Negative Chemical Ionization Mass Spectrometry Research Articles

Quantitative determination of memantine in human plasma by GC using negative ion chemical ionization MS detection after derivatization with a new reagent, o-(pentafluorobenzyloxycarbonyl)-2,3,4,5-tetrafluorobenzoyl chloride

A method is presented for the quantitative determination of memantine in plasma by use of the derivatization reagent o-(pentafluorobenzyloxycarbonyl)-2,3,4,5-tetrafluorobenzoyl chloride. Memantine can be quantitatively analyzed down to 49 pg per mL of plasma using a 250 μL sample and negative ion chemical ionisation mass spectrometry (GC-NICI-MS). Plasma samples were made alkaline with carbonate buffer and extracted with n-hexane. The extracts were treated with reagent solution for 20 min, concentrated, and submitted to GC-NICI-MS. The method is rapid because extraction and derivatization occur in one single step. Amantadine is used as an internal standard. The utility and robustness of the assay is demonstrated by giving data on specificity, linearity, accuracy and precision, benchtop stability, freeze-thaw stability, autosampler stability, aliquot analysis, and prospective analytical batch size accuracy.

Rapid analysis of polybrominated diphenyl ethers in soil by matrix solid‐phase dispersion using bamboo charcoal as dispersive sorbent

An expeditious and sensitive method for the analysis of eight major polybrominated diphenyl ethers (PBDEs) in soil is presented in this study. The method is based on matrix solid-phase dispersion (MSPD) extraction and gas chromatography with negative chemical ionization mass spectrometry. Bamboo charcoal, a cheap and potentially useful material, was selected for the first time as the MSPD dispersive sorbent. Parameters affecting the extraction efficiency, including the ratio of sorbent to sample, and the type and amount of eluent, were investigated and optimized in detail. Under optimal conditions, the spiked recovery of the PBDEs was in the range 71.7-105.9%, and the limits of detection varied from 10 to 400 pg g(-1) (dry weight). Excellent linearity with correlation coefficients (r(2)) of 0.9992-0.9999 was obtained over the concentration range of 0.10-500 ng g(-1) , except for BDE-209, for which the effective concentration range was 1.0-5000 ng g(-1) . The developed method has been successfully applied to the analysis of PBDEs in real soil samples.

Retracted: β-Carotene in Golden Rice is as good as β-carotene in oil at providing vitamin A to children

Golden Rice (GR) has been genetically engineered to be rich in β-carotene for use as a source of vitamin A. The objective was to compare the vitamin A value of β-carotene in GR and in spinach with that of pure β-carotene in oil when consumed by children. Children (n = 68; age 6-8 y) were randomly assigned to consume GR or spinach (both grown in a nutrient solution containing 23 atom% ²H₂O) or [²H₈]β-carotene in an oil capsule. The GR and spinach β-carotene were enriched with deuterium (²H) with the highest abundance molecular mass (M) at M(β-C)+²H₁₀. [¹³C₁₀]Retinyl acetate in an oil capsule was administered as a reference dose. Serum samples collected from subjects were analyzed by using gas chromatography electron-capture negative chemical ionization mass spectrometry for the enrichments of labeled retinol: M(retinol)+4 (from [²H₈]β-carotene in oil), M(retinol)+5 (from GR or spinach [²H₁₀]β-carotene), and M(retinol)+10 (from [¹³C₁₀]retinyl acetate). Using the response to the dose of [¹³C₁₀]retinyl acetate (0.5 mg) as a reference, our results (with the use of AUC of molar enrichment at days 1, 3, 7, 14, and 21 after the labeled doses) showed that the conversions of pure β-carotene (0.5 mg), GR β-carotene (0.6 mg), and spinach β-carotene (1.4 mg) to retinol were 2.0, 2.3, and 7.5 to 1 by weight, respectively. The β-carotene in GR is as effective as pure β-carotene in oil and better than that in spinach at providing vitamin A to children. A bowl of ~100 to 150 g cooked GR (50 g dry weight) can provide ~60% of the Chinese Recommended Nutrient Intake of vitamin A for 6-8-y-old children.

