Determination of trinexapac in wheat by liquid chromatography-electrospray ionization tandem mass spectrometry

A quantitative and confirmatory method for the analysis of trinexapac (free acid metabolite of trinexapac-ethyl) in wheat is described. Residues were extracted from wheat with acetonitrile in aqueous phosphate buffer (pH 7) overnight. The extract was directly injected into the HPLC system. Chromatographic separation was achieved on an octadecylsilica column, and detection was performed by negative ion electrospray ionization tandem mass spectrometry. The precursor ion of trinexapac [M - H](-) at m/z 223 was subjected to collisional fragmentation with argon to yield two intense diagnostic product ions at m/z 135 and 179, respectively. Accuracy and specificity for routine analysis of trinexapac were demonstrated. The validated concentration range was 10-200 microg/kg based on a 0.10 g/mL wheat sample extract. Recoveries were within the range of 71-94%, with associated relative standard deviations better than 10%. The limit of detection for trinexapac in wheat was estimated at 5 microg/kg. The method has been applied to a survey of 100 samples of wheat. In 46% of the samples analyzed, a quantifiable amount of trinexapac was detected, ranging from 10 to 110 microg/kg. It has been demonstrated that analyses of trinexapac accurately reflect the total amount of residues of the plant growth regulator, trinexapac-ethyl, in the wheat samples following field application. No residues of the parent compound, trinexapac-ethyl, in wheat were detected.     

Determination of furaltadone and nifursol residues in poultry eggs by liquid chromatography-electrospray ionization tandem mass spectrometry

The use of nitrofurans as veterinary drugs has been banned from intensive animal production in the European Union (EU) since 1993. The objective of the present study was to evaluate the accumulation and depletion of furaltadone and nifursol and their side-chain metabolites 5-methylmorpholino-3-amino-2-oxazolidinone (AMOZ) and 3,5-dinitrosalicylic acid hydrazide (DNSAH) in eggs after administration of therapeutic and subtherapeutic doses of the drugs to laying hens during three consecutive weeks. LC-MS/MS, with positive and negative electrospray ionization methods, was used for the determination of parent compounds and metabolites in yolk and egg white and was validated according to criteria established by Commission Decision 2002/657/EC. The decision limit (CCα) and the detection capability (CCβ) of the analytical methodology for metabolites were 0.1 and 0.5 μg/kg for AMOZ and 0.3 and 0.9 μg/kg for DNSAH, respectively. For the parent compounds, CCα and CCβ were 0.9 and 2.0 μg/kg for furaltadone and 1.3 and 3.1 μg/kg for nifursol, respectively. The data obtained show that the parent compounds are much less persistent than their side-chain metabolites in either yolk or egg white. Between the studied metabolites, AMOZ is the most persistent and could be detected in either yolk or egg white three weeks following withdrawal from treatment.     

Determination of oleandrin in tissues and biological fluids by liquid chromatography-electrospray tandem mass spectrometry

A rapid LC-MS/MS method, using a triple-quadrupole/linear ion trap mass spectrometer, was developed for the quantitative determination of oleandrin in serum, urine, and tissue samples. Oleandrin, the major cardiac glycoside of oleander (Nerium oleander L.), was extracted from serum and urine samples with methylene chloride and from tissues with acetonitrile. The tissue extracts were cleaned up using Florisil solid-phase extraction columns. Six replicate fortifications of serum and urine at 0.001 microg/g (1 ppb) oleandrin gave average recoveries of 97% with 5% CV (relative standard deviation) and 107% with 7% CV, respectively. Six replicate fortifications of liver at 0.005 microg/g (5 ppb) oleandrin gave average recoveries of 98% with 6% CV. This is the first report of a positive mass spectrometric identification and quantitation of oleandrin in tissue samples from oleander intoxication cases. The sensitivity and specificity of the LC-MS/MS analysis enables it to be the method of choice for toxicological investigations of oleander poisoning.     

