,线性范围0.05μg/L~20.0μg/L,加标回收率98.5%～110.8%,相对标准偏差为3.57%。     

Quantitative determination of mycotoxins in urine by LC-MS/MS

Naturally occurring mycotoxins are responsible for a wide array of adverse health effects. The measurement of urinary mycotoxin levels is a useful means of assessing an individual's exposure, but the development of sensitive and accurate analytical methods for detecting mycotoxins and their metabolites in urine samples is challenging. Urinary mycotoxins are present in low pg ml^–1 concentrations, and the chromatographic identification of their metabolites can be obscured by other endogenous metabolites. We developed an analytical method focused on the selection of two appropriate multiple-reaction monitoring transition for unambiguous identification and quantification of carcinogenic aflatoxin M₁ (AFM₁), ochratoxin A (OTA) and fumonisin B₁, B₂ (FB₁, FB₂) in urine samples from a small volunteer group in a pilot study. AFM₁, OTA, FB₁ and FB₂ were concentrated selectively, interfering substances were removed using an immunoaffinity column (IAC), and mycotoxins were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in combination with a stable-isotope standard-dilution assay (SIDA). The method was sensitive enough to measure mycotoxins and their metabolites at pg ml^–1 levels in urine. The combination of LC-MS/MS and SIDA was critical to distinguishing pseudo-OTα interference from genuine OTα. Twelve urine samples contained OTA ranging from 0.013 to 0.093 ng ml^?1 (mean = 0.031 ng ml^?1). AFM₁ were detected in one sample at a 0.002 ng ml^?1 level, while FB₁ and FB₂ were undetectable in all 12 samples. None of the samples in this pilot study contained a detectable level of OTα, despite the presence of OTA, and this may suggest the need for further epidemiological investigation of OTA exposure in the Korean population.     

UNE-EN ISO/IEC 17025:2005-accredited method for the determination of pesticide residues in fruit and vegetable samples by LC-MS/MS

A rapid, simple and sensitive multi-residue method was developed and validated for the simultaneous quantification and confirmation of 69 pesticides in fruit and vegetables using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The samples were extracted following the quick, easy, cheap, effective, rugged and safe method known as QuEChERS. Mass spectrometric conditions were individually optimised for each analyte in order to achieve maximum sensitivity in multiple reaction monitoring (MRM) mode. Using the developed chromatographic conditions, 69 pesticides can be separated in less than 17 min. Two selected reaction monitoring (SRM) assays were used for each pesticide to obtain simultaneous quantification and identification in one run. With this method in SRM mode, more than 150 pesticides can be analysed and quantified, but their confirmation is not possible in all cases according to the European regulations on pesticide residues. Nine common representative matrices (zucchini, melon, cucumber, watermelon, tomato, garlic, eggplant, lettuce and pepper) were selected to investigate the effect of different matrices on recovery and precision. Mean recoveries ranged from 70% to 120%, with relative standard deviations (RSDs) lower than 20% for all the pesticides. The proposed method was applied to the analysis of more than 2000 vegetable samples from the extensive greenhouse cultivation in the province of Almería, Spain, during one year. The methodology combines the advantages of both QuEChERS and LC-MS/MS producing a very rapid, sensitive, accurate and reliable procedure that can be applied in routine analytical laboratories. The method was validated and accredited according to UNE-EN-ISO/IEC 17025:2005 international standard (accreditation number 278/LE1027).     

Rapid multi-class multi-residue method for the confirmation of chloramphenicol and eleven nitroimidazoles in milk and honey by liquid chromatography-tandem mass spectrometry (LC-MS)