Quantitative method for determination of amphetamine in plasma using negative ion chemical ionisation GC‐MS of o‐(pentafluorobenzyloxycarbonyl)‐benzoyl derivatives

The use of a novel electrophoric derivatisation reagent, o-(pentafluorobenzyloxycarbonyl)-benzoyl chloride is described for the quantitative determination of amphetamine in plasma. Amphetamine can be quantitatively measured down to 49 pg/mL plasma using only 250 μL of sample due to the extraordinary sensitivity of the derivatives under negative ion chemical ionisation mass spectrometry. Plasma samples were made alkaline with carbonate buffer and treated with n-hexane and reagent solution for 20 min, which, after concentration was measured by negative ion chemical ionisation gas chromatography-mass spectrometry. The method is rapid as extraction and derivatisation occur in one single step. [(2)H(5)]-Amphetamine was used as an internal standard. Validation data are given to demonstrate the usefulness of the assay, including specificity, linearity, accuracy and precision, benchtop stability, freeze-thaw stability, autosampler stability, aliquot analysis and prospective analytical batch size accuracy.

A multi-residue method for pesticides analysis in green coffee beans using gas chromatography–negative chemical ionization mass spectrometry in selective ion monitoring mode

In this study, a new gas chromatography–mass spectrometry (GC–MS) method, using the very selective negative chemical ionization (NCI) mode, was developed and applied in combination with a modified acetonitrile-based extraction method (QuEChERS) for the analysis of a large number of pesticide residues (51 pesticides, including isomers and degradation products) in green coffee beans. A previously developed integrated sample homogenization and extraction method for both pesticides and mycotoxins analysis was used. An homogeneous slurry of green milled coffee beans and water (ratio 1:4, w/w) was prepared and extracted with acetonitrile/acetic acid (1%), followed by magnesium sulfate addition for phase separation. Aliquots from this extract could be used directly for LC–MS/MS analysis of mycotoxins and LC-amenable pesticides. For GC–MS analysis, a further clean-up was necessary. C18- and PSA-bonded silica were tested as dispersive solid-phase extraction (d-SPE) sorbents, separate and as a mixture, and the best results were obtained using C18-bonded silica. For the optimal sensitivity and selectivity, GC–MS detection in the NCI-selected ion monitoring (SIM) mode had to be used to allow the fast analysis of the difficult coffee bean matrix. The validation was performed by analyzing recovery samples at three different spike concentrations, 10, 20 and 50μgkg−1, with 6 replicates (n=6) at each concentration. Linearity (r2) of calibration curves, estimated instrument and method limits of detection and limits of quantification (LODi, LODm, LOQi and LOQm, respectively), accuracy (as recovery %), precision (as RSD%) and matrix effects (%) were determined for each individual pesticide. From the 51 analytes (42 parent pesticides, 4 isomers and 5 degradation products) determined by GC–MS (NCI-SIM), approximately 76% showed average recoveries between 70–120% and 75% and RSD≤20% at the lowest spike concentration of 10μgkg−1, the target method LOQ. For the spike concentrations of 20 and 50μgkg−1, the recoveries and RSDs were even better. The validated LOQm was 10, 20 and 50μgkg−1 for respectively 33, 3 and 6 of the analytes studied. For five compounds, the European Union method performance requirements for the validation of a quantitative method (average recoveries between 70-120% and repeatability RSD≤20%) were not achieved and 4 problematic pesticides (captan, captafol, folpet and dicofol) could not be detected as their parent compound, but only via their degradation products. Although the matrix effect (matrix-enhanced detector response) was high for all pesticides studied, the matrix interference was minimal, due to the high selectivity obtained with the GC–NCI-MS detection. Matrix-matched calibration for applying the method in routine analysis is recommended for reliable quantitative results.

