The determination of lactic acid in muscle

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Abstract
The determination of lactic acid in biologic fluid by oxidation to acetaldehyde and titration of the bisulphite bound by the aldehyde gives results ca. 10% too high owing to the interference of methylglyoxal. Other possible intermediates in the breakdown of sugar to lactic acid do not interfere markedly. The error can be avoided by distillation prior to the removal of sugar by CuSO4 and lime. Distillation after sugar removal is ineffective owing to the formation of some non-volatile substance (possibly a polymeride) from methylglyoxal. Attempts to remove the methylglyoxal by condensation with 2-4-dinitrophenylhydrazine were unsuccessful from the point of view of lactic acid determination. When methylglyoxal is oxidized by permanganate, the products bind bisulphite equivalent to 1\ molecules of acetaldehyde. Nevertheless by condensation with 2-4-dinitro-phenylhydrazine the only product which could be identified was acetaldehyde. Acetaldehyde 2-4-dinitrophenyl-hydrazone melts at 161[degree] C. and not 148[degree] C. as recorded in the literature.

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