The EOF pump was successfully used as a means of introducing samples into a capillary system. An improved sample injection device has been developed using a TeflonTM union (TU) to link the two capillaries together. The capillary applied high voltage served as the EOF pump to pull the liquid inside while the other one served the purposes of isolating the electric field. Using the bias degree (BD) and SD of bias (SDB), it was possible to quantitatively determine the sampling bias and evaluate the effectiveness of injection approaches in bias elimination. Several related factors were evaluated, and it was found that TU approach could fully eliminate the bias under the optimal conditions. The fracture did not affect the efficiency, leak, or dilute the sample significantly. This approach was effective under both normal and reverse EOF situations and adapted to real samples. Finally, a TU method using grounded injection electrode was proposed and shown to be suitable for samples with low conductivity and high injection voltage.
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