Determination of seven benzoylphenylurea insecticides in processed fruit and vegetables using high-performance liquid chromatography/tandem mass spectrometry

A liquid chromatographic method with electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) has been developed for the sensitive and selective determination of seven benzoylphenylurea insecticide residues (diflubenzuron, triflumuron, lufenuron, flufenoxuron, teflubenzuron, chlorfuazuron, hexaflumuron) in pear baby purée, concentrated lemon juice, and tomato pulp. The general sample extraction/partition method for our established multiresidue methods has been used. The entire procedure involves extraction of residues with acetone and partition into ethyl acetate/cyclohexane. Chromatographic determination was performed using a C18 column and isocratic elution. Fourteen MS/MS transitions of precursor ions were monitored (two for each pesticide) using negative ESI. The majority of mean recoveries at fortification levels of 0.002-0.020 and 0.020-0.200 mg/kg were in the range 77-102% with relative standard deviations between 2 and 10%. The excellent sensitivity and selectivity of this LC/MS/MS method allowed quantitation and identification at low levels in difficult matrices with a run time of 4 min.     

A multi-residue screening method for the determination of 73 pesticides and metabolites in fruit and vegetables using high-performance liquid chromatography/tandem mass spectrometry

A multi-residue screening method was developed for the simultaneous analysis of 73 pesticides and their metabolites using high-performance liquid chromatography coupled with electrospray tandem mass spectrometry. These pesticides were determined under a single set of experimental conditions involving a simple acetonitrile extraction without the requirement for a clean-up step. Validation was achieved at 0.01 and 0.1 mg kg(-1) levels in apple, lettuce and orange. Recoveries were in the range 77-124% for the majority of pesticides.     

Determination of triforine using high-performance liquid chromatography with tandem mass spectrometry

A method for determination of triforine using high-performance liquid chromatography with electrospray tandem mass spectrometry was developed. A simple ethyl acetate extraction with solvent exchange into water/methanol was used for sample preparation. The method was validated at 0.01 and 0.05 mg kg(-1) levels in apple, tomato and tinned blackcurrants. Recoveries were in the range 56.6-99.8% and no matrix suppression or enhancement effects were observed.     

Multiresidue determination of pesticides in fruit and vegetables by gas chromatography/tandem mass spectrometry

Pesticide residues in fruit and vegetables were determined by gas chromatography/tandem mass spectrometry (GC/MS/MS). Electron impact (EI)/MS/MS and chemical ionization (CI)/MS/MS were developed for 80 compounds, including organochlorine, organophosphorus, organonitrogen, and pyrethroids, providing unambiguous spectral confirmation for these complex matrixes. Residues were extracted from samples with acetone followed by a mixture of dichloromethane-petroleum ether. Two injections per sample were required for analysis of the entire pesticide list by EI/MS/MS and CI/MS/MS. Initial steps involving cleanup and concentration of extracts were eliminated. The excellent selectivity and good linearity allowed quantification and identification of low levels of pesticides in the most difficult matrixes. The method has been used for routine analysis of many vegetables.     

Determination of natural pesticides in fresh fruits using liquid chromatography/mass spectrometry

An analytical procedure was developed for the determination of some natural pesticides (piperonyl butoxide, nicotine, rotenone, spinosad, and abamectin B1a) in fruit matrixes. The quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was used for extraction. Analysis of the extract was performed by LC-electrospray ionization (ESI)-MS/MS. The ions prominent in the ESI spectra were [M+Na]+ for abamectin B1a, [M+NH4]+ for piperonyl butoxide, and [M+H]+ for the rest of the compounds. A Zorbax SB-C18 column was used with a programmed gradient mobile phase consisting of (A) water containing 0.1% formic acid and 5 mM ammonium formate, and (B) acetonitrile containing 2 mM sodium acetate. The method was linear within the investigated concentration range, displaying a calibration curve correlation factor of 0.99. The CVs obtained were below 20%, and recoveries were in the 70-110% range.     

