Technical note: Inexpensive modification of Exetainers for the reliable storage of trace-level hydrogen and carbon monoxide gas samples

Abstract. Atmospheric trace gases such as dihydrogen (H2), carbon monoxide (CO) and methane (CH4) play important roles in microbial metabolism biogeochemical cycles. Analysis of these at levels requires reliable storage discrete samples low volume. While commercial sampling vials Exetainers® have been tested for CH4 other greenhouse gases, no information on is available H2 CO. We show that sealed with butyl rubber stoppers are not suitable storing CO due to release from material. Treating septa NaOH reduced trace-gas release, but contamination was still substantial, mixing ratios air increasing by a factor 3 10 after 30 d conventional 12 mL Exetainers. All materials showed near-linear increase ratios, indicating zero-order reaction material degradation the underlying cause. Among tested, silicone lowest potential release. thus propose modifying Exetainers closing them plug minimise sealing stainless-steel bolt O-ring secondary diffusion barrier long-term storage. Such modified exhibited stable exceeding 60 atmospheric elevated (10 ppm) ratios. The measurable 9 times lower than treated septa; this can be corrected its linearity standard gas alongside samples. proposed modification inexpensive, scalable robust, it enables large numbers low-volume remote field locations.