Direct determination of paclobutrazol residues in pear samples by liquid chromatography-electrospray tandem mass spectrometry

A rapid and sensitive liquid chromatography/electrospray ionization/tandem mass spectrometry (LC-ESI-MS-MS) method has been developed for the determination of the plant growth regulator paclobutrazol in pear samples. Extraction was performed with methanol by using a high-speed blender Ultra-Turrax, and 10 microL of pear extract was directly injected in the LC-ESI-MS-MS system without any previous sample treatment. The highest sensitivity of the method was achieved under MS-MS conditions obtaining a limit of detection of 0.7 microg/kg and a quantification limit of 5 microg/kg, with a run time of only 5.5 min. Recoveries for paclobutrazol from spiked pear samples at 0.005, 0.05, and 0.5 mg/kg were around 82-102% with relative standard deviations between 2 and 7%. The method was applied to real treated and untreated samples of pears, using quality control samples as a evaluation of the method reliability. Two MS-MS transitions were selected, one for quantification (294 > 70) and the other for confirmation of the analyte (296 > 70). All the experiments were performed in compliance with good laboratory practices.     

Simultaneous determination of multiple phytohormones in plant extracts by liquid chromatography-electrospray tandem mass spectrometry

A rapid multiresidue method to quantify three different classes of plant hormones has been developed. The reduced concentrations of these metabolites in real samples with complex matrixes require sensitive techniques for their quantification in small amounts of plant tissue. The method described combines high-performance liquid chromatography with electrospray ionization tandem mass spectrometry. Deuterium-labeled standards were added prior to sample extraction to achieve an accurate quantification of abscisic acid, indole-3-acetic acid, and jasmonic acid in a single run. A simple method of extraction and purification involving only centrifugation, a partition against diethyl ether, and filtration was developed and the analytical method validated in four different plant tissues, citrus leaves, papaya roots, barley seedlings, and barley immature embryos. This method represents a clear advantage because it extensively reduces sample preparation and total time for routine analysis of phytohormones in real plant samples.     

Rapid determination of domoic acid in serum and urine by liquid chromatography-electrospray tandem mass spectrometry

A rapid, selective, and sensitive LC-MS/MS method was developed for the quantitative determination of domoic acid in serum and urine samples. Samples were prepared for analysis using an Oasis HLB SPE column. Determination was by a reversed phase HPLC using a mixture of methanol, acetonitrile, and water containing 1% acetic acid and an electrospray ionization (ESI) ion-trap mass spectrometer (Finnigan LCQ). The method was validated by analyzing five replicates each of negative control bovine serum or urine fortified with domoic acid at the 0.005 microg/g method detection limit (MDL) and at the 0.05 microg/g level. Recoveries ranged from 90 to 95% for fortifications at the MDL and from 92 to 98% for fortifications 10 times higher than the MDL. The diagnostic utility of the method was tested by analyzing samples from live animals showing clinical signs suggestive of domoic acid poisoning submitted to the veterinary toxicology laboratory.     

Determination of pesticides in apple-based infant foods using liquid chromatography electrospray ionization tandem mass spectrometry

A liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method was developed and validated to quantify and confirm trace levels of 13 pesticides including aldicarb sulfoxide, aldicarb sulfone, oxamyl, methomyl, formetanate, 3-hydroxycarbofuran, carbendazim, thiabendazole, aldicarb, propoxur, carbofuran, carbaryl, and methiocarb in apple-based infant foods such as apple sauces, apples and strawberries, apples and blueberries, and apples and plums. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring of two fragment ion transitions to provide a high degree of sensitivity and selectivity for both quantification and confirmation. LC/ESI-MS/MS quantitative results were significantly affected by matrices, and thus, the standard addition was employed to compensate for the matrix effects to achieve the best accuracy of the method. Recoveries of 13 pesticides, spiked at 5.0, 25.0, and 45.0 microg/kg, were around 100% using the LC/ESI-MS/MS standard addition. The method detection limits (S/N > or = 3:1) of 13 pesticides were less than 0.2 microg/kg.     

