Rapid ion-exchange matrix removal for a decrease of detection limits in the analysis of salt-rich reservoir waters for fluorobenzoic acids by liquid chromatography coupled with tandem mass spectrometry
Anal Bioanal Chem
Rapid ion-exchange matrix removal for a decrease of detection limits in the analysis of salt-rich reservoir waters for fluorobenzoic acids by liquid chromatography coupled with tandem mass spectrometry
Paweł Kubica 0 1 2 4 5
Véronique Vacchina 0 1 2 4 5
Tomasz Wasilewski 0 1 2 4 5
Stéphanie Reynaud 0 1 2 4 5
Joanna Szpunar 0 1 2 4 5
Ryszard Lobinski 0 1 2 4 5
0 CNRS-UPPA UMR 5254, Equipe de Physique et Chimie des Polymères (EPCP-IPREM) , Hélioparc, 2, Avenue Pr. Angot, 64053 Pau , France
1 UT2A, Hélioparc , 2, Avenue Pr. Angot, 64053 Pau , France
2 Department of Analytical Chemistry, Faculty of Chemistry, Gdańsk University of Technology , Narutowicza 11/12, 80-233 Gdańsk , Poland
3 Paweł Kubica
4 Department of Analytical Chemistry, Warsaw University of Technology , ul. Noakowskiego 3, 00-664 Warsaw , Poland
5 CNRS-UPPA, UMR 5254, Laboratoire de Chimie Analytique Bio-inorganique et Environnement (LCABIE-IPREM) , Hélioparc, 2, Avenue Pr. Angot, 64053 Pau , France
A matrix removal procedure with ion-exchange resin prior to analysis for 18 fluorinated benzoic acids (FBAs) tracers in saline (>25% salt) reservoir water was optimized. The elimination of >98% of salt and the simultaneous matrix sample cleanup allowed the direct analysis using the supernatant by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). This resulted in a gain in detection limits for most of the tracers in comparison with the reference method (direct analysis after minimum required dilution). The limits of detection (LODs) were in the range of 0.01-0.15 ng/ml and compared to other studies the developed method provided comparable limits of detection and advantage of simplified and shorter sample preparation. The presented method offers a considerable gain in simplicity and analysis time. Recoveries for all the tracers reached 80100%, except for 2-FBA and 2,6-dFBA for which they were ca. 60%. The low recoveries were corrected by the use of five isotopically labeled internal standards. The method was validated by the analysis of spiked samples and by an independent comparison of the results with those obtained by solid-phase extraction LC-MS/MS method.
Fluorinated benzoic acids; LC MS/MS; Matrix removal; Ion exchange
Introduction
Different fluorobenzoic acids are commonly used as
nonradioactive passive tracers in petroleum exploration [
1, 2
].
Hence, there is a need for their sensitive analysis in oil
reservoir waters, known for their highly dissolved organic matter
and salt (NaCl, CaCl2) content often exceeding 25% [3]. Gas
chromatography (GC) [
4
] or high-performance liquid
chromatography (HPLC) [
5–10
] with MS/MS detection have been
typically used to assure the separation of the tracer compounds
from each other while assuring their specific detection.
HPLC-MS/MS offers detection limits down to 0.01 ng/ml
for most of the fluorobenzoic acids in the selected reaction
monitoring (SRM) mode using the ion transition
corresponding to the loss of CO2 by the pseudomolecular ion employing
the-state-of-the-art triple quadrupole, Q-TOF [
7
] or
QOrbitrap [
11
] mass spectrometers. However, as the maximum
tolerable salt content in the solution injected on the column
used (Waters, Acquity UPLC BEH C18 column, 50 × 2.1 mm,
1.7 μm) has to be inferior to 1%, a dilution is required [
10
].
This represents for samples with 25% salinity a 25-fold
increase in the detection limits making the method virtually
useless for practical applications.
Sample preparation methods based on the solid-phase
extraction (SPE) of fluorobezoic acids were therefore developed
for the salt-removal and preconcentration of analytes. They
allowed to obtain detection limits for salt-rich samples
comparable with those obtained for standard solutions in water [
4,
7, 8
]. Moreover, methods presenting on-line SPE for
determination of drugs or pesticides in different kind of sample are
available as well [
9, 10
] However, the time necessary,
relatively large volumes of organic solvents requiring evaporation
made the procedures quite tedious for high-throughput
analysis. Gas chromatography MS/MS suffers from similar
drawbacks [11]. Although the detection limits are below 0.01 ng/
mL, the required sample preparation procedures are
timeconsuming (24 h). Moreover, the derivatization step is
incomplete and suffers from strongly compound-dependent yields
which limits the practical use [
11
].
In contrast to all the reported protocols, until now [
4, 7, 8
],
the objective of this method development was on the removal
of the matrix rather than on the extraction of the analytes. The
removal of salt matrix using mixed-bed ion-exchange resin
was investigated. The proposed approach allows to remove
matrix effects and thus resulting in a less noisy baseline and
lower detection limits.
Materials and methods
Samples collection
Samples originated from reservoir waters (Congo) contained
250 g/L of total salt (primary Na and Ca (...truncated)