Determination of fludioxonil and famoxadone in processed fruits and vegetables by liquid chromatography/electrospray tandem mass spectrometry

The feasibility of using liquid chromatography/ electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) for determining 2 fungicides (fludioxonil and famoxadone) in tomato pulp, pear purée, and concentrated lemon juice has been evaluated. A miniaturized extraction-partition procedure requiring small amounts of nonchlorinated solvents was used. The extracts (5 microL) were analyzed by LC/ESI-MS/MS without previous cleanup. Chromatographic determination was performed using a C18 column with isocratic elution. Four MS/MS transitions of precursor ions were monitored simultaneously (2 for each pesticide) by means of negative ESI. Mean recoveries from samples at fortification levels of 0.002-0.020 mg/kg (fludioxonil) and 0.010-0.100 mg/kg (famoxadone) ranged from 77.1 to 96.5%, with associated relative standard deviations between 4.2 and 11.5%.     

Determination of pesticides in vegetables using large-volume injection column liquid chromatography-electrospray tandem mass spectrometry

Direct injection of a large volume (900 microl) of a sample extract onto a liquid chromatographic (LC) column, LC separation and electrospray tandem mass spectrometric detection were used for the quantitative analysis of a wide polarity range of pesticides in carrots and potatoes. Rapid sample preparation involved extraction of a small amount of sample (2 g) with a small volume of organic solvent (3 ml), clean-up over a filter and dilution of the organic extract with the aqueous LC eluent. The extraction efficiency for the selected pesticides was studied using methanol, acetone and acetonitrile as solvents. Evaluation of the performance of the overall method, using extraction with acetonitrile and detection in the selected-reaction-monitoring mode, showed excellent linearity in the range of 2-100 microg/kg with limits of detection of 0.5-2 microg/kg for both types of vegetable. With relative standard deviations of the MS peak area measurements of less than 6.5% (n=8) the repeatability of the method was fully satisfactory.     

Determination of Tripamide in human urine by high-performance liquid chromatography and high-performance liquid chromatography/electrospray ionization tandem mass spectrometry

Tripamide is a drug widely used in clinical practice for the treatment of hypertension and edema. This work evaluated a screening method for Tripamide and its urinary metabolites in human urine, using high-performance liquid chromatography diode-array detection (HPLC/DAD). Identification of these metabolites was investigated by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) after dosing with 15 mg Tripamide. Acid hydrolysis showed that Tripamide is conjugated in the body. Two suspected metabolites were detected by HPLC/DAD. HPLC/ESI-MS/MS analysis suggested that these metabolites were probably hydroxylated together with loss of the -NH(2) group and dehydrogenation. These results will be useful in confirmation methods for Tripamide in doping control.     

Determination of abamectin in soil samples using high-performance liquid chromatography with tandem mass spectrometry

Abamectin, which is comprised of a mixture of avermectins B1a and B1b, is a natural pesticide used as an anti-parasitic agent in livestock, ornamental, and agricultural crops, which can potentially be transported to aquatic systems. These compounds are highly toxic to both aquatic vertebrates and invertebrates at low concentrations in water. This investigation developed high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) techniques to support automated extraction by an accelerated solvent extraction (ASE) system and chromatographic techniques to measure residues of avermectins in complex soil samples. HPLC along with atmospheric pressure chemical ionization (APCI) MS/MS was used for separation and determination of avermectin isomers in soil samples. Average method recovery for abamectin by UV was 91%, while detection by MS/MS resulted in a 68% recovery for abamectin. Individual method recoveries by MS/MS were 53.6% for avermectin B1a and 36.8% for avermectin B1b. The use of tandem technology eliminated matrix interferences and resulted in an approximately eight-fold increase in sensitivity.     

