Determination of Chloride, Sulfate, Nitrate, and Phosphate in N-Methyl-2-Pyrrolidone and γ-Butyrolactone by Capillary Electrophoresis

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Abstract
N-methyl-2-pyrroIidone (NMP) and γ-butyrolactone (BLO) are important solvents in the semiconductor and electronics industry. These applications demand solvents with low levels (<0.5 ppm) of anions. Traditionally, analytical methods have not kept pace with the requirements desired by the electronics industry. Recently, ion chromatography (IC) has provided lower detection levels for anions. However, capillary electrophoresis (CE) for anion analysis possesses unparalled resolution and efficiencies, with analysis times reduced by up to a factor of ten over IC. Using the method of standard additions, the concentrations of chloride, sulfate, nitrate and phosphate were determined in 1:20 aqueous dilutions of NMP and BLO A lower limit of detection for the undiluted solvent sample of 40 ppb (2 ppb limit for 1:20 dilution of sample) was found for each of the four anions of interest.