Gas chromatographic-mass spectrometric characterization of volatile organic compounds in Barcelona tap water

Barcelona's tap water is supplied by the Llobregat and Ter rivers, which have significant differences in raw water quality. Volatile organic compounds (VOCs) from Barcelona tap water were isolated by closed-loop stripping analysis (CLSA) and identified and determined by gas chromatography-mass spectrometry. The results showed that the Ter river gives the better quality tap water. VOCs, in particular solvents, phosphates, hydrocarbons, C3 and C4 alkylbenzenes and surfactant-related compounds such as C10-C13 alkylbenzenes and non-ionic compounds such as polyethoxylated nonylphenols and their brominated derivatives are present at the ppb level. The last two types of compounds have not previously been reported using the CLSA technique.     

Gas chromatographic-mass spectrometric determination of intact C3-hydroxylated benzodiazepine glucoronides in urine.

A method is described for the determination C3-hydroxylated benzodiazepine glucuronides in biological samples. Oxazepam and lorazepam glucuronides are measured as methyl esters and trimethylsilyl derivates by a gas chromatographic procedure. The applicability of the method has been tested on the urine of rats, guinea pigs, rabbits and man, receiving oxazepam orally. Oxazepam glucuronide was not found in rat urine but it was present in the urine of rabbits (5.7% of the administered dose), guinea pigs (9.5%) and man (13.4-26.9%).     

Gas chromatographic-mass spectrometric analysis of volatile constituents in saliva

Present methods for the development of metabolic profiles are limited to the use of headspace techniques and solvent extraction methods. A new method for the development of saliva profiles which provides information complementary to existing analyses has been developed. The results of the developed methodology provide a reliable, reproducible method for metabolic profiling. Gas chromatographic-mass spectrometric analysis of the volatile constituents provided positive identification of 39 compounds. Application of the developed protocol toward the investigation of saliva as a vehicle for the non-invasive detection of certain pathological states, specifically diabetes mellitus and liver disorders, may be possible.     

Gas chromatographic-mass spectrometric method for analysis of a pyrimido-s-triazine and some of its metabolites in dog urine.

3-Phenylpyrimido-[3,4-a]-s-triazines exhibit antiparasitic, antibacterial and antifungal activity. In order to study the metabolism of these heterocycles, 9,9-diethyl-3-phenyl-6,8-dioxo-2,3,4,5,6,7,8,9-octahydropyrimido[3 ,4-a]-s- triazine (TZ) was administered to dogs. Three potential metabolites were synthesized, and these models were identified and quantified with gas chromatography-mass spectrometry. The heterobicyclic compounds, TZ and its hydroxy derivative, underwent thermal degradation under chromatographic conditions. Dog urine spiked with the model metabolites was extracted, and the substances were quantified. The urine of dogs treated with TZ was studied, and two of the potential metabolites were recovered, identified and quantified.     

Gas chromatographic-mass spectrometric analysis of N-acetylated amino acids: the first case of aminoacylase I deficiency

During the metabolic work-up of a patient presenting with neonatal convulsions, we consistently observed the presence of unusual peaks in the gas chromatographic-mass spectrometric analysis of urinary organic acids. The gas chromatographic-mass spectrometric characteristics of the unusual peaks suggested that they corresponded to derivatives of N-acetylated amino acids. The tentative identification was confirmed by the identity of retention times and mass spectra of the trimethylsilyl derivatives of the authentic compounds. We describe our observations that led to the identification of the various N-acetylated amino acids in this first patient with a confirmed deficiency of aminoacylase I, an enzyme involved in the cytosolic degradation of N-terminally modified proteins. The potential and limitations of urinary organic acid analysis for the detection of N-acetylated amino acids was further studied using pure compounds. In addition, we provide mass spectral data for 37 trimethylsilyl derivatives from 17 N-acetylated amino acids, most of which have not been reported previously. Our data provide valuable information that will help the clinical laboratorians who are responsible for organic acid analysis to recognize this new condition and could aid its detection in other patients.     

Gas chromatographic-mass spectrometric quantitation of tri-, di- and monomethylxanthines and uric acids from hepatocyte incubation media

A gas chromatographic-mass spectrometric method is described for the measurement of the concentration of fourteen methylxanthines and methyluric acid metabolites of methylxanthines, especially caffeine, from cell incubation media. The method shows linearity, accuracy and recovery suitable for metabolic studies. The reproducibility of relative retention times is satisfactory (less than 0.07%) and allows rapid and conclusive identification of chromatographic peaks corresponding to metabolites. Moreover, this method enables the simultaneous determination of 3.7-methylxanthine and its 1.7-isomer, which are not chromatographically resolved. This method can be successfully applied when molecules labelled with stable isotopes are used as tracers for metabolic studies.     

Gas chromatographic-mass spectrometric detection of trace amounts of organic compounds in the intravenous solution Infusio Darrowi.

