Trace analysis of tiamulin in honey by liquid chromatography-diode array-electrospray ionization mass spectrometry detection

A liquid chromatography with diode array or electrospray ionisation mass spectrometry detection (LC-DAD-ESI-MS) method for the determination of tiamulin residues in honey is presented. The procedure employs a solid-phase extraction (SPE) on polymeric cartridges for the isolation of tiamulin from honey samples diluted in aqueous solution of tartaric acid. Chromatographic separation of the tiamulin is performed, in isocratic mode, on a C18 column using methanol and ammonium carbonate 0.1% in water, in proportion (30:70, v/v). Average analyte recoveries were from 88 to 106% in replica sets of fortified honey samples. The LC-ESI-MS method detection limits differ from 0.5 microg kg(-1) for clear honeys to 1.2 microg kg(-1) for dark honeys. The developed method has been applied to the analysis of tiamulin residues in multifloral honey samples collected from veterinary treated beehives.     

Determination of imazaquin residues in soil by solid-phase extraction and high-performance liquid chromatography

A method has been developed for the quantitation of imazaquin residues in soil. The herbicide was extracted from soil with methanol-water (2 + 1, v/v) and cleaned up by strong anion-exchange solid-phase extraction cartridges. Analysis was performed by using high-performance liquid chromatography with ultraviolet detection. Average recoveries through the method ranged from 90.7 to 100.6%, with relative standard deviation equal to or lower than 6.6%. The limit of detection was estimated to be 0.0015 mg/kg, and the minimum quantitation concentration of imazaquin in soil was 0.005 mg/kg. This method was successfully applied to evaluate imazaquin residue levels in soil and its dissipation rates in a soybean field in the Xisanqi District of Beijing, People's Republic of China. The dissipation study showed that the half life of imazaquin in soil was 10.37 +/- 0.0135 days at 3 different application rates.     

Residue analysis of fosthiazate in cucumber and soil by QuEChERS and GC-MS

A convenient method was developed for the determination and validation of fosthiazate in cucumber and soil. The procedure is based on liquid partitioning with acetonitrile followed by dispersive solid phase extraction as the clean-up step, after which samples were analysed by gas chromatography-mass spectrometry (GC-MS). The average recoveries ranged from 91.2 % to 99.0 % with relative standard deviations (RSDs) of less than 6.05 %, at three fortification levels (0.02 mg kg^?1, 0.1 mg kg^?1, 0.5 mg kg^?1) in cucumber and soil, and the limits of quantification (LOQs) for fosthiazate were all established at 0.02 mg kg^?1. The proposed method was applied successfully to analyses of the dissipation and residue of fosthiazate in field trials. The dissipation rate of fosthiazate was described using pseudo-first-order kinetics with a half-life of 4.33 days and 4.08 days in soil in Beijing and Shandong, respectively. In the terminal residue experiment, fosthiazate residues in cucumber and soil were clearly below the maximum residue level (MRL, 0.2 mg kg^?1) set in China.     

Validation of a method for the determination of chloramphenicol in poultry and swine liver by ultra-performance liquid chromatography coupled with tandem mass spectrometry

A sensitive and reliable method has been developed and validated for the determination of chloramphenicol in poultry and swine liver using SPE and ultra-performance liquid chromatography (UPLC)/MS/MS. The liver samples were extracted with ethyl acetate, defatted with n-hexane, and further cleaned up using SPE cartridges with polymeric sorbent. An Acquity BEH C18 column was used for gradient UPLC separation, with water and acetonitrile as the mobile phase. The multiple reaction monitoring mode was used for two precursor-product ion transitions for chloramphenicol and one for the internal standard. The method was validated at 0.1, 0.3, and 1.0 microg/kg. Mean recoveries from fortified samples ranged from 95.5 to 106.7% with an RSD of 12.2%. The method LOD was < 0.02 microg/kg.     