Determination of memantine in human plasma by GC using negative ion chemical ionization MS detection after derivatization with a new reagent

We describe a method for the determination of memantine in plasma by use of the derivatization reagent o-(pentafluorobenzyloxycarbonyl)-benzoyl chloride. Memantine can be quantitatively analyzed down to 49 pg per mL of plasma using a 250 μL sample and negative ion chemical ionisation mass spectrometry (GC-NICI-MS). Plasma samples were made alkaline with carbonate buffer and extracted with n-hexane. The extracts were treated with reagent solution for 20 min, concentrated, and submitted to GC-NICI-MS. The method is rapid because extraction and derivatization occur in one single step. Amantadine is used as an internal standard. The utility and robustness of the assay is demonstrated by giving data on specificity, linearity, accuracy and precision, benchtop stability, freeze–thaw stability, autosampler stability, aliquot analysis, and prospective analytical batch size accuracy.

Bis-pentafluorobenzyl derivatives of N-acetyl-l-methionine and N-acetyl-l-selenomethionine for the quantitative determination in human plasma by gas chromatography–negative ion chemical ionisation mass spectrometry

Targeted anti-cancer combination therapy with infusion of N-acetyl-l-methionine (NALM) and N-acetyl-l-selenomethionine (NASeLM) shows promising results in cancer treatment. Selenium has been recognised as a valuable additive in cancer therapeutics due to its ability to minimise side effects of chemotherapy and its role in cancer prevention and therapy. Due to the promising results of this new therapeutic approach evaluation of pharmacokinetic data for NALM and NASeLM is of ultimate importance. We have therefore elaborated a method for the quantitative measurement of these compounds in human plasma based on GC–negative ion chemical ionisation-MS. The derivatisation sequence elaborated can be regarded as a novel strategy for the chemical modification of delicate sulphur- and selenium-containing compounds, and underlines the enhanced reactivity of selenium-analogues of sulphur-containing amino acids. The target compounds were extracted from plasma with ethyl acetate and converted to the S/Se-pentafluorobenzyl-homocysteine pentafluorobenzyl ester derivative. Reaction conditions were optimised for derivative yield. Calibration graphs were established in the range of 2.938–481.105ng/0.5mL plasma (NALM) and 0.233–59.543ng/0.5mL plasma (NASeLM). Accuracy, precision and stability data were elaborated. The method was applied to pharmacokinetic profiling of the compounds after infusion into human volunteers.

(S)‐(−)‐N‐(Pentafluorobenzylcarbamoyl)prolyl chloride: a chiral derivatisation reagent designed for gas chromatography/negative ion chemical ionisation mass spectrometry of amino compounds

The synthesis of a novel chiral derivatisation reagent, (S)-(-)-N-(pentafluorobenzylcarbamoyl)prolyl chloride is described which is preferably useful for negative-ion chemical ionisation mass spectrometry. Preparation of the reagent followed a general strategy used to prepare enantioselective reagents based on the N-substitution of L-proline. Pentafluorobenzyl chloroformate smoothly reacted with L-proline to give the desired derivatisation reagent after conversion into the acyl chloride. The product was sufficiently pure to be used in the following steps without any additional purification. The reagent was tested against selected chiral and non-chiral analytical targets. Chromatographic enantioseparation was at least equal to the commonly used (S)-(-)-N-(heptafluorobutyryl)prolyl derivatives. The derivatives exhibit excellent mass spectral properties under negative ion chemical ionisation, i.e. reduced fragmentation and thus high ion current for the targeted m/z during analysis. With electron ionisation, the fragmentation that occurs is mainly directed by the introduced group. Enantioseparation with gas chromatography/negative-ion chemical ionisation mass spectrometry of the derivatives was demonstrated for the enantiomers of amphetamine, α-aminocaprylic acid methyl ester and threo-methylphenidate. The new derivatisation reagent shows highly improved mass spectral properties for negative-ion chemical ionisation mass spectrometry and is thus suitable for sensitive chiral detection of amino compounds. The reagent extends the applicability of dissociative resonance electron capture using pentafluorobenzyl derivatives to chiral analysis.

