IC6600 Ion Chromatography Case Study: Trace Anion Testing in Electronic-Grade Phosphoric Acid

Customer Background

Electronic-grade phosphoric acid (EGPA) is a critical wet chemical in the microelectronics and semiconductor industry. It is used in the production of large-scale integrated circuits and thin-film liquid crystal displays, mainly for chip and wafer cleaning and etching. Its purity and cleanliness directly affect the yield, performance and long-term reliability of electronic components. As integration density keeps rising, manufacturers apply increasingly strict limits on soluble impurities and require dependable trace-level anion data at very low concentrations.

The Analytical Challenge

Common methods for determining impurity anions in phosphoric acid have clear limitations. Ion-selective electrodes and visual turbidimetry produce large errors and cannot deliver reliable data when impurity anions are present at extremely low levels in electronic-grade phosphoric acid. Conventional ion chromatography is strongly affected by the high concentration of phosphate in the sample: the sample must be diluted many times before injection, which pushes trace impurities below the working range of the system. A technique that separates phosphoric acid from the impurity anions without additional dilution is therefore required.

The Solution: IC6600 with Valve-Switching Preconcentration and Ion Exclusion

Wanyi Technology developed an application solution based on the IC6600 ion chromatography system with a conductivity detector, following the GB/T 28159-2025 standard. A valve-switching preconcentration and ion exclusion method is applied: an exclusion column separates phosphoric acid from the impurity anions, and the anions are then determined by conductivity. Sample preparation is simple, sensitivity is high and linearity is excellent, making the method a practical reference for impurity anion testing in electronic-grade phosphoric acid.

Instrument Configuration

Reagents and Standards

Sample and Calibration Preparation

• Mixed standard working solution: 100 uL chloride, 100 uL nitrate and 500 uL sulfate standard solutions diluted to 10 mL, giving 10 mg/L chloride and nitrate and 50 mg/L sulfate.
• Sample test solution: 50 g of phosphoric acid diluted to 100 g with ultrapure water.
• Standard addition series: 0, 0.05, 0.125, 0.25, 1.25 and 2.5 mL of mixed standard made up to 25 g with sample test solution.
• Materials: 0.1 mg analytical balance, 50 mL and 10 mL centrifuge tubes, 0.45 um water-phase PES membrane, ultrapure water and 5 mL disposable syringes.

Calibration Levels of the Standard Addition Series (mg/kg)

Chromatographic Conditions

Results

The sample was analysed under the conditions above. All target peaks were well shaped and fully resolved from the phosphate matrix, with chloride eluting at 7.25 min, nitrate at 12.12 min and sulfate at 18.63 min.

Sample Test Results

Linearity, Quantification and Measured Content

Repeatability (Five Consecutive Injections)

Conclusion

Using the Wanyi Technology IC6600 ion chromatography system with a conductivity detector, the valve-switching preconcentration and ion exclusion method cleanly separated phosphoric acid from the impurity anions before detection. The chromatograms show well-shaped peaks, sensitivity that meets the national standard, correlation coefficients above 0.999 for all three anions and excellent precision across five consecutive injections, with area RSD values between 0.261% and 0.856%. The system therefore fully satisfies routine qualitative and quantitative anion testing and provides a reliable reference for quality control in electronic-grade phosphoric acid production.