Arc/spark is a specialized optical emission spectroscopy (OES) technique that is strongly associated with the analysis of metals. In principle, these instruments can be used with nonconductive materials if they are prepared by grinding and forming a mixture with powdered graphite. There are also dedicated systems with specialized electrodes for the analysis of liquids, generally engine lubricants.

In brief, the technique uses an electric current to provide the energy to stimulate light emission in the sample. The emitted light from the atoms is then analyzed in a spectrometer, yielding the elemental composition of the sample. Spark excitation involves a brief electrical discharge, while arc excitation uses an alternating current. Generally, systems can perform analysis in either mode.

Laboratory arc/spark systems can be quite sophisticated, and great care is taken to make the excitation and analysis repeatable, so that the method is highly quantitative. This also requires the use of argon gas to eliminate interferences in the air (such as carbon for steel analysis). The mobile and portable systems, included here typically do not use argon gas systems, although there are some that do.

Mobile systems are useful in many applications in foundries, scrapyards and other metal facilities. Simple instruments are used by relatively unskilled technicians to identify metals and metal alloys. Mobile units of greater sophistication are involved more closely in metal production, and these systems are generally ruggedized for such environments. For some of these applications, handheld x-ray fluorescence has become a very competitive technology.

Mobile arc/spark spectrometry systems have become both more common and more sophisticated since Spectro Analytical introduced the first one in 1979. Spectro Analytical, which was acquired by AMETEK in June 2005 (see IBO 6/15/05), remains the world leader in both lab and mobile arc/spark spectrometry. The third generation of its Spectrotest system was introduced in mid-2005.

After AMETEK, the next largest vendors of mobile arc/spark spectrometers are Worldwide Analytical Systems and Oxford Instruments, which acquired Metorex in 2004 (see IBO 9/15/04).

Another participant in this market is Arun Technology. Arun was acquired by AMETEK as part of its acquisition of Roxboro Solartron (see IBO 8/31/05), but separated from AMETEK in a management buyout in March 2006 (see IBO 9/30/06). Of the other participants in the mobile arc/spark market, Spectro is notable in that it manufactures only specialized systems for the analysis of wear metals in lubricants, mostly for military customers.

In 2006, the market for mobile arc/spark spectrometry systems was approximately $34 million.

Mobile Arc/Spark at a Glance:

Leading Suppliers

• AMETEK

• Oxford Instruments

• Worldwide Analytical Systems

Largest Markets

• Metals

• Lubricants

Instrument Cost

• $20,000–$90,000