Electrokinetic supercharging in CE for the separation and preconcentration of barbiturate drugs in urine samples

Abstract

Three barbiturate drugs, barbital, phenobarbital, and secobarbital were separated and analyzed by electrokinetic supercharging. The influence of different parameters on electrokinetic supercharging performance was evaluated using both univariated and multivariated optimization processes. The parameters studied were sample pH, concentration, and length of the leading and terminating electrolytes, electrokinetic injection of the sample and composition and hydrodynamic injection of the solvent plug. The leading electrolyte (50 mM NaCl) was hydrodynamically injected (50 mbar × 120 s) prior to the sample that was adjusted to pH 9.6 and electrokinetically injected at -8.5 kV for 300 s. The terminating electrolyte (100 mM of 2-(cyclohexylamino) ethanesulphonic acid) was then hydrodynamically injected (50 mbar × 140 s). The results showed that this strategy enhanced detection sensitivity around 1050-fold compared with normal hydrodynamic injection, providing detection limits ranging between 1.5 and 2.1 ng/mL for standard samples with good repeatability in terms of peak area (values of relative standard deviation, %RSD < 3). The applicability of the optimized method was demonstrated by the analysis of human urine samples spiked with the studied compounds at different concentration levels and further liquid-liquid extraction step. The estimated detection limits obtained in the urine samples extract ranged between 8 and 15 ng/mL.

In-line Solid-phase Extraction–Capillary Zone Electrophoresis for the Determination of Barbiturate Drugs in Human Urine

“…In the literature, different techniques, such as LC, GC and CE, have been used for the determination of barbiturate drugs in biological samples, [14][15][16][17][18][19][20][21][22]26,27 as summarized in Table 2. In these papers, samples such as urine, 14,16,19,21,26,27 plasma, 15 serum, 22 meat 17,18 and meconium 20 were analysed.…”

“…In these papers, samples such as urine, 14,16,19,21,26,27 plasma, 15 serum, 22 meat 17,18 and meconium 20 were analysed. As can be observed from the table, the LODs obtained in our study are generally lower than those reported in other papers that focused on the determination of barbiturate drugs in urine samples by CE, except for the case of Kadi et al 26 and Botello et al 27 who reported similar LODs. In those papers the authors use a stacking technique, SRMP or EKS, in combination with CE; in both cases a sample pretreatment technique, as LLE or SPE, was needed, as in our case, to obtain a clean extract in order to be able to apply a preconcentration strategy in the same separation capillary.…”

“…The potential of CE for the determination of barbiturates in biological samples has also been demonstrated by some authors. [19][20][21][22][23][24][25][26][27] For example, Jiang et al 19 reported on the determination of barbiturates in urine by CE using a dynamically coated capillary with polycationic polymers. The LODs for standard samples were in the range of 870 to 3500 ng/mL.…”

“…On the other hand, our research group showed the potential of an electrokinetic stacking procedure, in particular electrokinetic supercharging (EKS); the obtained LODs ranged from 8 to 15 ng/mL for human urine samples. 27 The principal aim of this work was the determination, for the first time, of a group of barbiturate drugs in urine samples by in-line SPE-CE-UV. The optimization of the in-line SPE-CE system in the determination of the studied barbiturates was performed by evaluating different parameters affecting the preconcentration factors.…”

CE‐MS with electrokinetic supercharging and application to determination of neurotransmitters

“…This approach overcomes the limits on FASI, wherein a limited amount of sample can be injected before excessive band broadening reduces separation quality, by using tITP to re‐concentrate such bands. Since its introduction in 2003 , EKS has been combined with ultraviolet (UV) absorbance detection to measure low abundance analytes such as rare earth metals , environmental contaminants , protein complexes , DNA , peptides , and drugs .…”