Determination of polar organophosphorus pesticides in vegetables and fruits using liquid chromatography with tandem mass spectrometry: selection of extraction solvent

A method based on liquid chromatography (LC)-mass spectrometry (MS)/MS was developed for sensitive determination of a number of less gas chromatography (GC)-amenable organophosphorus pesticides (OPs; acephate, methamidophos, monocrotophos, omethoate, oxydemeton-methyl and vamidothion) in cabbage and grapes. For extraction, several solvents were evaluated with respect to the possibility of direct injection, matrix-induced suppression or enhancement of response, and extraction efficiency. Overall, ethyl acetate was the most favourable solvent for extraction, although a solvent switch was required. For some pesticide/matrix combinations, reconstitution of the residue after evaporation required special attention. Extracts were analysed on a C18 column with polar endcapping. The pesticides were ionised using atmospheric pressure chemical ionisation on a tandem mass spectrometer in multiple reaction monitoring mode. The final method is straightforward and involves extraction with ethyl acetate and a solvent switch to 0.1% acetic acid/water without further cleanup. The method was validated at the 0.01 and 0.5 mg/kg level, for both cabbage and grapes. Recoveries were between 80 and 101% with R.S.D. < 11% (n = 5). The limit of quantification was 0.01 mg/kg and limits of detection were between 0.001 and 0.004 mg/kg.     

Determination of propamocarb in vegetables using polymer-based high-performance liquid chromatography coupled with electrospray mass spectrometry

A method for the determination of propamocarb in vegetables with liquid chromatography-electrospray ionisation mass spectrometry (LC-ESI-MS) was developed. The performance of a polymer-based analytical LC column for the separation was investigated. Residues of propamocarb were extracted from the matrix with methanol. Subsequently, the extract was directly injected into the LC-MS system, without any additional concentration or cleanup procedures. Separation of propamocarb from the matrix components was achieved on a polymethacrylate-based analytical column. Propamocarb was concurrently detected with electrospray ionisation mass spectrometry in the selected ion monitoring mode and two-stage full scan MS application. Quantitation was done with matrix-matched calibration standards of propamocarb. Unambiguous confirmation was achieved by comparison of the full scan product ion mass spectrum of the chromatographic peak in the sample with the spectrum of a standard solution of propamocarb at the same retention time. The analytical performance of the method was validated for five relevant matrices, spiking propamocarb at fortification levels from 0.05 to 15.0 mg kg(-1). This covers the range of maximum residue limits in agricultural commodities, stated in the Dutch national legislation. The mean recovery of propamocarb was better than 90% with a precision of less than 10% in both scanning applications. As could be concluded from the calibration curve and matrix background levels, observed in blank control samples, the estimated limit of detection was 25 microg kg(-1) for the two-stage full scan MS application. The method has been applied in a survey of 285 samples of lettuce, radish, leek, and cabbage for the presence of residues of propamocarb. In 50% of the samples analysed, a residue of propamocarb was detected.     

Multi-residue determination of pesticides in tropical fruits using liquid chromatography/tandem mass spectrometry

Monitoring pesticide residues in tropical fruits is of great interest for many countries, e.g., from South America, that base an important part of their economy on the exportation of these products. In this work, a LC-MS/MS multi-residue method using a triple quadrupole analyzer has been developed for around 30 pesticides in seven Colombian tropical fruits of high commercial value for domestic and international markets (uchuva, tamarillo, granadilla, gulupa, maracuya, papaya, and pithaya). After sample extraction with acetonitrile, an aliquot of the extract was diluted with water and directly injected into the HPLC-MS/MS system (electrospray interface) without any cleanup step. The formation of sodium adducts—of poor fragmentation—was minimized using 0.1% formic acid in the mobile phase, which favored the formation of the protonated molecule. However, the addition of ammonium acetate made the formation of the ammonium adducts in some particular cases possible, avoiding the presence of the sodium adducts. The highest sensitivity was observed in positive electrospray ionization for the wide majority of pesticides, with a few exceptions for acidic compounds that gave better response in the negative mode (e.g., 2,4-D, fluazinan). Thus, simultaneous acquisition on the positive/negative mode was applied. Two MS/MS transitions were acquired for each compound to ensure a reliable quantification and identification of the compounds detected in samples, although for malathion a third transition was acquired due to the presence of interfering isobaric compounds in the sample extracts. A detailed study of matrix effects was made by a comparison of standards in solvent and in matrix. Both ionization suppression and ionization enhancement were observed depending on the analyte/matrix combination tested. Correction of matrix effects was made by the application of calibration in matrix. Three matrices were selected (uchuva, maracuya, gulupa) to perform matrix calibration in the analysis of all seven fruit varieties studied. The method was validated by recovery experiments in samples spiked at two levels (0.05 and 0.5 mg/kg). The data were satisfactory for the wide majority of analyte/matrix combinations, with most recoveries between 70% and 110% and the RSD below 15%. Several samples collected from the market were finally analyzed. Positive findings were confirmed by evaluating the experimental Q/q ratios and retention times, and comparing them with those of reference standards.     

