Determination of trace levels of pyrethroid metabolites in human urine by capillary gas chromatography-high resolution mass spectrometry with negative chemical ionization

Summary Applications of high-resolution gas chromatography and high-resolution mass spectrometry (GC-MS) for identification and quantitation of trace amounts of pyrethroid metabolites in human urine samples are demonstrated. The method covers the pyrethroid metabolitescis- andtrans-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropane carboxylic acid (cis- andtrans-DCCA),cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DBCA), 4-fluoro-3-phenoxybenzoic acid (FPBA), and 3-phenoxybenzoic acid (3-PBA). After acid-induced hydrolysis of urine samples and exhaustive solvent extraction, a carbodiimide-coupled esterification of the free carboxylic acids with hexafluoroisopropanol (HFIP) is applied. Identification of the derivatives formed is achieved by low-resolution electron-impact mass spectrometry (EIMS) using an ion-trap detector. Quantitation was by capillary gas chromatography—high-resolution mass spectrometry using negative chemical ionization (GC-NCIMS). 2-Phenoxybenzoic acid (2-PBA) served as internal standard. The limits of detection forcis- andtrans-DCCA,cis-DBCA, FPBA and 3-PBA were 0.03 μg L⁻¹ or below. The applicability of the presented method was tested on urine samples of persons exposed to low levels of pyrethroids.     

Determination of benzidine in urine using capillary gas chromatography and negative-ion chemical ionisation mass spectrometry

Summary A highly sensitive and specific gas chromatographic-mass spectrometric (GC-MS) assay for the determination of benzidine in urine is reported. It is based on the solvent extraction of the hydrolysed benzidine conjugates, together with the deuterium-labelled benzidine-d₈ added as an internal standard, and a two-phase derivatisation procedure using pentafluoropropionic anhydride (PFPA) in the presence of pyridine as the phase-transfer catalyst. The reaction is complete within 5 min at room temperature. The pentafluoropropyl derivatives are quantified through capillary column GC-MS using selected ion monitoring (SIM) in the negative-ion chemical ionisation mode (NICI). The lower limit of detection for benzidine was 0.5 g/l and the calibration plot showed linearity between 2 g/l and 200 g/l. The recovery of the analyte added to pooled urine was above 82%. Analysis of 20 urine samples from un-exposed persons and 20 urine specimens of workers employed in a polyurethane-making plant using this procedure showed no substances likely to manifest false positive results in the range of interest.     

Detection of trace levels of triclopyr using capillary gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry

Triclopyr, after esterification, is shown to be a suitable candidate for detection by gas chromatography-electron-capture negative-ion chemical ionization mass spectrometry forming a characteristic carboxylate anion which offers a high detection sensitivity. A detection limit of 70 fg reaching the ionizer is indicated. Low backgrounds and an absence of chemical interferences are shown for vegetation extracts, using a simple method of extraction and derivatisation. A similar behaviour is demonstrated for 2,4-D and 2,4,5-T.     

Detection of trace levels of trichothecenes in human blood using capillary gas chromatography-electron-capture negative ion chemical ionisation mass spectrometry

A sensitive and selective method has been developed for the simultaneous detection in blood of eleven trichothecenes of widely varying polarity. The procedure involved precipitation of blood proteins with acetone followed by a clean-up using reversed-phase Sep-Pak C18 cartridges. The extracted trichothecenes were derivatised as their pentafluoropropionyl esters, separated using capillary gas chromatography and detected using electron-capture negative ion chemical ionisation with methane reagent gas and selected-ion monitoring. Optimum sensitivity and selectivity were obtained using low source temperatures (60 degrees C indicated) and high source pressures (1 Torr indicated). Detection limits on 1-ml blood samples were in the range 0.1-5 ppb. The method was readily adaptable to the detection of other trichothecenes. A protocol was used which minimised the risk of cross-contamination. The method was validated in collaborative studies by the successful analysis of 42 blood samples spiked and submitted blind by two independent laboratories for analysis.     

