On-line technique for the determination of the [[delta].sup.37]Cl of inorganic and total organic Cl in environmental samples

Here we describe an on-line method for measuring b37CI values of chloride bearing salts, waters, and organic materials using multicollector continuous-flow isotope ratio mass spectrometry (CF-IRMS). Pure AgCl quantitatively derived from total Cl in water, inorganic Cl salts, and biological samples was reacted with iodomethane in evacuated 10-mL stopper sealed glass vials to produce methyl chloride gas. A GV Instruments Multicollector CF-IRMS with C[H.sub.3]Cl optimized collector geometry was modified to accommodate a headspace single-sample gas injection port prior to a GC column. The GC column was a 2-m Porapak-Q packed column held at 160[degrees]C. The resolved sample C[H.sub.3]Cl was introduced to the IRMS source in a helium stream via an open split. [[delta].sup.37]Cl values were calculated by measurement of C[H.sub.3]Cl at m/z 52/50 and by comparison to a reference pulse of C[H.sub.3]Cl calibrated to standard mean ocean chloride. Sample C[H.sub.3]Cl analysis time was ~6 min. Injections of 40 [micro]L of pure C[H.sub.3]Cl gas yielded a repeatability ([+ or -] SD) of [+ or -] 0.06 [per thousand] for [[delta].sup.37]Cl (n = 10). Combined GC and IRMS source linearity for C[H.sub.3]Cl was