Determination of saponins in aerial parts of barrel medic (Medicago truncatula) by liquid chromatography-electrospray ionization/mass spectrometry

Triterpene saponins from aerial parts of Medicago truncatula cv. Jemalong A-17, M. truncatula Gaertn.var. longispina Urb., and M. truncatula Gaertn. var. truncatula were profiled and quantified using reverse-phase liquid chromatography with on-line photodiode array detection and electrospray ionization mass spectrometry (LC-PDA/ESI/MS/MS). The determination was based on standard curves obtained for the 18 available saponin standards, previously isolated from Jemalong A-17. Aerial parts of all three subspecies contained 17 saponins previously identified and also a substantial amount of astragaloside VIII (3-GlcA-Xyl-Rha soyasapogenol B), not previously reported in M. truncatula. The compositions of saponin mixtures were very similar in the three subspecies with three dominant groups, recognized as zanhic acid, medicagenic acid, and soyasapogenol glycosides. Relative proportions of these three groups were also similar in the three subspecies: var. longispina had 49.5, 48.1, and 2.4%; var. truncatula, 41.5, 53.4, and 5.1%; and Jemalong A-17, 42.1, 56.6, and 1.3% of zanhic acid, medicagenic acid, and soyasapogenol glycosides, respectively. Jemalong A-17 had 30% lower total content of saponins as compared to M. truncatula var. longispina and M. truncatula var. truncatula; in relation to the dry matter, var. longispina contained 0.22%, var. truncatula, 0.22%, and Jemalong A-17, 0.15% dry matter of saponins. If one takes into consideration that this determination was performed on spring-collected samples, it can be concluded that the concentration of saponins in M. truncatula is similar to the concentration in alfalfa (Medicago sativa); the proportions of the three groups of saponins in these species are slightly different from those found in alfalfa, having a higher content of zanhic acid glycosides.     

Analytical study of trichlorfon residues in Kaki fruit and cauliflower samples by liquid chromatography-electrospray tandem mass spectrometry

A detailed analytical study on trichlorfon residues in selected vegetables samples has been carried out, focused on the reliable quantification and confirmation of this compound, and on stability of residues under storage. As a consequence, a rapid and sensitive LC-ESI-MS/MS method has been developed for the determination of residues of this insecticide in kaki fruit (flesh and peel) and cauliflower samples. Extraction was performed with acetonitrile using a high-speed blender. After 4-fold dilution of the extract with water, 20 microL was directly injected in the LC-ESI-MS/MS system (triple quadrupole), using matrix-matched standards calibration for quantification. Under optimized MS/MS conditions, limit of detections between 0.006 and 0.013 mg/kg were reached, and a limit of quantification of 0.05 mg/kg was established, with a runtime of only 15 min. Recoveries from spiked blank samples at 0.05 and 0.5 mg/kg were in the range 83-101% with relative standard deviations lower than 10%. The method was applied to treated and untreated samples collected from field residues trials, using quality control samples analysis for the evaluation of the method. Despite the acquisition of two MS/MS transitions in selected reaction monitoring mode, the analysis of treated samples revealed the presence of a chromatographic peak close to the analyte that corresponded to a trichlorfon isobaric compound that shared the same MS/MS transitions. This unusual situation in LC-MS/MS-based procedures required the application of an efficient chromatographic separation to avoid this interference. All experiments have been made in compliance with the principles of Good Laboratory Practices (GLP) and following the European SANCO guidelines for pesticides residue analysis (PRA).     

Analysis of bisphenol A and alkylphenols in cereals by automated on-line solid-phase extraction and liquid chromatography tandem mass spectrometry

An on-line solid-phase extraction (SPE) following a liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method was established for the simultaneous analysis of bisphenol A (BPA), nonylphenol (NP), and octylphenol (OP) in cereals (including rice, maize, and wheat). The target compounds were extracted by acetonitrile, purified by an automated on-line SPE cartridge, and analyzed by LC-MS/MS under the negative-ion mode. Mean recoveries fortified at three concentration levels ranged from 81.6 to 115.7%, and the coefficient of variation ranged from 4.6 to 19.9% (n = 6). The limits of quantification (LOQs) of the method were 0.5, 0.5, and 0.25 μg/kg for BPA, NP, and OP, respectively, in both rice and maize, while the LOQs in wheat were 0.5, 1.25, and 0.5 μg/kg for BPA, NP, and OP, respectively. This method was applied in the analysis of rice, maize, and wheat from a local market. As a result, NP occurred in all cereal samples at the concentration range of 9.4-1683.6 μg/kg and BPA was detected in a few samples.     

