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Method for analysis of polar volatile trace components in aqueous samples by gas chromatography
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
2005 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 77, no 10, 3365-3371 p.Article in journal (Refereed) Published
Abstract [en]

A new method has been developed for direct analysis of volatile polar trace compounds in aqueous samples by gas chromatography. Water samples are injected onto a short packed precolumn containing anhydrous lithium chloride. A capillary column is coupled in series with the prefractionation column for final separation of the analytes. The enrichment principle of the salt precolumn is reverse to the principles employed in conventional methods such as SPE or SPME in which a sorbent or adsorbent is utilized to trap or concentrate the analytes. Such methods are not efficient for highly polar compounds. In the LiCl pre-column concept, the water matrix is strongly retained on the hygroscopic salt, whereas polar as well as nonpolar volatile organic compounds show very low retention and are eluted ahead of the water. After transfer of the analytes to the capillary column, the retained bulk water is removed by backflushing the precolumn at elevated temperature. For direct injections of 120 μL of aqueous samples, the combined time for injection and preseparation is only 3.5 min. With this procedure, direct repetitive automated analyses of highly volatile polar compounds such as methanol or tetrahydrofuran can be performed, and a limit of quantification in the low parts-per-billion region utilizing a flame ionization detector is demonstrated.

Place, publisher, year, edition, pages
2005. Vol. 77, no 10, 3365-3371 p.
Keyword [en]
Capillarity, Distillation columns, Gas chromatography, Ionization
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-4913DOI: 10.1021/ac040170kISI: 000229206800042Scopus ID: 2-s2.0-18844442547OAI: oai:DiVA.org:kth-4913DiVA: diva2:6849
Note
QC 20100922. Uppdaterad från Submitted till Published (20100922). Tidigare Titel "A new method for analysis of polar volatile trace components in aqueous samples by gas chromatography". Available from: 2008-12-23 Created: 2008-12-23 Last updated: 2017-12-06Bibliographically approved
In thesis
1. New concepts and techniques for quantification and trace analysis by gas chromatography
Open this publication in new window or tab >>New concepts and techniques for quantification and trace analysis by gas chromatography
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the first part of this thesis, strategies for avoiding systematic errors when quantifying the main components in mixtures of solvents has been developed (paper I). It is shown that variations in density caused by variations in sample composition and/or volume contraction need to be taken into account. In this way, quantification can be improved.

The second part (paper II-V) describes a number of new methods for the analysis of organic trace components present in gaseous or aqueous samples, after an overview of the most commonly applied sample enrichment techniques has been given.

For the enrichment of volatile trace compounds from gaseous samples, the concept of open tubular trapping has been further developed. A simplified procedure for preparing ultra-thick film, sorptive open tubular traps (OTTs) is described (paper III). The traps are coated with an irregular film of PDMS, and it is shown that the performance in terms of breakthrough volume is only marginally affected by the use of such traps. In paper IV, it is shown both experimentally and with a theoretical model that the enrichment capacity of OTTs can be significantly increased by increasing the inner diameter of the traps.

A fully automated procedure for high-capacity sorption enrichment of trace organic analytes present in water is also reported (paper II). Time-based non-equilibrium extractions are feasible, enabling fast extractions that still allow sub-ppt limits of detection. The high flexibility of the automated system makes it possible to sample from process streams or off-line sources.

Finally, the development of a new 2-dimensional precolumn-backflush method for the analysis of polar volatile trace analytes in water is described (paper V). This concept is based on the action of a hygroscopic salt which has a strong affinity for water, in a precolumn. Organic trace compounds, such as volatile alcohols or ketones show little retention on the precolumn and are eluted ahead of the bulk amount of the water onto a capillary column for subsequent high resolution separation. The residual water is removed from the system by backflushing the precolumn. The procedure allows the direct injection of aqueous sample volumes of at least 100 µl, and the pre-fractionation is accomplished within only a few minutes. Quantification limits for selected polar trace components were in the low ppb-region.

Place, publisher, year, edition, pages
Kemi, 2004. x, 77 p.
Keyword
Chemistry, quantitative accuracy, calibration, extenal standards, valume contraction, molar excess volume, Kemi
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-44 (URN)91-7283-827-2 (ISBN)
Public defence
2004-11-12, Kollegiesalen, KTH, Valhallavägen 79, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2008-10-10 Created: 2008-10-10 Last updated: 2012-03-21Bibliographically approved

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