Analysis of Two Single and Three Double Long-Chain Quaternary Ammonium Compounds via Non-Aqueous Capillary Electrophoresis with Indirect Ultraviolet Detection

Abstract

A novel method utilizing non-aqueous capillary electrophoresis (NACE) with indirect ultraviolet detection (IUD) has been developed for the analysis of five quaternary ammonium compounds (QACs). The QACs analyzed in this study include dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, dioctyl dimethyl ammonium chloride, octyldecyl dimethyl ammonium chloride and didecyl dimethy ammonium bromide. The separation process was carried out on an uncoated fused quartz capillary with a total length of 50.2 cm (effective length 40.0 cm) and a diameter of 50 μm. The separation buffer consisted of a mixture of MeOH/ACN (90:10, v/v) containing 2 mmol/L sodium acetate, 2 mmol/L trifluoroacetic acid (TFA) and 16 mmol/L dodecyl dimethyl benzyl ammonium chloride. The sample buffer utilized a mixture of MeOH/ACN (20:80, v/v) containing 2 mmol/L TFA. During analysis, a separation voltage of 7 kV was applied, resulting in a current of approximately 2.3 μA. The detection wavelength was set at 214 nm to ensure optimal sensitivity. Under optimal conditions, the method exhibited excellent performance characteristics, with a limit of detection of 0.5 mg/L and a limit of quantitation of 5.0 mg/L for the five QACs. Linear calibration curves were obtained in a concentration range of 5.0 to 100.0 mg/L, with correlation coefficients exceeding 0.999 for all compounds. The recoveries of the five QACs ranged from 92.3% to 114.7%, with relative standard deviations below 7.4%. To assess the applicability of the NACE-IUD method, 17 commercially available samples were successfully analyzed. The results confirmed the suitability of the method for accurate determination of the five QACs in disinfectant products. Notably, this method offers an environmentally friendly approach for the analysis of these QACs.

Comparison of aqueous and non-aqueous capillary electrophoresis for the determination of four benzalkonium chloride homologues in compound chemical disinfectants

“…In this experiment, a constant composition of MeOH-ACN 60:40 (v/v), 60 mmol/L TFA, and 20 mmol/L SDS was maintained, while investigating the effects of NaAc, Na 2 HPO 4 , NaH 2 PO 4 , and NH 4 Ac. After comparing and referring to the separation conditions of single long-chain and double long-chain quaternary ammonium compounds [ 2 ], NaAc was selected and its concentration was optimized.…”

“…Drawing inspiration from the separation of two single long-chain and three double long-chain quaternary ammonium salts by NACE [ 2 ], TFA was also selected as the acid in the separation buffer.…”

“…This discrepancy may be due to the presence of other commonly used single-long-chain or double-long-chain quaternary ammonium salt components. The product labeling indicates the total amount of quaternary ammonium salt, which is quantitatively combined with the two single-long-chain quaternary ammonium salts (C 12 -TMA, C 14 -TMA) and three double-long-chain quaternary ammonium salts (di-C 8 , di-C 9 , di-C 10 ) established using the NACE combined with UV detection method [ 2 ]. This suggests that there are still issues with the labeling accuracy of commercially available compound quaternary ammonium salt disinfectants.…”

“…According to the information obtained from the National Disinfection Product Filing Information Service Platform [ 1 ], it is becoming increasingly common for disinfection products to combine benzalkonium chloride (BAC) with ultraviolet (UV) absorption and those without UV absorption as mentioned in articles published by our laboratory [ 2 ] to enhance bactericidal efficacy. BAC, also known as alkyl dimethyl benzyl ammonium chloride, is typically highly soluble in polar and protonic solvents such as water and alcohol.…”

“…When used for the analysis of high-content disinfectant components, the large dilution factor may result in significant quantitative errors. Moreover, as cationic surfactants, BAC easily contaminates the ion source and needs frequent cleaning, which is a cumbersome process and reduces the ion source's lifespan [ 2 ].…”