In CE/MS analysis, when using a running buffer containing nonvolatile compounds such as CD or surfactant, the polarity of the CE is commonly selected so that compounds do not enter the Adrucil source , ,  and . Normal-polarity (NP) prevents HS-γ-CD, an anionic compound, from entering the ion source when using an untreated fused-silica capillary. HS-γ-CD countermigrates to the detector under these analytical conditions. However, NP would not prevent HS-γ-CD being introduced into the ion source in the case that a Type S capillary was used, because the mobility of the EOF would be greater than that of the ATS-HS-γ-CD anionic complexes. Although this might be an undesirable phenomenon, adverse effects on the detection of ATS were rarely seen. In previous study, it was verified that HS-γ-CD was not introduced into the ESI+ MS detector when ATS-HS-γ-CD anionic complexes were sprayed at the ion source . Since HS-γ-CD is a strong anion, it did not enter the ESI+ MS detector, but remained on the ion sweep cone. In fact, a slight adhesion of white powder was observed at an area on the ion sweep cone in front of the ESI sprayer. We cleaned the MS interface each week (the measurement time was about 40 h per week), and were able to collect data without any problems.