A confirmatory method was developed to allow for the analysis of eleven nitroimidazoles and also chloramphenicol in milk and honey samples. These compounds are classified as A6 compounds in Annex IV of Council Regulation 2377/90 (European Commission 1990) and therefore prohibited for use in animal husbandry. Milk samples were extracted by acetonitrile with the addition of NaCl; honey samples were first dissolved in water before a similar extraction. Honey extracts underwent a hexane wash to remove impurities. Both milk and honey extracts were evaporated to dryness and reconstituted in initial mobile phase. These were then injected onto a liquid chromatography-tandem mass spectrometry (LC-MS/MS) system and analysed in less than 9 min. The MS/MS was operated in multiple reaction monitoring (MRM) mode with positive and negative electrospray ionization. The method was validated in accordance with Commission Decision 2002/657/EC and is capable of analysing metronidazole, dimetridazole, ronidazole, ipronidazole and there hydroxy metabolites hydroxymetronidazole, 2-hydroxymethyl-1-methyl-5-nitroimidazole, and hydroxyipronidazole. The method can also analyse for carnidazole, ornidazole, ternidazole, tinidazole, and chloramphenicol. A recommended level of 3 µg l^?1/µg kg^?1 for methods for metronidazole, dimetridazole, and ronidazole has been recommended by the Community Reference Laboratory (CRL) responsible for this substance group, and this method can easily detect all nitroimidazoles at this level. A minimum required performance level of 0.3 µg l^?1/µg kg^?1 is in place for chloramphenicol which the method can also easily detect. For nitroimidazoles, the decision limits (CCα) and detection capabilities (CCβ) ranged from 0.41 to 1.55 µg l^?1 and from 0.70 to 2.64 µg l^?1, respectively, in milk; and from 0.38 to 1.16 µg kg^?1 and from 0.66 to 1.98 µg kg^?1, respectively, in honey. For chloramphenicol, the values are 0.07 and 0.11 µg l^?1 in milk and 0.08 and 0.13 µg kg^?1 in honey. Validation criteria of accuracy, precision, repeatability, and reproducibility along with measurement uncertainty were calculated for all analytes in both matrices.     

高效液相色谱-质谱联用测定乳制品中6种四环素类抗生素

建立了乳制品中6种四环素类抗生素残留的高效液相色谱-电喷雾离子阱质谱联用测定方法。该方法采用多反应监测正离子模式，可一次对6种四环素类抗生素进行定性和定量分析。该方法的检出限0．5-4．0μg/L，测定低限牛奶0．6-4.5μ/L，乳粉为6．0-45．0μg/kg，线性范围4．0-100．0μg／L，加标回收率56．1％-104．9％，相对标准偏差为2．5％-15．0％。该法具有样品预处理简单，灵敏度高，分析时间短等优点。     

LC-MS/MS测定蔬菜中丁草胺残留量的不确定度分析

依据GB/T20769-2008《水果和蔬菜中450种农药及相关化学品残留量的测定液相色谱-质谱/质谱法》对蔬菜中丁草胺残留量的测量不确定度进行分析和评定。分析蔬菜中丁草胺残留测量的不确定的来源,并进行评定,采用合成的方法来计算和评定总的不确定度。本次试验的合成扩展不确定为(4.07±0.47)μg/kg。     

酶联免疫法与液相色谱-串联质谱法检测猪肉中沙丁胺醇

运用酶联免疫法（ELISA）与液相色谱-串联质谱法（LC-MS/MS）对猪肉中沙丁胺醇残留进行测定,并比较了二者在灵敏度、准确性和重现性等方面的差异。结果显示,ELISA法和LC-MS/MS法在猪肉样品中的检测限可达到0.5 μg/kg和0.25 μg/kg,分别向猪肉样品中添加3个质量浓度水平（1.0 μg/kg、2.0 μg/kg、4.0 μg/kg）的沙丁胺醇时,回收率分别为83.7%～90.9%和86.6%～93.5%,变异系数（CV）分别为5.4%～10.3%和6.0%～8.3%。用酶联免疫法实际样品进行检测,筛选出2个阳性样品,经液相色谱-串联质谱法确证亦为阳性,测定结果一致。研究表明,酶联免疫法重复性较好、准确度较高,适用于进行猪肉样品中沙丁胺醇的快速筛选,液相色谱-串联质谱法适用于阳性样品的确证和精确定量。     

