Ultra trace determination of fluorinated aromatic carboxylic acids in aqueous reservoir fluids by solid phase extraction in combination with negative ion chemical ionisation mass spectrometry after derivatisation with pentafluorobenzyl bromide

A new GC/MS method for the ultra trace analysis of fluorinated aromatic carboxylic acids after solid phase extraction and derivatisation with pentafluorobenzyl bromide is described. The pentafluorobenzyl esters formed were determined by negative ion chemical ionisation GC/MS in aqueous reservoir samples in concentrations as low as 0.010 μg/L. Determination of selected fluorinated aromatic carboxylic acids in aqueous reservoir samples, already injected as water tracers in North Sea reservoirs, confirmed the applicability of the method. Received: 5 September 1997 / Revised: 21 January 1998 / Accepted: 26 January 1998     

Determination of N-n-alkyl-dimethylmorpholines and their metabolites by high resolution GC/MS

An analytical method is described to determine simultaneously cis/trans N-n-alkyl-dimethylmorpholines and their metabolites, the 4-(ω-carboxy-n-alkyl) cis/trans-2,6-dimethylmorpholines by pyrolytic alkylation and high resolution GC/MS in aqueous systems and sediments. The substances in the sediment phase were analyzed by GC/MS after extraction with methanol and water, substances in the water phase could be directly determined by GC/MS. The analytical procedure also allows the determination of further carboxylic acids in complex aqueous systems. Received: 9 April 1996 / Revised: 10 June 1996 / Accepted: 14 June 1996     

Direct sensitive simultaneous determination of fluorinated benzoic acids in oil reservoir waters by ultra high-performance liquid chromatography-tandem mass spectrometry

A direct ultra-high performance reverse-phase HPLC (UHPLC)--electrospray MS/MS method was developed for the simultaneous determination of 16 fluorinated benzoic acids (FBAs) in oil reservoir waters. The separation was achieved within 5 min in a non-linear gradient mode using a 1-ml sample aliquot. The method detection limits were in the lower ng/ml range (between 0.05 and 50 ng/ml, depending on the compound) owing to the use of the travelling-wave collision cell technology. The method developed was more sensitive, faster (by avoiding sample preconcentration and purification steps) and more robust than the GC/MS methods currently used in oil industries. The accuracy of the method was verified by comparison with GC/MS results. It was applied to the determination of FBAs in water samples coming from reservoir tracing campaigns.     

Determination of N-n-alkyl-dimethylmorpholines and their metabolites by high resolution GC/MS

An analytical method is described to determine simultaneously cis/trans N-n-alkyl-dimethylmorpholines and their metabolites, the 4-(ω-carboxy-n-alkyl) cis/trans-2,6-dimethylmorpholines by pyrolytic alkylation and high resolution GC/MS in aqueous systems and sediments. The substances in the sediment phase were analyzed by GC/MS after extraction with methanol and water, substances in the water phase could be directly determined by GC/MS. The analytical procedure also allows the determination of further carboxylic acids in complex aqueous systems.     

HS-SPME determination of volatile carbonyl and carboxylic compounds in different matrices

Specific chromatographic methodologies are developed for the analysis of carboxylic acids (C(2)-C(6), benzoic) and aldehydes (C(2)-C(10)) of low molecular weight in diverse matrices, such as air, automotive exhaust gases, human breath, and aqueous matrices. For carboxylic acids, the method is based on their reaction with pentafluorobenzyl bromide in aqueous solution, followed by the separation and identification of the resultant pentafluorobenzyl esters by means of headspace (HS)-solid-phase microextraction (SPME) combined with gas chromatography (GC) and electron capture detection (ECD). Detection limits in the microg/m(3) range are reached, with relative standard deviation (RSD) less than 10% and linear response (R(2) > 0.99) over two orders of magnitude. The analytical methodology for aldehydes is based on SPME with simultaneous derivatization of the analytes on the fiber, by reaction with pentafluorophenylhydrazine. The derivatization reagent is previously deposited on the SPME fiber, which is then exposed to the gaseous matrix or the HS of the sample solution. The pentafluorophenyl hydrazones formed on the fiber are analyzed selectively by means of GC-ECD, with detection limits in the ng/m(3) range, RSD less than 10%, and linear response (R(2) > 0.99) over two orders of magnitude.     

