New quantitative approach in trace elemental analysis of single fluid inclusions: Applications of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS)

Laser ablation inductively coupled plasma mass spectrometry has been used for the in situ elemental analysis of individual fluid inclusions with artificially prepared fluid inclusions as external standards. Artificial fluid inclusions standards were prepared by drawing a standard solution of known composition into microcapillary tubes. An ICP-MS equipped with an Nd:YAG laser operating in the UV region (266 nm) was used for data acquisition. The laser was focused and fired on 25-30 μm spots on the microcapillary tubes until the fluid was reached, The content of the microcapillary tube then emptied and was transported with argon to the torch. The average volume of fluid released, per pulse of laser, was approximately 100) pl. Calibration curves were created by plotting signal intensity versus concentration. The long-term precision (RSD%) of measurements for Sr were 1.1-3.1% for a 1000 ppm solution, 2.7-4.9% for a 500 ppm solution and 3.1% for a 250 ppm solution. Similar measurements on the same solutions for Rb gave values of 1.9-2.3% for a 1000 ppm solution, 5.1-6.3% for a 500 ppm solution and 1.7% for a 250 ppm solution. The technique was tested on fluid inclusions in halite from the Palo Duro Basin, Texas, USA. The results show that concentrations for Sr range from 90 to 153 ppm, and for Rb from 98 to 100 ppm. The precision of analysis for individual natural fluid inclusions ranges from 5 to 31% for both Sr and Rb. The concentration of Sr calculated by this method is in agreement with earlier work.