Multi-screening approach to monitor and quantify 42 antibiotic residues in honey by liquid chromatography-tandem mass spectrometry

A multi-screening approach for monitoring potential chemical contaminants in honey by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) has been developed. A total of 42 veterinary drugs (5 tetracyclines, 7 macrolides, 3 aminoglycosides, 8 beta-lactams, 2 amphenicols and 17 sulfonamides) were surveyed with the ultimate goal of unambiguously confirmed and quantified these analytes at a concentration level of 20 microg/kg. A basic sample preparation including four subsequent liquid/liquid extraction steps was necessary to adequately extract the compounds of interest from the honey. The four extracts were injected into the LC-ESI-MS/MS using a stacking injection procedure. Validation of the entire procedure was carried out according to the European Union directive 2002/657/EC at three concentration levels, i.e., 10, 20 and 30 microg/kg. Good performance data were obtained for 37 analytes, out of the 42 studied. Limit of compliance and detection limit were calculated based on an internal limit set at 20 microg/kg for all the compounds and ranged between 24-30 and 27-80 microg/kg, respectively. A limited survey on honeys of different geographical origins has demonstrated that positive honey samples were often contaminated by more than one class of drugs, thus highlighting the usefulness of such multi-screening approach to ensure and warrants the quality of honey.     

Determination of eight sulfonamides in bovine kidney by liquid chromatography/tandem mass spectrometry with on-line extraction and sample clean-up

A sensitive, high performance liquid chromatography/tandem mass spectrometric (i.e. mass spectrometry/mass spectrometry; LC/MS/MS) method with on-line extraction and sample clean-up for the screening and confirmation of residues of sulfonamides in kidney is described. The sulfonamides are extracted from homogenized kidney with methanol. After centrifugation of the extract, an aliquot of the extract is directly injected on the LC/MS/MS system with further extraction and clean-up of the sample on-line. Detection of the analytes was achieved by positive electrospray ionization (ESI) followed by multiple reaction monitoring. For each sulfonamide the collisional decomposition of the protonated molecule to a common, abundant fragment ion was monitored. The method has been validated for sulfadimethoxine, sulfaquinoxaline, sulfamethazine, sulfamerazine, sulfathiazole, sulfamethoxazole, sulfadiazine and sulfapyridine. Calibration curves resulting from spiked blank kidney samples at the 10-200 microg/kg level showed good linear correlation. At the level of 50, 100 and 200 microg/kg both within- and between-day precision, as measured by relative standard deviation (RSD), were less than 16%. The limits of detection (LODs) ranged from 5 to 13.5 microg/kg. The recoveries ranged from 78 to 82%. The procedure provides a rapid, reliable and sensitive method for the determination of residues of sulfonamides in bovine kidney. The advantage of this method over existing methods is its decreased sample preparation and analysis time, which makes the method more suitable for routine analysis.     

Simultaneous determination of 16 sulfonamides in honey by liquid chromatography/tandem mass spectrometry

A method is described for the determination of 16 sulfonamides in honey. Samples are dissolved in phosphoric acid solution (pH2), cleaned up with 2 solid-phase extraction (SPE) cartridges, an aromatic sulfonic cation-exchange cartridge and an Oasis HLB SPE cartridge, and analyzed both qualitatively and quantitatively by liquid chromatography/tandem mass spectrometry (LC/MS/MS) under the selected conditions. Without exception, calibration curves were linear (r = > 0.995), when sulfamethizole was between 1.0 and 25.0 microg/kg; sulfacetamide, sulfapyridine, sulfadiazine, sulfachloropyridazine, sulfamethoxazole, sulfamerazine, sulfisoxazole, sulfamonomethoxine, and sulfadoxine were between 2.0 and 50.0 microg/kg; sulfamethoxypyridazine, sulfadimethoxine, and sulfathiazole were between 4.0 and 100.0 microg/kg; sulfamethazine and sulfameter were between 8.0 and 200.0 microg/kg; and sulfaphenazole was between 12.0 and 300.0 microg/kg. Average recoveries at 4 fortification levels in the range of 1.0-300 microg/kg in honey were 70.9-102.5%, and relative standard deviations were 2.02-11.52%. The limits of quantitation for the 16 sulfonamides were between 1.0 and 12.0 microg/kg, with the LC/MS/MS method.     

