Price Randi, Wan Ping
University of Florida, Department of Chemistry, Gainesville, FL 32611, USA.
J AOAC Int. 2010 Sep-Oct;93(5):1542-52.
A potentiometric titration for determining the quaternary ammonium compounds (QAC) commonly found in antimicrobial products was validated by a single laboratory. Traditionally, QACs were determined by using a biphasic (chloroform and water) manual titration procedure. Because of safety considerations regarding chloroform, as well as the subjectivity of color indicator-based manual titration determinations, an automatic potentiometric titration procedure was tested with quaternary nitrogen product formulations. By using the Metrohm Titrando system coupled with an ionic surfactant electrode and an Ag/AgCl reference electrode, titrations were performed with various QAC-containing formulation products/matrixes; a standard sodium lauryl sulfate solution was used as the titrant. Results for the products tested are sufficiently reproducible and accurate for the purpose of regulatory product enforcement. The robustness of the method was measured by varying pH levels, as well as by comparing buffered versus unbuffered titration systems. A quantitation range of 1-1000 ppm quaternary nitrogen was established. Eight commercially available antimicrobial products covering a variety of matrixes were assayed; the results obtained were comparable to those obtained by the manual titration method. Recoveries of 94 to 104% were obtained for spiked samples.
一个实验室对用于测定抗菌产品中常见的季铵化合物（QAC）的电位滴定法进行了验证。传统上，QAC是通过双相（氯仿和水）手动滴定程序测定的。由于氯仿的安全性问题，以及基于颜色指示剂的手动滴定测定的主观性，对季铵氮产品配方进行了自动电位滴定程序测试。通过使用万通Titrando系统，结合离子表面活性剂电极和Ag/AgCl参比电极，对各种含QAC的配方产品/基质进行滴定；使用标准十二烷基硫酸钠溶液作为滴定剂。所测试产品的结果对于监管产品执法目的而言具有足够的可重复性和准确性。通过改变pH值以及比较缓冲滴定系统和非缓冲滴定系统来测量该方法的稳健性。建立了1-1000 ppm季铵氮的定量范围。对涵盖各种基质的八种市售抗菌产品进行了分析；获得的结果与通过手动滴定法获得的结果相当。加标样品的回收率为94%至104%。
