FIRE ASSAY

Determination of Gold and Platinum Group Metals (PGMs) by lead collection, ICP-OES finish.

 

PROCEDURE

 

•  Gold, platinum and palladium are collected by lead collection Fire Assay using silver as a co-collector to facilitate easier handling of prills as well as to minimise losses during the cupellation process.
•  A catch weight of sample is mixed with 200g of fire assay flux and spiked with silver.
•  The mixture is loaded into a furnace and left for at least 55 minutes.
•  The resulting melt is poured into moulds and left to solidify.
•  During cooling of the melt, a lead button settles to the bottom of the mould and is separated from the slag. 
•  The button is then cupelled for 60 minutes to remove the lead, leaving behind a prill, containing the silver, gold and PGMs of interest.
•  The prill is digested using Hydrochloric and Nitric acid and made up to a 5ml volume.
•  The resulting solutions are used for gold testing, platinum testing and palladium testing by the technique of ICP-OES (Inductively Coupled Plasma – Optical Emission Spectrometry).
 
Determination of Rhodium by lead collection is done using the same procedure as the silver prill collection, but substituting palladium in the place of the silver.

 

QUALITY CONTROL

 

The samples are handled in batches of up to 50, being the size of the furnace tray.

 

Each batch of 50 samples shall contain one blank sample, two QC samples and 2 duplicates. These duplicates are repeats of randomly chosen samples from the batch. Batches of less than 50 samples shall contain at least one duplicate, one QC sample and a blank.
 
Additional repeats may also be done upon evaluation of the results. These samples to be repeated shall be selected by looking for obvious outliers or chosen randomly by experienced chemists.
 
The value obtained for the QC sample/s shall be within specified control limits.
 

Determination of Platinum, Palladium, Rhodium, Iridium and Ruthenium by NiS collection, ICP-MS finish

 

PROCEDURE

 

•  PGMs in samples are collected in a single fusion step, using the nickel sulphide (NiS) fusion technique.
•  The NiS buttons are subjected to leaching, precipitation and filtration processes in order to separate the PGMs.
•  The PGMs are dissolved using aqua regia. The resulting solutions are analysed by ICP-MS (Inductively Coupled Plasma – Mass Spectrometry) to determine the concentrations of Pt, Pd, Rh, Ir and Ru contained in a sample.

 

QUALITY CONTROL

 

The samples are handled in batches up to 35. Each batch of 35 samples (or less) shall contain one blank sample, one QC sample and 1 duplicate. These duplicates are repeats of randomly chosen samples from the batch.
 
Additional repeats may also be done upon evaluation of the results. These samples to be repeated shall be selected by looking for obvious outliers or chosen randomly by experienced chemists.

 

The value obtained for the QC sample/s shall be within specified control limits.
 
 

ICP (INDUCTIVELY COUPLED PLASMA OPTICAL EMISSION SPECTROSCOPY)

 

ICP analysis is one of the most versatile methods of inorganic chemistry covering large ranges from ppm to percentage levels of most elements.

 

 Set Point Laboratories uses this technique to determine the concentration of metals and metalloids at trace, minor and major concentrations. A variety of digestions are offered with this technique such as Aqua Regia (partial dissolution ), four acid (total dissolution of most elements except for few such as Cr, V, Ti)  and Peroxide fusion ( which is suitable if the non-soluble elements of the four acid digestion are required).

 

ICP is used to analyse Fire Assay samples, i.e. Lead collection which is used to accurately determine Au, Pt,  Pd (and Rh if required) and Nickel Sulphide  collections which determines all PGE elements (6E) and  offers up to 42 multi elements scan package.
 
ICP-OES is usually done in conjunction with ICP-MS( Inductively Coupled Plasma Mass Spectroscopy) which is used to accurately determine lower detection limits, ppb levels

 

BASE METALS AND MULTI ELEMENTS

 

Depending on the testing requirements, XRF or ICP-OES / ICP-MS can be employed to offer a full range of testing services for base and multi elements.
 

URANIUM AND RARE EARTHS

Set Point Laboratories offers a range of earth analysis by XRF,ICP AND ICP-MS. We are accredited for U-analysis by XRF pressed pellet and are a certified member of NNR. 

 

 

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