Determination of pentafluorobenzyl derivatives of phosphonic and phosphonothioic acids by gas chromatography-mass spectrometry

A method based on gas chromatography-mass spectrometry (GC/MS) has been evaluated and standardized for the analysis of pentafluorobenzyl (PFB) derivatives of alkylphosphonic, O-alkyl alkylphosphonic and phosphonothioic acids. The pentafluorobenzyl (PFB) derivatives are much more stable as compared to the conventionally used trimethylsilyl derivatives. The conditions for the derivatization and analysis have been optimized to achieve the best detection limits in negative chemical ionization (NCI) mode.     

Gas chromatographic determination of amino acids via one-step phase-transfer catalytic pentafluorobenzylation-preconcentration

The gas chromatographic determination of amino acids via their simultaneous extraction, preconcentration and pentafluorobenzylation is reported. Using phase-transfer catalysis (PTC), the amino acids under study were transformed to their pentafluorobenzyl adducts. The method was tested for different catalysts and tetrabutylammonium bromide provided favorable features in comparison to the other PTCs. The derivatization procedure was optimized and the best reaction conditions are given. With the exception of arginine, 19 amino acids were converted to volatile derivatives and analyzed with GC/MS and GC/FID at low concentration levels with acceptable sensitivity and good reproducibility. The LODs were found to range from 0.7 to 2.3microM for the GC/MS analyses and from 1.7 to 6.9microM for GC/FID analyses. The method practicability and applicability were confirmed by the analysis of urine, fruit juice and wheat flour for the determination of the amino acids under study. Protein-bound amino acids were analyzed after an alkaline hydrolysis step with 5M NaOH applying this method to wheat flour with an overall procedure duration less than 12h. The optimized protocol was applied to these samples without any pretreatment and their amino acid concentrations were calculated from the appropriate calibration plots.     

Organic compounds in precipitation

Summary Precipitation samples collected in Hannover (Germany) mainly in 1989 (and in part also in 1988 and 1990) were analyzed for n-alkanes, fatty acids, aldehydes, phenols and polycyclic aromatic hydrocarbons. The analytical methods employed were: GC/FID for alkanes, GC/MS for fatty acids and phenols, HPLC for aldehydes and PAHs.     

Solid-supported reagents for the simultaneous extraction and derivatization of carboxylic acids from aqueous matrices. Studies on optimization of reaction conditions

Solid-supported reagents for affecting a simultaneous extraction and derivatization of lipophilic and hydrophilic carboxylic acids from aqueous matrices were further investigated. The reagent consisted of pentafluorobenzyl bromide impregnated on the macroreticular resin XAD-2. New impregnation methods were developed which reduced the amount of pentafluorobenzyl bromide required and which were compatible with existing methods that utilize XAD-2 as an adsorbant. Factors affecting pentafluorobenzylation of these analytes were studied and the reaction conditions were optimized. Compatibility with simple biological samples was demonstrated using arachidonic acid as a model. Evidence was obtained suggesting that metal ions on the resin may be catalytic factors.     