Signal suppression/enhancement in high-performance liquid chromatography tandem mass spectrometry

The review discusses the pitfalls of the matrix effect in mass spectrometry detection hyphenated to liquid chromatography separation. Matrix effect heavily influences both qualitative and quantitative analyses, giving rise to suppression or enhancement of the signal. As generally recognised, the predominant cause is the presence of undesired components that co-elute in the chromatographic separation and alter the ionisation process. The interfering species can be components of the sample, compounds released during the pre-treatment/extraction process or reagents added to the mobile phase to improve chromatographic resolution. The different mechanisms proposed in literature to explain the suppression or the enhancement of the signal both in electrospray and atmospheric pressure chemical ionisations are presented and the results observed in the different experimental conditions are compared and discussed. All data together lead to conclude that the chemical properties of the target analyte, the kind of matrix, the matrix to analyte concentration ratio, the extraction process, the chromatographic conditions as well as the kind of the mass spectrometry instrumentation and the ionisation conditions can play a role. Likely all these potential causes act in a synergic way and the final effect observed is hardly due to only one of them. Depending on an unpredictable combination of conditions, signal suppression or enhancement can be observed. The review discusses the matrix effects observed in HPLC–MS and HPLC–MS/MS analysis proposes hypotheses to explain the observed behaviours and proposes methods and strategies to overcome the matrix effects.     

Determination of iodoacetic acid using liquid chromatography/electrospray tandem mass spectrometry

A rapid analytical method based on liquid chromatography/tandem mass spectrometry (LC/MS/MS) using electrospray ionization in negative ion detection mode was developed for the analysis of underivatized iodoacetic acid in water. The method was applied to model reaction mixtures in the study of the formation of iodoacetic acid after chlorinated tap water was boiled in the presence of potassium iodide or iodized table salt. Samples can be directly analyzed by the LC/MS/MS system without extraction or chemical derivatization. Limit of detection was determined to be 0.3 microg/L (or 0.3 ng/mL) and limit of quantitation was about 1 microg/L (1 ng/mL).     

Determination of acidic herbicides in fruits and vegetables using liquid chromatography tandem mass spectrometry (LC-MS/MS)

The use of quick, easy, cheap, effective, rugged and safe method followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) was found to be the best combination for multiresidue determination of eight acidic herbicides in fruits and vegetables in terms of high recovery, short time of analysis, low cost and safety. Recent few articles were published for determination of different classes of acidic herbicides in single multiresidue method. In the present study, mass spectrophotometric conditions were individually optimised for eight acidic herbicides, namely 2,4-dichlorophenoxyacetic acid, bentazone, bromoxynil, fluazifop, fluroxypyr, imazethapyr, ioxynil and triclopyr to achieve maximum sensitivity and selectivity in multiple reaction monitoring (MRM) mode allowing simultaneous identification and quantification in a single run. Identity confirmation and quantitation were attained by using negative electrospray ionisation LC-MS/MS (ESI?) in MRM mode. Due to LC-MS/MS signal suppression, determination of pesticide residues was based on matrix-matched standard calculations. Most of the evaluated compounds showed a recovery ranging from 81% to 113% with relative standard deviations less than 16 % indicating acceptable precision. The precision and accuracy of the method were determined from recovery experiments on six replicates of spiked blank strawberry and green beans samples at 0.01, 0.05 and 0.1 mg/kg. The developed assay was linear over concentration range of 0.01–0.5 µg/mL, with correlation coefficient greater than 0.99 at the limit of quantitation 0.01 µg/mL. The proposed assay was successfully applied for the analysis of the studied acidic herbicides residues in two proficiency test samples. This wide scope assay protocol is applicable for monitoring acidic herbicides residues in fruits and vegetables by national regulatory authorities and accredited labs in order to help ensuring the safety of such widely used food products.     