Polybrominated diphenyl ether levels in wild and farmed Chilean salmon and preliminary flow data for commercial transport

AbstractThis pilot study documented the occurrence and levels of brominated flame retardants in the tissues of farmed and wild salmon in southern Chile. Samples of Coho salmon and rainbow trout were obtained from fish farms, rivers and lakes in the Patagonia in Aysen Region, Chile. The samples were analyzed by Gas Chromatography Negative Chemical Ionization Mass Spectrometry for the different polybrominated diphenyl ether (PBDE) congeners. Contaminants were observed in all the samples, and the congeners BDE 17, 28, 47 and 66 were observed in all both farmed and wild samples. The concentrations were higher in the farmed Coho salmon, presenting significant differences with wild salmon. The levels reached 182 pg/g wet weight (ww) vs. 120 ww. In the case of the rainbow trout, the concentrations were lower, although the congener profile was quite similar. The levels reached an average of 100 pg/g ww in the farmed fish versus 110 pg/g ww in wild fish, and no significant difference was observed between the species. In both species, the congener with the highest concentration was BDE 47. Based on this information, the BDE flow was estimated for commerce, which is a form of pollutant transport not usually considered in POP pollution studies. A preliminary estimation indicated that the quantity of PBDEs mobilized by commerce was in the order of kg, and in the case of Chile might reach almost 1 kg.

Microdialysis of melatonin in the confluens sinuum of the rat following quantification by gas chromatography-mass spectrometry in the negative chemical ion mode.

In this study, an original surgical implantation technique in the confluens sinuum via the superior sagittal vein was developed to quantify melatonin secretion by the pineal gland. Melatonin (CAS 73-31-4) was determined using gas chromatography couples to negative ion chemical ionisation mass spectrometry following liquid extraction and derivatisation by penta-fluoropropionic acid anhydride (PFPA). The minimum detectable amount was 40 fg per injection, corresponding to 1 pg.ml-1 in dialysate. The assay was linear in the range 20-1000 pg.ml-1. This method was suitable for routine melatonin determination in dialysats of peripheral and central circulation with coefficients of variation of 11.2 and 24.6%, respectively for within and between analyses. Profiles of melatonin concentration were obtained (n = 3 rats) over a 2-day experimentation with a slowly diminution of the filtration capacity of the probe during the second day. The nocturnal concentrations of melatonin in the confluens sinuum dialysat ranged from 1003.9 to 2345 pg.ml-1 in the dialysat, indicating wide interindividual variations in the melatonin levels.

Simultaneous determination of nicotine and PAH metabolites in human hair specimen: A potential methodology to assess tobacco smoke contribution in PAH exposure

The present methodology was developed to simultaneously assess chronic exposure to PAHs and to tobacco from the analysis of one hair specimen per examined individual. The method is a two step extraction of twelve mono-hydroxy-PAHs and of nicotine, and their separate analysis by optimized methods using gas chromatography–negative chemical ionization-mass spectrometry. After method validation and assessment of the hair decontamination procedure, 105 hair specimens from smokers and non-smokers were analyzed. All the hair samples tested positive for nicotine. Median concentration was 10.7ng/mg for smokers and 0.5ng/mg for non-smokers. 70% of the samples tested positive for OH-PAHs. The most common one was 2-naphthol (61%) and its concentration was significantly higher in smokers than in non-smokers (median: 111 vs 70pmol/g, p=0.006). 2-OH-benzo(c)phenanthrene and 6-OH-chrysene were only detected once in a non-smoker's hair. The concentration of the sum of all PAH-metabolites ranged from 24 to 67190pmol/g (median: 118pmol/g). Only six samples tested positive for more than two different metabolites. The simultaneous detection of nicotine and OH-PAHs in hair is possible and provides reliable results. This represents a useful tool for the accurate biomonitoring of chronic exposure to PAH and correct identification of the sources of exposure.