Determination of lincomycin and tylosin residues in honey by liquid chromatography/tandem mass spectrometry

A simple and rapid analytical method was developed for the determination of lincomycin and tylosin residues in honey as part of field studies examining the efficacy and target animal safety of these antibiotics to control American foulbrood disease in honey bees. Residues of the antibiotics were determined using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). Honey samples were diluted and injected directly into the LC/MS/MS system without additional cleanup by solid-phase extraction or liquid-liquid partitioning. A six-port valve system was utilized to selectively route eluant from the LC column into the mass spectrometer only during a relatively short portion of the chromatographic run corresponding to the elution of the analytes of interest. Minimal contamination of the MS source chamber was observed despite the analysis of large numbers of samples. Using internal standard quantitation, excellent accuracy and precision were obtained with no apparent matrix-to-matrix variation. Based on the analysis of fortified replicates, the mean percent deviation from the theoretical concentration and the percent relative standard deviation were both less than 10% for tylosin over an analytical range of 10-1000 microg/kg. Slightly higher mean percent deviations and relative standard deviations were observed for the analysis of lincomycin in fortified replicate samples. The method detection limits were determined to be 5 and 2 microg/kg for lincomycin and tylosin, respectively.     

Study of matrix effects on the direct trace analysis of acidic pesticides in water using various liquid chromatographic modes coupled to tandem mass spectrometric detection

This study investigated the effects of matrix interferences on the analytical performance of a triple quadrupole mass spectrometric (MS-MS) detector coupled to various reversed-phase liquid chromatographic (LC) modes for the on-line determination of various types of acidic herbicides in water using external calibration for quantification of the analytes tested at a level of 0.4 microg/l. The LC modes included (i) a single-column configuration (LC), (ii) precolumn switching (PC-LC) and (iii) coupled-column LC (LC-LC). As regards detection, electrospray (ESI) and atmospheric pressure chemical ionization (APCI) in both positive (PI) and negative (NI) ionization modes were examined. Salinity and dissolved organic carbon (DOC) were selected as interferences to study matrix effects in this type of analysis. Therefore, Milli-Q and tap water samples both fortified with 12 mg/l DOC and spiked with sulfometuron-methyl, bentazone, bromoxynil, 2-methyl-4-chlorophenoxyacetic acid, and 2-methyl-4-chlorophenoxypropionic acid at a level of about 0.4 microg/l were analyzed with the various LC-MS approaches. Direct sample injection was performed with volumes of 0.25 ml or 2.0 ml on a column of 2.1 mm I.D. or 4.6 mm I.D. for the ESI and APCI modes, respectively. The recovery data were used to compare and evaluate the analytical performance of the various LC approaches. As regards matrix effects, the salinity provided a dramatic decrease in response for early eluting analytes (k value of about 1) when using the LC mode. Both PC-LC and LC-LC efficiently eliminated this problem. The high DOC content hardly effected the responses of analytes in the ESI mode, while in most cases the responses increased when using APCI-MS-MS detection. Of all the tested configurations, LC-LC-ESI-MS-MS with the column combination Discovery C18/ABZ+ was the most favorable as regards elimination of matrix effects and provided reliable quantification of all compounds using external calibration at the tested low level. The major observed effects were verified with statistical evaluation of the data employing backwards ordinary least-square regression. All tested column-switching modes hyphenated to ESI- or APCI-MS-MS allowed the on-line multi-residue analysis of acidic pesticides in the reference water down to a level of 0.1 microg/l in less than 10 min, emphasizing the feasibility of such an approach in this field of analysis.     

固相萃取-液相色谱-质谱/质谱法同时测定蜂蜜中的多类药物残留

建立了采用固相萃取-液相色谱-质谱/质谱(SPE-LC-MS/MS)对蜂蜜中磺胺类、硝基咪唑类、喹诺酮类、大环内酯类、林可酰胺类和吡喹酮共计6大类54种药物残留同时测定的方法。蜂蜜经磷酸盐缓冲溶液(pH 8)稀释,Oasis HLB固相萃取柱净化后,通过液相色谱-质谱联用技术进行检测(正离子方式,多反应监测模式)。采用同位素稀释内标法或外标法进行定量,线性关系良好,相关系数大于0.992。方法的定量限(LOQ,以信噪比(S/N)大于10计)分别为磺胺类和硝基咪唑类药物1.0 μg/kg,喹诺酮类和林可酰胺类药物2.0 μg/kg,大环内酯类药物3.0 μg/kg,吡喹酮0.3 μg/kg。总体回收率为32.6%～114%,相对标准偏差为1.3%～28.9%。该方法的定量限满足目前国内外药物的最大残留限量要求,可作为蜂蜜中相关药物残留量的筛选检测方法。     

