Florin Analytical Services
 Established 1999, Assaying and Process Testing
Platinum and Palladium

Florin Analytical ServicesThe Determination of Platinum and Palladium by Inductively Coupled Plasma Optical Emission Spectrometry

Information Circular: PGM2001
Date: January 2001

Platinum and Palladium Analysis

This information circular describes the general procedure utilized by Florin Analytical Services LLC (FAS) for assaying platinum and palladium in ores, concentrates and industrial products.

Fire assaying is the preferred method for the separation of platinum and palladium from gangue minerals and pre-concentration of the precious metals prior to analysis by instrumental techniques.

Assay Procedure

FAS utilizes fire assay lead pre-concentration methods prior to analysis for platinum and palladium by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES).

Fusion Process
A known sample weight (typically 30 grams) of pulverized geological material is thoroughly mixed with flux. The flux consists of a mixture of litharge (PbO), soda ash (Na2CO3), borax (Na2B4O7), silica (SiO2), flour and silver (Ag or possibly Au inquart). The mixture of flux and sample is placed into a fire-clay crucible that is then loaded into a furnace set at 1050°C and allowed to fuse for 45 minutes. During the fusion process, the litharge is reduced to metallic lead by the flour and the lead collects the precious metals.

Cupellation Process
When the fusion is complete, the crucible is removed from the furnace and the molten fusion product is poured into a conical mold. The lead, with the precious metals collected, drops to the bottom of the mold and is allowed to cool. After cooling, the lead button is removed from the mold and any slag is knocked off utilizing a hammer. The lead button is then placed into a pre-heated cupel in a muffle furnace set at 950°C. The cupellation process, in which lead is converted to lead oxide that is absorbed into the cupel leaving a dore bead of precious metals, takes between 30 and 40 minutes. The cupel is removed from the furnace and allowed to cool slowly to room temperature. Any discolorations or sprouting of the bead found after cooling is noted in the assay worksheets.

Digestion
The dore bead is removed from the cupel and quantitatively digested with nitric acid followed by aqua-regia. The resulting solution is analyzed for Pt and Pd by ICP-OES.

Solution Analysis
FAS utilizes a Perkin-Elmer Optima 3000 ICP-OES as the primary instrument for analyzing platinum and palladium in solutions obtained following the fire assay process. This instrument is routinely checked (internally) utilizing a Flame Atomic Absorption Spectrometer (FAAS) and externally by an Inductively Coupled Plasma Mass Spectrometer (ICP-MS).

The fire assay pre-concentration procedure followed by ICP-OES is affected by a minimal amount of spectral interferences. By utilizing ICP-OES, these interferences can easily be visualized and eliminated.

Comments

The fire assay lead collection technique utilized by FAS is an excellent method for the quantitative analysis of platinum and palladium. Blanks and commercial standards are run with each job to monitor for the presence of platinum and palladium. Metal spikes are also introduced on a regular basis to confirm precious metal recovery. Spectral interferences are examined closely on each run and a multi-line spectral analysis is conducted for each element in order that any significant interferences are identified and taken into account.

FAS routinely assays samples for platinum and palladium in duplicate (high grade samples in triplicate) and reports the results of each separately. Slag and cupel material are routinely assayed to confirm the quantitative collection of the platinum and palladium values. FAS has spent a considerable amount of resources in developing its ICP-OES technique. FAS has participated in several round-robins with other groups utilizing similar and differing finishing techniques. These comparisons were utilized in the development of the method and are now utilized as part of on-going QC and QA protocols.