Development of a solid-phase extraction and derivatization method for polar carboxylic acids from aqueous extracts of inorganic multi-component incineration residues

A rapid and reliable GC/MS (EI and CI) method was developed for the identification of short-chain mono- and dicarboxylic acids in complex and strongly alkaline residues of municipal waste incineration. Such residues contain organic carboxylic acids in the mg/kg to μg/kg range, which may contribute to the mobilization of heavy metals. However, the alkalinity and the high salt loads of the matrix were found to be a serious problem in the analysis of short chain acids. Extraction with water, solid phase extraction, and derivatization were studied under these conditions. Solid-phase extraction with polymeric sorbents and derivatization with diazomethane can be combined in a reproducible manner to yield a robust and simple method which can be applied for screening unknown solids due to its wide applicability and the well identifiable methyl esters. Absolute recovery rates varied between 20 and 85% depending on the individual acids. Received: 13 November 1997 / Revised: 17 February 1998 / Accepted: 18 February 1998     

A continuous two-phase reaction system coupled on-line with capillary chromatography for the determination of polar solutes in water

Gas chromatographic procedures are described for the determination of carboxylic acids and chlorinated anilines in water samples. Propionic acid and 2,6-difluorobenzoic acid in aqueous solution have been simultaneously alkylated and extracted by means of a continuous two-phase reaction system, and then quantitated by on-line coupled capillary gas chromatography; tetrahexyl-ammonium hydrogen sulfate was used as phase transfer catalyst and pentafluorobenzyl bromide as reagent. A factorial design approach was used to optimize on-line derivatization of aqueous propionic acid with regard to pH and concentration of phase transfer catalyst. Alkylation and extraction, under optimized conditions, followed by quantitation of the pentafluorobenzyl ester by flame ionization detection furnished a linear calibration for concentrations between 0.1 and 10 μg/ml. The relative standard deviation was 9–15 %. The continuous two-phase reaction system was also used to determine (chlorinated) anilines present in water at concentrations of 0.1–1 μg/ml; pentafluorobenzoyl chloride was used as reagent and analysis was performed by capillary gas chromatography with flame ionization or electron capture detection. The on-line acylation of p-chloroaniline was optimized with regard to pH, reagent concentration, and reaction time. The on-line reaction system worked satisfactorily for both applications, although excess reagent caused some problems with the chromatography.     

Determination of aromatic sulfonic acids in industrial waste water by ion-pair chromatography

A method for the identification and quantification of aromatic sulfonic acids in industrial waste water has been developed. The preparation of the samples comprises a clean-up step and an enrichment step, utilizing i) reversed-phase extraction and ii) ion-pair solid phase extraction. The aromatic sulfonic acids are separated by ion-pair chromatography with diode-array detection. An advantage of the developed ion-pair chromatographic method is the separation of linear alkylbenzenesulfonic acids (LAS), lignosulfonic acids and aromatic sulfonic acids in one chromatographic run. Also described is an optimized clean-up procedure for collected fractions of a preparative chromatographic run to identify monosulfonic acids with GC/MS after methylation. The detection limits for aromatic sulfonic acids in industrial waste waters are at the g/l level.     

Application of a pentafluorobenzyl bromide derivatization method in gas chromatography/mass spectrometry of trace levels of halogenated phenols in air, water and sediment samples.

An analytical method using pentafluorobenzyl bromide (PFBB) derivatization and gas chromatography/mass spectrometry (GC/MS) has been applied to identify and quantify chloro-, bromo- and dichlorophenols in air, water and sediment samples. Phenols in air sample were collected with a PS-2 Sep-PAK cartridge, and eluted with 2-propanol. For water and sediment samples, liquid-liquid extraction with dichloromethane was carried out, and the solvent was exchanged to 2-propanol. The phenols in the solution reacted with PFBB to form the corresponding pentafluorobenzyl esters. After extracting the derivatives into hexane, the determination was carried out by GC/MS with selected-ion monitoring. The detection limits of phenols in air, water and sediment were 0.0033 - 0.0073 microg/m3, 0.0066 - 0.0147 microg/L and 0.33 - 0.73 microg/kg, respectively. More than 90% recoveries of the halogenated phenols were obtained from real environmental samples spiked by the halogenated phenols. The three isomers of mono-chlorophenols were detected in sediment samples in the range of 5.2 - 9.2 microg/kg in wet weight basis.     

