Ion Chromatograph Analysis

Gideon Analytical Laboratories received a flex circuit with a mystery corrosion on the polyimide and silicone pressure sensitive adhesive (PSA). There was corrosion by-product, and the silicone adhesive appeared more like a gelatinous material than a tactic PSA. Contrary to popular belief, flex circuits are not training for a future bodybuilding competition, they are a technology for assembling electronic circuits by mounting electronic devices on flexible plastic substrates, such as polyimide, PEEK or transparent conductive polyester film. Additionally, flex circuits can be screen printed silver circuits on polyester. Flexible electronic assemblies may be manufactured using identical components used for rigid printed circuit boards, allowing the board to conform to the desired shape, or to flex during its use. A polyimide is a polymer of imide monomers, and have been in mass production since 1955 due to their diverse applications. The goal was to figure out what the mysterious corrosive substance on the polyimide and silicone PSA on the flex circuit was.

Gideon Analytical Laboratories received three samples in polyethylene bottles to develop an analytical procedure for determining chloride using an ion chromatograph. Ion chromatography is a process that allows the separation of ions and polar molecules based on their charge. Using ion chromatography, one can identify concentrations of major anions, including elements like sodium, lithium, calcium, and many others. Aqueous samples are quantitatively measured in the parts-per-million range.

The two solutions were diluted 1:25 with DI water (18.2megaohm) water from a point of use Millipore purification system. The samples were then analyzed by ion chromatography; it was carried out with an instrument that consisted of HP1050 pump and autosampler with a Dionex AMMS suppressor and conductivity detector. Data was captured using an HP Chemstation. Displayed in the table below is the ion chromatograph readings of the respective samples. The picture shows the first sample (in red) at 3.4 PPM and the second sample (in blue) at 35.1 PPM. The results of the ion chromatography revealed the certain presence of chloride; absolute identity was made by spike, subtraction, and standards.