Quantitative Analysis of QACs in Milk Using a QuEChERs Sample Preparation Approach

User Benefits

- Sensitive and selective detection of BAC C8–C18 and DDAC C8–C12. - Limits of quantification suitable for surveillance and compliance testing. - Fast sample preparation compatible with routine laboratory throughput.

Introduction

Quaternary ammonium compounds (QACs) such as benzalkonium chlorides (BACs) and didecyldimethyl-ammonium chloride (DDAC) are widely used cationic disinfectants. Their surface active, antimicrobial properties make them effective as teat dips, equipment sanitizers, and detergents in dairy farms and dairy processing facilities, but incomplete rinsing or improper application can lead to residues in raw milk and dairy products. Routine, sensitive analysis of QACs in milk is therefore essential to ensure product quality, protect consumers, and maintain regulatory compliance. This application note demonstrates a robust LC-MS/MS method for the simultaneous determination of common QAC homologues in milk at low ng/mL levels. Under current European guidance, there are no harmonized EU maximum residue limits (MRLs) specifically set for most QAC disinfectants in milk; however, the European Commission and national authorities apply general food safety laws (Regulation (EC) No 178/2002) and contaminants/legislative frameworks requiring that residues are not present as a risk to consumers. National guidance values and tolerance levels have been published in some Member States (typically in the low mg/kg to µg/kg range depending on compound and context), and monitoring is carried out to ensure levels do not interfere with processing (e.g., starter cultures) or pose toxicological concerns.

April 16, 2026 GMT