High precision measurements of gallium isotopic compositions in geological materials by MC-ICP-MS

• Published in: Journal of analytical atomic spectrometry Vol. 31; no. 8; pp. 1673 - 1679
• Main Authors: Zhang, Ting, Zhou, Lian, Yang, Lu, Wang, Qian, Feng, Lan-ping, Liu, Yong-sheng
• Format: Journal Article
• Language: English
• Published: 01.01.2016
• Subjects: Blanks; Gallium; Geology; Ion exchange; Mathematical analysis; Reference materials; Rhyolite
• ISSN: 0267-9477; 1364-5544
• DOI: 10.1039/c6ja00202a

An analytical protocol for the accurate and precise determination of the gallium isotope ratio in geological materials is presented for the first time by using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). Separation of Ga from natural sample matrices was achieved by using a three-column ion-exchange chromatograph with one anion exchange AG MP-1M column and two cation exchange AG 50W-X8 columns. This approach provides an efficient purification with a low blank and high yield of Ga from an excess amount of Fe existing in geological samples. The instrument mass bias was monitored and corrected by using a model of standard-sample bracketing with internal normalization, and copper was used as an internal standard which was added to both the sample and standard solutions. The long-term external reproducibility of δ 71/69 Ga obtained is 0.04‰ (2SD). Ga isotopic compositions of geological reference materials including basalt, andesite, rhyolite, granodiorite, soil, sediment, carbonatite and shale were measured using the proposed approach. The 71 Ga/ 69 Ga ratio in these geological reference materials spanned over a rather narrow range between 0.74‰ and 0.90‰, relative to NIST SRM 994. A new MC-ICP-MS approach is reported for highly precise and accurate determination of the Ga isotope ratio in geological samples.