Determination of alkylphosphonic acids using micellar electrokinetic chromatography with laser-induced fluorescence detection and high-salt stacking

Abstract

Methyl-, ethyl- and propylphosphonic acids (MPA, EPA, and PPA, respectively) were derivatized with panacyl bromide in dry N,N-dimethylformamide (DMF). After mixing with a high-salt dilution buffer, the derivatives were separated by micellar electrokinetic chromatography in 35 min and detected by laser-induced fluorescence (He–Cd laser excitation at 325 nm and detection at 500 nm). Baseline resolution was achieved using a separation buffer containing 50 m M sodium cholate, 40% (v/v) of acetonitrile and 50 m M borate. Addition of 400 m M NaCl to the dilution buffer allowed the injection time to be increased to 30 s while still maintaining baseline resolution. Limits of detection for MPA, EPA, and PPA were 0.13 μ M (12 ppb), 0.13 μ M (14 ppb) and 0.14 μ M (17 ppb) injected, respectively. The reproducibility of corrected peak area at 15 μ M was 3.7∼4.3%.