Ion-pair in-tube solid phase microextraction for the simultaneous determination of phthalates and their degradation...

An in-tube solid phase microextraction, coupled with high-performance liquid chromatography with diode array detection (IT-SPME-HPLC-DAD) method, has been developed for the simultaneous determination of 13 diesters (from dimethyl to dioctylphthalate plus diisobutyl, benzylbutyl, di-2-ethylhexyl, diisononyl and diisodecylphthalate) and 2 monoesters of phthalic acid (mono-butyl and mono-(2-ethylhexyl) phthalate) in particulate matter (PM₁₀). Triethylamine at pH=3 was used as an ion-pair reagent with a double function, of regulating the chromatographic retention of the monoesters and the most hydrophilic diesters on a monolithic silica column, and of improving their extraction on a porous polymer with divinylbenzene-4-vinylpyridine capillary. The chromatographic separation was achieved in 13min. A previous ultrasound-assisted extraction from PM₁₀filters was also optimized using methanol as solvent. The method detection limits were 0.09-0.52ngm^-3, the inter-day precision at concentration of 20ngmL^-1 was between 4.2% and 12.7% (n=15), and the average recovery was 87.3%. The average absolute IT-SPME recovery was 26.2% and the linear range reached up to 109ngm^-3 for most analytes. The method was applied to PM₁₀ samples from different environments collected in Galicia (Spain). DiBP was the major phthalate, followed by its isomer DnBP in urban sites and by DEP in the suburban area. In all samples, DEHP quantified correlates with the isomers of dibutylphthalate. Total PAE concentration was between 14.5 and 245.5ngm^-3. To the best of our knowledge, this is the first time that a method allows the simultaneous determination of 13 phthalates and their degradation products in particulate matter.