The determination of sulfonamides in honey by high performance liquid chromatography--mass spectrometry method (LC/MS)

The sulfonamides (SAs) are stable chemotherapeutics used against the bacterial disease affecting bees, known as American foulbrood (Bacillus larvae), so their residues could appear in the honey of treated bees. Their presence at a concentration above the limit value could be a potential danger to human health. Therefore, a simple, rapid, and reliable method for determination of 11 available SAs in honey was optimized. The samples were homogenized and cleaned with extraction on solid phase by means of Chromabond C18 end-capped cartridge followed by LC/MS analyses. A detection limit of 25 microg/kg was achieved for all analytes. The repeatability of the method was proven and the optimal parameters for temperature and pH of the mobile phase and acetic buffer, respectively, were determined. In this study, 20 samples of domestic honey were included. Six of the analyzed samples were positive, but all results were below the Croatian permissible limit value (100 microg/kg).     

Development and validation of a liquid chromatography-electrospray tandem mass spectrometry method for mebendazole and its metabolites hydroxymebendazole and aminomebendazole in sheep liver

A quantitative liquid chromatography-electrospray tandem mass spectrometry method for the determination of mebendazole and its hydrolysed and reduced metabolites in sheep liver has been developed and validated. The benzimidazole substances were extracted with ethyl acetate after the sample mixture had been made alkaline. The HPLC separation was performed on a reversed-phase C18 column with gradient elution using a mobile phase consisting of water containing 0.1% formic acid and acetonitrile. The analytes were detected after atmospheric pressure electrospray ionization on a tandem quadrupole mass spectrometer in MS-MS mode. The components were measured by the MS-MS transitions of the molecular ion to the two most abundant daughter ions. The detection limits are lower than 1 microg kg(-1). For this application, the validation limit was set at 50 microg kg(-1). The examined validation parameters were in accordance with the permitted tolerances ranges stipulated in the proposed new European validation criteria for residue surveillance. For the three analytes, the overall recovery was higher than 90%. The RSD for the repeatability ranged from 5 to 11%. The range for the within-laboratory reproducibility was between 2 and 17%. The decision limits for mebendazole, the hydrolysed and the reduced metabolite were 56.6, 61.8 and 64.2 microg kg(-1), respectively. The detection capabilities for these substances were 60.0, 86.1 and 90.9 microg kg(-1), respectively.     

Determination of selected sulfonamide antibiotics and trimethoprim in manure by electrospray and atmospheric pressure chemical ionization tandem mass spectrometry

A method for the determination of sulfonamides and trimethoprim in the complex matrix liquid manure has been developed using reversed-phase liquid chromatography and atmospheric pressure chemical ionization (APCI) tandem mass spectrometry. A comparison was made between electrospray and atmospheric pressure chemical ionization. APCI proved to be more robust and less sensitive to matrix effects. High-performance liquid chromatographic (HPLC) separation of the analytes was achieved in less than 7 min. The compounds were extracted with ethyl acetate and the extracts were cleaned up by solid-phase extraction on an aminopropyl column. Recoveries were not dependent on the concentration level. The mean recoveries were as follows: trimethoprim 79.0%, sulfadiazine 80.5%, N(4)-acetylsulfadiazine 91.0%, sulfamerazine 78.6%, sulfadimidine 77.2% and sulfamethoxazole 82.8%. Linearity was established over a concentration range of 5 to 5000 microg/kg with correlation coefficients greater than 0.99. The method had a limit of quantitation (LOQ) of 5 microg/kg manure.     

Simultaneous determination of betamethasone and dexamethasone residues in bovine liver by liquid chromatography/tandem mass spectrometry

In this study a new method for the simultaneous confirmation of betamethasone and dexamethasone residues in bovine liver is presented. A Quattro LCZ triple quadrupole mass spectrometer, equipped with an atmospheric pressure ionization (API) source, was coupled to a high performance liquid chromatograph (HPLC) system. Spiked liver samples were first extracted with acetonitrile, and the extracts were purified on C-18 columns. LC separations were performed on a Hypercarb column, with acetonitrile/water (90:10, v/v, +0.3% formic acid) as the mobile phase. Retention times for dexa- and betamethasone were 6.60 and 8.50 min, respectively. Fluorometholone had a retention time of 6.70 min and was used as the internal standard. The detection of the analytes was performed in the multiple reaction monitoring (MRM) mode. The assay was linear over the range of 0.5 to 8 microg/kg for both analytes. The estimated determination limits were 0.2 microg/kg for both beta- and dexamethasone and the quantification limits were 0.4 microg/kg for dexamethasone and 0.3 microg/kg for betamethasone. Analysis precision at 1, 2 and 4 microg/kg was lower than 6.1% (relative standard deviation, RSD) and accuracy was at least 97.5%. Recoveries at 1, 2 and 4 microg/kg ranged between 56 and 69%.     

