C30 N-Alkane Lab Report

C5-C30 n-alkanes were used to made retention indices (RI) and 2,4,6-trimethylpyridine (TMP, purity 99 %, I.S.) was used to internal standard which were purchased from Sigma-Aldrich Trading Co., Ltd (Shanghai, China). Mono Trap (MT) (Diameter 2.9 mm ×Length 5 mm, Hole Diameter 1 mm) (ODS, silica gel and activated carbon) was used for headspace MMSE was obtained from GL Science (Shinjuku, Tokyo, Japan).
Extraction of volatile compounds
Fish sauce samples were extracted volatile compounds by Monolithic Material Sorptive Extraction (MMSE). 5 mL of each fish sauce sample was pipetted into a vial (15mL). Internal standard (I.S.) was 1000 ppm 2,4,6-trimethylpyridine (TMP, purity 99 %). A Mono Trap (MT) rod was used for headspace MMSE with a sample.
Volatile compounds including 3 alkane, 4 aldehyde, 11 alcohols, 3 ester, 2 furan, 6 ketone, 11 nitrogen-containing compounds, 11 aromatic compounds, 18 acids and 10 other compounds. Acids were the most volatile compounds in 14 fish sauce samples. Volatile acid class represents the major constituents for the sauce samples and can be produced as a result of either lipolysis or from amino acid metabolism in terms of valine deamination [13]. Volatile compounds in the most of samples were identified trimethylamine (TMA), acetone, 1-propanol, acetic acid, 2-butanone, benzene, propanoic acid, 3-methyl-1-butanol, 2-methyl-1-butanol, butanoic acid, 2-methyl butanoic acid, 3-methyl butanoic acid, 4-methyl pentanoic acid, phenol and benzaldehyde. It has been reported that TMA, benzaldehyde and 4 to 7 carbon chain acids are the most important contributors to the aroma of fish sauce. 3-Methylbutanal and 2-methylbutanal were also present at concentrations greater than their thresholds of 0.2 and 3 ppb, respectively [14,15], in addition 2-methyl and 3-methylbutanal, dimethyldisulfide and benzaldehyde were major aroma-active compounds. Thai fish sauce also has been evaluated and 4 odor active compounds were detected (2-methylpropanal, 2-methylbutanal, 2-ethylpyridine and dimethyl trisulfide) using GCO-aroma extract dilution
In addition some volatile compound was different may can indicate to different odor. Vietnamese fish sauce samples were identified some volatile compounds which were not found in other samples including S-ethyl ethanethioate, cyclohexanone, 2-ethyl-3-methylpyrazine, 2-methyl-1,3-dithiacyclopentane, 2-acetylthiazole, α-methyl benzenemethanol, 2-ethyl-3,5-dimethyl pyrazine, phenylmethyl ester acetic acid, ethyl ester benzeneacetic acid, 3-acetyl-2,5-dimethylthiophene and triacetin. K2 sample which produced from Sand lance fish could identified different volatile compounds with other samples including isobutyronitrile, tetrahydro-3-methylfuran, 2-methyl butanenitrile, 3-(methylthio)-propanenitrile and benzyl nitrile. While K3 sample which produced from wild fish could identified 3-methyl butanamide and dimethyl phthalate which different with other samples. Table 2 Concentration of volatile compounds in fourteen fish sauce samples (Mean ±