A method for the determination of trace amounts of off-flavor compounds such as 2-methyl isoborneol (MIB), geosmin and 2,4,6-trichloroanisole (TCA) in drinking water is described based on dynamic headspace coupled to selectable onedimensional or two-dimensional gas chromatography – mass spectrometry with simultaneous olfactory detection (DHS1D/2D GC-O/MS). Automated DHS using a Tenax TA packed tube as trap was performed on a 10 mL-sample containing 30 % NaCl at 80ºC, and followed by thermal desorption of the trap. Combining heart-cutting with fast temperature programming (100ºC/min) of the second column resulted in improvements in both separation and analyte limits of determination due to decreased background signal of the monitored mass ion and the increased analyte peak height. Compared to DHS-1D GC-O/MS analysis, signal-to-noise ratios (S/N) were improved by a factor of 12 for MIB, 9 for geosmin, and 3 for TCA. The method showed good linearity over the concentration range from 1 to 100 ng/L with correlation coeffi cients (r2) greater than 0.9942. The limits of detection (LODs) for these compounds ranged from 0.15 to 0.22 ng/L. Simultaneous olfactory- and MS detection was succesfully performed for the lowest level sample spiked at 1 ng/L.

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Dynamic Headspace (DHS)

Automated Dynamic Headspace (DHS) is available for the GERSTEL MultiPurpose Sampler (MPS). The DHS station efficiently extracts and concentrates VOCs from liquid or solid sample placed in standard Headspace vials (DHS) or in larger sample containers up to 1 L volume (DHSLarge). The sample is thermostated and agitated while the headspace is purged with a controlled flow of inert gas, providing controlled and efficient extraction conditions. Sample temperatures can be selected from 10oC to 200oC. Lowering the temperature provides a means of reducing the amount of water vapor released and ultimately retrapped. The DHS station additionally holds a replaceable adsorbent- or sorbent filled tube used for analyte concentration. The temperature of the adsorbent tube during the DHS process can be varied from 20oC to 70oC for optimal trapping of the analytes in question.

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Selectable 1D/2D-GC/MS

An extra GC dimension at your finger tips

Gas chromatography (GC) experts rely on sharp peaks and baseline resolution to provide accurate answers. To perform chromatographic analysis of real-world samples, analysts often must deal with either complex sample types such as essential oils and petroleum fractions, or complex matrices like biological fluids, foods, sludge, or polymers. Once the sample has been prepared for analysis, separation of all the individual compounds present by means of a single chromatographic separation can be challenging due to the compounds having different ranges of polarity, boiling point, solubility, MW, and concentration. It is therefore necessary to use innovative yet robust techniques that go beyond using a single chromatographic dimension to achieve compound separation.

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