title: Determination of inorganic anions in saliva by electroosmotic flow controlled counterflow isotachophoretic stacking under field-amplified sample injection.
abstract: Under a strong counter-electroosmotic flow, five salivary inorganic anions, bromide, iodide, nitrite, nitrate and thiocyanate were determined by field-amplified sample injection in combination with isotachophoretic stacking. Separation and concentration conditions were investigated. A terminating electrolyte, 5mM borate, was added in the sample. Under the optimized conditions, Br(-), I(-) and SCN(-) were concentrated online using 150mM HCl-Tris buffer at pH 7.8 in a bare fused capillary, providing more than ten thousand of sensitivity enrichment compared with normal injections. The relative standard deviations (RSDs, n=5) were less than 1% in migration times, 8% in peak areas. Using direct UV detection at 200nm and 226nm, the limits of detection (LODs, S/N=3) were of 0.002-0.01μM. Unfortunately, NO2(-) and NO3(-) could be observed in purified or deionized water. Therefore, a low dilution factor was applied to saliva samples. Due to the matrix effect, samples were injected in a shorter time, and standard addition method was applied to determine all the five inorganic anions in saliva. The RSDs of the migration times and peak areas were in a range of 0.2-0.4% and 3.0-4.0%, respectively. The LODs were 0.2-2.0μM. The salivary levels of the anions obtained were in accord with the reference data. The external standard method can not be adapted to real samples due to biases caused by electrokinetic injection and errors from high dilutions.
authors: Key Laboratory of Chemistry of Northwestern Plant Resources, CAS and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
authors: Haixia
authors: H
authors: Ren
authors: Hongdeng
authors: H
authors: Qiu
authors: Xiaojing
authors: X
authors: Liang
authors: Xusheng
authors: X
authors: Wang
authors: Shengxiang
authors: S
authors: Jiang
mesh_terms: D000838:Anions / Q000032:analysis; D001965:Bromides / Q000032:analysis*; D053841:Electroosmosis / Q000379:methods*; D006801:Humans; D007454:Iodides / Q000032:analysis*; D057625:Isotachophoresis / Q000379:methods*; D057230:Limit of Detection; D016014:Linear Models; D009573:Nitrites / Q000032:analysis*; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry*; D013861:Thiocyanates / Q000032:analysis*
chemical_list: D000838:Anions; D001965:Bromides; D007454:Iodides; D009573:Nitrites; D013861:Thiocyanates
keywords: Capillary ion electrophoresis; Electrokinetic injection; Preconcentration; Stacking