QuEChERS-LC-MS/MS联用技术对浆果中多种农药残留的测定

为建立检测浆果中多种农残的方法,运用QuEChERS前处理技术,结合高效液相色谱与串联质谱联用（HPLC-MS/MS）技术同时测定浆果中10种农药残留。结果显示,最优分散剂组合为10 g样品中加入PSA 50 mg,GCB 2.5 mg和C18 50 mg进行基质的净化,此条件下平均回收率达到75.38%。10种农药对照品在1～100 μg/L范围内,呈现良好的线性关系,测定蓝莓中10种农药残留的加标回收率为95.31%～111.26%,相对标准偏差为0.90%～4.16%,测定葡萄中10种农药残留的加标回收率为90.37%～116.20%,相对标准偏差为0.80%～5.09%。该方法简便、快速、准确,适用于常见浆果中农药残留的分析。     

Determinative and confirmatory method for residues of tetracyclines in honey by LC-MS/MS

A limited number of substances are authorised for the treatment of bees. Maximum residue limits (MRLs) are set for tetracyclines in several matrices, but not for honey. Nevertheless, tetracycline antibiotics may be used in order to prevent bacterial diseases and the loss of honey bee populations. In this study, a sensitive multi-residue LC-MS/MS method was developed and optimised for the quantitative and qualitative determination of tetracycline residues in honey. Homogenisation of samples under acidic conditions was performed and solid-phase extraction was carried out. The eluate was evaporated under nitrogen and dissolved in an aqueous methanol solution prior to filtration. A mobile phase composed of acetic acid–water and acetic acid–acetonitrile was used. Separation of tetracycline, oxytetracycline, chlortetracycline and doxytetracycline was achieved by using gradient elution on a C18 chromatography column. The analytical method was validated according to Commission Decision 2002/657/EC by the analysis of spiked samples around the recommended concentration of 20 μg kg^?1 by EURL Guidance Paper, December 2007. A matrix effect was observed, so quantification was based on an external matrix calibration curve. Calculated decision limits (CCα) were lower than 10 μg kg^–1 for all tetracyclines. Good linearity, repeatability and within-laboratory reproducibility were achieved.     

采用LC/MS/MS测定侧流卷烟烟气中挥发性羰基化合物的方法研究

挥发性羰基化合物是卷烟烟气中的一类重要有害物质,准确测定卷烟烟气中,特别是侧流卷烟烟气中的挥发性羰基化合物还有许多问题有待解决。实验中采用2,4-二硝基苯肼（DNPH）酸性溶液捕集侧流烟气中的羰基化合物,乙腈水溶液稀释后,以对羟基苯甲酸丁酯为内标物,用带有负离子电喷雾的LC/MS/MS定量分析侧流烟气中8种挥发性羰基化合物。实验证明,此方法有较好的重复性:对8种羰基化合物测定的相对标准偏差在6%以下;具有较高的灵敏度:8种挥发性羰基化合物的检出限均低于2.8 ng/ cig;较高的准确性:8种挥发性羰基化合物的回收率在87.2%～104.7%之间。与以往的分析方法相比,该方法具有更高的选择性,实现了烟气中巴豆醛、2-丁酮的DNPH衍生物的同分异构体的分离,对巴豆醛、2-丁酮定量更为准确,分析方法的灵敏度也明显提高。      

LC-MS/MS法测定食用油中的辣椒素和二氢辣椒素

建立了用氨基固相萃取小柱净化提取液,液相色谱串联质谱（LC-MS/MS）法测定食用油中辣椒素和二氢辣椒素含量的检测方法。结果表明,辣椒素在0～100 ng/mL范围内线性关系良好（R2 = 0.998 6）,平均回收率在70.6%～90.5%,相对标准偏差（RSD,n=3）在3.1%～8.9%,检出限为0.03 μg/kg;二氢辣椒素在0～20 ng/mL范围内线性关系良好（R2 = 0.998 8）,平均回收率在71.5%～100.7%,相对标准偏差（RSD,n=3）在6.0%～13.2%,检出限为0.006 μg/kg。该方法简便快速、准确可靠,是鉴别地沟油和测定食用油中辣椒素类物质的有效方法。     

