Use of phosphobetaine-type zwitterionic surfactant for the determination of alkali and alkaline earth metal ions and ammonium ion in human saliva by capillary electrophoresis.
With conventional capillary electrophoresis (CE), it was difficult to directly analyze samples containing proteins as a result of the irreversible adsorption of proteins onto the inner surface of the capillary column. This difficulty, however, was completely overcome by adding N-dodecylphosphocholine (DPC, a phosphobetaine-type zwitterionic surfactant) to the background electrolyte (BGE). DPC made two essential contributions to the determination of common inorganic cations in the protein-containing samples: protein adsorption onto the capillary walls was completely avoided, and the resolution of the analyte cations was essentially improved. The optimal BGE for analysis of biological samples was found to be 5 mM DPC, 5 mM copper(II) acetate/10 mM ethylenediamine (pH 8). The detection limits (signal-to-noise ratio =3 and UV at 215 nm) of sodium, potassium, calcium, magnesium, and ammonium ions were 25, 31, 24, 45, and 60 micro M, respectively. These five species of the common inorganic cations in human saliva samples were detected successfully within 2 min by the proposed system with direct sample injection.
National Institute of Advanced Industrial Science and Technology, Seto 489-0884, Japan. masanobu-mori@aist.go.jp
Masanobu
M
Mori
Wenzhi
W
Hu
Kiyoshi
K
Hasebe
Shunitz
S
Tanaka
Kazuhiko
K
Tanaka
D000468:Alkalies / Q000032:analysis*; D001622:Betaine / Q000031:analogs & derivatives* / Q000737:chemistry; D002414:Cations, Monovalent / Q000032:analysis; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D008673:Metals, Alkaline Earth / Q000032:analysis*; D008823:Micelles; D010767:Phosphorylcholine / Q000737:chemistry; D011506:Proteins; D000644:Quaternary Ammonium Compounds / Q000032:analysis*; D012463:Saliva / Q000737:chemistry*; D012680:Sensitivity and Specificity; D012996:Solutions; D013501:Surface-Active Agents / Q000737:chemistry*
D000468:Alkalies; D002414:Cations, Monovalent; D008673:Metals, Alkaline Earth; D008823:Micelles; D011506:Proteins; D000644:Quaternary Ammonium Compounds; D012996:Solutions; D013501:Surface-Active Agents; D010767:Phosphorylcholine; D001622:Betaine