Article

Identification of control parameters for the sulfur gas storability with bag sampling methods.

Department of Environment & Energy, Sejong University, Seoul 143-747, Republic of Korea.
Analytica chimica acta (Impact Factor: 4.31). 08/2012; 738:51-8. DOI: 10.1016/j.aca.2012.06.010
Source: PubMed

ABSTRACT Air samples containing sulfur compounds are often collected and stored in sample bags prior to analysis. The storage stability of six gaseous sulfur compounds (H(2)S, CH(3)SH, DMS, CS(2), DMDS and SO(2)) was compared between two different bag materials (polyvinyl fluoride (PVF) and polyester aluminum (PEA)) at five initial concentrations (1, 10, 100, 1000, and 10,000ppb). The response factors (RF) of these samples were determined after storage periods of 0, 1, and 3 days by gas chromatography-pulsed flame photometric detector (GC-PFPD) combined with an air server (AS)/thermal desorber (TD) system. Although concentration reduction occurred more rapidly from samples of the high concentration standards (1000 and 10,000ppb), such trends were not evident in their low concentration counterparts (1, 10, and 100ppb). As such, temporal changes in RF values and the associated loss rates of most sulfur gases were greatly affected by their initial concentration levels. Moreover, the storability of oxidized sulfur compound (SO(2)) was greatly distinguished from that of reduced sulfur compounds (RSCs), as the former almost disappeared in the PVF bag even after one day. The results of our study confirm that storability of gaseous sulfur species is affected interactively by such variables as initial gas concentration level, bag material type, and oxidation status with the associated reactivity.

2 Bookmarks
 · 
164 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The classes and concentrations of volatile organic compounds (VOC) released from fresh and decaying strawberries were investigated and compared. In this study, a total of 147 strawberry volatiles were quantified before and after nine days of storage to explore differences in the aroma profile between fresh strawberries (storage days (SRD) of 0, 1, and 3) and those that had started to decay (SRD = 6 and 9). In terms of concentration, seven compounds dominated the aroma profile of fresh strawberries (relative composition (RC) up to 97.4% by mass, sum concentration): (1) ethyl acetate = 518 mg∙m-3, (2) methyl acetate = 239 mg∙m-3, (3) ethyl butyrate = 13.5 mg∙m-3, (4) methyl butyrate = 11.1 mg∙m-3, (5) acetaldehyde = 24.9 mg∙m-3, (6) acetic acid = 15.2 mg∙m-3, and (7) acetone = 13.9 mg∙m-3. In contrast, two alcohols dominated the aroma profile of decayed samples (RC up to 98.6%): (1) ethyl alcohol = 94.2 mg∙m-3 and (2) isobutyl alcohol = 289 mg∙m-3. Alternatively; if the aroma profiles are re-evaluated by summing odor activity values (ΣOAV); four ester compounds ((1) ethyl butyrate (6,160); (2) ethyl hexanoate (3,608); (3) ethyl isovalerate (1,592); and (4) ethyl 2-methylbutyrate (942)) were identified as the key constituents of fresh strawberry aroma (SRD-0). As the strawberries began to decay; isobutyl alcohol recorded the maximum OAV of 114 (relative proportion (RP) (SRD = 6) = 58.3%). However, as the decay process continued, the total OAV dropped further by 3 to 4 orders of magnitude-decreasing to 196 on SRD = 6 to 7.37 on SRD = 9. The overall results of this study confirm dramatic changes in the aroma profile of strawberries over time, especially with the onset of decay.
    Sensors 01/2013; 13(6):7939-7978. · 2.05 Impact Factor

Full-text (3 Sources)

View
179 Downloads
Available from
Jun 1, 2014