Determination of higher carboxylic acids in snow samples using solid-phase extraction and LC/MS-TOF

• Published in: Analytical and bioanalytical chemistry 2008-12, Vol.392 (7-8), p.1459-1470
• Main Authors: Kippenberger, Matthias, Winterhalter, Richard, Moortgat, Geert K
• Format: Article
• Language: English
• Subjects: Adipic acid; Aliphatic compounds; Analytical Chemistry; Biochemistry; Carbon; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Chromatographic methods and physical methods associated with chromatography; dicarboxylic acids; Exact sciences and technology; Extraction; Fee glacier; Flow rate; Food Science; Laboratory Medicine; Mathematical analysis; Monitoring/Environmental Analysis; Original Paper; Other chromatographic methods; phthalic acid; Pinonic acid; Snow; Snow samples; solid phase extraction; Spectrometric and optical methods
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-008-2440-y

The objective of this work was to develop a method to determine the concentrations of higher organic acids in snow samples. The target species are the homologous aliphatic α,ω-dicarboxylic acids from C₅ to C₁₃, pinonic acid, pinic acid and phthalic acid. A preconcentration procedure utilizing solid phase extraction was developed and optimized using solutions of authentic standards. The influences of different parameters such as flow rate during extraction and the concentration of the eluent on the efficiency of the extraction procedure were investigated. The compounds of interest were separated by HPLC and detected by a quadrupole time-of-flight mass spectrometer (qTOF-MS). The recovery rate (extraction efficiency) of the extraction procedure was found to vary between 41% for tridecanedioic acid and 102% for adipic acid. The limits of detection were determined for all compounds and were between 0.9 nmol/L (dodecanedioic acid) and 29.5 nmol/L (pinonic acid). An exception is pinic acid, for which a considerably higher detection limit of 103.9 nmol/L was calculated. Snow samples were collected in December 2006 and January 2007 at the Fee glacier (Switzerland) from locations at heights from 3056 to 3580 m asl and from different depths within the snow layer. In total, the analysis of 61 single snow samples was performed, and the following compounds could be quantified: homologous aliphatic α,ω-dicarboxylic acids with 5-12 carbon atoms and phthalic acid. Tridecanedioic acid, pinonic and pinic acid were identified in the samples but were not quantified due to their low concentrations. The three most abundant acids found in the molten snow samples were glutaric acid (C₅-di; 3.90 nmol/L), adipic acid (C₆-di; 3.35 nmol/L) and phthalic acid (Ph; 3.04 nmol/L).