RESUMO
A chromatographic method using ultra performance LC with ultraviolet spectrophotometry detection system (UPLC-UV-visible (UV/Vis)) (UPLC, ultra performance LC) was developed to determine Chimassorb 944 and Tinuvin 770, high- and low-molecular mass hindered amine light stabilizers, respectively. The use of a bridge ethylene hybrid-based particles C(18) UPLC column, being compatible with a buffered mobile phase adjusted to pH 11.5, was used to achieve a satisfactory elution of possible non-ionizated units of polymeric Chimassorb 944. In addition, a HPLC with positive ion mode ESI and hybrid linear ion trap (LTQ) Fourier transform (FT) Orbitrap MS detection system (HPLC-UV/Vis-ESI-LTQ(FT)Orbitrap) was used for screening and identification purposes. Reliable determinations of monomeric units of Chimassorb 944 and molecule of Tinuvin 770 were achieved by HPLC-ESI(+)-LTQ FT Orbitrap MS method using scan mode. Quality parameters of UPLC-UV/Vis method were evaluated. Obtained LODs and LOQs were 3.41 and 11.4 mg/L for Tinuvin 770 and 0.83 and 2.78 mg/L for Chimassorb 944, respectively. Satisfactory quality parameters of this chromatography method provided the chance to count on a good tool to know the compliance with legal requirements.
RESUMO
In this work, a novel, fast, and sensitive method was developed for perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) and PFOS precursor's determination in seawater. The proposed method consists in a vortex-assisted liquid-liquid microextraction (VALLME) combined with liquid chromatography (LC) and LTQ-Orbitrap high resolution mass spectrometry (LTQ-Orbitrap HRMS) determination. Several parameters affecting both the HPLC-LTQ Orbitrap HRMS determination and the VALLME were studied, with special attention to blank contamination problem. The use of LTQ-Orbitrap-HRMS in full mode, quantifying the target analytes using the exact mass, provides a very powerful detection in terms of sensitivity and specificity maintaining all the information provided by the full mass spectra, allowing, also, the identification of non-target substances. The use of matrix-matched calibration, together with labelled surrogate standards, minimize matrix effects and compensate potential recovery losses, resulting in recoveries between 95 and 105%, with excellent sensitivity (quantitation limit between 0.7 and 6â¯ngâ¯L-1) and precision (4-10%). The proposed method requires only 35â¯mL of sample and 100⯵L of extracting solvent, is fast and avoids the use of other solvents to obtain the dispersive cloudy solution, simplifying the procedure and improving the existing procedures for the determination of per- and polyfluoroalkyl substances (PFASs) in seawater in terms of green analytical chemistry. The method was successfully validated by participating in a proficiency test assay provided by the National Measurement Institute of the Australian Government for the determination of PFOA, total PFOS and linear PFOS in waters. A revision of the state of the art in the last twelve years of methods for the analysis of PFASs in seawater and other types of water was performed, and a critical comparison between the developed method and the previously published was included. Finally, the method was applied to the analysis of samples from Ría de Vigo, a sensitive and semiconfined coastal area located in the northwest of Spain. PFOS, N-methyl perfluorooctanesulfonamide (n-MeFOSA) and N-ethyl perfluorooctanesulfonamide (n-EtFOSA) were detected in samples at levels lower than the maximum allowable concentration (MAC) established by Directive 2013/39/EU, but above the annual average (AA) levels.