Development of Isotope Dilution Cold Vapor Inductively Coupled Plasma Mass Spectrometry and Its Application to the Certification of Mercury in NIST Standard Reference Materials

Abstract

An isotope dilution cold vapor inductively coupled plasma mass spectrometry (ID-CV-ICPMS) method featuring gaseous introduction of mercury via tin chloride reduction has been developed and applied to the quantification and certification of mercury in various NIST standard reference materials: SRM 966 Toxic Metals in Bovine Blood (30 ng x mL(-1)); SRM 1641d Mercury in Water (1.6 microg x mL(-1)); and SRM 1946 Lake Superior Fish Tissue (436 ng x g(-1)). Complementary mercury data were generated for SRMs and NIST quality control standards using cold vapor atomic absorption spectroscopy (CVAAS). Certification results for the determination of mercury in SRM 1641d using two independent methods (ID-CV-ICPMS and CVAAS) showed a degree of agreement of 0.3% between the methods. Gaseous introduction of mercury into the ICPMS resulted in a single isotope sensitivity of 2 x 10(6) counts x s(-1)/ng x g(-1) for 201Hg and significantly reduced the memory and washout effects traditionally encountered in solution nebulization ICPMS. Figures of merit for isotope ratio accuracy and precision were evaluated at dwell times of 10, 20, 40, 80, and 160 ms using SRM 3133 Mercury Spectrometric Solution. The optimum dwell time of 80 ms yielded a measured 201Hg/202Hg isotope ratio within 0.13% of the theoretical natural value and a measurement precision of 0.34%, on the basis of three replicate injections of SRM 3133.

Certification of NIST Standard Reference Material 1575a pine needles and results of an international laboratory comparison

“…This CV-IDMS method has been described in detail elsewhere (Christopher, et al, 2001) and a brief description is included here. The Hg vapor was generated using a 10% (mass/volume) SnCl 2 in 7% (volume fraction) HCl reductant, and separated from the liquid phase using a commercially available reaction separator cell.…”

Assessment of chronic mercury exposure within the U.S. population, National Health and Nutrition Examination Survey, 1999–2006

“…Many sources of variation exist in the measurement of inorganic mercury including temperature, storage time, and experimental error (Christopher et al 2001;Bornhorst et al 2005). As storage time increases before measurement, so does sample variation around the mean.…”

Comparison of Mercury Burdens in Chronically Debilitated and Healthy Loggerhead Sea Turtles (Caretta Caretta)

“…Total Hg concentration (based on wet mass) in blood and scutes was determined using isotope dilution cold vapor inductively coupled plasma mass spectrometry at the National Institute of Standards and Technology (Hollings Marine Laboratory, Charleston, South Carolina, USA) using methods described in detail elsewhere (Christopher et al, 2001). Samples were prepared in quartz vessels using microwave-assisted acid digestion (Perkin-Elmer Multiwave, Shelton, Connecticut, USA) and analyzed on a Plasma Quad 3 ICPMS (VG Elemental, Winsford, UK).…”