Determination of cobalamins using capillary electrophoresis inductively coupled plasma mass spectrometry

The determination of cobalamins using capillary electrophoresis inductively coupled plasma mass spectrometry (CE-ICP-MS) was investigated. Both capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) modes of operation were studied. The optimal separation of four cobalamin species (cyanocobalamin, hydroxocobalamin, methylcobalamin, and 5′-deoxyadenosylcobalamin) and a potentially harmful corrinoid analogue (cobinamide dicyanide) was obtained using CZE at a pH of 2.5. Both 20 mM phosphate and 20 mM formate buffers were used with success, although the formate buffer provided improved resolution. The CZE-ICP-MS method was used to quantify cyanocobalamin in a vitamin supplement and the analytical results were in good agreement (±5%) with values obtained by ICP-MS for total Co levels. The solution detection limits for cobalamins using CZE-ICP-MS were approximately 50 ng/ml. MEKC was found to be useful for the screening of vitamin preparations because it provided a rapid means of distinguishing cyanocobalamin (the form most commonly used in vitamin preparations) from free cobalt. The separation of free cobalt and cyanocobalamin using MEKC was achieved in less than 10 min.     

Detection of trace levels of thiodiglycol in blood, plasma and urine using gas chromatography-electron-capture negative-ion chemical ionisation mass spectrometry

A sensitive method has been developed for the detection and quantitative determination of thiodiglycol in blood, plasma and urine. Samples were extracted from Clin Elut columns and cleaned up on C18 Sep-Pak cartridges (blood, plasma) or Florisil Sep-Pak cartridges (urine). Tetradeuterothiodiglycol was added to the sample prior to extraction as internal standard. Thiodiglycol was converted to its bis-(pentafluorobenzoate) derivative and analysed by capillary gas chromatography-electron-capture negative-ion chemical ionisation mass spectrometry using selected ion monitoring. Levels of thiodiglycol down to 1 ng/ml (1 ppb) could be detected in 1-ml spiked blood and urine samples; calibration curves were linear over the range 5- or 10-100 ng/ml. Blood and urine samples from a number of control subjects were analysed for background levels of thiodiglycol. Concentrations up to 16 ng/ml were found in blood, but urine levels were below 1 ng/ml.     

Determination of beta-agonist residues in bovine urine using liquid chromatography-tandem mass spectrometry

A multiresidue method was developed and validated to screen bovine urine samples for 10 beta-2-adrenergic agonistic drugs--brombuterol, cimaterol, clenbuterol, clenpenterol, isoxsuprine, mabuterol, ractopamine, ritodrine, salbutamol, and tulobuterol--at the 2 microg/L level. The method is also quantitative in the range of 1 to 4 microg/L for all analytes except salbutamol. The procedure uses enzymatic digestion, liquid-liquid extraction, and cleanup on solid-phase extraction columns, followed by detection using a liquid chromatograph-tandem quadrupole mass spectrometer operated in the positive-ion atmospheric pressure chemical ionization multiple-reaction monitoring mode. Method validation included assessment of recoveries, repeatabilities, linearity of responses, decision limits, and detection capabilities. Overall average recoveries ranged from 70-91%; recoveries were generally lower for salbutamol. The decision limits ranged from 0.4-1.0 microg/L, and detection capabilities from 0.6-1.7 microg/L.     

Determination of methotrexate in human urine at trace levels by solid phase extraction and high-performance liquid chromatography/tandem mass spectrometry

For biological monitoring of hospital personnel occupationally exposed to antineoplastic agents, highly sensitive and specific methods are required. In order to detect trace MTX urinary concentrations, a precise and accurate high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) procedure, incorporating solid phase extraction, has been developed. Urine samples were purified by solid phase extraction (SPE) on octadecyl bonded, endcapped silica SPE columns. After eluting with methanol, the solvent was evaporated obtaining a 25-fold concentration of the analyte. This procedure was validated by using 7-OHMTX as internal standard. Calibration curves had correlation coefficients always higher than 0.999, and the limit of detection was assessed at 0.2 microg L(-1). High specificity of the HPLC-MS/MS technique assures that no interfering substances are detected rather than the analyte of interest.     

