On-line in-tube solid phase microextraction-capillary liquid chromatography method for monitoring degradation products of di-(2-ethylhexyl) phthalate in waters

• DEHP and their main degradation products were analyzed.
• The whole sample is processed on-line in less than 30 min.
• Capillary LC coupled to in-tube solid phase microextraction is employed for analysis.
• For MEHP estimation it is crucial acidifying the sample at pH = 3.

The main di-(2-ethylhexyl) phthalate (DEHP) degradation products, (2-ethylhexyl) phthalate (MEHP), diethyl phthalate (DEP) and dibutyl phthalate (DBP), have been tested. The proposed cost-effective method combines on-line, in-tube solid-phase micro extraction (IT-SPME) in in-valve configuration and capillary liquid chromatography with UV diode array detection (Cap-LC-DAD). Acidification of the samples at pH 3 improved markedly the estimation of MEHP. Aliquots of 4 mL of acidified water samples were directly processed. After sample loading, the analytes were desorbed with the mobile-phase and transferred to the monolithic capillary column. Satisfactory linearity and precision, absence of matrix effect and suitable limits of detection (LODs): 0.005, 0.1, 0.1 and 1.5 μg/L for MEHP, DEP, DEHP and DBP, respectively have been achieved. The main advantages are speed and the reduction of background signal by minimizing sample preparation. Real water samples have been analyzed.