A capillary gas chromatographic (GC) method has been developed for the separation and determination of policosanol components extracted from rice bran wax. A Varian CP-sil 8 CB column was employed, and an oven temperature was programmed. Gas chromatography-mass spectrometry (GC-MS) was used to identify the composition of policosanol. Quantitative analysis was carried out by means of hydrogen flame ionization detector (FID) with dinonyl phthalate (DNP) as internal standard. The results indicated that the extract obtained by dry saponification has the highest contents of octacosanol and triacontanol among extracts by all used extraction methods including dry saponification, saponification in alcohol, saponification in water (neutralized and non-neutralized), and transesterification. Meanwhile, the GC-MS fingerprint of policosanol extracted by dry saponification has been established. Euclidean distance similarity calculation showed remarkable consistency of compositions and contents among 12 batches of policosanol from a rice bran wax variety. This protocol provided a rapid and feasible method for quality control of policosanol products.
An effective method was developed to determine phenolic compounds in soil by ultrasonic extraction-gas chromatography (GC). The soil sample was extracted with methylene dichloride-hexane (2:1, v/v) for 3 min with the extraction temperature lower than 50 degrees C for 3 times. The extract was purified by alkaline aqueous solution (pH > 12), and the phenolic compounds were dissolved in aqueous solution. After the organic solution was discarded, the aqueous solution was adjusted to pH <3 and subsequently extracted with methylene dichloride-ethyl acetate (4:1, v/v) twice. The analytes were determined by GC-FID and quantified by external standard method. The limits of quantification for all tested phenolic compounds were 0.01-0.06 mg/kg in about 10 g soil samples. The recoveries were between 62.9% and 111.4% with the relative standard deviations (RSDs) in the range of 4.3%-24.0% (n = 6). The results showed that this method is sensitive, accurate, and suitable for the determination of the 21 phenolic compounds in soil.
A high performance liquid chromatography−photodiode array detection−electrospray ionization mass spectrometry (HPLC-PDA-ESIMS) method has been developed for separation and identification of relative substances in hydroquinone bis(2-hydroxyethyl) ether (HQEE), a kind of polyurethane chain extender synthesized by hydroquinone (HQ) and ethylene oxide (EO). HQEE and all relative substances were baseline separated on a reverse-phase C18 column with gradient elution of methanol and water. Of them, six relative substances were identified by ESIMS coupled with HPLC in positive ionization mode. The UV spectrum feature from online PDA and chromatographic retention behavior were adopted as evidence to conclude the rest relative substances. The results showed that EO combines with HQ in molar ratio of 1:1−5:1, and the tetra- (4:1) and penta-substitution (5:1) products are pairs of isomers, respectively. Therefore, the chromatographic fingerprint of industrial HQEE has been drawn on the basis of qualitative analysis of these products of different molar ratios.
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