Determination of carboxylic acids in water by gas chromatography–mass spectrometry after continuous extraction and derivatisation

• Published in: Talanta (Oxford) Vol. 93; pp. 224 - 232
• Main Authors: Jurado-Sánchez, Beatriz, Ballesteros, Evaristo, Gallego, Mercedes
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.05.2012; Elsevier
• Subjects: Analytic Sample Preparation Methods - methods; Analytical chemistry; Carboxylic acids; Carboxylic Acids - analysis; Carboxylic Acids - chemistry; Carboxylic Acids - isolation & purification; Chemistry; Chromatographic methods and physical methods associated with chromatography; Derivatives; Exact sciences and technology; Extraction; Gas chromatographic methods; Gas Chromatography-Mass Spectrometry - methods; Gas chromatography–mass spectrometry; Heating; Methyl alcohol; Microwave assisted derivatisation; Microwaves; Ovens; Solid Phase Extraction - methods; Solid-phase extraction; Spectrometric and optical methods; Standard deviation; Time Factors; Water; Water - chemistry; Water; Microwave assisted derivatisation; Carboxylic acids; Solid-phase extraction; Gas chromatography–mass spectrometry; Solid phase extraction; Silylation; Microwave; Mixture; Chemical enrichment; Target; Sample preparation; Microwave oven; Carboxylic acid; Chlorides; Detection limit; pH; Dicarboxylic acid; Standard deviation; Acid medium; Methanol; Tricarboxylic acid; Elution; Stability; Use; Acetamide; Method; Gas chromatography-mass spectrometry; Vaporization; Gas chromatography; Reagents; Butanol; Yield; Mass spectrometry
• DOI: 10.1016/j.talanta.2012.02.022
• ISSN: 0039-9140

► A new approach for the determination of 35 carboxylic acids in water samples is presented. ► Miniaturisation of the sample treatment system using a continuous solid-phase extraction unit. ► Simplification of the derivatising reaction through the use of a household microwave oven that reduces the reaction time to ca. 3min. ► Successful analysis of drinking and natural waters. This paper describes a new approach for the determination of monocarboxylic, dicarboxylic and tricarboxylic acids (35 compounds) in water. The analytes, in acid medium (pH ∼1.3), were sorbed on an 80mg LiChrolut EN–Supelclean ENVI-18 (1:1) column and subsequently eluted with methanol. After evaporation of the extract to ∼10μL, the analytes were spiked with 60μL of the derivatising reagent and derivatised in a household microwave oven for 3min. Among the reagents tested (BF3/1-butanol; acetyl chloride/1-butanol; isobutyl chloroformate/1-butanol; trimethylphenylammonium hydroxide, N,O-bis-(trimethylsilyl)acetamide, N,O-bis-(trimethylsilyl)trifluoroacetamide and trimethylchlorosilane), the best results in terms of reaction yield and stability of the derivatives were obtained with the mixture of 1% trimethylchlorosilane in N,O-bis-(trimethylsilyl)trifluoroacetamide. Microwave assisted derivatisation was used as an alternative heating approach for the rapid silylation of carboxylic acids. The proposed method proved to be a suitable analytical procedure for several types of carboxylic acids in water, with limits of detection within the range 0.6–15ngL−1, precision values from 4.0 to 6.0% (as within-day relative standard deviation) and recoveries from 93 to 101% for all the target analytes.