Analysis of abamectin residues in avocados by high-performance liquid chromatography with fluorescence detection

In this work an analytical method for the determination of abamectin residues in avocados is developed using high-performance liquid chromatography (HPLC) with fluorescence (FL) detection. A pre-column derivatization with trifluoroacetic anhydride (TFAA) and N-methylimidazole (NMIM) was carried out. The mobile phase consisted of water, methanol and acetonitrile (5:47.5:47.5 v/v/v) and was pumped at a rate of 1 mL/min (isocratic elution). The fluorescence detector was set at an excitation wavelength of 365 nm and an emission wavelength of 470 nm. Homogenized avocado samples were extracted twice with acetonitrile:water 8:2 (v/v) and cleaned using C(18) solid-phase extraction (SPE) cartridges. Recovery values were in the range 87-98% with RSD values lower than 13%. The limits of detection (LODs) and quantification (LOQs) of the whole method were 0.001 and 0.003 mg/kg, respectively. These values are lower than the maximum residue limit (MRL) established by the European Union (EU) and the Spanish legislation in avocado samples.     

Simultaneous Analysis of Herbicide Metribuzin and Quizalofop-p-ethyl Residues in Potato and Soil by GC-ECD

A robust and sensitive method was developed for the simultaneous analysis of metribuzin and quizalofop-p-ethyl residues in potato and soil, based on solid-phase extraction (SPE) coupled to capillary gas chromatography with electron capture detector (GC-ECD). Residues of two herbicides were extracted from potato and soil with acetone and methanol–water, followed by SPE to remove coextractives, before analysis by GC-ECD. SPE procedures were performed on Florisil cartridges (500 mg, 3 mL), the analytes from potato and soil matrix were eluted with petroleum ether-acetic ether (9:1 v/v, 5 mL) and petroleum ether-acetic ether (8:2 v/v, 2 mL), respectively. Limits of quantification of the method were 0.01 mg kg^?1, and the mean recoveries ranged from 72.9 to 109.5% with relative standard deviation ranging from 0.7 to 9.2% at the three spike levels (0.01, 0.1, and 0.5 mg kg^?1). The proposed method was successfully applied to the analysis of metribuzin and quizalofop-p-ethyl residues in potato and soil samples from an experimental field. Direct confirmation of the analytes in real samples was achieved by gas chromatography-mass spectrometry (GC–MS).     

串联双柱固相萃取-高效液相色谱-电喷雾多级质谱法测定盐酸二甲双胍制剂中的盐酸二甲双胍及残留物三聚氰胺和双氰胺

建立了串联双柱固相萃取-高效液相色谱-电喷雾多级质谱（HPLC-ESI-MSⁿ）确认及测定盐酸二甲双胍制剂中的盐酸二甲双胍及残留物三聚氰胺和双氰胺的方法。盐酸二甲双胍制剂样品在超声辅助下,采用含0.1%（v/v）乙酸的无水乙醇溶液提取,选择Cleanert PCX-C18串联固相萃取双柱净化富集,以5%（v/v）氨水甲醇溶液为洗脱剂进行洗脱。采用Kromasil-C18色谱柱（100 mm×4.6 mm,3.5 μm）分离,梯度洗脱,在电喷雾多级质谱、选择离子模式下检测,外标法定量。通过比较制剂残留物在不同萃取溶剂、固相萃取柱及洗脱液等条件下的回收率,优化了前处理方法。结果表明,在各自的线性范围内,3种目标物的峰面积与质量浓度呈良好的线性关系,相关系数（r²）≥0.9992;方法的检出限为1.48~13.61 μg/kg,定量限为5.96~45.67 μg/kg。3种目标物在低、中、高加标水平下的平均回收率为65.02%~118.33%,相对标准偏差（RSD）≤13.41%（n=5）。该法操作简单,净化效果好,准确度高,重现性好,适用于检测和分析不同盐酸二甲双胍制剂中盐酸二甲双胍及残留物三聚氰胺和双氰胺。     

