ABSTRACT
A combination technique of LC/ESR, LC/MS and spin trapping was used to identify and characterize the carbon-centered free radicals formed from lipoxygenase-catalyzed peroxidation of dihomo-γ-linolenic acid(DGLA). The spin trap, α-[4-pyridyl-1-oxide]-N-tert-butyl nitrone(POBN), could react with short-lived carbon-centered radicals to form relatively stable adducts. Based on the same retention time of POBN radical adduct in LC/UV/ESR and LC/MS, molecular weight of adduct could be confirmed and the structure of adduct could be confirmed by their LC/MS2 fragment pattern. The results showed that free radicals formed in lipoxygenase-catalyzed peroxidation of DGLA, including ~·C_7H_(13)O_2, ~·C_(10)H_(17)O_2 and ~·C_5H_(11), all stemmed from β-scission of DGLA alkoxyl radicals(8-, 11-, 15-LO~·). The results were helpful for further study of biological activities of these radicals in vivo.
ABSTRACT
Correspondence analysis was used for determining the important factors from the six factors influencing analysis of cephalosporin in reversed phase-high performance liquid chromatography (RP-HPLC). Experiments were planed by U7（76）, then the synthetical correspondence between a series of optimizations and the factors was calculated. Result indicated that that proportion of organic solvent, pH and concentration of buffer were three most important factors. It showed that the correspondence analysis was a better method to determining the important factors in RP-HPLC
ABSTRACT
A spectrophotometric method for the determination of trace amounts of mercury (Ⅱ ) was described based on the formation of a complicated ion-association complex of Hg (Ⅱ )-Ⅰ-Rhodamine B in ihe presence of polyvinyl alcohol. The maximum absorption of the ion-association complex was at 595nm, Beer's law was obeyed for mercury (Ⅱ ) in the range of 0~5?g/25ml. The apparent molar absorptivity was 7. 36 ?105L/mol?cm. The recovery of mercury was 97. 0% ~ 103. 0%,RSD