Standard and Reference has a long-term and ongoing commitment to
research and development, which leads to unique and quantifiable
steps in method development.
The following methods reflect our commitment to classical methods
over less accurate instrumental methods at high concentrations.
The techniques developed at Standard and Reference,
are complimented by those developed and refined at other laboratories
within the Inspectorate group.
Silver - Concentrates
Samples are assayed by fire assaying with a gravimetric finish.
If the sample contains Gold, the Silver is dissolved, the Gold quantified
and subtracted from the total.
The extra steps taken on concentrates samples are:
Silver corrections - if the sample is
parted, the resultant Gold is dissolved and any retained silver
quantified to add to the silver result.
Slag and cupel corrections - for samples with relatively high silver
content (>1000g/T) the assay slag and cupel is refired, and the
recovered silver is added to the initial result.
Cupel recoveries - Silver retained in the cupel is recovered, quantified,
and added to the main portion of Silver.
For high Silver levels
this is done in addition to the slag and primary cupel recoveries
i.e the process involves recovery of Silver from two cupels.
Gold – Concentrates
Samples are assayed by fire assaying with a gravimetric finish.
Extra corrections to improve precision and accuracy include:
Slag and cupel corrections – the assay slag and cupel are
refired, and the Gold content quantified by AAS to correct the Gold result
Silver corrections – the solid gold retrieved from the initial
fire assay process is dissolved and any contained silver is quantified
by AAS to remove any errors from the Gold result
These corrections are carried out on all Gold party assays.
Gold – Lower Levels
Samples are assayed by fire assaying.
For Gold levels greater than 2g/T the resultant prill is parted
and the Gold quantified gravimetrically to 0.1micrograms.
For levels less than 2g/T the entire resultant prill is dissolved
and the gold quantified by AAS.
Copper - Concentrates
Short Iodide Titration
The sample is digested and titrated with sodium thiosulfate.
Electro-Gravimetric
The sample is digested and the Copper plated out onto platinum electrodes.
The resultant Copper is quantified gravimetrically.
Copper – Lower Levels
AAS Analysis
The sample is digested and quantified by AAS.This method can be
combined with other AAS-readable elements.
Lead
The sample is digested and the lead precipitated, removed from impurities
and redissolved before titrating
with Ethylene Diamine Tetraacetic
Acid (EDTA).
Zinc
The sample is digested and the impurities removed before titrating
the zinc with EDTA.
The separated impurities are redissolved and the zinc content quantified
by AAS to improve the accuracy.
The entire process takes at least 3 days.
Nickel
The sample is digested and the nickel is precipitated with Dimethyl
Glyoxime (DMG).
The precipitate is filtered and quantified gravimetrically.
As an extra step, the precipitate can be redissolved
and precipitated to remove any possible copper precipitate that could cause an erroneously
high result.
Other Elements
When extra elements are required, other suitable methods are available.
These other methods include:
· Platinum / Palladium
– via fire assay, graphite furnace (ETA)
· Sulphur – gravimetric
precipitation analysis
· Aluminium – sodium
hydroxide fusion
· Chloride – potentiometric
or ion selective electrode
· Fluoride – ion
selective electrode
· Mercury – hydride
generation
· Magnesium – gravimetric
or titration
· Iron – dichromate
titration
Other Metals – various digests
and dilutions to suit your requirements.
In addition to the specialised
assays listed here, we also offer mainstream geochemical analytical
methods.