Determination of pesticides in soy-based infant formula using liquid chromatography with electrospray ionization tandem mass spectrometry

A sensitive method using liquid chromatography with electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) was developed and validated to quantify and confirm 13 pesticides, including aldicarb sulfoxide, aldicarb sulfone, oxamyl, methomyl, formetanate, 3-hydroxycarbofuran, carbendazim, thiabendazole, aldicarb, propoxur, carbofuran, carbaryl, and methiocarb, in soy-based infant formula. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring of 2 fragment ion transitions to provide a high degree of sensitivity and selectivity for both quantitation and confirmation. Different approaches to constructing calibration curves were compared and discussed to address issues of the extraction efficiency or recovery, and matrix effects. Matrix-matched standard calibration curves with the use of isoprocarb as an internal standard were finally used to achieve the best accuracy of the method. Under most circumstances, recoveries of 13 pesticides, spiked at 5.0, 25.0, and 45.0 microg/kg, were close to 100%. The method detection limits (signal-to-noise ratio > or =3:1; microg/kg) of 13 pesticides were 0.2 for thiabendazole and methiocarb, 0.6 for aldicarb, and 0.1 for the others.     

Investigations on the degradation of aspartame using high-performance liquid chromatography/tandem mass spectrometry

Aspartame is a widely used sweetener,the long-term safety of which has been controversial ever since it was accepted for human consumption.It is unstable and can produce some harmful degradation products under certain storage conditions.A high-performance liquid chromatography/tandem mass spectrometry method was developed for the simultaneous analysis of aspartame and its four degradation products,including aspartic acid,phenylalanine,aspartyl-phenylalanine and 5-benzyl-3,6-dioxo-2-piperazieacetic acid in water and in diet soft drinks.Aspartame and its four degradation products were quantified by a matrix matched external standard calibration curve with excellent correlation coefficients.The limits of detection were 0.16–5.8 mg/L,which exhibited higher sensitivity than common methods.This method was rapid,sensitive,specific and capable of eliminating matrix interferences.It was also applied to the study of the degradation of aspartame at various pH and temperatures.The results indicated that aspartame was partly degraded under strong acidic or basic conditions and the extent of degradation increased with increasing temperature.     

Multiresidue analysis of pesticides with hydrolyzable functionality in cooked vegetables by liquid chromatography tandem mass spectrometry

It would be preferable for pesticide residues substituted by hydrolyzable functionality to be analyzed after cooking because their structures are apt to degrade during boiling and/or heating. A liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method for the quantitative determination of 44 pesticide residues with hydrolyzable functional group in five typical vegetable widely consumed in Republic of Korea is described. The sample clean‐up was carried out according to the method of Food Code No. 83 established by the Korea Food and Drug Administration (KFDA). Zorbox XDB‐C₁₈ column was selected for the analysis because of the best peak separation. The LC mobile phase consisted of water and 5 mm methanolic ammonium formate, which resulted in a peak shape with good symmetry at each run. Tandem mass spectroscopic (MS/MS) experiments were performed in ESI positive mode and the multiple reaction monitoring modes. A conventional matrix effect was modified to more comprehensive form 100γ_ij (%). A high matrix effect (相似文献