Flow injection analysis with electrochemical detection was used for lipase
assay in pharmaceutical preparations. The method is based on the fact that
the current of voltammetric prepeak, accompanied by the reduction of 2-meth
yl-1,4-naphthoquinone (vitamin K-3, VK3) due to the effects of fatty acids,
is proportional to the acid concentration. A sample solution containing li
pase was incubated with olive oil (substrate) at 37 degrees C with stirring
for 15 min, and the released fatty acids were extracted by ether. No emuls
ifying agent was needed in the incubation of the enzyme reaction mixture. A
n acid test solution prepared by dissolving the extracts in ethanol contain
ing 3 mM VK3 and 38 mM LiClO4 (the same composition as the carrier solution
) was injected into the flow injection system. The flow signal was linear t
o the lipase activity ranging from 10 to 1500 U/l for sample solutions obta
ined from the digestive preparations. By this method, analysis of the fat d
igestive power of the commercially available preparations could be accompli
shed with good results, thus showing this method to be practically useful.
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