Parallel between offline-SPE-LC-MS and direct injection LC-MS methods for acrylamide detection in drinking water at parts per trillion level

Abstract

The presence of acrylamide, a potential human carcinogen, in treated drinking water has been a long-time concern for public health agencies. Due to this, acrylamide is included among the substances to be monitored in drinking water with a stated maximum admissible level of 0.1 µg/L in Europe. The necessity for ultra-trace level detection of acrylamide has led to development of an Offline-SPE-LC-MS method that involves SPE extraction of acrylamide using a strong adsorbent like activated charcoal followed by concentration. Simultaneously, a simple and rapid large volume Direct Injection LC-MS method was optimized from the previous method to detect acrylamide without the resource and time-consuming SPE step. A comprehensive comparison between the efficiency and sensitivity of the two methods is made. Optimization of LC-MS parameters (column temperature, mobile phase composition and flow, collision energy, fragmentor voltage, capillary voltage or MRM transitions) allowed high detection sensitivity. Due to Acrylamide high polarity, a Synergi Fusion-RP column with amide polar embedded groups was chosen to achieve reasonable retention and peak shape for acrylamide with a short run-time of only 3 min. The two methods provided excellent sensitivity, with reasonably low LOQ values of 2 ng/L for the Offline-SPE-LC-MS method and 30 ng/L for the Direct Injection LC-MS method. Intra-day and inter-day precision (RSD%) were 7.3 and 10.3%, for the Offline-SPE-LC-MS method and 2.4% and 6.2%, respectively for the Direct Injection LC-MS method. The analysis of acrylamide was successfully performed in drinking water from different location consumers and water treatment plants in Romania. Acrylamide was found in drinking water samples with levels between 5.2 and 35.7 ng/L using the Offline-SPE-LC-MS method. The direct injection method can only be used for acrylamide levels higher than its LOQ value (30 ng/L).