Separation of phenolic acids in soil and plant tissue extracts by co-electroosmotic capillary electrophoresis with direct UV detection

Abstract

A capillary zone electrophoretic method for the analysis of phenolic acids in soil and plant extracts was developed with direct UV detection using a phosphate electrolyte solution. The electrophoretic separation required the phenolic acids to be charged at a pH above their pKa in order to achieve their migration towards the anode. Electroosmotic flow (EOF) was reversed in direction by adding tetraclecyhrimethylammonium bromide (gAB). Factors affecting the separation selectivib,, including the buffer pH and EOF modifiers, were investigated systematically Eight phenolic acids were separated and detected in 10 min using an electrolyte containing 25 mM phosphate, 0.5 mM gAB and 15% acetonitrile (v/v) at pH of Z20. Linear plots for the test phenolic acids were obtained in a concentration range of 0.01 -1 mM with detection limits in the range of 1.0-ZO #M. The recoveries ranged from 92.8 to 102.3% in soil and plant tissues samples spiked at 100 #M and the relative standard deviation based on the peak area were ranged 2.0 to 4.5%. The proposed method was used for the determination of phenolic acids in plant tissue and soil extracts with direct injection.

Determination of 3-methylhistidine and 1-methylhistidine in untreated urine samples by capillary electrophoresis

“…Parameters of the linear regression analysis are summarized in Table 2. The values of LOD found in the present study are comparable with those reported for low-molecular weight species in untreated urine with direct UV detection [27,28].…”

Separation of arsenic species by capillary electrophoresis with sample-stacking techniques

“…1). This can be attributed to the migration direction of As species being the same as that of the EOF, and resulted from dynamic modification of the fused-silica surface with TTAB [33,34,35,36]. Consequently, As(V) with a higher mobility appeared prior to As(III) having a lower mobility.…”

“…To achieve fast separation, co-EOF mode is frequently used for the separation of anions by addition of cationic surfactant such as TTAB, which results in a faster migration as the anionic solutes co-migrate with the EOF [33,34,35,36]. Since co-EOF migration in alkaline electrolyte was needed to achieve the complete separation of As species with different mobility, it was necessary to find a suitable buffer pH in co-EOF mode for the separation of target As species.…”

Enhanced selectivity and sensitivity for inorganic anions using an ion-pairing reagent and sample stacking in capillary zone electrophoresis with direct UV detection

“…1, the observed mobility of anions increased with increasing electrolyte pH. As both the EOF and effective mobility of the anion increased with increasing electrolyte pH, this led to an increase the mobility of the anions [23,24,25]. However, the best resolution between Cl -and I -was achieved at pH 8.0, and this pH was therefore used for all further experiments.…”

“…Separation selectivity depends on the mobility of an anion and the EOF, which is related to electrolyte pH and the type and concentration of EOF modifier [23,24,25,26]. The influence of electrolyte pH on the mobility of anions was tested using an electrolyte containing 20 mmol L -1 NaH 2 PO 4 and 20 mmol L -1 TMAOH.…”