A gas chromatographic-mass spectrometric procedure was employed to confirm the presence of trace amounts of organic compounds in the intravenous solution Infusio Darrowi. Organic contaminants in the solution analysed were concentrated by microextraction with n-pentane. The main compounds detected were 2,6-di-tert.-butyl-4-methylphenol, 2,6-di-tert.-butyl-4-ethylphenol, 2,6-di-tert.-butyl-4-methoxyphenol, benzothiazole, isomeric C9 alkyl phenols and di(n-butyl) phthalate. These impurities were leached from rubber stoppers during their sterilization into the intravenous solution at levels ranging ca. from 5 x 10(-6) to 5 x 10(-8) g/l.     

Chromatographic profile of high boiling point organic acids in human urine

The profile of high boiling point organic acids in urine samples from both normal subjects and patients suspected of having some form of metabolic disorder has been determined by combined gas chromatography-mass spectrometry. Fifteen different compounds eluting after hippuric acid have been identified, including two, cinnamoylglycine and acetyltributylcitrate, which have not been recognised previously. Relative retention times and abbreviated mass spectra of the identified compounds are presented.     

Gas chromatographic-mass spectrometric characterization of flavanones in citrus and grape juices.

A method for the characterization of flavanones in fruit juices, involving solvent extraction, hydrolysis to the corresponding aglycones, trimethylsilylation and combined gas chromatography-mass spectrometry, is reported. The application of the method is demonstrated for the analysis of orange, lemon, grapefruit and grape juices.     

Gas chromatographic-mass spectrometric investigations on lipophilic anthropogenic substances in environmental samples

Summary A newly developed device is presented that splits the eluent of a capillary gas Chromatograph (GC) into four streams, allowing the simultaneous use of up to four different detectors. The rather insensitive but unspecific flame ionisation detector (FID) was combined with 1–3 more or less element-specific detectors.All parts of the splitter are commercially available and can be mounted simply in a modular gas chromatograph. The system was developed especially for the identification of unknown anthropogenic compounds in environmental materials. Gas chromatography-mass spectrometry (GC-MS) investigations facilitate best the identification of unknown GC-peaks, despite the interfering matrix that occurs in high concentrations in environmental samples over the whole retention area of the chromatograms.The additional information obtained by the element-specific detectors allows a directed search for certain substance peaks during a GC-MS analysis under identical conditions in a very narrow range of the total ion chromatogram of the mass spectrometer (MS). Substance peaks that are overlapping and completely covered by much greater matrix peaks also can be investigated.Even without GC-MS analysis the GC driven by the four-fold eluent splitter gave valuable information. As the peak areas of a substance from the various detectors must be in a certain ratio to each other, simultaneous multidetection allows at least a good semiqualitative estimation of the substance amounts.The capability of the splitter described here is demonstrated by an investigation of a water sample from the river Elbe, FRG.

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Gas-chromatographischer Eluatstromteiler zur simultanen Aufzeichnung von Capillar-Gas-Chromatogrammen mit Hilfe von bis zu vier verschiedenen GC-Detektoren

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Part I of this series: (1985) Fresenius Z Anal Chem 320:1     

Gas chromatographic-mass spectrometric method for trazodone and a deuterated analogue in plasma

A plasma assay method for trazodone and a 2H4 analogue is described which uses gas chromatography--electron-impact selected-ion monitoring mass spectrometry. Etoperidone is used as an internal standard. The analytes are extracted from basic medium into n-butyl chloride, then back extracted into aqueous 0.1 M hydrochloric acid. The aqueous layer is made basic and re-extracted with n-butyl chloride. The solvent is reduced under nitrogen at 35 degrees C and the residue is redissolved in toluene for gas chromatographic--mass spectrometric analysis. The ions monitored are m/z 231, 235, and 225 for trazodone, [2H4] trazodone and etoperidone, respectively. Quantitation is in the range 40-1000 ng/ml with acceptable precision and accuracy. The method is suitable for biopharmaceutical studies.     

Gas chromatographic-mass spectrometric investigations on lipophilic anthropogenic substances in marine organisms

Summary Methods are needed for the trace analytical identification of anthropogenic substances in marine matrices. Here we are mainly concerned with lipophilic compounds which may be enriched through food chains and, thus, represent a potential danger. Their investigation by capillary gas chromatography-mass spectrometry is difficult as it requires a very efficient previous separation from the matrix of lipids which accompany them due to their similar chemical nature. — Clean-up methods which are usual for the determination of the classical organohalogen compounds were insufficient. The ECD detector discriminates large excesses of lipids from the matrix. But the latter falsifies the mass spectra of the relevant substances completely.Several combinations of clean-up methods were checked. One of them proved to be extraordinarily effective. It consists of a liquid-liquid partitioning between dimethylformamide (DMF) and hexane followed by a reversed phase (octadecyl) partitioning. By its application, organohalogenides from commercial cod-liver oil could be separated in a capillary gas chromatograph and identified by mass spectrometry. Remarkable is that more -HCH is present than -HCH as the latter is a pesticide and the former merely its (more toxic) by-product. Similarly, DDT's are only present in minute amounts, whereas p,pDDE, the main degradation product, produced the main peak. Furthermore, various PCB's, toxaphenes and chlordanes were present in significant amounts.