固相萃取-气相色谱法测定茶叶中残留的92种农药

建立了茶叶中92种农药多残留的气相色谱分析方法。茶叶样品用乙腈一次性提取后,有机磷类农药经Envi-Carb固相小柱净化,用10 mL乙腈-甲苯(体积比为3∶1)洗脱剂淋洗,气相色谱-火焰光度检测器(GC-FPD)检测;有机氯类和拟除虫菊酯类农药经串联Envi-Carb和NH2固相小柱净化,用5 mL乙腈-甲苯(体积比为3∶1)洗脱剂淋洗,GC-电子捕获检测器(ECD)检测。采用外标法定量。添加回收试验的结果表明:92种农药的平均回收率为80.3%～117.1%,相对标准偏差为1.5%～9.8%。方法的检出限为0.0025～0.10 mg/kg。该方法的灵敏度、准确度和精密度均符合农药残留测定的技术要求。     

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.     

Simultaneous determination of thiamethoxam,clothianidin, and metazachlor residues in soil by ultrahigh performance liquid chromatography coupled to quadrupole time‐of‐flight mass spectrometry

A rapid pioneering method has been developed to simultaneously determine residues of three pesticides (thiamethoxam, clothianidin, and metazachlor) in soil by ultrahigh performance liquid chromatography coupled to a mass spectrometry detector (quadrupole time‐of‐flight). An efficient extraction procedure (90–105% average analyte recoveries) has also been proposed, involving solid–liquid extraction by a mixture of water and methanol (60:40, v/v), centrifugation, and concentration. A chromatographic analysis of the compounds was achieved in 5.5 min by means of a core–shell technology based column (Kinetex^® EVO C₁₈, 50 × 2.1 mm, 1.7 μm, 100 Å). The mobile phase (0.3 mL/min, gradient elution mode) consisted of 0.1% v/v formic acid in water and 0.1% v/v formic acid in acetonitrile. The method was fully validated in terms of selectivity, detection and quantification limits, matrix effect, linearity, trueness, and precision. Low limits of detection and quantification were obtained, ranging from 0.2 to 3.0 μg/kg, which are similar to those published in previous studies, while the absence of a significant matrix effect allowed quantification of the pesticides with standard calibration curves. The proposed method was applied for an analysis of pesticides in several soil samples from experimental fields dedicated to oilseed rape cultivars.     

Trace analysis of fumagillin in honey by liquid chromatography-diode array-electrospray ionization mass spectrometry

In this work a new liquid chromatography with diode array detection and electrospray ionization mass spectrometry (LC-DAD-ESI-MS) method has been developed for the determination of fumagillin residues in honey. This procedure involves a solid-phase extraction on polymeric cartridges for the isolation of fumagillin from diluted honey. Chromatographic separation of fumagillin was performed in isocratic mode, on a C(18) column (150 mm x 4.60mm i.d., 5 microm), the mobile phase consisted of a mixture of ammonium formate 20mM in water and acetonitrile (61/39, v/v), at 35 degrees C and the flow rate was set at 1.0 mL/min. Average analyte recoveries, influenced by the botanical origin were from 88 to 96% in replica sets of fortified honey samples. The detection limits of the LC-DAD-ESI-MS method were between 24 and 1 microg/kg for clear honeys (rosemary) and between 45 and 4 microg/kg for dark honeys (heather). The developed method has been applied to the analysis of fumagillin residues in honey samples collected from veterinary treated beehives, infected by Nosema ceranae and fed with the technical product at different doses.     

Determination of quinolones in chicken tissues by liquid chromatography with ultraviolet absorbance detection

This paper presents an analytical method for the determination of quinolones in chicken tissues. The procedure involves pre-treatment by solid-phase extraction (SPE) and subsequent liquid chromatography (LC) with UV absorbance detection. Different SPE disposable cartridges and extractants of the tissue samples were tested, and various columns were systematically tested. The mobile phase was composed of acetonitrile and citric buffer at pH 4.5, with an initial composition of acetonitrile-water (12:88, v/v) and using linear gradient elution. Recoveries were 66-91% in the concentration range 30-300 microg kg(-1). The detector response was linear in this range. The limits of detection were 16-30 microg kg(-1). These values were lower than the maximum residue limits established by the European Union.     

