RESUMO
A semi-automated and sensitive method was developed for simultaneous determination of the six most consumed artificial sweeteners (AS) in surface waters using thin-film solid-phase microextraction (TF-SPME) and high-performance liquid chromatography (HPLC). A triple quadrupole mass spectrometer and an electrospray ionization source (ESI-MS) run in negative ionization and multiple reaction monitoring modes were employed for instrumental analysis. The TF-SPME method was optimized for the extraction phase, sample pH, desorption solvent, extraction time, and desorption time. In-house-synthetized-hydrophilic-lipophilic balance weak anion exchange (HLB-WAX) particles imbedded within a polyacrylonitrile (PAN) binder were selected as the extraction phase for the thin-film coating due to their cost-effectiveness and enhanced sensitivity for artificial sweeteners. Suitable analytical parameters that include linearity (R2 > 0.9914), recovery > 80%, inter, and intra-reproducibility less than 18% were obtained for the AS compounds studied. The developed method estimated limits of detection (LODs) ranging from 0.004 to 0.038 ng mL-1 The SPME method was successfully applied for the determination of ultra-trace levels of AS in water samples collected from Grand River (Ontario, Canada), downstream of three municipal wastewater treatment plants (WWTPs). Concentrations ranging from 0.03 to 20.3 ng mL-1 were found for the AS compounds studied.
RESUMO
A novel strategy for the analysis of 20 organochlorine pesticides (OCPs) monitoring in marine surface waters through ethylenevinyl acetate (EVA) passive samplers was developed and validated. The approach is based on the coupled of ultrasound-assisted solvent extraction (UASE) and headspace solid-phase microextraction (HS-SPME) as extraction method for OCPs from EVA samplers. The UASE-HS-SPME method was optimized with a 27-4 Plackett-Burman design, while the significant factors (salting out, temperature and extraction time) were optimized using a central composite design (CCD) combined with desirability function (DF). The OCPs detection was performed using multiple reaction monitoring (MRM) by gas chromatography-tandem mass spectrometry (GC-MS/MS). The optimum experimental conditions comprised: salting out: 23% wv-1 NaCl, temperature: 75°C and extraction time: 55 min. The optimized method was validated in terms of linearity (R2>0.9946), recovery (>61%) and inter-day and intra-day reproducibility (<19%) for 20 OCPs studied. The limits of detection (LODs) were ranging from 0.01 ng for α-hexachlorocyclohexane and 0.27 ng for endrin aldehyde. Finally, the methodology was tested in marine surface seawater of Southern Chile using EVA samplers, where twelve OCPs were detected at ultra-trace levels (ngL-1).