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Gas-chromatographisch-massenspektrometrische Untersuchung lipophiler anthropogener Stoffe in marinen OrganismenI. Ein Verfahren zur Probenvorbereitung durch Flüssig-flüssig- und Umkehrphasen (Octadecyl)-Verteilung

Zusammenfassung Benötigt werden Methoden zur spurenanalytischen Identifizierung anthropogener Substanzen in marinen Matrices. Hier geht es vor allem um lipophile Stoffe, die im Verlauf der Nahrungsketten angereichert werden und so ein Gefahrenpotential darstellen. Ihre Untersuchung durch Capillar-Gas-Chromatographie-Massenspektrometrie ist schwierig, da sie eine vorangehende weitgehende Abtrennung von den sie aufgrund ihrer ähnlichen Eigenschaften begleitenden Lipiden voraussetzt. Die bei der gas-chromatographischen Bestimmung der klassischen Organohalogenide üblichen clean-up-Verfahren erwiesen sich als unzureichend. Der ECD-Detektor diskriminiert zwar große Lipidüberschüsse aus der Matrix. Jene verfälschen jedoch die zu gewinnenden Massenspektren völlig.Bei der Überprüfung verschiedener miteinander kombinierter clean-up-Verfahren erwies sich schließlich eine Kombination als außerordentlich erfolgreich. Sie besteht aus einer Flüssig-flüssig-Verteilung zwischen DMF und Hexan und einer Reversed-Phase-Verteilung an einer Octadecylphase. Damit konnten in handelsüblichem Lebertran vorhandene Organohalogenide chromatographisch getrennt und massenspektrometrisch untersucht werden. Bemerkenswert sind die relativ großen Mengen -HCH, einem besonders toxischen Nebenprodukt des Pesticides -HCH. (Von letzterem hingegen sind wesentlich kleinere Mengen vorhanden.) DDT's sind nur in unbedeutenden Mengen zugegen. Dafür stellt p,p-DDE, das hauptsächliche Abbauprodukt, den größten Peak überhaupt. Bemerkenswert ist ferner die deutliche Präsenz von PCB's, Chlordanen und Toxaphenen.

     

Gas chromatographic-mass spectrometric analysis of methylphenidate and p-hydroxymethylphenidate using deuterated internal standards

A gas chromatography-mass spectrometry assay is described for the simultaneous determination of threo-dl-methylphenidate and threo-dl-p-hydroxymethylphenidate in plasma and urine using selected ion monitoring of electron impact generated fragments of their pentafluoropropionyl derivatives. The use of recently available deuterated analogues as internal standards improves overall performance relative to previous methods. The practical limit of quantifiable detection of the assay is 0.5 ng/ml for both methylphenidate and p-hydroxymethylphenidate. p-Hydroxymethylphenidate appears to be a significant urinary metabolite of methylphenidate in rats but not in humans.     

Gas chromatographic-mass spectrometric determination of alkylphosphonic acids from aqueous samples by ion-pair solid-phase extraction on activated charcoal and methylation

In the present paper, we report an improved ion-pair solid-phase extraction (IP-SPE) method for the analysis of alkylphosphonic acids, namely, methyl, ethyl and propylphosphonic acids, present in the aqueous sample. The aqueous sample was mixed with an ion-pair reagent, phenyltrimethylammonium hydroxide (PTMAH) and passed through activated charcoal SPE cartridge. The retained chemicals in the cartridge were extracted with methanol and analysed by gas chromatography-mass spectrometry (GC-MS) under the electron impact ionization (EI) mode. The analytes were converted to their methyl esters by pyrolytic methylation in the hot GC injection port. The recoveries of alkylphosphonic acids were above 95% and the minimum detection limits were as low as 10 ng/mL. The recovery of the test chemicals was tested with solvents, dichloromethane, n-hexane, ethyl acetate, acetone, acetonitrile and methanol. The chemicals could be efficiently extracted by the hydrophilic solvents. The method did not work at the highly acidic pH (when acidified with dilute HCl) but worked well from pH 4.0 to 14.0. The present method was also tested with other tetra-(methyl, ethyl, propyl and n-butyl)ammonium hydroxides. The test chemicals were not converted to their methyl and ethyl esters with tetramethyl and tetraethylammonium hydroxides, whereas they were converted to their corresponding propyl and n-butyl esters with tetrapropyl and tetra(n-butyl)ammonium hydroxides. The method was also applied to two highly cross-linked polymeric sorbents DSC-6S and Oasis HLB. The recovery of the chemicals on these sorbents was observed to be poor. Methylation using phenyltrimethylammonium hydroxide is non-hazardous and advantageous over methylation using diazomethane. The method was applied to the analysis of aqueous samples given in one of the official proficiency tests conducted by the Organization for the Prohibition of Chemical Weapons and all the spiked chemicals were identified as methyl esters.