超高效液相色谱-串联质谱法测定水稻基质中阿维菌素残留量

建立了超高效液相色谱-串联质谱法(UPLC-MS/MS)测定水稻基质中阿维菌素残留量,考察了基质效应,并对实际样品进行了检测.稻田土、稻壳、糙米和稻杆经乙腈振荡提取,稻田水经乙酸乙酯液液分配提取后,用C18固相萃取小柱或弗罗里硅土柱净化,采用UPLC-MS/MS正离子扫描测定残留的阿维菌素.稻田土、稻田水和糙米的3种添加浓度(1.0,10.0和100 μg/kg或μg/L)的平均回收率为84％～107％,相对标准偏差为4.7％～13.6％.稻壳和稻杆的2档添加浓度(10.0和100 μg/kg)的平均回收率为90％和103％,相对标准偏差为8.4％～12.9％.本方法在稻田水、糙米和稻田土中的检出限为0.3μg/kg在稻壳和稻杆中检出限为3.0 μg/kg,低于欧盟和日本在稻米中制定的阿维菌素最大残留限量值.阿维菌素在2.0～100 μg/L范围内线性关系良好( r＞ 0.999).     

Comparison of solvent extraction and solid-phase extraction for the determination of organochlorine pesticide residues in water.

Solid-phase extraction (SPE) of organochlorine pesticide residues from environmental water samples was evaluated using octadecyl (C18)-bonded porous silica. The efficiency of SPE of these pesticide residues from reagent water samples at 1-5 micrograms dm-3 levels was compared with those obtained by solvent extraction with hexane and Freon TF (trichlorotrifluoroethane). Average recoveries exceeding 80% for these organochlorine pesticides were obtained via the SPE method using small cartridges containing 100 mg of 40 microns C18-bonded porous silica. The average recovery by solvent extraction with hexane and Freon TF exceeded 90% in both instances. It was concluded that the recoveries and precision for the SPE of organochlorine pesticides were poorer than those for the solvent extraction method. Organochlorine pesticide residue levels in environmental water samples from two major rivers flowing through predominantly rice-growing areas were monitored by gas chromatography using the solvent extraction method with hexane. Exceptionally high levels of organochlorine pesticide residues such as BHC, DDT, heptachlor, endosulfan and dieldrin were found in these water samples.     

固相萃取-毛细管液相色谱测定食品和水样中有机磷和氨基甲酸酯类杀虫剂残留

采用乙腈提取、固相萃取（SPE）富集浓缩技术结合自行研制开发的毛细管液相色谱（CLC）仪,同时分离测定了食品和水样中1种有机磷和3种氨基甲酸酯类杀虫剂残留。对影响SPE效率和CLC分离检测的各类因素进行了优化,包括固相萃取柱种类、样品pH、洗脱剂种类和体积、上样速率、盐效应、上样体积、检测波长、流动相种类和比例等。结果表明,4种杀虫剂在6 min内达到完全分离,检出限为0.35~1.20 μg/kg,定量限为1.17~4.00 μg/kg。使用该SPE-CLC法对西红柿、黄瓜、苹果样品和自来水、湖水水样进行加标回收测定,得到食品中加标回收率为72.41%~107.15%,相对标准偏差≤8.12%;水样中加标回收率为71.45%~109.25%,相对标准偏差≤9.28%。该法能够满足农药多残留分析要求。     

Determination of imidazole and triazole fungicide residues in honeybees using gas chromatography-mass spectrometry

An analytical method employing clean up by high-performance gel permeation chromatography (HPGPC) and solid-phase extraction (SPE) on Florisil cartridges was developed to determine residues of eleven imidazole and triazole ergosterol-biosynthesis-inhibiting (EBI) fungicides in honeybee samples. Detection was by means of gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode. The method was validated by fortifying control samples at levels of 0.01 and 0.05 micro g/bee. Mean recoveries for each analyte except imazalil were between 79 and 99% with relative standard deviations of 12.3% or less. Mean recoveries of imazalil were 51% at 0.01 micro g/bee and 81% at 0.05 micro g/bee. Limits of detection for the analytes investigated ranged from 0.005 to 0.001 micro g/bee.     

