Abstract
In 1969, Zaltkis and Zak reported that O-phthalaldehyde was available for the determination based on their report and revealed that the method was less interfered by Bilirubin and other substances.
Author have attempted to evaluate this method and study on the reason of the difference among o-PA method and Zak-Henly modification method.
This is the report of my study.
o-PA method
As the result of my experiments, I found this method was not interfered by Bilirubin and light. I also found that the accuracy and the reproducibility of this method was satisfactory to use as the direct micro determination of cholesterol. Therefore, I consider that the o-PA method is one of the most satisfactory one at present and pays a role of the rationalization of the cholesterol determination.
Difference between the value of the o-PA method and that of Zak-Henly modification method.
1. From the regression study, the o-PA method give the 7% higher value than that of Zak-Henly modification method.
2. Ferric chloride-sulfuric acid reaction is obviously affected by the concentration of FeCl3·6H2O.
3. Although the concentration of Ferric chloride in the reaction mixture of standard of the Zak-Henly modification method is 75 mg/dl, the concentration in the reaction mixture of deproteinized solution from serum sample is 57 mg/dl. Resultantly, the value of the Zak-Henly modification method is calculated lower than the true value.
4. It is preferable to use 57 mg/dl of Ferric chloride-acetic acid solution for the standard reaction mixture.
5. Correlation between the residual concentration of Ferric chloride in deproteinized solution and the protein concentration of the sample shows not a negative regression line but negative regression curve.
Finally, I concluded that the difference between o-PA method and the Zak-Henly nodification method depends on the inadequate treatment of the satandard with Zak-Henly modification method.
