Reproducible digestion method for ion-chromatographic analysis of anions in 30% hydrogen peroxide

Semiconductor-grade hydrogen peroxide (30%) is analyzed for anion contamination to be certain the levels of each analyte do not exceed 30 ppb (w/w). This paper presents a reproducible, platinum-decomposition approach that uses ion chromatography to quantify the various analytes (fluoride, chloride, sulfate, bromide, nitrate, and phosphate). Important to the success of the method are: (1) use of disposable HDPE bottles for the digestion, (2) immersion of the bottles in a water bath, (3) careful re-mixing of the digesting peroxide after two (of six total) hours, and (4) careful clean-up and sample-handling procedures (to avoid contamination). Except for fluoride and nitrate, all analytes exhibited recoveries from 89.6 to 98.3%, with +/- prediction intervals (at the 95% confidence level) from 1.5 to 3.0 ppb. Fluoride's recovery was low (74.9%), but reproducible (+/- prediction interval at 95% confidence=2.0 ppb). Nitrate reeovery was 99.1%, but noisy (+/- prediction interval at 95% confidence=8.7 ppb); this imprecision was thought to be due to contamination from atmospheric nitrite. A Dionex DX 500 microbore ion chromatograph with AS15 column and 1-ml sample loop were used for all determinations; detection was by conductivity. Statistical analyses were performed using JMP software.