The Challenges of Precious Metals Analysis — and the XRF, OES, and ICP-OES Solutions

Precious metals require — and reward — careful analysis. Their high monetary value means purity is a prime consideration when trading in these metals or products made from them. Different alloys must be identified and their composition verified. Adulteration, while not always easy to detect, can dramatically affect value. From the rapid assessment of an item of jewelry to determining minute traces in ore, detecting and measuring precious metals present substantial challenges.

Traditional techniques of analysis are either inaccurate or time-consuming and skill-dependent. XRF, OES, and ICP-OES analyzers meet these challenges — for jewelers, gold dealers, refiners, electronics and automotive manufacturers, metal recyclers, and others.

Let's take a top-line review:

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ED-XRF Analysis of Precious Metals

ED-XRF is the most widely used analytical technique in the precious metals industry. Unlike many spectroscopic methods, it doesn't require atomizing the sample to enable excitation. So it can analyze solid samples directly. Unlike methods requiring fusion or dissolution, it's nondestructive. This is critical to its usefulness in analyzing jewelry and other valuable items without damaging or removing precious metal. ED-XRF can also quantify all the sample's elements of interest in a single measurement. Finally, it's ideal for counterfeiting detection and other forensic work.

• In hallmarking centers, the SPECTRO MIDEX can deliver scanning results in as little as 15 seconds with good precision and accuracy. Elsewhere, the instrument's lower detection limits for some trace concentrations enable refiners to avoid overpayment due to over-measuring gold content.
• Designed for high-throughput applications such as hallmarking centers, the SPECTROCUBE provides fast and easy positioning of samples and measurement times as low as 15 seconds.
• SPECTROSCOUT is a fully portable, lower-cost alternative to the SPECTRO MIDEX. It's battery-powered, weighs less than 26.7 lb. (12 kg), and delivers laboratory-quality elemental analysis of precious metals in seconds.
• SPECTRO XEPOS is SPECTRO Analytical's most powerful XRF analyzer. It furnishes previously impossible sensitivity boosts of up to 10x previous models — optimized to target precious metals elemental groups and can also achieve notably low limits of detection (LODs).

OES Analysis of Precious Metals

Refiners and alloy producers have particular requirements in determining precious metals' impurities. Optical emission spectrometry (OES) is an ideal technique for their needs. Like ED-XRF, OES can be used directly on metallic samples such as pins. It is, however, not wholly nondestructive; a tiny amount of material is atomized by the spark used to excite the sample.

• The SPECTROLAB's perfected solid-state detectors using proprietary CMOS+T technology ensure exceptionally accurate analysis. Its low detection limits, ultra-high speed, future-proof flexibility and ease of use are ideal for refining quality and process control.

ICP-OES Analysis of Precious Metals

Due to its high sensitivity and wide dynamic range, inductively coupled plasma optical emission spectrometry (ICP-OES) is a popular technique for analyzing exploration samples such as ores and stream sediments and measuring impurities in precious metals. Advanced ICP-OES instruments can achieve limits of detection (LODs) in the parts per billion (ppb) (μg/kg) range.

Because ICP-OES requires putting sample material into solution, nonhomogeneity can be dealt with more easily than in EDXRF or OES analysis, as long as sampling procedures are carefully designed. In addition, excitation, spectral resolution, and detection must be optimized for best performance.

• SPECTRO GENESIS is a compact, fully simultaneous spectrometer with the benefits of ICP-OES technology but the affordability of flame absorption spectrometry (AAS) instruments. It provides simple calibration and a vast dynamic range but is faster than AAS or nonsequential ICP-OES models.
• The high-end SPECTRO ARCOS simultaneous ICP-OES spectrometer represents the latest state-of-the-art technology for the most demanding elemental analyses in the precious metals field. Its option for true axial and radial viewing of the plasma in a single instrument is particularly well suited for measuring traces of impurities in gold and other precious metals. The unique "MultiView" configuration provides enhanced sensitivity for trace analysis and high stability for analyzing major elements.

The Next Step

For a more detailed, technology- and application-focused, analytical results-driven discussion, get the 15-page white paper, Analyzing Precious Metals.

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