Determination of capsaicin and dihydrocapsaicin in capsicum fruits by liquid chromatography-electrospray/time-of-flight mass spectrometry

A simple, highly selective, sensitive, and reproducible liquid chromatography-electrospray ionization/time-of-flight mass spectrometry method has been developed for the direct and simultaneous determination of capsaicin and dihydrocapsaicin in Capsicum fruit extracts. Capsaicin and dihydrocapsaicin are the two major members of the so-called capsaicinoid family, which includes other minor analogues, and usually account for at least 90% of the pungency trait in Capsicum fruits. Chromatographic separation of capsaicin and dihydrocapsaicin was achieved with a reversed-phase chromatography column, using a gradient of methanol and water. Quantification was done using as an internal standard (4,5-dimethoxybenzyl)-4-methyloctamide, a synthetic capsaicin analogue not found in nature. Analytes were base-peak resolved in less than 16 min, and limits of detection were 20 pmol for capsaicin and 4 pmol for dihydrocapsaicin. The intraday repeatability values were lower than 0.5 and 12% for retention time and peak area, respectively, whereas the interday repeatability values were lower than 0.6 and 14% for retention time and peak area, respectively. Analyte recoveries found were 86 and 93% for capsaicin and dihydrocapsaicin, respectively. The method developed has been applied to the identification and quantification of capsaicin and dihydrocapsaicin in fruit extracts from different Capsicum genotypes, and concentrations found ranged from 2 to 6639 mg kg(-1).     

Determination of benzoxazinone derivatives in plants by combining pressurized liquid extraction-solid-phase extraction followed by liquid chromatography-electrospray mass spectrometry

A new analytical method based on the use of pressurized liquid extraction (PLE) followed by solid-phase extraction with LiChrolut RP C18 cartridges was evaluated for the sample preparation, extraction, and cleanup of eight naturally occurring benzoxazinone derivatives, 2-beta-D-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one, 2-beta-D-glucopyranosyloxy-4-hydroxy-7-methoxy-1,4-benzoxazin-3-one, 2,4-dihydroxy-1,4-benzoxazin-3-one (DIBOA), 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one, 2-hydroxy-1,4-benzoxazin-3-one, 2-hydroxy-7-methoxy-1,4-benzoxazin-3-one, benzoxazolin-2-one, and 6-methoxybenzoxazolin-2-one in plant samples. Afterward, liquid chromatography-electrospray mass spectrometry, using the selected ion monitoring mode and internal standard (2-MeO-DIBOA, indoxyl-beta-D-glucoside, and quercetin-3-O-rutinoside) quantification method was performed. This paper demonstrates the effectiveness of the PLE method, in conjunction with sensitive and specific mass spectrometric detection, for the quantitative recovery of compounds of the benzoxazinone class from plants. The recoveries of the analytes ranged from 66 to 110% with coefficients of variation ranging from 1 to 14%. This method gave detection limits between 1 and 27 microg/g. The method was applied to foliage and roots of three different wheat cultivars, and the analytes were detected in the range of 11-3261 microg/g of dry weight.     

蜂蜜中26种磺胺及其增效剂类药物残留检测方法研究

利用QuEChERS前处理技术和超高效液相色谱-串联质谱(UHPLC-MS/MS),建立了可同时检测蜂蜜中23种磺胺和3种磺胺增效剂类药物残留的分析方法.蜂蜜样品经水溶解,以乙腈为提取溶剂,提取液经乙二胺-N-丙基硅烷(PSA)和C18固相分散萃取吸附剂净化后,采用多反应监测模式(MRM)进行测定.26种药物在0.5～...     

