"On the role of lead acetate in arsenic salt limit inspection"

Arsenic salt inspection is a key link in drug quality control. Lead acetate plays an important role in it.

In the arsenic salt limit inspection method, the interference of impurities in the test sample often affects the accuracy of the results. The primary function of lead acetate is to remove interfering substances such as hydrogen sulfide. Because hydrogen sulfide can react with hydrogen arsenide, the results are biased. Lead acetate can react quickly with hydrogen sulfide to form lead sulfide precipitation, effectively avoiding interference. For example, in the classic Gu Cai's method, the test sample is treated to produce hydrogen arsenide gas. If hydrogen sulfide is present in this process, it will react with the mercury bromide test paper, causing the test paper to change color and confusing the judgment of arsenic spots. After absorbing hydrogen sulfide by lead acetate cotton, the hydrogen arsenide can be purified and reacted with mercury bromide test paper, showing clear arsenic spots, which helps to accurately determine the arsenic limit.

In addition, whether the lead acetate cotton is filled moderately or not has an impact on the rate of hydrogen arsenide gas passage. If the filling is too tight, the gas will be blocked, and the hydrogen arsenide cannot fully react with the test paper; if the filling is too loose, the hydrogen sulfide will not be removed. Therefore, it is necessary to accurately control the filling of lead acetate cotton to ensure the accuracy and reliability of the inspection.

In short, lead acetate in the arsenic limit inspection provides a solid guarantee for the accurate determination of the arsenic limit in drugs by removing interfering substances and regulating the rate of gas passage. It is of great significance for drug quality control.