Preconcentration of 3-nitrotyrosine in urine by transient isotachophoresis in MEKC

Abstract

Transient isotachophoresis (tITP), usually performed in CZE, is a useful on-line sample preconcentration technique for high saline samples. However, only a few papers have applied tITP in MEKC especially SDS system. This study compared tITP in MEKC with that in CZE for 3-nitro-tyrosine (NT) analysis in urine. No sample clean-up was required. Self-stacking occurred simultaneously as chloride in urine acted as a leading ion. HEPES–Tris buffer at pH 8.2 was used as a terminating electrolyte and separation buffer. UV detection wavelength was set at 426nm. Experiments showed that tITP in MEKC exhibited much higher peak efficiency (up to 1000000), and improved 4-fold sensitivity, compared with those by tITP in CZE. The limit of detection was 0.07μM for 3-nitrotyrosine in urine.