NEW LC-MS/MS METHOD FOR THE DETERMINATION OF EIGHT NITROSAMINES IN DRINKING WATER

A new sensitive, selective and accurate LC-MS/MS method with positive electrospray ionisation was developed to detect eight nitrosamines from drinking water. The method separates all nitrosamines using a Zorbax Eclipse Plus C18 column (100 x 2.1 mm, 3.5 gm) kept at 15 degrees C and a mobile phase consisting of aq. 0.005% formic acid and acetonitrile in the ratio 90/10 (v/v). A strong gradient applied in 8 min up to 90% ACN allowed analyte separation. A low mobile phase flow-rate of 0.2 ml/min was used to enhance ESI ionisation. Collision energy, fragmentor and capillary voltages were optimised to enhance analyte S/N ratio. Optimisation of LC-MS parameters generated low instrumental LOQ values between 0.05-1.84 mu g/l. Detector response was linear in the range 1-100 mu g/l (R-2 > 0.99) for all nitrosamines. SPE using activated charcoal cartridges was used to concentrate nitrosamines from drinking water. Overall method LOQs were situated in the range 1.23-4.12 ng/l. LC-MS/MS method was fully validated with respect to specificity, linearity, precision, accuracy and LOQ, and provided good results. The method was tested on six tap water samples collected from different regions of Bucharest and the determined nitrosamine total content ranged between 2.8 and 14.8 ng/l.