HPLC Urinary Organic Acid Profiling: Role of the Ultraviolet and Amperometric Detectors

Abstract

The profiling of urinary organic acids is an important aspect of the diagnosis of inborn metabolic disorders. The carboxylic acids of interest may contain additional functional moities such as phenyl, hydroxyl, oxo, etc. The state-of-the-art method of organic acid analysis is by GC/MS. Prior to GC/MS analysis, the carboxylic acids must be isolated from urine by extraction or ion exchange chromatography and made volatile by derivatization. This is a lengthy procedure that does not lend itself to rapid analysis. We have developed a rapid procedure for the profiling of urinary α, B-unsaturated, aromatic and α-ketocarboxylic acids.

Urine containing an internal standard, 3-hydroxy-4-methoxy-benzyl alcohol, is filtered through a 0.3 um Millipore filter and injected on to an HPX-87 organic acid HPLC column (Bio-Rad). The mobile phase, 4.5 mN H₂SO₄, is passed through the column at 0.8 ml/min. Detection is effected by an UV detector at 200 nm in series but upstream from an electrochemical detector with a glassy carbon working electrode at +1.15V vs. an Ag/AgCl reference electrode. At this electrode potential, phenolic, methoxyphenyl, eneolic and α-ketocarboxylic acids are oxidized and can be electrochemically detected with a glassy carbon electrode.     

Characterization of carboxylic acids in atmospheric aerosols using hydrophilic interaction liquid chromatography tandem mass spectrometry

A sensitive hydrophilic interaction liquid chromatography/electrospray ionization mass spectrometry (HILIC/ESI-MS/MS) method was developed for determination of selected aliphatic (i.e. malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic, maleic, fumaric, glycolic and pyruvic acid), alicyclic (i.e. cis-pinonic and pinic acid) and aromatic (i.e. trimesic, phthalic acid and its isomers) carboxylic acids. Analytes were separated on an amide column using a gradient elution with a 10mM constant ionic strength mobile phase containing acetonitrile and aqueous ammonium acetate buffer (pH 5.0). The influence of the buffer type, pH, polar modifier and temperature on analyte retention under HILIC was studied. Static sonication-assisted solvent extraction was optimized for sample preparation prior to analysis. The recoveries obtained were higher than 90% for most analytes. The method was proven to be sensitive with limits of detection ranged from 0.03 to 16.0 μg/L in selected reaction monitoring mode (SRM). The repeatability and intermediate precision of the method, expressed as RSD (%) of the peak area ratio between analytes and their internal standards were generally lower than 5%. The method was successfully applied for determination of the studied acids in samples of ambient aerosol particles. A big advantage of the new method is also its ability to detect and separate the isobaric compounds of the selected carboxylic acids. Our results demonstrate that the method is specific and sensitive for the determination of a wider range of polar carboxylic acids at low concentrations in complex samples of aerosol particles.     

Ultra trace detection of perfluorocarbon tracers in reservoir gases by adsorption/thermal desorption in combination with NICI-GC/MS

A new method for the analysis of perfluorocarbon tracers (PFTs) in reservoir samples based on adsorption/thermal desorption in combination with NICI-GC/MS is presented. The tracer compounds were trapped in tubes filled with a carbon molecular sieve and in a two-step procedure thermally desorbed before they were analyzed with NICI-GC/MS. The chromatographic background noise, visible on GC/ECD-systems, due to compounds normally present in petroleum reservoir gases, could not be seen with NICI-GC/MS. Determination of the perfluorocarbons in reservoir gas samples confirmed the applicability of the method. Tracer concentrations as low as 42 femtoliter/liter were detected.     

Ultra trace detection of perfluorocarbon tracers in reservoir gases by adsorption/thermal desorption in combination with NICI-GC/MS

A new method for the analysis of perfluorocarbon tracers (PFTs) in reservoir samples based on adsorption/thermal desorption in combination with NICI-GC/ MS is presented. The tracer compounds were trapped in tubes filled with a carbon molecular sieve and in a two-step procedure thermally desorbed before they were analyzed with NICI-GC/MS. The chromatographic background noise, visible on GC/ECD-systems, due to compounds normally present in petroleum reservoir gases, could not be seen with NICI-GC/MS. Determination of the perfluorocarbons in reservoir gas samples confirmed the applicability of the method. Tracer concentrations as low as 42 femtoliter/liter were detected.     

