Assessment of stable carbon isotope 13 С/ 12 С ratio in phthalates from surface waters using HPLC-HRMS-TOF approach.

A method for estimating the ratio of stable carbon isotopes 13 С/ 12 С in the composition of phthalates from surface water at a trace concentration level is proposed. It is based on the concentration of hydrophobic components of water using an analytical reversed phase HPLC column followed by their gradient separation and detection of eluted phthalates using a high-resolution time-of-flight mass spectrometer (ESI-HRMS-TOF) in the form of molecular ions. The ratio of stable carbon isotopes 13 С/ 12 C in phthalates is calculated as a ratio of integrals under the monoisotopic [M+1+H] + and [M+H] + peaks. The Δ 13 C value is calculated relatively to the 13 C/ 12 C ratio in commercial DnBP and DEHP phthalates used as standards. The minimal concentration of DnBP and DEHP in water required for a reliable determination of Δ 13 C value is estimated by the level of ca. 0.2 μg L -1 . The technique has been verified during the monitoring of priority phthalates in the waters of Lake Baikal.