多壁碳纳米管固相萃取技术同时测定蜂蜜中多类兽药残留

采用多壁碳纳米管固相萃取-超高效液相色谱-串联质谱技术同时测定蜂蜜中的磺胺类、喹诺酮类、硝基咪唑类和四环素类等52种兽药残留. 样品用Na₂EDTA-Mcllvaine提取,经改性的多壁碳纳米管固相萃取小柱净化,通过Waters C₁₈色谱柱分离,以乙腈和0.1%（体积分数）的甲酸水溶液为流动相进行梯度洗脱,采用电喷雾-正离子多反应监测的质谱模式,以基质外标法进行定量分析. 实验结果表明,52种兽药在相应的浓度范围内线性相关系数均大于0.99,该方法的定量限为1.5 ~7.5 μg/kg. 在7.5,25和50 μg/kg 3个浓度添加水平下,各种兽药的回收率为67.3% ~117.8%,相对标准偏差为1.9% ~17.4%. 结果表明,多壁碳纳米管固相萃取材料具有较好的净化效果,适用于蜂蜜中多类兽药残留的同时检测.     

Applicability of gradient liquid chromatography with tandem mass spectrometry to the simultaneous screening for about 100 pesticides in crops

A method was developed for screening crops for a range of pesticide residues by liquid chromatography/tandem mass spectrometry (LC/MS/MS). A complete set of LC, electrospray ionization (ESI), and tandem MS acquisition parameters was established for the determination of 108 analytes; these parameters were used for the simultaneous acquisition of 98 analytes in the positive ESI mode and 10 analytes in an additional MS/MS method in the negative ESI mode. The entire procedure involves extraction of residues with methanol-water and partition into dichloromethane. The utility of the method is demonstrated by the analysis of crops of 5 matrix types (water-containing, acidic, dry, sugar-containing, and fatty). Of 108 pesticides/metabolites tested, 104 showed sufficient stability in most matrixes for determination by LC/MS/MS. These analytes belong to 20 chemical classes, which demonstrate the general applicability of the method for multiclass analysis. By using matrix-matched standards, 67 compounds could be determined in most matrixes with recoveries of 70-120% and a relative standard deviation of < or = 25% at the 0.01 mg/kg level.     

Selenium speciation by HPLC with tandem mass spectrometric detection

An HPLC/MS-MS method was developed for the analysis of selenium species. Tandem mass spectrometry (MS-MS) was chosen as a detector to provide structural and molecular information allowing the identification of species, which are not commercially available as standards. A new separation method for selenium species was developed, based on porous graphitic carbon (PGC) as the stationary phase. The applicability of the optimized HPLC/MS-MS system was demonstrated by the analysis of a mixture containing Se-methyl-selenocysteine, selenomethionine, selenocystine, selenoethionine and selenocystamine. All peaks were baseline-resolved and eluted within 16 min. Positive ionization led to higher intensities than negative ionization. Signal suppression tests showed that electrospray ionization (ESI) is a more effective ionization method than atmospheric pressure chemical ionization (APCI) for selenium species in a matrix containing pentafluoropropionic acid, heptafluorobutyric acid or ammonium formate. Comparative experiments with a triple quadrupole mass spectrometer (Quattro LC) and a time-of-flight instrument (Q-Tof-2) showed a 20 fold higher mass resolution of the latter mass spectrometer (m/Am= 5000) and significantly lower intensities for analyte signals as well as background noise compared to the triple quadrupole instrument. MS-MS spectra of the investigated selenium species including characteristic fragmentation patterns are presented.     