Determination of ng/mL levetiracetam using ultra-high-performance liquid chromatography-photodiode absorbance

This paper demonstrates the analysis of levetiracetam, a new chiral antiepileptic drug, at ng/mL levels using an ultra-high-performance liquid chromatography (UHPLC)-photodiode absorbance (PDA) method. Three different sample preparation methods, liquid-liquid extraction with Extrelut, solid phase extraction (SPE) with Oasis HLB and Oasis MAX SPE cartridges, and protein precipitation with organic solvents were carried out. The last preparatory method is the simplest and provides the best recoveries: between 97.1% and 100.4% with RSD value below 5%. The column for separation is BEH C18 column (1.7 μm particle size and 100 × 2.1 mm i.d.) and acetonitrile-phosphate buffer (pH = 6.6; 0.01 M) (10/90 v/v) is the mobile phase. The results obtained are compared to analysis conducted by the HPLC method. The UHPLC method was validated in the range of 2-100 μg/mL levetiracetam concentration (R(2) = 0.9997). LOD and LOQ are 10 ng/mL and 33 ng/mL, respectively. The developed UHPLC method was applied to plasma samples of patient with epilepsy.     

Optimization of a Multiresidue Analysis of 65 Pesticides in Surface Water Using Solid-Phase Extraction by LC-MS/MS

An analytical method was developed and validated for simultaneous quantitation of 65 pesticides, including one single solid-phase extraction (SPE) procedure in surface water by liquid chromatography coupled to tandem mass spectroscopy. Different parameters that have an influence on extraction efficiency were evaluated in this research. Different types of cartridges, elution solvents, and sorbent drying time were investigated, and the most appropriate one was selected. Moreover, various pretreatment techniques were applied to remove sediments from water without the loss of pesticides. Centrifugation was introduced as the best option at the beginning of sample preparation to resolve the clogging of the sorbent cartridges. The recoveries of all pesticides ranged from 70% to 120%, with a relative standard deviation of less than 13.7%. The feasibility of the method was evaluated on 10 surface water samples with different concentrations of sand, sediment, and particles.     

Quantitation of nifedipine in human plasma by on-line solid-phase extraction and high-performance liquid chromatography

An analytical methodology for nifedipine quantitation in plasma by on-line solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) is described. The SPE cartridges contain C₂ and the analytes nifedipine and nitrendipine (internal standard) are separated on a C₁₈ column with a mobile phase consisting of acetonitrile–13 mM phosphate buffer pH 7 (65:35, v/v) followed by UV detection at 338 nm. Validation of the method demonstrated good recoveries (>90%), sensitivity (limit of quantification, 2 ng/ml), based on a 500 μl sample volume, accuracy and precision (<5.5% in concentrations greater than the limit of quantitation). This methodology has been used for bioequivalence studies.     

饮用水中9种卤乙酸的超高效液相色谱法测定

建立了固相萃取/超高效液相色谱(SPE/UPLC)测定饮用水中9种痕量卤乙酸(HAAs)的分析方法.对固相萃取和液相色谱等分析条件进行了优化,选择Lichrolut EN固相萃取小柱富集饮用水中的HAAs,三乙胺-磷酸缓冲液和甲醇作为UPLC的流动相.在优化的分析条件下,9种卤乙酸在6min内实现基线分离,所有目标物在一定质量浓度范围内线性良好,相关系数为0.995 7～0.9999;一氯乙酸(MCAA)的检出限为10.85μg/L,其它8种化合物的检出限为0.25～0.70μg/L;除MCAA外,其它目标物在低、中、高3种加标水平的回收率为60%～106%.方法的相对标准偏差(RSD,n=5)为2.0%～5.7%.将此方法应用于我国北方某城市自来水中卤乙酸的测定,5种HAAs被检出.方法灵敏度高、简便快捷,可用于生活饮用水中痕量卤乙酸的测定.