Determination of low levels of perchlorate in lettuce and spinach using ion chromatography-electrospray ionization mass spectrometry (IC-ESI-MS)

A sample preparation method was developed to quantify environmentally relevant (low micrograms per liter) concentrations of perchlorate (ClO4(-)) in leafy vegetables using IC-ESI-MS. Lettuce and spinach were macerated, centrifuged, and filtered, and the aqueous extracts were rendered water-clear using a one-step solid-phase extraction method. Total time for extraction and sample preparation was 6 h. Ion suppression was demonstrated and was likely due to unknown organics still present in the extract solution after cleanup. However, this interference was readily eliminated using a Cl(18)O4(-) internal standard at 1 microg/L in all standards and samples. Hydroponically grown perchlorate-free butterhead lettuce was spiked to either 10.3 or 37.7 microg/kg of fresh weight (FW), and recoveries were between 91 and 98% and between 93 and 101%, respectively. Five types of lettuce and spinach from a local grocery store were then analyzed; they contained from 0.6 to 6.4 microg/kg of FW. Spike recoveries using the store-bought samples ranged from 89 to 100%. The method detection limit for perchlorate in plant extracts is 40 ng/L, and the corresponding minimum reporting limit is 200 ng/L or 0.8 microg/kg of FW.     

Bound fumonisin B1: analysis of fumonisin-B1 glyco and amino acid conjugates by liquid chromatography-electrospray ionization-tandem mass spectrometry

To study the formation of fumonisin artifacts and the binding of fumonisins to matrix components (e.g., saccharides and proteins) in thermal-treated food, model experiments were performed. Fumonisin B(1) and hydrolyzed fumonisin B(1) were incubated with alpha-d-glucose and sucrose (mono- and disaccharide models), with methyl alpha-d-glucopyranoside (starch model), and with the amino acid derivatives N-alpha-acetyl-l-lysine methyl ester and BOC-l-cysteine methyl ester (protein models). The reaction products formed were analyzed by liquid chromatography-electrospray ionization-tandem mass spectrometry. The incubation of d-glucose with fumonisin B(1) or hydrolyzed fumonisin B(1) resulted in the formation of Amadori rearrangement products. Whereas conjugates were found following the reaction of sucrose, methyl alpha-d-glucopyranoside, and the amino acid derivatives with fumonisin B(1), the heating with hydrolyzed fumonisin B(1) yielded no artifacts. For structural determination, the stable reaction product formed by heating of methyl alpha-d-glucopyranoside (as starch model) with fumonisin B(1) was purified and identified by nuclear magnetic resonance spectroscopy as the diester of the fumonisin tricarballylic acid side chains with methyl alpha-d-glucopyranoside. These model experiments demonstrate that fumonisins are able to bind to polysaccharides and proteins via their two tricarballylic acid side chains.     

Determination and confirmation of 5-hydroxyflunixin in raw bovine milk using liquid chromatography tandem mass spectrometry

A method was developed and validated to determine 5-hydroxyflunixin in raw bovine milk using liquid chromatography tandem mass spectrometry (LC/MS/MS). The mean recovery and percentage coefficient of variation (%CV) of 35 determinations for 5-hydroxyflunixin was 101% (5% CV). The theoretical limit of detection was 0.2 ppb with a validated lower limit of quantitation of 1 ppb and an upper limit of 150 ppb. Accuracy, precision, linearity, specificity, ruggedness, and storage stability were demonstrated. A LC/MS/MS confirmatory method using the extraction steps of the determinative method was developed and validated for 5-hydroxyflunixin in milk from cattle. Briefly, the determinative and confirmatory methods were based on an initial solvent (acetone/ethyl acetate) precipitation/extraction of acidified whole milk. The solvent precipitation/extraction effectively removed incurred ((14)C) residues from milk samples. The organic extract was then purified by solid phase extraction (SPE) using a strong cation exchange cartridge (sulfonic acid). The final SPE-purified sample was analyzed using LC/MS/MS. The methods are rapid, sensitive, and selective and provide for the determination and confirmation of 5-hydroxyflunixin at the 1 and 2 ppb levels, respectively.     

