Determination of long-chain fatty acids in bryophyte plants extracts by HPLC with fluorescence detection and identification with MS

A sensitive method for the determination of long-chain fatty acids (LCFAs) (>C20) using 1-[2-(p-toluenesulfonate)-ethyl]-2-phenylimidazole-[4.5-f]-9,10-phenanthrene (TSPP) as tagging reagent with fluorescence detection and identification with post-column APCI/MS has been developed. The LCFAs in bryophyte plant samples were obtained based on distillation extraction with 1: 1 (v/v) chloroform/methanol as extracting solvent. TSPP could easily and quickly label LCFAs at 90 degrees C in the presence of K2CO3 catalyst in DMF. Eleven free LCFAs from the extracts of bryophyte plants were sensitively determined. Maximal labeling yields close to 100% were observed with a five-fold excess of molar reagent. Separation of the derivatized fatty acids exhibited a good baseline resolution in combination with a gradient elution on a reversed-phase Eclipse XDB-C-8 column. Calculated detection limits from 1.0 pmol injection, at a signal-to-noise ratio of 3, were 26.19-76.67 fmol. Excellent linear responses were observed with coefficients of >0.9996. Good compositional data were obtained from the analysis of the extracted LCFAs containing as little as 0.2 g of bryophyte plant samples. Therefore, the facile TSPP derivatization coupled with HPLC/APCI/MS analysis allowed the development of a highly sensitive method for the quantitation of trace levels of LCFAs from biological and natural environmental samples. (c) 2006 Elsevier B.V. All rights reserved.

Hydroisomerization of long-chain alkane over Pt/SAPO-11 catalysts synthesized from nonaqueous media

SAPO-11 molecular sieves were synthesized from nonaqueous media. The effects of Si and Al sources as well as solvents on the catalytic performance of SAPO-11 were investigated by the hydroisomerization reaction of n-dodecane. The samples were characterized by XRD, XRF, N-2-adsorption, SEM, NH3-TPD, IR-NH3 and Si-29 CP MAS NMR. The SAPO-11 samples synthesized with tetraethoxysilane as the Si source showed higher Si incorporation contents than the SAPO molecular sieves prepared with polymeric Si sources (fumed silica and Si colloidal gel). The reaction results showed that Pt/SAPO-11 catalysts synthesized from ethylene glycol and glycerol media with the monomeric Si and Al sources (tetraethoxysilane, aluminum isopropoxide) exhibited higher catalytic activities than those catalysts with the polymeric Si or Al (pseudo-boehmite) sources, due to the larger external surface area and higher acidity of the former ones. Especially, the catalyst synthesized in an ethylene glycol medium possessed the highest catalytic activity. Over this catalyst, 88% conversion of n-dodecane was achieved at a low temperature of 250 degrees C.