HPLC-MS/MS测定猪肉和猪肝中氯霉素残留量的研究

建立高效液相色谱-串联质谱法(HPLC-MS/MS)检测猪肉和猪肝中氯霉素药物残留的分析方法。样品经4%的氯化钠溶液和乙腈提取并沉淀蛋白质,正己烷脱脂净化,乙酸乙酯液液萃取,再浓缩定容,上HPLC-MS/MS仪器,用Syncronis C18柱分离,以乙腈-水(40∶60)作为流动相,采用电喷雾离子源(ESI),负离子模式,多反应监测(MRM)方式检测,用氯霉素-D5作内标物来定量。在该试验条件下,氯霉素在1～15ng/mL浓度呈良好的线性关系,r=0.999 2,最低检出浓度为0.1μg/kg,样品的加样回收率在90.0%～110.0%,重复性好RSD<3.0%。该方法能对猪肉和猪肝中氯霉素残留进行定性及定量分析,方法精密度较好、准确度较高、选择性好,结果满意。     

Corticosteroids in liver and urine in Sicilian cattle by a LC-MS/MS method

The presence of corticosteroid residues was assessed in urine and liver samples from livestock of Sicily. A total of 630 bovine samples were collected from farms and slaughterhouses. The samples were analysed using solid-phase extraction (SPE) coupled with ultra-performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS). All the corticosteroids found were under the maximum residue limit imposed by Commission Regulation (EC) 37/2010. About 4% of liver samples showed dexamethasone levels above the limit of detection (LOD), with a mean of 1.5 ± 0.2 µg kg^?1. Betamethasone was found only in seven liver samples, with a mean of 1.6 ± 0.1 µg kg^?1. Furthermore, prednisolone and prednisone were found only in urine and liver samples from slaughterhouse, probably related to the high rate of stress for bovines. These results suggest good control practices adopted by Sicilian farms, able to ensure the quality of food products.     

Absence of 2'-deoxyguanosine-carbon 8-bound ochratoxin A adduct in rat kidney DNA monitored by isotope dilution LC-MS/MS

The contribution of DNA adduct formation in the carcinogenic action of the mycotoxin ochratoxin A (OTA) has been subject to much debate. Recently, a carbon-bonded ochratoxin A-2'-deoxyguanosine adduct (dGuoOTA) formed by photochemical reaction in vitro has been shown by 32P-postlabeling/TLC to comigrate with a spot detected in DNA isolated from rat and pig kidney following exposure to OTA. Considering the large body of evidence arguing against covalent DNA binding of OTA and the poor resolution and specificity of postlabeling analysis, we developed a stable isotope dilution LC-MS/MS method to analyze dGuoOTA in kidney DNA isolated from rats treated with OTA. dGuoOTA and nitrogen-15-labeled dGuoOTA (15N(5)-dGuoOTA) were prepared by photoirradiation of OTA in the presence of dGuo or nitrogen-15-labeled dGuo. Conditions for DNA hydrolysis were optimized using a synthetic oligonucleotide containing dGuoOTA to ensure complete release of dGuoOTA. The LOD of the method (S/N > 3) was 10 fmol dGuoOTA on-column. However, dGuoOTA was not detected in DNA samples isolated from male F344 rats treated with OTA for up to 90 days at doses known to cause renal tumor formation. Detection limits, calculated for each individual sample based on the absolute LOD and the amount of DNA injected, were as low as 3.5 dGuoOTA/10(9) nucleotides. These data are consistent with previous results showing lack of DNA adduct formation by OTA and demonstrate that dGuoOTA is not formed in biologically relevant amounts under physiological conditions in vivo.     

Surveillance study of novobiocin and phenylbutazone residues in raw bovine milk using liquid chromatography-tandem mass spectrometry

A simple method permitting the simultaneous determination of trace residues of novobiocin and phenylbutazone in raw milk samples using liquid chromatography-tandem mass spectrometry was developed. Raw milk samples were mixed with acetonitrile to facilitate the concurrent precipitation of milk proteins and extraction of both veterinary drugs. Without additional clean-up or concentration of the resulting extract, the analytes could be quantified at concentrations as low as 0.0025 and 0.001 µg ml^?1 for phenylbutazone and novobiocin, respectively. The analysis of a series of fortified raw milk samples at analyte concentrations ranging from 0.005 to 0.1 µg ml^?1 and from 0.01 to 0.2 µg ml^?1 for phenylbutazone and novobiocin, respectively, yielded average recoveries ranging from 89.2% to 104.3% with standard deviations below 7%. The analytical method was applied to the analysis of raw milk samples collected from transport trucks upon delivery at dairy-processing plants throughout Alberta, Canada. Novobiocin was detected in 13 of 1072 samples tested at concentrations ranging from 0.001 to 0.007 µg ml^?1. Phenylbutazone was not detected in any of the samples tested.     

