Preventing glucolysis in blood samples.

When blood samples are set aside at room temperature with no preservative, the sugar content as measured by the reduction of picric acid diminishes markedly. This is most pronounced on the first day, and continues, until in the course of two to four days the glucose may have entirely disappeared. Commercial glucose added to the sample is similarly destroyed. If the samples are not chilled or treated chemically, sugar determinations are of little value unless the analyses are made immediately. It is not always practicable to make determinations promptly, nor can the samples always be kept on ice in the interim. An inquiry was therefore made to find practical means of checking, or if possible, completely preventing glucolysis.

Blood preservatives have been recommended in various scientific journals 1 but these were found to be unsatisfactory, and a systematic investigation was therefore undertaken.

The work has been done on the blood of herbivorous animals with a large number of substances, and is now being continued on human specimens. The fluorides recommended by other workers 1 were first tested. These inhibit glucolysis, and in most human specimens keep the blood sugar nearly constant for several days, but can not be relied on for all specimens over the 10 days required as a minimum by the Prudential Laboratory. In addition to the fluorides a large nuniber of substances varying widely in their properties have been tried. Eventually the work has narrowed down to halogen derivatives of hydro-carbons. It was found that trichlor-ethelene mixed wit'h NaF is fully as effective as thymol and NaF. Neither CCl₂=CHCl nor NaF alone are of any vahe. Trichlor-methane and tetra-chlor-methane were soon discarded as worthless for our purposes. Chlor-benzol and brom-benzol keep the sugar content of blood samples near its initial value for days, and in combination with NaF have so.