气相色谱-质谱法分析蜂蜜中的多种农药残留

开展了蜂蜜中23种农药残留的气相色谱-电子轰击离子源质谱(GC-EI/MS)分析方法的研究,并对其中3种农药的EI/MS碎片离子的断裂机理与结构进行了初步解析。探讨了蜂蜜试样前处理条件的优化与选择。将蜂蜜试样用乙酸乙酯提取剂超声提取、Florisil硅藻土色谱柱净化和正己烷-乙酸乙酯(体积比为7∶3)混合洗脱剂洗脱后,以PCB103为内标物,采用选择离子监测(SIM)方式下的GC-EI/MS分析。当试样的加标浓度为50,100和200 μg/kg时,加标回收率为82%～120%,相对标准偏差小于11.0%。23种农药的检测限都小于10.0 μg/kg,线性范围为10～500 μg/kg,相关系数都大于0.995。此分析方法已成功地应用于蜂蜜中23种痕量农药残留的分析。     

A simple hollow fiber renewal liquid membrane extraction method for analysis of sulfonamides in honey samples with determination by liquid chromatography–tandem mass spectrometry

A sensitive and precise analysis using hollow fiber renewal liquid membrane (HFRLM) extraction followed by high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) is described for determination of five sulfonamides in honey samples. In this procedure, the organic solvent introduced directly into the sample matrix extracts the sulfonamides and carries them over the polypropylene porous membrane. An organic solvent is immobilized inside the polypropylene porous membrane, leading to a homogeneous phase. The stripping phase at higher pH in the lumen of the membrane promotes the ionization of the target compounds releasing them to this phase. The most important parameters affecting the extraction efficiency were optimized by multivariable designs (pH and sample mass, pH and buffer for stripping phase, extraction temperature and time, type and volume of extractor solvent and use of salt to saturate the sample). Detection limits in the range of 5.1–27.4 μg kg⁻¹ and linearity coefficient of correlation higher than 0.987 were obtained for the target analytes. The results obtained for the proposed method show that HFRLM–LC–MS/MS can be used for determination of the five sulfonamides studied in honey samples with excellent precision, accuracy, practicality and short analysis time.     

Pharmacokinetic study of free mangiferin in rats by microdialysis coupled with microbore high-performance liquid chromatography and tandem mass spectrometry

Mangiferin (2-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthen-9-one) has been isolated from the herbal root of Anemarrhena asphodeloides Bung showing antioxidative, antiviral, and anticancer effect. An in vivo microdialysis sampling method coupled to microbore high-performance liquid chromatography (HPLC) was employed for continuous monitoring of free mangiferin in rat blood. Microdialysis probes were inserted into the jugular vein/right atrium and brain striatum of Sprague-Dawley rats, and mangiferin at doses of 10, 30 or 100 mg/kg were then administered via the femoral vein. Dialysates were collected every 10 min and injected directly into a microbore HPLC system. Mangiferin was separated by a reversed-phase C18 microbore column (150 x 1 mm) from dialysate within 10 min. The mobile phase consisted of acetonitrile-0.05% phosphoric acid-tetrahydrofuran (10:75:15, v/v/v) with a flow-rate of 0.05 ml/min. The wavelength of the UV detector was set at 257 nm. The limit of quantification for mangiferin was 0.05 microg/ml and in vivo recovery of mangiferin at concentrations of 1, 5 and 10 microg/ml was in range of 37.7-39.8%. The results indicate that the pharmacokinetics of mangiferin at doses of 10-30 mg/kg reveals a linear relation, while doses of 30-100 mg/kg show a nonlinear pharmacokinetic phenomenon. Mangiferin was undetectable in brain dialysate. The proposed method provides a technique for rapid and sensitive analysis of free mangiferin in rat blood and further application in pharmacokinetic study. Furthermore, the metabolites of mangiferin in the rat bile were confirmed by LC electrospray ionization (ESI) tandem mass spectrometry (MS-MS).     

Determination of sulfonamides by liquid chromatography, ultraviolet diode array detection and ion-spray tandem mass spectrometry with application to cultured salmon flesh.

Ion-spray mass spectrometry was investigated for the analysis of 21 antibacterial sulfonamide drugs. All of the sulfonamides analyzed gave positive ion mass spectra with abundant protonated molecules and no fragmentation. Tandem mass spectrometry (MS-MS) using collision-induced dissociation provided structural information, allowing the identification of common fragmentation pathways and the differentiation of isomeric and isobaric sulfonamides. A reversed-phase high-performance liquid chromatographic method was developed, using gradient elution and ultraviolet diode-array detection (DAD), enabling the separation of 16 of the sulfonamides. Combined liquid chromatography (LC)-MS was accomplished using the ion-spray interface. Analyses of a mixture of sulfonamide standards were performed with gradient elution and the mass spectrometer configured for full-scan acquisition, selected-ion monitoring, or selected-reaction monitoring. Procedures for the analysis of sulfadimethoxine (SDM), a representative sulfonamide used in the aquaculture industry, are described. The presence of SDM in cultured salmon flesh was confirmed at levels as low as 25 ng/g by a combination of LC-DAD and LC-MS-MS.     

