MMI-M ANALYSIS AT SGS PERTH

INTRODUCTION
SGS Minerals Services is a world leader in trace geochemical analysis and has over ten years experience in the analysis of Mobile Metal Ion (MMI) solutions. The recent acquisition of MMI technology will result in all samples currently received in Australia being sent to the new state-of-the-art SGS Perth facility. SGS Minerals Services is constantly striving to improve both the quality of MMI analysis and the sample processing time, through new technologies and increased instrumentation at its laboratories. This document will explain the high level of quality control SGS Minerals Services employs in the analysis of MMI samples for both existing and new clients.

Multi-element MMI (MMI-M) is a pH neutral extraction that aids in the identification of polymetallic targets and multi-element associations for specific styles of mineralization. MMI-M analysis involves a weak partial extraction of the sample followed by automated analysis using Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

DETECTION LIMITS
Detection limits are based on both the instrument capability and the reproducibility of individual elements. They range from sub-ppb levels (e.g. Au) to ppm levels for major component elements (e.g. Al, Mg and Fe). The table below shows a comparison of detection limits between SGS Perth and ALS-Chemex Perth. For most elements, there is not a significant difference between the two laboratories in terms of data interpretation for anomalies. New instrumentation recently purchased for the Perth facility will achieve or improve on the ALS detection limits where appropriate (e.g. Cr).

INTER-LABORATORY COMPARISON OF RESULTS
A reference standard (MMI-SRM16) was analyzed by both laboratories and the results are shown below. Good agreement was achieved for the elements. Results are based on the mean of twenty analyses.

STANDARD REPEATABILITY
Standard reference materials and method blanks are analyzed with every batch of 46 samples to ensure digestion and analysis are in control. The chart shown below is for silver analysis with a mean result of 19ppb (expected value 19ppb), and 8%R.S.D. showing good repeatability over time for the SGS Perth laboratory.

PRECISION OF DUPLICATE ANALYSIS
Duplicate results are analyzed at a frequency of one every 12 samples. At right is the precision graph for copper, based on 129 duplicate pairs, with r2 = 0.9994. Computed precision is 7% at 500ppb Cu and <5% at concentrations of greater than 2500ppb Cu. This shows excellent repeatability achieved by SGS Perth for the MMI-M analysis.