High-sensitivity determination of the degradation products of chemical warfare agents by capillary electrophoresis-indirect UV absorbance detection

Capillary electrophoresis coupled with indirect UV absorbance detection was employed for the determination of the chemical warfare agent degradation p roducts: methylphosphonic acid, ethyl methylphosphonate, isopropyl methylph osphonate, and pinacolyl methylphosphonate. Glutamic acid was used as a buf fering agent at its isoelectric point (pH 3.22). In its zwitterionic form, glutamic acid does not act as a competing co-anion in the system, thus prov iding buffering capacity while maintaining high sensitivity. The indirect p robe (phenylphosphonic acid) concentration was lowered to 1 mM from the 10 mM in previous literature studies, further enhancing sensitivity. Detection limits of 2 muM were achieved with hydrodynamic injection and up to 100-fo ld lower using electrokinetic injection. The increased buffering capacity o f this system over previous methods led to migration time reproducibility R SD values of 0.18 to 0.22%. This represents a 10-fold improvement in reprod ucibility over previous studies with comparable or improved sensitivity. (C ) 2001 Elsevier Science B.V. All rights reserved.