Technical Note: Stable Chloride Measurements at CAMS

Abstract. We present a new method for preparing silicate samples for stable chloride analysis using the low-energy injection components of an accelerator mass spectrometry (AMS) system. This method uses Nb over AgBr as a bulking agent during sample preparation which drastically reduces background Cl signals (ion source memory) by a factor of ~100 and allows for faster, cheaper, and more precise analyses on low-Cl samples (<10 μg Cl). We demonstrate this approach with measurements of stable chlorine isotope ratios (³⁵Cl/³⁷Cl) performed on silicates, prepared in both AgBr and Nb matrices, that characterize chlorine concentrations of samples containing ~1–500 ppm Cl. While this method was developed primarily to interrogate silicates, it performs equally well on other commonly analyzed sample matrices including carbonates and water. This Nb-based method is now the standard procedure at the Center for Accelerator Mass Spectrometry (CAMS) for preparing all stable Cl targets, including those accompanying ³⁶Cl analyses.