超高效液相色谱-串联质谱法测定牛尿液中的甲状腺抑制剂(英文)

Five thyreostats(TSs),namely tapazole,thiouracil,methylthiouracil,propylthiouracil,and phenylthiouracil,were determined in bovine urine using ultra-high performance liquid chromatography-tandem mass spectrometry(UHPLC-MS/MS)in positive electrospray ionization mode.Extraction and clean-up were achieved using a ChemElut cartridge with tert-butyl methyl ether,without a derivatization step.Separation was achieved on an Acquity UPLC SS T3 column.The mobile phase was acetonitrile and water containing 0.2%(v/v)formic acid.The mass spectrometer was operated in multiple reaction monitoring mode.Urine samples were spiked with TS solution at levels corresponding to 5,10,15,and 20μg/L.The accuracy(internal standard corrected)ranged from 92%to 107%,with a repeatability precision(relative standard deviation,RSD)less than 15%for all five analytes.The RSDs within-laboratory reproducibility was less than 26%.The decision limits(CCα)and detection capabilities(CCβ)were obtained from a calibration curve and were in the ranges of 3.1-6.1μg/L and 4.0-7.4μg/L,respectively.The CCαand CCβvalues were below the recommended concentration,which was set at 10μg/L.The results show that the described method is suitable for the direct detection of TSs in bovine urine.This method can also be used to determine TSs in porcine urine.     

Determination of trace amounts of bisphenol A in urine by negative-ion chemical-ionization-gas chromatography/mass spectrometry.

We improved an analytical method for determining trace amounts of bisphenol A (BPA) in urine. BPA was subjected to enzymolysis and then to solid phase extraction with a C18 cartridge. The extract was eluted with methanol, and the eluate was concentrated under a nitrogen stream, and then pentafluorobenzylized in an alkali solution. The obtained pentafluorobenzylized compound was purifed using a florisil cartridge, followed by a determination using NCI-GC/MS. This method exhibited an excellent selectivity and reproducibility with a determination limit of 0.1 ng/ml.     

Determination of trace levels of iron in a seawater sample using isotope dilution/inductively coupled plasma mass spectrometry.

An analytical method for trace levels of iron in a seawater sample using isotope dilution ICP-MS was developed. Preconcentration of iron and the removal of major elements in seawater such as alkali and alkaline-earth elements can be carried out quickly using a chelating resin disk by adjusting the sample pH to 3. The collision cell option of the ICP-MS instrument method was used to improve the performance of the instrument for iron measurements since ArO and ArN interferences could be reduced using this analytical method. About 4 ml min(-1) helium, as the collision gas, were introduced into the cell. 40Ar14N and 40Ar16O which interfere with 54Fe and 56Fe in water had their amounts decreased by 5 orders of magnitude. Then, the isotope dilution method was used for iron determination below ng g(-1) level of trace iron in four environmental reference materials (river water standard sample JAC-0031 (Japan Soc. for Analytical Chemistry), estuarine standard sample SLEW-2 (NRC Canada) and seawater standard samples CASS-3 and NASS-5 (NRC Canada)) were measured. Good agreement between analytical results and certified values of reference materials was obtained, which confirmed the effectiveness of this method.     

Simultaneous determination of antidepressants by non-aqueous capillary electrophoresis-time of flight mass spectrometry

Simultaneous determination of 20 antidepressants in plasma samples was carried out by non-aqueous capillary electrophoresis with time of flight mass spectrometry via electrospray ionization, where a mixture of 60 mM ammonium acetate and 1M acetic acid in acetonitrile, and water, as well as methanol (100:1:0.5, v/v/v) was selected as the background electrolyte. By using time of flight mass spectrometry, accurate mass information was obtained and the background noise was dramatically decreased, thus causing a great improvement in qualitative ability. As for the plasma sample, solid phase extraction with Oasis HLB was used. The limits of detection and quantification were in the range of 0.5-1 and 1-5 ng/ml, respectively. The sensitivity of the present method was found better, i.e. approximately 10-60 folds compared to that using photo diode array detectors because the analyte peak could be clearly distinguished from the background derived from the plasma. The present method was found very useful and practical as regards to routine analysis of plasma samples.     

