Large volume sample stacking of cationic tetracycline antibiotics toward 10 ppb level analysis by capillary electrophoresis with UV detection

Abstract

This paper aimed to build up a sensitive CE method for the analysis of tetracyclines (TCs) antibiotics (including tetracycline, chlorotetracycline, oxytetracycline, and doxycycline) with conventional UV detection. Here, the large volume sample stacking was applied to achieve in capillary preconcentration of the targets. To achieve large volume sample stacking, the essential step was a large volume of sample (around 83.3% of total capillary length from inlet to detection window) hydrodynamically loaded. Then, the reserved voltage was added in order to push the sample matrix out of the capillary. Due to different pH between sample solution (pH 4.6) and BGE (pH 11.0), the cationic TCs would turn into negatively charged while the sample matrix was removing from the capillary. Finally, the anionic TCs were stacked at the inlet for the subsequent separation. Although the loss of sample existed during their charge transformation, the LODs could be improved around 40 times than that obtained by normal hydrodynamic injection CE method. Here, the LODs were in the range of 8.1-14.5 μg/L, around 10 ppb that close to the level by electrochemiluminescence or laser-induced fluorescence detection of TCs by CE. The precision was characterized by RSDs of migration times and peak areas, which were in the range of 0.19-0.24% and 0.97-2.54%, respectively. The recoveries of the developed method were in the range of 95-112% by spiking TCs in the tap water. The proposed inline preconcentration CE method could be a simple, speed, and sensitive method for the quantitative analysis of TCs.

Recent progress of sample stacking in capillary electrophoresis (2016–2018)

“…A pH‐assisted stacking method was described by Wu et al. for the determination of cationic tetracycline antibiotics (tetracycline, chlorotetracycline, oxytetracycline and doxycycline). The analytes were stacked from a large volume of introduced acidic sample (pH 4.6) by charge reversal at the inlet due to high pH of the BGE (30 mM Na 2 HPO 4 , 1.5 mM Na 2 EDTA and NaOH at pH 11.0).…”

Recent developments in capillary and microchip electroseparations of peptides (2015–mid 2017)

“…Special reviews and papers deal with the particular sample clean‐up techniques, such as SPE , solid‐phase microextraction (SPME) , electromembrane extraction , selective electromembrane extraction based on isoelectric point , magneto‐immuno capture , and on‐line electrodriven sample‐stacking techniques . The latter electrodriven procedures include field amplified sample stacking , field enhanced or field‐amplified sample injection (FESI or FASI) ; large volume sample stacking (LVSS) , transient‐ITP (t‐ITP) , multiple capillary ITP (CITP) with repetitive hydrodynamic injection , dynamic pH junction , electrokinetic supercharging , and sweeping . The classical off‐line formats of SPE are nowadays being substituted by their on‐line modes.…”

Recent advances in enhancing the sensitivity of electrophoresis and electrochromatography in capillaries and microchips (2016–2018)

“…performed LVSS by injecting sample solution of cationic tetracycline at pH 4.6, which became negatively charged while the sample matrix was being removed by BGE (pH 11.0) on the application of negative voltage. Although some loss of cationic tetracycline was observed, it reduced with an increase in BGE pH with an enhancement factor of 35–44 obtained at pH 11 .…”