Fig 1.
Map of field samples collected in the present survey.
Geographical location of the river and lake surface water samples collected at large spatial scale across Canada. Base maps were obtained from Natural Earth (free vector and raster map data available at naturalearthdata.com).
Fig 2.
Derivatization reactions of the targeted amino acids with 9-fluorenylmethyl chloroformate (FMOC-Cl).
Table 1.
Optimization of sample preparation.
Experimental design applied in the optimization of sample preparation conditions. Bold font indicates the parameter(s) being tested for each experiment.
Fig 3.
Optimization of derivatization reaction time and temperature.
Response surface of BMAA signal upon full-factorial experimental design optimization of FMOC derivatization reaction time and temperature. FMOC-BMAA areas were normalized to the observed maximum (maximum set to 100%) across the 18 tested combinations (n = 3 per condition).
Fig 4.
Influence of UHPLC mobile phase modifier.
Influence of the concentration of ammonium acetate in the UHPLC mobile phase on signals of FMOC-derivatized AEG, BAMA, DAB, and BMAA. For each compound, the absolute area was normalized to the observed maximum (maximum set to 100%) across the tested conditions. Error bars represent standard deviations (n = 3).
Fig 5.
Chromatographic performance of the optimized method.
Extracted chromatograms obtained using the present FMOC derivatization–on-line pre-concentration and desalting–UHPLC-HRMS method, including derivatized BMAA and isomers in (a) method procedural blank, (b) blank surface water matrix, (c) blank surface water matrix spiked at 5 ng L-1 with the targeted analytes, and (d) blank surface water spiked at 200 ng L-1 with the internal standard.
Fig 6.
Assessment of filtration recovery.
Influence of filter type on analyte recovery (%) during the surface water pre-filtration step. The detailed procedure is highlighted in Section 2.5. Error bars represent standard deviations (n = 3).
Table 2.
Analytical method performance.
Summary of the analytical performance in surface water matrix, including method limits of detection (LOD, ng L-1) and limits of quantification (LOQ, ng L-1), linearity range (ng L-1) and associated determination coefficients (R2), and accuracy (%) and precision (RSD%) at the two tested spike levels (QC1: 75 ng L-1; QC2: 750 ng L-1).
Table 3.
Application to field samples—Lakes.
Concentration ranges (ng L-1) of AEG, BAMA, DAB, and BMAA in selected lake samples (n = 61) with HAB monitoring activities.
Table 4.
Application to field samples—Rivers.
Concentrations (ng L-1) of AEG, BAMA, DAB, and BMAA in background surface water samples (n = 21) collected in the St. Lawrence River watershed (QC, Canada).