Fire-Assay and ICP (Inductively Coupled Plasma) analysis is a widely accepted method in the Precious Metals industry. It is a common practice for all Precious Metals collecting and refining companies to credit only 80% upon preliminary XRF results and credit full value upon ICP results. These two combined methods are taking advantage of the Fire Assay’s full Precious Metal collection technique and ICPs simultaneous trace elemental analysis.
Why ICP analysis?
- Higher accuracy than XRF
- Trusted method in the industry
- Analyzing both major and traces elements simultaneously.
Fire Assay is one of the oldest refining and analytical techniques for Precious Metals in the world. Even though modern instrumentation and machinery improved the time requirements, analysis performance, and reproducibility, the basic method remains the same. Powders are mixed with specific fluxes (according to the material's unique properties) together with a metallic collector (usually Pb) and then fused. During fusion, the fluxes and metal wash all metallics out of the powder and leave two separate parts of (A) a metallic “button” which contains all metals in the sample, and (B) a slag which contains all other remaining elements. The button is then dissolved in acid and analyzed by spectrometers.
ICP is an emission spectrometry method that identifies each element by its unique wavelength characteristic. The acidic dissolved samples, like the buttons produced from the fire assay fusion, are charged in the high-temperature plasma (approx. 7000 K). The emissions signals are received by a camera that collects and focuses the spectrum onto the Charge Injection Device (CID) detector. The software then matches the received spectrum and compares the wavelength of each element producing a final result.
ICP-OES or ICP-AES
ICP-OES (Optical Emission Spectroscopy) or ICP-AES (Atomic Emission Spectroscopy) both represent the same technique
It is a technique that uses plasma as a source and relies on optical emission for analysis.
It has become the leading technology for routine analysis of liquid samples as well as materials that can be easily turned into a liquid form by dissolution or digestion.
ICP-MS (Mass Spectrometry) has a very low detection limit (ppt) comparing to the OES detection limit (ppb)
That's why it is most commonly used for other trace analysis (environmental analysis) and not Precious Metals determination.
The main reason is that in such concentrations, usually Precious Metals are not recoverable.
the Difference of ICP Analysis comparing to XRF and AAS
ICP is the method of choice when you want to measure multiple elements.
The ICP-OES principle uses the fact that atoms and ions can absorb energy to move electrons from the ground state to an excited state.
It is known and used for its ability to detect metals and several non-metals in liquid samples at very low concentrations. It can detect different isotopes of the same element, which makes it a versatile tool in Isotopic labeling.
X-ray Spectrometers have gradually increased their effectiveness over the past decade, introducing new hardware and most importantly software analytics.
However, the XRF results depend to a great extent on the sample preparation and especially on the sample particle size and homogeneity, as it analyzes only a small part of the sample’s surface. During sample preparation or pellet pressing, element segregation may occur resulting in usually small but sometimes big differences. At this stage, an XRF analysis can only be confirmed by the classical Fire-Assay/ICP method.
Atomic Absorption Spectrometer (AAS) is a viable, steady, and cheaper than ICP analytical method for Precious Metals. Nevertheless, comparing ICP to AAS
Compare to ICP, AAS is
1. Much slower technique analyzing only a single element at a time.
Interested in selling your materials based on ICP Analysis results?
At Ecotrade, we have a trained team of chemists for assaying your material. We use Fire Assay, Cupellation, Titration, XRF, and ICP Analysis. We have the ability to analyze apart from Scrap Catalytic Converters all Precious Metals containing material like Electronic Waste (Scrap PCBs), PGM Industrial and Petrochemical Catalysts, Karat Gold & Sterling Silver, Precious Metals Slags or Residues.