An automated system for preconcentration/matrix-removal followed by ICP-MS determination of organic phosphorus in oil production water

摘要

Scale inhibitors based on phosphinepolycarboxylic acid (PPCA) have been successfully used in offshore oil production for preventing deposition of barium and strontium sulfates. A system was developed for the automated pretreatment of PPCA-containing water samples, followed on-line or off-line by phosphorus determination using ICP mass spectrometry. During pretreatment, the previously acidified inhibitor solution is adsorbed on a C18-reversed phase column and then eluted with 0.025 mol l(-1) borate solution. Using a 3.5-ml sample volume, analytical frequency in the on-line mode is about 9 samples per hour and 17 in off-line operation. Detection limit of phosphorus in the borate solution was 0.20 mug l(-1), using a crossflow nebulizer and a Ryton(R) spray chamber. Recoveries were, typically, in the range of 90% to 100% and repeatability about 5%. The method has been applied for monitoring inhibitor concentrations during laboratory and field squeeze tests. (C) 2004 Elsevier B.V. All rights reserved.