Search

Rapid determination of trace level (parts-per-trillion) volatile organic compounds cannot always be achieved with conventional analytical techniques. In this study, a device was developed to sample a large volume of air in a short time period. The basic design involves packing sorbent layers concentrically around an empty permeable tube. Single digit parts-per-trillion detection limits were reached in less than 25min with this sampling system using gas chromatography-mass spectrometry for analysis. The concentric packed trap can sample at high flow rates (>10L/min) because it has a large sampling surface cross-section and short combined sorbent bed. Additionally, the large sorbent amount (>1g) provides large breakthrough volume (>100L) required to achieve low detection limits. The trapped analytes were thermally desorbed and transferred into a needle trap device for final analysis. This high flow sampling system was explored for detection of low ppt benzene, toluene, ethylbenzene and xylenes (BTEX) in air., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Efficiency and resolution in capillary liquid chromatography (LC) can be significantly affected by extra-column band broadening, especially for isocratic separations. This is particularly a concern in evaluating column bed structure using non-retained test compounds. The band broadening due to an injector supplied with a commercially available capillary LC system was characterized from experimental measurements. The extra-column variance from the injection valve was found to have an extra-column contribution independent of the injection volume, showing an exponential dependence on flow rate. The overall extra-column variance from the injection valve was found to vary from 34 to 23 nL. A new mathematical model was derived that explains this exponential contribution of extra-column variance on chromatographic performance. The chromatographic efficiency was compromised by ∼130% for a non-retained analyte because of injection valve dead volume. The measured chromatographic efficiency was greatly improved when a new nano-flow pumping system with integrated injection valve was used., (Copyright © 2014 Elsevier B.V. All rights reserved.)