Chlorine Isotope Analysis of Submicromole Organochlorine Samples by Sealed Tube Combustion and Thermal Ionization Mass Spectrometry.

Improved sensitivity in the analysis of stable chlorine isotopes of organochlorines (δ37Cl-OCl) has been established using sealed tube combustion in conjunction with thermal ionization mass spectrometry (TIMS). TIMS of chlorine isotopes was performed on < 85 nmol of Cl with an achievable precision of < 0.25‰ for pure inorganic chloride samples and 0.46‰ for chloride liberated from organochlorines (OCls). This makes possible significant reductions in the overall sample size requirement, as compared to the techniques of gas source stable isotope ratio mass spectrometry (SIRMS). Yields in excess of 99% were demonstrated in the dechlorination of <0.14 μmol 1,1, l- trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), and the overall yield, including purification of liberated chloride, was 86-97%. The accuracy of TIMS in the measurement of chlorine isotopes derived from OCls was con- finned by analysis of a DDT sample previously analyzed with SIRMS. Using the described method for TIMS, the DDT sample gave a bulk chlorine isotope ratio of δ37Cl -4.42 ± 0.46‰ (1σ). The reported value from SIRMS analysis is -4.34 ± 0.25‰ indicating the conformity of the two methods. [ABSTRACT FROM AUTHOR]