Bowers G N, McComb R B, Upretti A
Clin Chem. 1981 Jan;27(1):135-43.
We studied 53 lots of 4-nitrophenyl phosphate (I), obtained from 20 different commercial suppliers, and used this information to set specifications for it. Using these well-defined specifications, we classified 21 lots of I as "unacceptable," 26 lots as "borderline," and six as "acceptable." All lots were shown to contain some 4-nitrophenol and inorganic phosphate. However, "acceptable" I had < 0.3 mmol of 4-nitrophenol and < 10 mmol of inorganic phosphate per mole of I. The mole concentration of I (based on disodium hexahydrate, formula weight 371) was determined by enzymic conversion to 4-nitrophenol in five lots of "acceptable" materials. The mole fraction of I ranged from 0.982 to 0.998. From these measurements and from estimates of impurities that absorb at 311 nm, as determined by liquid chromatography and spectrophotometry at other wavelengths, our best estimate of the molar absorptivity of I at 311 nm in 10 mmol/L NaOH at 25 degrees C was 9867 L x mol-1 x cm-1, with a total uncertainty of 76 L x mol-1 x cm-1. We recommend that I used in clinical laboratories for measurement of alkaline phosphatase activity in serum meet the specifications given in this paper: I content > 98%, maximum activity > 98% in comparative testing with other "acceptable" lots of I, and impurities not to exceed the values cited above.
我们研究了从20个不同商业供应商处获得的53批对硝基苯磷酸酯（I），并利用这些信息为其制定规范。根据这些明确的规范，我们将21批I归类为“不可接受”，26批为“临界”，6批为“可接受”。所有批次均显示含有一些对硝基苯酚和无机磷酸盐。然而，“可接受”的I每摩尔I中对硝基苯酚含量<0.3 mmol，无机磷酸盐含量<10 mmol。通过酶促转化为对硝基苯酚，在五批“可接受”材料中测定了I（基于六水合二钠，分子量371）的摩尔浓度。I的摩尔分数范围为0.982至0.998。根据这些测量结果以及通过液相色谱法和其他波长的分光光度法测定的在311 nm处有吸收的杂质估计值，我们对I在25℃下于10 mmol/L NaOH中在311 nm处的摩尔吸光率的最佳估计值为9867 L·mol⁻¹·cm⁻¹，总不确定度为76 L·mol⁻¹·cm⁻¹。我们建议临床实验室用于测定血清碱性磷酸酶活性的I应符合本文给出的规范：I含量>98%，在与其他“可接受”批次的I进行比较测试时最大活性>98%，且杂质不超过上述值。
