Determination of iodine in polyamide by inductively-coupled plasma/mass spectrometry.

A method was developed for the determination of iodine in polyamide (PA). This method is needed as PA containing iodine (such as CuI/KX (X = I or Br) heat stabilizing agent), may represent a risk of corrosion for electronic parts in the automotive industry. The method involved a microwave assisted digestion method using nitric acid followed by inductively coupled plasma mass spectrometry (ICP-MS) analysis. A dilution in 0.5% NH was needed prior to ICP-MS analysis to suppress memory effect. The limit of quantification was estimated to be 0.9 mg kg which allows the control of very low iodine content PA used for applications in sensitive electronic parts. Spiking with iodide at 50 mg kg gave recovery factors of 100 ± 0.8%. The acid digestion method was compared with microwave assisted extraction of PA with 5% NH solution. Alkaline extraction gave slightly lower results (10% below). Finally, the acid digestion method was applied to the analysis of raw materials PA pellets and molded parts (used or not). Obtained iodine contents were ranged from < 0.9-1000 mg kg with relative standard deviation (RSD) on samples in the range 2.2-4.5%.