Validation of a Simple Spectrophotometric Method for the Measurement of Quaternary Ammonium Compound Residue Concentrations in Food Production Facility

Abstract

Quaternary ammonium compound (QAC) residues can increase with each application and build up over a period of time during sanitation of food plants. Therefore, it is crucial to establish a simple but accurate method for routine measurement of QAC residues in food plants. In this study, a spectrophotometric method was validated and applied for the quantification of QAC residues on stainless steel surfaces. This method was based on the formation of a colored ion pair between the quaternary ions and Eosin-Y in the presence of Triton X-100. QAC residues were recovered from surfaces using swabs and were subsequently sonicated, and the isolated extracts were analyzed with a spectrophotometer (535 nm). The method was shown to be selective in the presence of interfering substances, and a linear relationship between the absorbance and concentration of QACs was detected in the concentration range from 0.5 to 10 mg L−1 (r 2 > 0.99). The limit of detection and limit of quantitation were 0.53 and 1.77 mg L−1, respectively. Satisfactory accuracy (93–97 %) and precision (relative standard deviation (RSD) < 2.7 %) were obtained for the method. Assessment of the effect of swabbing protocol on the recovery, repeatability and intermediate precision of the method revealed that the mean recovery of residues was 90 %. Moreover, the percent RSD was less than 8.8 and 9.4 % for repeatability and intermediate precision, respectively. QAC residues were found to be stable on stainless steel surfaces for at least 6 days following deposition, a treatment that could be a potential risk especially in dry cleaning processes.