Determination of halosulfuron-methyl residues and dissipation in wheat by QuEChERS and LC-MS/MS

A sensitive and rapid analytical method based on QuEChERS (quick, easy, cheap, effective, rugged and safe) sample preparation and LC-MS/MS detection was developed for the analysis of halosulfuron-methyl residues in wheat. The recoveries of halosulfuron-methyl in both the wheat plant and grain ranged from 87% to 119% and from 75% to 97%, respectively, with relative standard deviations (RSDs) of 3–9%. The limit of quantification (LOQ) was 0.005 mg kg^?1 for wheat plant and 0.001 mg kg^?1 for wheat grain. The half-life of halosulfuron-methyl in the wheat plant was 0.9–9.5 days. The terminal residue levels of halosulfuron-methyl in wheat grain were below 0.01 mg kg^?1 at harvest.     

液相色谱—质谱/质谱法测定猪肉中4种磺胺类药物残留量的不确定度评定

目的：对采用液相色谱—质谱/质谱法测定猪肉中磺胺间甲氧嘧啶、磺胺二甲氧嘧啶、磺胺甲噁唑和磺胺二甲嘧啶残留量的不确定度进行评定。方法：分析猪肉中磺胺类药物残留量测定过程中的各种影响因素,包括称量、标准溶液的配制、样品提取净化、仪器测量、回收率等进行分析评定。结果：该方法测定磺胺间甲氧嘧啶、磺胺二甲氧嘧啶、磺胺甲噁唑和磺胺二甲嘧啶残留量的扩展不确定度分别为9.4,18.1,12.0,15.6 μg/kg。结论：试验的不确定度主要由测量重复性、标准溶液的配制和标准曲线拟合引入。     

Determination of naturally occurring progestogens in bovine milk as their oxime derivatives using high performance liquid chromatography–electrospray ionization–tandem mass spectrometry

BACKGROUND: Hormones and hormone‐like substances which are present in the environment have been repeatedly accused of being the cause of most endocrine disruption. However, the possible role of endogenous hormones in food of animal origin deserves to be discussed as well. The relation between steroid hormones and several human health problems has been previously reported, such as prostate and breast cancer, perturbation of human reproduction and endocrine disruption on humans and wildlife. This research is particularly concerned with cow's milk, which contains a considerable amount of sex hormones. RESULTS: A liquid chromatography–tandem mass spectrometry method has been developed for the simultaneous detection and quantification of four naturally occurring steroid hormones in commercial bovine milk (pregnenolone (P₅), progesterone (P₄), 17‐hydroxypregnenolone (17‐OHP₅), 17‐hydroxyprogesterone (P₄)). Oxime derivatives of steroids were analyzed in positive ionization and multiple reaction monitoring mode. Methodology has been validated according to Decision 2002/657/EC criteria. CONCLUSION: This method has been successfully used in real samples. It is fast and easy‐handling and provides a useful tool for the assessment of progestogens in bovine milk. Copyright © 2010 Society of Chemical Industry     

微波辅助萃取-液相色谱-串联质谱法检测猪肉中四种氟喹诺酮类药物残留

建立了微波辅助萃取-液相色谱-串联质谱法检测猪肉中氧氟沙星、诺氟沙星、环丙沙星、恩诺沙星四种氟喹诺酮类药物残留的方法。样品经微波辅助萃取,正己烷脱脂,无水硫酸钠除水,浓缩提取物至干,用1.0mL0.1%甲酸溶液溶解后上机检测。采用Hypersil GOLD-1.9μm,50 mm×2.1 mm(i.d)色谱柱分离,在多反应监测模式下检测,外标法定量。结果表明:四种氟喹诺酮类药物在浓度10～200μg/L范围内线性关系良好,相关系数r=0.9956～0.9991,定量限为10μg/kg。在不同添加水平下,其平均回收率为88%～101%,变异系数为1.4%～4.1%。