Capillary zone electrophoresis was coupled on-line via a tricoaxial sh
eath flow interface with a benchtop quadrupole mass spectrometer (CZE-
MS) equipped with a (pneumatically assisted) electrospray ionization s
ource. Experimental parameters were optimized for operation in the neg
ative-ion scan mode. The system was applied to the fingerprinting of a
n alkylsulphate detergent, to the identification of an impurity in a c
hloramine-T disinfectant, to the characterization of a complex polyeth
oxylated alkylphosphate emulgator, to the analysis of phenoxy acid her
bicides and to the impurity profiling of MCPP. The optimized system wa
s found to fully maintain the CZE separation performance, showing up t
o I million theoretical plates for the low-molecular-mass analytes stu
died. The sensitivity in the full-scan mode was typically in the picog
ram range and sufficient for the separation and identification of mino
r impurities in these industrial chemicals, down to the 0.1% level. In
addition, the feasibility of on-column transient isotachophoresis (IT
P-CZE-MS) under high electroosmotic flow conditions has been demonstra
ted for sample preconcentration and subsequent identification of trace
impurities.