Optical Emission Spectrometer: ARL Fire Assay Analyzer

 The fire assay analysis is the method of choice for the analysis of precious metals traces in ores. Traditionally a complex and long preparation process, including the so-called "cupellation" is followed by analysis by gravimetry, ICP-OES or ICP-MS that require a few hours at least.. With the Thermo Scientific ARL Fire Assay Analyzer (ARL FAA) that includes the latest developments in optical emission spectroscopy, the cupellation is suppressed and all the precious metals are measured at the requested levels in less than a minute.

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Traditionally the ore sample is crushed, ground and weighed before being heated and mixed with a flux containing in particular litharge (Pb oxide), a reducing agent (e.g. flour) and compounds forming a slag. The litharge is reduced into metallic Pb, which quantitatively extracts the precious metals. The fused mix is then poured in a mold where the lead containing the PM's sinks to the bottom, while undesired impurities are moved into the slag floating on the top. After cooling down and removal of the slag, the obtained button is heated in a "cupel" placed in an open furnace. The Pb is oxidized by the air and absorbed by the cupel, leaving only a PM's bead, which is analyzed by various techniques, according to the purpose of the precious metals determination, e.g.:

• Gravimetric analysis for total precious metals (TPM) determination, for obtaining plant data in the platinum industry
• ICP-MS or ICP-OES for individual platinum group elements determination, for accurate analysis (e.g. for metal accounting).

The method has survived because it is accurate, sensitive, can accommodate virtually any ore type and is relatively inexpensive. However, in the modern world, it has increasing disadvantages considering productivity and costs. Optical Emission Spectroscopy (OES) can be used to measure the precious metals concentrations directly in the lead buttons, providing numerous advantages:

• Suppression of the cupellation that simplifies and speeds the process, and saves costs on cupels, furnaces, power consumption, chemicals, laboratory equipments, etc.
• The environmental unfriendly and labor intensive cupellation, sample preparation techniques and analyses are replaced by a simple and clean techniques
• High-quality results on all the PM's simultaneously in about a minute, making it suitable even for the most demanding operations (e.g. plant control and metals accounting)
• Highest availability for analysis through high stability and low maintenance
• Operations by a minimum of relatively untrained people
• Possible automation of sample preparation and handling, ensuring high throughput and reliability of the analyses

The Thermo Scientific ARL Fire Assay Analyzer (ARLFAA) made the fire assay lead button analysis possible with an optical emission spectrometer thanks to two important new capabilities:

• The patented Current Controlled Source (CCS) has the flexibility in selecting all parameters of the spark discharge. In particular its unique capability in generating very low currents permits achieving highest sensitivity, excellement reproducibility and spark areas of small dimensions on the limited size fire assay buttons.
• The Time Resolved Spectroscopy (TRS) system, which permits the setting of the appropriate time window for data acquisition when the signal to noise ratio is the msot favorable allows also optimizing sensitivity and precision for trace analysis.

The ARL FAA can be factory calibrated to allow easy and rapid installation and commissioning which, in turn, optimizes the payback of your investment. Among many advantages, the instrument includes:

• Paschen-Runge vacuum polychromator with a focal length of 1 m, allowing excellent resolution
• Special cast iron cabinet, temperature controlled to ±0.1° at 38°C
• Argon flushed, water-cooled table with self-contained, closed loop coolant system
• Ultimate detection limits, reproducibility and accuracy, shortest analysis time
• Unrivaled quality, stability and reliability.
• Most modern OXSAS software running under Windows®XP and Vista Business
• Lowest cost of ownership: easy to maintain, opportunity to increase productivity
• Easy integration to increase productivity
• Ergonomically designed cabinet for rapid input of the sample and its identification.

The ARL FAA is built under strict manufacturing and quality control procedures to provide the unique reliability, stability, precision, and accuracy that are the cornerstones of Thermo's long history in optical emission spectrometry.  By combining this experience with innovation, the ARL FAA is the instrument of choice for people looking for ultimate performance around the clock through the full year.

The ARL FAA is commonly coupled to an automatic sample handling system (SMS-2000) which in turn is coupled with automatic sample equipment systems. Working 24 hours a day and 7 days a week, the instrument delivers dependable performance year after year.

Our long experience in metals analysis comes from an installed base of more than 10'000 spectrometers worldwide. The ARL Fire Assay Analyzer is the answer to simplify the analysis of precious metals in ores.