Vacuum-assisted evaporative concentration combined with LC-HRMS/MS for ultra-trace-level screening of organic micropollutants in environmental water samples

Abstract

Vacuum-assisted evaporative concentration (VEC) was successfully applied and validated for the enrichment of 590 organic substances from river water and wastewater. Different volumes of water samples (6 mL wastewater influent, 15 mL wastewater effluent, and 60 mL river water) were evaporated to 0.3 mL and finally adjusted to 0.4 mL. 0.1 mL of the concentrate were injected into a polar reversed-phase C18 liquid chromatography column coupled with electrospray ionization to high-resolution tandem mass spectrometry. Analyte recoveries were determined for VEC and compared against a mixed-bed multilayer solid-phase extraction (SPE). Both approaches performed equally well (≥ 70% recovery) for a vast number of analytes ( n = 327), whereas certain substances were especially amenable to enrichment by either SPE (e.g., 4-chlorobenzophenone, log D ow,pH7 4) or VEC (e.g., TRIS, log D ow,pH7 − 4.6). Overall, VEC was more suitable for the enrichment of polar analytes, albeit considerable signal suppression (up to 74% in river water) was observed for the VEC-enriched sample matrix. Nevertheless, VEC allowed for accurate and precise quantification down to the sub-nanogram per liter level and required no more than 60 mL of the sample, as demonstrated by its application to several environmental water matrices. By contrast, SPE is typically constrained by high sample volumes ranging from 100 mL (wastewater influent) to 1000 mL (river water). The developed VEC workflow not only requires low labor cost and minimum supervision but is also a rapid, convenient, and environmentally safe alternative to SPE and highly suitable for target and non-target analysis. Electronic supplementary material The online version of this article (10.1007/s00216-019-01696-3) contains supplementary material, which is available to authorized users.

New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMS

“…To avoid the loss of very polar compounds during enrichment, the samples were concentrated via vacuum-assisted evaporative concentration using the Syncore® Analyst (BÜCHI, Switzerland) with slight modifications to the method validated by Mechelke et al (2019): 60 mL sample volume was filled into BÜCHI glass vials (0.3 mL appendix volume), spiked with 224 isotope labelled internal standards (ILIS) and evaporated at 20 mbar and 45 °C to 1-5 mL using the back-flush unit. The BÜCHI glass vials were rinsed with 1.5 mL H2O/methanol mix (85:15) to reduce analyte losses by sorption on the glass surface.…”

Passive sampling of organic contaminants across the water-sediment interface of an urban stream

“…4, pattern 2). Compounds following this pattern were reviewed for retention time plausibility using the linear relationship (r 2 =0.67) between predicted logDOW (at mobile phase pH 3) and STD retention times (n=590) from literature for the same liquid chromatographic system (predicted retention time = (predicted logDOW,pH3 + 5.4) × 0.42 -1 min) (Mechelke et al, 2019). In case of duplicates at different retention times, only the most intense compound was considered (resulting in n=802 TP suspects).…”

A simple field-based biodegradation test shows pH to be an inadequately controlled parameter in laboratory biodegradation testing

“…Internal standard peak areas for hydrochlorothiazide were extremely low and inconsistent (average absolute yield of 2.0%), while evaporation enhanced baseline noise for methotrexate-D3 sufficiently such that no internal standard peak was visible. Mechelke et al 15 also reported a relatively low yield of 16.6% for hydrochlorothiazide in a surface water matrix.…”

“…The 20 mL samples were transferred to glass vials with 0.3 mL residual volume before they were spiked with 10 mL of an internal standard mixture (2.5 ng of each isotope-labeled standard in methanol). Concentration followed the method of Mechelke et al, 15 reducing samples to less than 0.5 mL under 20 mbar, 200 orbital revolutions per minute, and a slightly modi-ed temperature of 60 C over approximately 4 to 5 hours. The sides of the vials were washed down rst twice with 0.75 mL methanol, and then with 1 mL Milli-Q water when the evaporation neared completion.…”

“…The limit of detection (LOD) and limit of quantication (LOQ) were calculated as described in Mechelke et al 15 with minor modications (Table S2 †). The LOD and LOQ in Milli-Q water were identied as the lowest standard concentration for which the signal-to-noise ratio was greater than 3 : 1 and 10 : 1 respectively, and that produced a chromatographic peak containing at least three data points.…”