title: Determination of cadmium in grains by isotope dilution ICP-MS and coprecipitation using sample constituents as carrier precipitants.
abstract: A coprecipitation method using sample constituents as carrier precipitants was developed that can remove molybdenum, which interferes with the determination of cadmium in grain samples via isotope dilution inductively coupled plasma mass spectrometry (ID-ICPMS). Samples were digested with HNO3, HF, and HClO4, and then purified 6 M sodium hydroxide solution was added to generate colloidal hydrolysis compounds, mainly magnesium hydroxide. Cadmium can be effectively separated from molybdenum because the cadmium forms hydroxides and adsorbs onto and/or is occluded in the colloid, while the molybdenum does not form hydroxides or adsorb onto the hydrolysis colloid. The colloid was separated by centrifugation and then dissolved with 0.2 M HNO3 solution to recover the cadmium. The recovery of Cd achieved using the coprecipitation was >97%, and the removal efficiency of Mo was approximately 99.9%. An extremely low procedural blank (below the detection limit of ICPMS) was achieved by purifying the 6 M sodium hydroxide solution via Mg coprecipitation using Mg(NO3)2 solution. The proposed method was applied to two certified reference materials (NIST SRM 1567a wheat flour and SRM 1568a rice flour) and CCQM-P64 soybean powder. Good analytical results with small uncertainties were obtained for all samples. This method is simple and reliable for the determination of Cd in grain samples by ID-ICPMS.
authors.affiliation: Environmental Standards Section, National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology, Tsukuba central 3-10, Umezono 1-1-1, Tsukuba, Ibaraki 305-8563, Japan. k-inagaki@aist.go.jp
authors.forename: Kazumi
authors.initials: K
authors.lastname: Inagaki
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Narukawa
authors.forename: Takashi
authors.initials: T
authors.lastname: Yarita
authors.forename: Akiko
authors.initials: A
authors.lastname: Takatsu
authors.forename: Kensaku
authors.initials: K
authors.lastname: Okamoto
authors.forename: Koichi
authors.initials: K
authors.lastname: Chiba
mesh_terms: D002104:Cadmium / Q000032:analysis*; D011232:Chemical Precipitation; D002523:Edible Grain / Q000737:chemistry*; D007201:Indicator Dilution Techniques; D007553:Isotope Labeling; D008274:Magnesium / Q000737:chemistry; D017616:Magnesium Compounds / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D008982:Molybdenum / Q000032:analysis; D009566:Nitrates / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012972:Sodium Hydroxide / Q000737:chemistry
chemical_list: D017616:Magnesium Compounds; D009566:Nitrates; D002104:Cadmium; D012972:Sodium Hydroxide; C018330:magnesium nitrate; D008982:Molybdenum; D008274:Magnesium