Determination of three natural pesticides in processed fruit and vegetables using high-performance liquid chromatography/tandem mass spectrometry

This paper describes a method for the sensitive and selective determination of two macrocyclic lactones (abamectin and spinosad) and azadirachtin in apple purée, concentrated lemon juice, tomato purée and canned peas. The general sample extraction-partitioning method for our gas chromatography and liquid chromatography multiresidue methods has been used. The analytical procedure involves an extraction with acetone and liquid-liquid partitioning with ethyl acetate/cyclohexane combined in one step. The extracts are analyzed by liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) without any further clean-up step. The pesticides are separated on a reversed-phase C12 column using a gradient elution. Thirteen simultaneous MS/MS transitions of precursor ions were monitored. Studies at fortification levels of 2.5-10 microg/kg and 25-100 microg/kg gave mean recoveries ranging from 70-100% for all compounds with satisfactory precision (relative standard deviation (RSD) from 3-20%). The excellent selectivity and sensitivity allows quantification and identification of low levels of pesticides in canned peas, tomato and apple purées (limits of quantitation (LOQs) 1-5 microg/kg) and in concentrated lemon juice (LOQs 2-10 microg/kg). The quantification of analytes was carried out using the most sensitive transition for every compound and by 'matrix-matched' standards calibration.     

Identification and quantification of polar naphthalene derivatives in contaminated groundwater of a former gas plant site by liquid chromatography-electrospray ionization tandem mass spectrometry

A liquid chromatography (LC) method followed by electrospray ionization (ESI) and tandem mass spectrometry (MS-MS) was developed for the quantification of acidic naphthalene derivatives in the concentration range 0.1 to 100 microg/l without excessive sample preparation. For optimal sensitivity the LC-MS-MS measurements were performed recording mass fragmentation by collision induced dissociation in the multiple reaction mode. The collision energy was optimized for every analyte. The matrix effects of the sample were investigated by spiking standards of 1-naphthoic acid with humic acid (HA) and with calcium chloride. While HA decreased the signal intensity an increase was observed in the presence of calcium chloride. For the investigated groundwater samples of a tar oil contaminated site a complete separation of the analytes from the sample matrix by reversed-phase separation could be obtained. The absence of matrix effects on quantification results was confirmed by comparison of results based on external calibration with those based on standard addition of the analytes to a groundwater sample. In four groundwater samples of the contaminated site naphthalene derivatives like 1-naphthoic acid, 2-naphthoic acid, 1-naphthylacetic acid, 2-naphthylacetic acid, 1-hydroxy-2-naphthoic acid, 2-hydroxy-3-naphthoic acid, and naphthyl-2-methylenesuccinic acid have been detected.     

Analyses of pesticide residues in fruit-based baby food by liquid chromatography/electrospray ionization time-of-flight mass spectrometry

A liquid chromatography/electrospray ionization time-of-flight mass spectrometry (LC/ESI-TOFMS) method has been developed for the determination of 12 pesticides (namely, carbendazim, thiabendazole, imazalil, tridemorph, triadimefon, bitertanol, prochloraz, flutriafol, myclobutanil, iprodione, diphenylamine and procymidone) in fruit-based baby food (multi-fruit jars and juices intended for infant consumption). The developed method consists of a sample treatment step based on liquid-liquid extraction using acetonitrile, followed by a clean-up step based on dispersive solid-phase extraction (SPE) with a primary-secondary amine (PSA). Multi-fruit and apple juices were processed by a SPE procedure using Oasis HLB cartridges. Subsequent identification and quantitation was accomplished by LC/ESI-TOFMS analysis: the confirmation of the target pesticides was based on accurate mass measurements of selected ions (protonated molecules ([M+H]+) and fragment ions). Confirmation studies were accomplished at low concentration levels (10 microg kg-1) and accuracy errors lower than 2 ppm were obtained in most cases. Baby food extracts spiked at 10 microg kg-1 fortification level yielded average recoveries in the range 78-105% with relative standard deviations less than 10% for most of the analytes. Limits of detection (LODs) were between 0.1 and 4 microg kg-1 depending on the pesticide studied. Finally, the proposed method was applied to a total of 33 baby food samples from Spain and the United Kingdom. Although imazalil, thiabendazole and carbendazim were detected in a high number--over 60%- of baby food samples, none of the samples tested were found to be above the 0.01 mg kg-1 EU standard.