Lead (Pb), atomic number 82 on the Periodic Table, is a chemical element in the carbon group. Lead is a unique material known for its high density, high malleability, corrosion resistance, low melting point, and unusual electrical properties.
Most of the world’s supply of lead is used in lead-acid battery manufacturing, but lead is used many other applications and products that may affect our daily lives, including building construction, glass and enamel, television picture tubes, computer video display terminals, weights, as part of solders, and as radiation shields.
Lead-acid batteries are widely used in automobiles, and rechargeable lead-acid batteries are the most popular type available. Because of the widespread use of lead-acid batteries, improper disposal has become a major environmental concern, and recycling has emerged as the solution. The recycling market from battery scrap represents a large volume of the world’s lead production. According to the EPA, 96% of all lead-acid batteries are recycled, and a typical lead-acid battery contains 60 to 80% recycled lead and plastic. Most U.S. state laws require retailers that sell lead-acid batteries to collect them back for recycling.
Lead is often alloyed with other metals depending on its specific use. Lead-acid car batteries are made from alloys containing either calcium or antimony which must be combined in exact percentages to produce the desired qualities in the finish product. Elemental analysis instrumentation is a critical part of lead-acid battery manufacturing to be certain that the appropriate alloy content and quality standards are being met. Furthermore, with so much lead coming from recycled sources, it is also important to verify the composition of recycled lead and rule out the presence of contaminants.
Optical emission spectrometry (OES) using Arc/Spark excitation is an excellent technique for evaluating lead and lead alloys for quality control and production analysis. OES analyzers apply a spark to supply energy to the atoms in a metallic sample, which causes them to emit characteristic wavelengths of light. The intensity of the light is proportional to the element’s concentration in the sample. The light is converted to an electrical signal by PMTs (Photomultiplier tubes) capturing the light a discrete spectral positions corresponding to emission lines of the elements of interest, or by one or several solid-state detectors generating a wider spectral pattern. By measuring electrical intensities from PMTs or intensities of the lines of interest in the spectrum from the solid-state detector, OES analyzers provide qualitative and quantitative analysis of the metal and reveal important information about whether modifications need to be made to the manufacturing process.
Quantitative elemental analysis of solid lead sample with OES begins with careful sample preparation using a lathe or a milling machine. Grinding is not possible due to the risk of contamination. Once the measurement is completed, the resulting spectral intensities are converted into concentrations according to calibrations established for the qualities of lead and lead alloys of interest.
The accuracy is a very important factor to consider when choosing OES for this application. Accuracy depends particularly on the calibration standards, on instrumental factors (e.g. spectral resolution and excitation source parameters) and on appropriate corrections to reduce or eliminate matrix effects and spectral interferences. Other factors like instrument stability, precision and limits of detection have to be considered to guarantee reliable, quality analyses of the tested lead samples on the long-term. View data on various lead samples analyzed using this technology.