Gas chromatography–negative ion chemical ionisation mass spectrometry using o-(pentafluorobenzyloxycarbonyl)-2,3,4,5-tetrafluorobenzoyl derivatives for the quantitative determination of methylphenidate in human plasma

A novel electrophoric derivatisation procedure using o-(pentafluorobenzyloxycarbonyl)-2,3,4,5-tetrafluorobenzoyl chloride for the quantitative determination of methylphenidate in human plasma is described. The drug can be quantitatively measured down to 0.006 pg/mL plasma due to the extraordinary sensitivity of the derivatives under negative ion chemical ionisation mass spectrometry. Plasma samples were made alkaline with carbonate buffer and treated with extraction solvent (n-hexane) and reagent solution for 15 min, which, after concentration was measured by GC–NICI–MS. The method is rapid as extraction and derivatisation occur in one single step. A stable isotope labelled internal standard was used. Validation data are given to demonstrate the usefulness of the assay, including selectivity, linearity, accuracy and precision, autosampler stability, aliquot analysis, robustness, and prospective analytical batch size accuracy. The method has been successfully applied to pharmacokinetic profiling of the drug after oral administration.

Quantitative determination of methylphenidate in plasma by gas chromatography negative ion chemical ionisation mass spectrometry using o-(pentafluorobenzyloxycarbonyl)-benzoyl derivatives

The use of a novel electrophoric derivatisation reagent, o-(pentafluorobenzyloxycarbonyl)-benzoyl chloride, for the quantitative determination of methylphenidate in plasma is described. The drug can be quantitatively measured down to 72 pg/mL plasma using only 250 μL of sample due to the extraordinary sensitivity of the derivatives under negative ion chemical ionisation mass spectrometry. Plasma samples were made alkaline with carbonate buffer and treated with extraction solvent n-hexane and reagent solution for 30 min, which, after concentration, was measured by GC-NICI-MS. The method is rapid as extraction and derivatisation occur in one single step. A stable isotope-labelled internal standard was used and its synthesis described. Full validation data are given to demonstrate the usefulness of the assay, including specificity, linearity, accuracy and precision, long-term stability, short-term stability, freeze-thaw stability, stock solution stability, autosampler stability, aliquot analysis, robustness, matrix effect, and prospective analytical batch size accuracy. The method has been successfully applied to pharmacokinetic profiling of the drug after oral application.

Determination of midazolam and 1-hydroxymidazolam from plasma by gas chromatography coupled to methane negative chemical ionization mass spectrometry after sublingual administration of midazolam

A sensitive and selective gas chromatographic mass spectrometric method for the determination of midazolam and its biologically active metabolite, 1-hydroxymidazolam, in rabbit plasma has been developed and validated. Sample preparation includes mixed-mode solid-phase extraction and derivatization with silylating reagents. Midazolam-d4 was used as an internal standard for the determination of parent drug and its active metabolite. The instrumentation consisted of a capillary column gas chromatography and a single quadrupole mass spectrometer with a negative chemical ionization. The method was found to be valid in terms of selectivity, linearity, precision, accuracy, and recovery over the concentration range of 2–200 ng/ml and 1–100 ng/ml for midazolam and 1-hydroxymidazolam, respectively. For both analytes, the lower limit of quantification was 2 ng/ml. Midazolam was stable in stock solutions stored three months at −20 °C and in human plasma stored for three months at −80 °C. In addition, no degradation of midazolam was found after three freeze–thaw cycles, in short-term stability at room temperature for 24 h, or in post-preparative stability in the autosampler. The validity of the method was further tested by performing a pharmacokinetic study of sublingual administration of midazolam in rabbits. The method will be used in studies related to a formulation development of novel midazolam formulations for use in paediatric anaesthesia.

