Influences of relative humidities and temperatures on the collection of C2-C5 aliphatic hydrocarbons with multi-bed (Tenax TA, Carbograph 1TD, Carboxen 1003) sorbent tube method

Abstract

Volatile organic compounds (VOCs) are measured with sorbent tubes followed by thermal desorption (TD) analysis. Water vapor in the atmosphere affects sampling breakthrough and results in low collection efficiency. This paper reports the effect of relative humidity (RH) and temperature on the collection of 57 ozone precursors with a multi-bed tube composed of three different strengths of adsorbents (Tenax TA, Carbograph 1 TD, and Carboxen 1003). Unacceptable breakthrough values for volatile C 2 -C 5 aliphatic compounds were observed under high (>60%) RHs. The breakthrough volumes (BV) for C 2 aliphatic compounds were reduced 13 -22 fold under 90% RH.Dry-purge with inert helium gas removes excessive water content before the TD analysis but also causes a maximum of 40% loss of target analytes. Condensation is another pathway for water retention. The tube temperature should be regulated at 5-10 • C above the air temperature to minimize condensation under RHs >30%.

VOCs emission profiles from rural cooking and heating in Guanzhong Plain, China and its potential effect on regional O<sub>3</sub> and SOA formation

“…All pre-conditioned and sampled tubes were capped and shipped at 0 ℃. Insignificant breakthrough (<5%) was observed either in field or laboratory demonstration under this sampling flow and volume (Ho et al, 2017). Two sorbent tube samples were thus collected in each test and one field blank was collected on each sampling campaign.…”

“…Duplicate samples were collected and the reproducibility was better than 95%. Detailed sampling and analytical method was shown in Ho et al (2017).…”

“…formation (Ho et al, 2017;Iinuma et al, 2010). The contributions of photochemical reactivity of VOCs from solid fuel burning to SOA formation was thus estimated as well.…”

Origin and Transformation of Ambient VOCs during a Dust-to-Haze Episode in Northwest China

“…The loaded tubes were analyzed using a thermal desorption and gas chromatography/mass spectrometry (TD-GC/MS) method. In previous developmental work, humidity and temperature during sampling were found to impact significantly on the analyses; for this study, all sample collections were made under optimized conditions (Ho et al, 2017;Ho et al, 2018). Sixteen airborne carbonyls (including mono-and dicarbonyls) were collected over diurnal cycles (i.e., 20:00-08:00 local time [LT] and 08:00-20:00 LT) by 2,4-dintrophenyhydrozine (DNPH) coated-cartridges.…”

“…Sixteen airborne carbonyls (including mono-and dicarbonyls) were collected over diurnal cycles (i.e., 20:00-08:00 local time [LT] and 08:00-20:00 LT) by 2,4-dintrophenyhydrozine (DNPH) coated-cartridges. Detailed sampling and analytical procedures for VOCs and carbonyls can be found in previous publication (Ho et al, 2017;Dai et al, 2012). PM2.5 filter samples were sampled with mini-volume samplers (Model Mini-Vol, Air Metrics Co., Oregon, USA) with a flow rate of 5 L min -1 (Cao et al, 2005).…”