Determination of flunixin in edible bovine tissues using liquid chromatography coupled with tandem mass spectrometry

An accurate, reliable, and reproducible assay was developed and validated to determine flunixin in bovine liver, kidney, muscle, and fat. The overall recovery and percent coefficient of variation (%CV) of twenty-eight determinations in each tissue for flunixin free acid were 85.9% (5.9% CV) for liver, 94.6% (9.9% CV) for kidney, 87.4% (4.7% CV) for muscle, and 87.6% (4.4% CV) for fat. The theoretical limit of detection was 0.1 microg/kg (ppb, ng/g) for liver and kidney, and 0.2 ppb for muscle and fat. The theoretical limit of quantitation was 0.3, 0.2, 0.6, and 0.4 ppb for liver, kidney, muscle, and fat, respectively. The validated lower limit of quantitation was 1 ppb for edible tissues with the upper limit of 400 ppb for liver and kidney, 100 ppb for fat, and 40 ppb for muscle. Accuracy, precision, linearity, specificity, ruggedness, and storage stability were demonstrated. Briefly, the method involves an initial acid hydrolysis, followed by pH adjustment ( approximately 9.5) and partitioning with ethyl acetate. A portion of the ethyl acetate extract was purified by solid-phase extraction using a strong cation exchange cartridge. The eluate was then evaporated to dryness, reconstituted, and analyzed using LC/MS/MS. The validated method is sensitive and specific for flunixin in edible bovine tissue.     

Determination of oryzalin in water, citrus fruits, and stone fruits by liquid chromatography with tandem mass spectrometry

A new methodology is described for rapidly determining the herbicide oryzalin in water, citrus fruits, and stone fruits by liquid chromatography with negative ion electrospray ionization tandem mass spectrometry (LC/MS/MS). Oryzalin is extracted from water using a polymeric sorbent solid phase extraction (SPE) column and from fruit using methanol. The water samples require no further purification, but an aliquot of the fruit sample extracts is diluted with water and purified using a polymeric 96 well SPE plate. Purified extracts are concentrated prior to determination by LC/MS/MS at m/z 345 (Q1) and m/z 281 (Q3) using an external standard for calibration. The validated limits of quantitation were 0.05 microg/L in water (drinking water, surface water, and groundwater) and 0.01 microg/g in citrus fruits (oranges and lemons) and stone fruits (peaches and cherries). Recoveries averaged 102% for water samples and 85-89% for the various types of fruit samples. For all fortification levels combined, the relative standard deviations ranged from 4 to 6% for water and from 2 to 4% for fruit.     

Development of a new high-performance liquid chromatography-electrospray ionization time-of-flight mass spectrometry method for the determination of low molecular mass organic acids in plant tissue extracts

A liquid chromatography-electrospray ionization time-of-flight mass spectrometry method has been developed for the direct and simultaneous determination of 10 low molecular mass organic acids in different plant tissue extracts. The method does not include a derivatization step. Quantification was accomplished using (13)C-labeled malic and succinic acids as internal standards. Good limits of detection (0.05-1.27 pmol) were obtained for malic, 2-oxoglutaric, succinic, quinic, shikimic, cis-aconitic, and citric acids, whereas for oxalic, ascorbic, and fumaric acids limits of detection were 255, 25, and 11 pmol, respectively. Repeatability values for the retention time and peak area were <5%, with the exception of ascorbic acid. Analyte recovery was between 92% and 110% in most cases, with the exception of oxalic (39-108%), 2-oxoglutaric (44-69%), and ascorbic (22-86%) acids, which may require specific extraction procedures and use of the corresponding (13)C-labeled organic acid as internal standards to improve accuracy. The method was applied to three types of plant materials: sugar beet leaf extracts, tomato xylem sap, and commercial orange juice.     

Separation and characterization of phenolic compounds in fennel (Foeniculum vulgare) using liquid chromatography-negative electrospray ionization tandem mass spectrometry

Liquid chromatography (LC) diode array detection (DAD) coupled to negative electrospray ionization (ESI) tandem mass spectrometry (MS/MS) was used for the rapid and sensitive identification of water-soluble phenolic compounds in fennel waste. The plant material was first extracted and then chromatographed on Sephadex LH-20 to afford seven fractions, each of them being subjected to LC-MS analysis. Identification of the compounds was carried out by interpretation of UV, MS, and MS/MS spectra. Forty-two phenolic substances were identified, 27 of which had not previously been reported in fennel, including hydroxycinnamic acid derivatives, flavonoid glycosides, and flavonoid aglycons.