Fast and fully automated analytical method for the screening of residues of aziridine and 2-chloroethylamine in pharmaceutical active principles

A simple, fast and fully automated method for the screening of aziridine (AZD) and 2-chloroethylamine (CEA) in active pharmaceutical ingredients (API) has been developed. The method is based on the in-fiber derivatization of the amines extracted from the sample headspace (previously dissolved or suspended in alkaline water) with 2,3,4,5,6-pentafluorobenzoyl chloride (PFBCl) previously adsorbed in the PDMS/DVB solid phase microextraction (SPME) fiber. The derivatives formed are further desorbed and analyzed in a gas chromatograph with negative ion chemical ionization mass spectrometry (GC–NCI-MS) using methane as reagent gas. The different operational parameters of the procedure have been optimized to get highest sensitivity. The validation of the method, however, revealed a poor repeatability, particularly evident in water-soluble APIs (RSD > 20% for AZD). In spite of that, the low detection limits (1–3 ng g −1 for AZD and CEA), speed (44 min total analysis time) and automation make that this method can be satisfactorily used as screening tool to accept or reject API batches attending to their volatile amine content and a critical specified value derived from the 1.5 μg/day Threshold of Toxicological Concern (TTC) and maxima daily dosages. This was shown by analyzing seventy-five fluvoxamine maleate samples containing known levels of AZD and CEA (between 0.05 and 1.05 μg g −1) in intermediate reproducibility conditions to get reliable estimations of precision and linearity. From these data, acceptance, rejection and non-conclusive areas of response are defined for both analytes at different confidence and replication levels using normal statistics. The method was satisfactorily applied to real fluvoxamine maleate samples.

Quantification of Dechlorane Plus in Human Serum by Gas Chromatography Coupled with Negative Chemical Ionization Mass Spectrometry

Abstract A gas chromatography coupled with negative chemical ionization mass spectrometry (GC-NCI-MS) was developed for the determination of two dechlorane plus (DP) isomers in human serum sample. Target compound and serum lipid were extracted by liquid-liquid extraction. After the sulfuric acid treatment to remove extracted lipids from the samples, samples were further cleaned up with a silica/sulfuric acid column. Identification and quantification of DP were carried out by MS. The detection limit of instrument was 0.5–0.7 pg. The detection limit of the method was 15–20 pg per sample. Recoveries of DP spiked in human serum samples were in the range of 70.2%–85.7%. The developed method was further validated in human serum. DP concentrations were analyzed in 20 electronics dismantling workers and 20 reference humans; DP concentration in dismantling workers and reference humans were 7.8–465 ng g−1 lipid and 0.93–50.5 ng g−1 lipid, respectively.

An examination of pentafluorobenzoyl derivatization strategies for the analysis of fatty alcohols using gas chromatography/electron capture negative ion chemical ionization–mass spectrometry

Gas chromatography/electron capture negative ion chemical ionization–mass spectrometry (GC/ECNICI–MS) combined with pentafluorobenzoyl derivatization (PFBoyl) is frequently used for the sensitive detection of fatty alcohols (FOH). However, this derivatization technique suffers from a lack of established reaction protocols, time-consuming reactions, and the presence of reagent artifacts or unwanted derivatization by-products which can hinder analyte detection. Here, strategies are presented to reduce the problems associated with PFBoyl-derivatization, including (1) the optimization of reaction conditions (derivatization time and temperature) for a variety of PFBoyl-derivatized FOH, (2) an investigation of microwave-accelerated derivatization (MAD) as a rapid alternative heating mechanism for the PFBoyl-derivatization of FOH, and (3) an analysis of an alternative strategy employing a solvent extraction procedure post-derivatization to reduce the detrimental effects commonly associated with PFBoyl derivatization reagents. The optimal reaction conditions for the PFBoyl-derivatization of FOH were determined to be 60 °C for 45 min. The investigation in MAD demonstrated the potential of obtaining comparable PFBoyl-derivatizations to those obtained using traditional heating methods, albeit in a reaction time of 3 min. An examination of several solvents for post-derivatization extraction revealed improved relative response factors in comparison to those obtained without solvent extraction. The best solvents for the PFBoyl–FOH extraction, dichloromethane and tert-butyl methyl ether, were also compared to the no solvent extraction samples with standard response curves and PFBoyl-derivatized FOH in Bligh–Dyer extracted rat plasma.

