Quantitative determination of nonylphenol polyethoxylate surfactants in marine sediment using normal-phase liquid chromatography-electrospray mass spectrometry

A new comprehensive analytical method based on normal-phase liquid chromato graphy-electrospray ionization mass spectrometry (LC-ESI-MS) has been devel oped for the quantitative determination of individual nonylphenol ethoxylat e (NPEO) surfactants in complex environmental matrices. Clean-up of sample extracts was performed on cyanopropyl silica solid-phase extraction cartrid ges. Complete NPEO oligomer separation was achieved by using normal-phase L C. Because the non-polar solvents used in normal-phase LC are incompatible with ESI, unique LC-ESI-MS interface conditions were adopted that provided a functional interface and also enhanced the detection response of NPEOs. T hese provided enhanced ESI signal intensity and stability and facilitated t he detection of NPEOs as sodium adducts at parts-per-billion concentration levels. The overall analytical method was validated for accuracy and precis ion by analyzing sediment samples spiked with known amounts of NPEOs. The m ethod is superior to those currently used for NPEO analysis (LC-W, LC-fluor escence, LC-thermospray-MS, LC-field desorption-MS, LC-particle beam-MS and GC-MS) in terms of detection limits, specificity and speed of analysis. Th e validated method was successfully applied to determine levels of NPEOs in sediments from the Strait of Georgia, British Columbia. This work also dem onstrates that by proper selection of normal-phase LC-ESI-MS interface cond itions this technique is capable of solving separation problems which are n ot amenable with reversed-phase LC-ESI-MS. (C) 1999 Elsevier Science B.V. A ll rights reserved.