The Intehaction of Aqueous Solutions of Chlorine with Malic Acid,Tartaric Acid,and Various Fruit Juices: A Source of Mutagens

Abstract

The interactions of aqueous solutions of chlorine with some fruit acids (citric acid, DL-malic acid, arid L-tartaric acid) at different pH values were studied. Diethyl ether extraction followed by GC/MS analysis indicated that a number of mutagens (certain chlorinated propanones and chloral hydrate) are present as major products in some of these samples. A number of fruit juices (orange, grape, apple, pineapple, and grapefruit) were also treated with aqueous solutions of chlorine at their pH values. The products were analyzed by GC/MS. The same mutagens that were formed by the pure acids (citric acid and DL-malic acid) were identified as major products in ether extracts of these samples. Another mutagen, dichloroacetonitrile, was also identified as a minor product in some of these juice samples. All of the major products observed in the chlorination of all five fruit juices are potentially derived from reactions of aqueous solutions of chlorine with citric or malic acid and with trace amounts of acetaldehyde and acetone in the juices. The minor product, dichloroacetonitrile, is likely derived from the chlorination of certain amino acids in the fruit juices.     

Pentafluorobenzylation of the fungicide metabolite fenpropimorphic acid for GC/MS investigations of soil samples

For the determination of fenpropimorphic acid in soil samples, a derivatization step with pentafluorobenzylbromide has been established in order to perform GC/MS with negative chemical ionization. In spite of forming the electrophilic pentafluorobenzyl ester, only the fenpropimophic acid anion was detected. Additional derivatization reactions with diazomethane and 2,2,2-trichloroethanol showed that the formation of this acid anion was depending on the leaving group. In comparison with the determination of the methyl ester with GC/MS and electron impact ionization, the detection limit was however improved from 10 microg/kg to 2 microg/kg dry soil and the analytical quality was ensured due to higher stability of the pentafluorobenzyl ester standards.     

Identification of chlorinated fatty acids in fish by gas chromatography/mass spectrometry with negative ion chemical ionization of pentafluorobenzyl esters

This paper reports the development of a technique for identifying and confirming chlorinated fatty acids previously detected in fish by gas chromatography (GC) with halogen-specific detection (XSD). Fatty acid methyl esters (FAMEs) including chlorinated FAMEs within fractions of reversed-phase high-performance liquid chromatography of transesterified fish extracts were derivatized to pentafluorobenzyl esters, which were subjected to GC/mass spectrometry (MS) with negative ion chemical ionization (NICI). Pentafluorobenzyl esters displayed reasonably good GC characteristics, a very high ionization efficiency and a low degree of fragmentation. Chloride ion chromatograms extracted at m/z 35 and 37 from full scans were utilized for locating traces of chlorinated unknowns in the GC elution profile so that their mass spectra could be readily displayed. Significant ions displayed in the mass spectrum scanned in a narrow range of retention time where a chlorinated unknown was located were evaluated using ion chromatograms extracted at the m/z of these ions. The chromatographic peaks of those ions derived from the analyte were expected to center at that specific retention time, whereas those originating from matrix compounds were not. The isotopic patterns of chlorinated ions were also examined against their theoretical relative abundances. Using this approach, three metabolism-related dichloro fatty acids previously identified by GC/XSD in filet extracts of white sucker sampled downstream from a bleached kraft pulp mill were confirmed: dichlorooctadecanoic, dichlorohexadecanoic and dichlorotetradecanoic acids. In addition, an isomer of dichlorotetradecanoic acid was found in a reference fish sample. As sample preparation is critical in this application, improved conditions for hydrolysis and pentafluorobenzyl esterification are also discussed.