Determination of bupivacaine and metabolites in rat urine using capillary electrophoresis with mass spectrometric detection

A method using capillary electrophoresis-mass spectrometry (CE-MS) was developed for the structural elucidation of bupivacaine and metabolites in rat urine. Prior to CE-MS analysis, solid-phase extraction (SPE) was used for sample cleanup and preconcentration purposes. Exact mass and tandem mass spectrometric (MS/MS) experiments were performed to obtain structural information about the unknown metabolites. Two instruments with different mass analyzers were used for mass spectrometric detection. A quadrupole time-of-flight (Q-TOF) and a magnetic sector hybrid instrument were coupled to CE and used for the analysis of urine extracts. Hydroxybupivacaine as well as five other isomerically different metabolites were detected including methoxylated bupivacaine.     

Determination of 4,4'-methylenebis(2-chloroaniline) in urine using capillary gas chromatography and negative ion chemical ionization mass spectrometry.

A highly sensitive and specific gas chromatographic-mass spectrometric (GC-MS) assay for the determination of 4,4'-methylenebis(2-chloroaniline) (MBOCA) in urine is reported. It is based on the solvent extraction of the hydrolysed MBOCA conjugates, together with deuterium-labelled benzidine-d8 added as an internal standard, and a two-phase derivatization procedure involving use of pentafluoropropionic anhydride in the presence of ammonia as the phase-transfer catalyst. The reaction is complete within 2 min at room temperature. The pentafluoropropyl derivatives are determined by use of capillary column GC-MS with selected-ion monitoring in the negative ion chemical ionization mode. The lower limit of detection for MBOCA was 1 microgram dm-3 and the calibration graph showed linearity between 10 and 250 micrograms dm-3. The recovery of the analyte added to pooled urine was above 86%. Thirty urine specimens from workers employed in a polyurethane-producing plant were analysed for MBOCA by this method.     

Peptide mapping using capillary electrophoresis offline coupled to matrix-assisted laser desorption ionization time of flight mass spectrometry

This article reports the results of a study carried out to evaluate the offline hyphenation of capillary zone electrophoresis with matrix-assisted lased desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) for the analysis of low-abundant complex samples, represented by the tryptic phosphorylated peptides of phosphoproteins, such as α-casein, β-casein, and fetuin. The proposed method employs a latex-coated capillary and consists in the online preconcentration of the tryptic peptides by a pH-mediated stacking method, their separation by capillary zone electrophoresis, and subsequent deposition of the separated analytes onto a MALDI target for their MS analysis. The online preconcentration method allows loading a large sample volume (～150?nL), which is introduced into the capillary after the hydrodynamic injection of a short plug of 1.0?M ammonium hydroxide solution and is sandwiched between two plugs of the acidic background electrolyte solution (BGE) filling the capillary. The sample spotting of the separated analytes onto the MALDI target is performed either during or postseparation using an automatic spotting device connected to the exit of the separation capillary. The proposed method allows the separation and identification of multiphosphorylated peptides from other peptides and enables their identification at femtomole level with improved efficiency compared with LC approaches hyphenated to MS.     