O‐(Pentafluorobenzyloxycarbonyl)benzoyl chloride: a novel electrophoric derivatisation reagent for amino compounds designed for negative ion chemical ionisation mass spectrometry

The synthesis of a novel electrophoric derivatisation reagent, o-(pentafluorobenzyloxycarbonyl)benzoyl chloride, is described. The reagent was tested against selected primary and secondary amino compounds as analytical targets. The derivatives exhibit excellent mass spectral properties under negative ion chemical ionisation (NICI), i.e. reduced fragmentation and thus high ion current for the targeted m/z during analysis. Since the reagent bears a pentafluorobenzyl ester group, resulting mass NICI mass spectra were expectedly dominated by dissociative resonance electron capture typically observed with these compounds. The reagent is suitable for detecting volatile primary and secondary amines with high sensitivity. Background is reduced by a shift in detected m/z and retention time, as demonstrated for the analysis of the drug methylphenidate from human plasma.

Method optimization to measure polybrominated diphenyl ether (PBDE) concentrations in soils of Bratislava, Slovakia

We modified an analytical method to determine polybrominated diphenyl ethers (PBDEs) in urban soils of Bratislava (Slovakia). Gel permeation chromatography (GPC) introduced as a clean-up step for soil extracts substantially reduced matrix enhancements when PBDEs were measured with gas chromatography–negative chemical ionization–mass spectrometry (GC–NCI–MS). The resulting method proved to be accurate, precise, and showed low detection limits. The sum of 15 PBDE concentrations in surface horizons of Bratislava soils ranged from 87 to 627 pg g −1. PBDE concentrations were mostly higher in surface than deeper horizons probably because of atmospheric deposition and lack of substantial vertical transport. Lower brominated PBDEs undergo more soil–atmosphere exchanges or are more scavenged and transferred with litter fall to the soil organic matter than higher brominated ones as suggested by the correlation between lower brominated PBDEs and soil organic C (C org) concentrations.

Measurement of Urinary F2-Isoprostanes as Markers of in Vivo Lipid Peroxidation: A Comparison of Enzyme Immunoassays with Gas Chromatography–Mass Spectrometry in Domestic Animal Species

F(2)-isoprostanes are useful markers for assessing oxidant injury; however, the validity of measuring urinary 15-F(2t)-isoprostane concentration by enzyme-linked immunosorbent assay (ELISA) has not been evaluated in veterinary species. The current study assesses the agreement between 2 commercially available urinary isoprostane kits and gas chromatography and negative ion chemical ionization-mass spectrometry (GC/NICI-MS). The results indicate that only feline urinary isoprostane measurement by glucuronidase (GL)-ELISA has acceptable agreement with GC/NICI-MS. Urinary isoprostane concentration was highly variable in critically ill animals, but there were too many variations between healthy and critically ill animals to draw meaningful conclusions. Currently, GC/NICI-MS is the only method that can be recommended for the assessment of urinary isoprostanes in dogs, cattle, and horses. Feline urinary isoprostanes can be assessed by GL-ELISA, but caution is still warranted when comparing data from manuscripts using different methods given the relatively low Spearman rank correlation coefficient. Future studies may require large sample sizes or focused inclusion criteria to account for variability in isoprostane concentration.