1 PROCEEDINGS PIT IAGI LOMBOK 2010 THE 39 TH IAGI Annual Convention and Exhibition Metode ICP-MS untuk Studi Rare Earth Elements Batuan Beku di Daerah Kab. Kulonprogo dan Sekitarnya (Elements Study of Igneous and Altered Rocks in Kulonprogo and Its Surrounding Using ICP-MS) Ronaldo Irzon dan Sam Permanadewi Techical Instruments Division, Centre of Geology Survey, Ministry of Mineral Resources Jl. Diponegoro No. 57 Bandung Keywords: instrument, accuracy, geo-science ABSRACT Instrumentation has recently become a very important tool in geo-science development to provide accurate, quick, precise and wide range of data will facilitate geologists to make further decision even conclusion on their research. Output data would be meaningless whenever it can’t optimally be explained. Thus, the collaboration between instruments and geologists in taking and selecting samples, defining proper instrument, exact preparation and running method, as well as data processing are urgently needed. ICP-MS is a relatively new instrument and rapidly developed in analyzing trace and rare earth elements which provides a very low detection limit (as low as part per trillion), good precision, good accuracy, and can test such a lot of elements in one very few sample in only less than four minute. ICP-MS method has also been developed on isotopes in solid and liquid samples. In 2008, the Centre of Geology Survey set a working plan and the standard of the Technical Devices Management Activities, which is in charge of the Laboratory Execution Activities. This activity was aimed at optimalizing the performance of the ICP-MS for igneous and altered rocks, in the appropriation of the preparation as well as in the instrumentation setting. On Field work we use the Geology Map of Kulonprogo Area and Its Surrounding on scale system 1: 100,000 by Centre of Geology Survey Bandung (Raharjo et all, 1995). The samples chosen in this activity were taken from Kebobutak Formation (Tmok), Sentolo Formation (Tmps), Andesit Unit (a) and some from Dasit Unit (d) and Alluvium (Qa). The sampling and the geological observation was done by random sampling. The first step in carrying-out the sample for laboratory works is selecting samples which are represent each Formation after taking the field description on their position and site conditions. The Samples were then crushed, washed, dried and homogenized in the Centre of Geology Survey’s laboratory. The grinding step shall be able to produce a good sample size by minimalizing dust and or unknown element then carried a good homogenization. Chemical preparation starts on weighing samples before destruction step by Acids. Samples than diluted to appropriate condition before analyst using ICP-MS. Data shows that three samples need three times of destruction and only one sample turn reddish after dilution. It is important to make standard solutions for calibration curve which each element are needed. Before running a program, ICP-MS is should be preconditioned to make sure there will be at low at possible back-ground on the program. ICP-MS only need 3-4 minutes to test one sample for >60 elements/isotopes in normal condition. All elements analyze gain > 0.9995 of correlation curve. This work also used three Standard Reference Materials (AGV2 and GBWs) to cross-check the result, it shows that all elements output are close (<20%) from the SRM’s certificates. Each sample taken three times to be analyst and %RSDs are very low (the highest is Sm in RO 64=18.11%) that inform about good stability of the instrument. This results than normalized with Sun and McDonough value for Primitive Mantel, before then transferred to spider