Simultaneous determination of six toxic alkaloids in human plasma and urine using capillary zone electrophoresis coupled to time‐of‐flight mass spectrometry

A novel capillary zone electrophoresis separation coupled to electro spray ionization time‐of‐flight mass spectrometry method was developed for the simultaneous analysis of six toxic alkaloids: brucine, strychnine, atropine sulfate, anisodamine hydrobromide, scopolamine hydrobromide and anisodine hydrobromide in human plasma and urine. To obtain optimal sensitivity, a solid‐phase extraction method using Oasis MCX cartridges (1 mL, 30 mg; Waters, USA) for the pretreatment of samples was used. All compounds were separated by capillary zone electrophoresis at 25 kV within 12 min in an uncoated fused‐silica capillary of 75 μm id × 100 cm and were detected by time‐of‐flight mass spectrometry. This method was validated with regard to precision, accuracy, sensitivity, linear range, limit of detection (LOD), and limit of quantification (LOQ). In the plasma and urine samples, the linear calibration curves were obtained over the range of 0.50–100 ng/mL. The LOD and LOQ were 0.2–0.5 ng/mL and 0.5–1.0 ng/mL, respectively. The intra‐ and interday precision was better than 12% and 13%, respectively. Electrophoretic peaks could be identified by mass analysis.     

Screening by tandem mass spectrometry for trace levels of alkylbenzenes

Product ion spectra derived from molecule ions as the precursor ions for 14 alkylbenzenes have been studied under electron ionization and methane chemical ionization. The data have provided a satisfactory screening method for both detection and confirmation of such compounds at low parts per million levels.     

Determination of caffeine and its metabolites in urine by capillary electrophoresis-mass spectrometry

The caffeine content of foods and beverages varies considerably, interfering with our ability to obtain valid interpretations in many human studies with regard to the mechanism of action(s) of caffeine and/or its metabolites. The rate of metabolism of caffeine and other xanthine drugs also varies greatly from one individual to another. Therefore, it is extremely important to develop accurate, reliable analytical methods to quantify caffeine and its metabolites in simple and complex matrixes. A simple method is described for the separation and characterization of caffeine and its major metabolites employing capillary electrophoresis (CE) coupled to ultraviolet-absorption and mass spectrometry (MS) detection. After optimization of the electrophoresis separation conditions, a reliable separation of caffeine and 11 of its major metabolites was achieved in 50 mM ammonium carbonate buffer, pH 11.0. The volatile aqueous electrolyte system used with a normal electroosmotic flow polarity also provided an optimal separation condition for the characterization of the analytes by MS. The CE method achieved baseline resolution for all 12 compounds in less than 30 min. The CE-MS method is suitable for use as a routine procedure for the rapid separation and characterization of caffeine and its metabolites. The usefulness of this method was demonstrated by the extraction, separation, and identification of caffeine and its 11 metabolites from normal urine samples. The urine specimens were first acidified to obtain optimum binding efficiency to the sorbents of the off-line, solid-phase extraction procedure employed here, and an acidified eluent solvent was employed for the desorption step to maximize the recovery of the bound analytes.     

Determination of pyrethroid metabolites in human urine by capillary gas chromatography-mass spectrometry

Summary An analytical method for the simultaneous determination of the pyrethroid metabolites cis and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid, cis 3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylic acid, 3-phenoxybenzoic acid and 4-fluoro-3-phenoxybenzoic acid in human urine samples is described. The urine is subjected to acid-induced hydrolysis followed by exhaustive solvent extraction, covering both conjugated and free acids, followed by a common derivatisation step yielding the corresponding methyl esters. Quantitation was by diastereomeric, capillary gas chromatography-mass spectrometry. It appears that 4-fluoro-3-phenoxybenzoic acid is a characteristic urinary marker for cyfluthrin exposure. The limits of determination are 0.5–1.0 g L^–1 urine depending on the metabolites concerned. The applicability of the method was tested on urine samples from pest control operators exposed occupationally to cypermethrin and cyfluthrin.     

Determination of trace elements using multi-parameter coincidence spectrometry

In this study, sensitive trace element analyses were carried out without chemical separation by the combination of neutron activation analysis and multi-parameter coincidence spectroscopy. A long-lived radioisotope ¹²⁹I in algae samples and iridium in geological samples were analyzed.