Capillary electrophoresis: An integrated system with a unique split-flow sample introduction mechanism

The performance of an integrated capillary electrophoresis system with a novel split-flow sample injection mechanism and special high sensitivity UV absorbance detector is described. Sample introduction into the capillary is accomplished with a standard HPLC-type microliter syringe. The injected sample is divided proportionally between the separation capillary and an adjustable splitvent. The volume of sample introduced into the capillary can be manipulated by varying the length or the i.d. of the splitvent tubing; or the volume of sample injected. Data are presented showing reproducibility of retention time, peak height, and peak area; minimum detectability; and operation at short UV wavelengths.     

Poly(methacrylic acid-ethylene glycol dimethacrylate) monolith in-tube solid-phase microextraction applied to simultaneous analysis of some amphetamine derivatives in urine by capillary zone electrophoresis

A method based on in-tube solid-phase microextraction and capillary zone electrophoresis (CZE) was proposed for simultaneously determining four amphetamines (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethamphetamine) in urine. A poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column, which can provide sufficient extraction efficiency, was introduced for the extraction of amphetamines from urine samples. The hydrophobic main chains and acidic pendant groups of the monolithic column make it a superior material for extraction of basic analytes from aqueous matrix. After extraction, the samples were analyzed by CZE. The best separation was achieved using a buffer composed of 0.1 M disodium hydrogen phosphate (adjusted to pH 4.5 with 1 M hydrochloric acid) and 20% methanol v/v, with a temperature and voltage of 25 degrees C and 20 kV, respectively. By applying electrokinetic injection with field-amplified sample stacking, detection limits of 25-34 microg/L were achieved. Excellent method of reproducibility was found over a linear range of 0.1-5 mg/L. Determination of these analytes from abusers' urine sample was also demonstrated.     

Determination of terbinafine in pharmaceuticals and dialyzates by capillary electrophoresis

A capillary electrophoresis method has been developed for the separation and determination of terbinafine (TER) in various pharmaceutically relevant matrices. Capillary zone electrophoresis (CZE) separation and UV absorbance photometric detection were carried out in a 160 mm capillary tube with a 300 μm i.d., hydrodynamically (membrane) closed. The influences of pH, carrier cation and counterion on migration parameters of TER were studied and the following conditions were selected: a 20 mmol l⁻¹ glycine running buffer adjusted to pH 2.7 with acetic acid, 0.2% (w/v) methylhydroxyethylcellulose (m-HEC) as an electro-osmotic flow (EOF) suppressor, a 250 μA driving current, and 20 °C. The optimized separation conditions were convenient for the determination of TER in commercial tablets and spray and in dialyzates. Here, the dialysis was used to investigate in vitro permeation of TER through the skin from the gel. The samples of dialyzates were examined with and without simple extraction procedure and the results were compared. A permeation profile of the drug present in the gel of given composition was obtained analyzing pretreated samples. The proposed electrophoretic method was successfully validated. It was suitable for the simple, sensitive, rapid and highly reproducible assay of TER. CZE analysis was completed within 5.5 min. The detection limit of TER was 1.73 μmol l⁻¹ at a 224 nm detection wavelength. The intra- and inter-laboratory precisions over the concentration range 6.0-60.0 μmol l⁻¹ were between 0.32-0.69% and 1.04-1.44% including R.S.D. of migration times and peak areas, respectively. The mean absolute recoveries of drugs from samples were found to be 98.34 (tablets) and 99.47% (spray). It is suggested that there are potentialities to determine TER present in unpretreated complex samples, as CZE in a hydrodynamically closed separation system may be easily on-line combinable with purification and preconcentration CE modes (e.g., isotachophoresis, ITP).     

Determination of imazalil by on-line coupled capillary isotachophoresis with capillary zone electrophoresis

A simple, rapid and reproducible capillary isotachophoretic on-line coupled with capillary zone electrophoresis (CITP-CZE) method for the determination of IMz in food packaging extracts and its residues in apples is described. A good separation of the IMZ from other sample constituents was achieved within 15 minutes without any sample clean up. Method characteristics (linearity, accuracy, intra-assay and detection limit) were determined. Less amount of time involved, sufficient sensitivity and low running cost are the important attributes of CITP-CZE method.     

Artificial neural networks for quantification in unresolved capillary electrophoresis peaks

The application of the combination of experimental design (ED) and artificial neural networks (ANNs) for the quantification of overlapped peaks in capillary zone electrophoresis is described. When the total separation cannot be achieved by separation techniques, the use of ED-ANN can be a suitable approach. The unstability of EOF causes peak shift that has to be corrected in order to apply ED-ANN methods. In this work, normalization procedure of electropherograms with consequent application of ANNs for quantification purpose was developed. Both, spectra and electropherograms can be used as multivariate data. In general, both kinds of data were found to be suitable for unresolved peaks quantification by ED-ANN approach.     

Thermal-Adsorptive Concentration

Methods for concentrating dilute fluids using adsorption followed by partial thermal regeneration were studied using the simulation package ADSIM. The systems studied were NaCl in liquid water on Amberlite XD-2 resin and benzene vapor in nitrogen on activated carbon. Cycles studied included counter-current regeneration with pure hot fluid, co-current regeneration with pure hot fluid, a new process called Hot Feed Addition (HFA) consisting of co-current regeneration with pure hot fluid followed by hot feed, and cycling zone adsorption (co-current alternating hot and cold feeds with no pure regeneration fluid). The optimum system depends upon the conditions of the system and the value function chosen to evaluate the systems. For example, for benzene in nitrogen with hot regeneration gas at 467.4 K, cycling zone adsorption used no carrier gas, had the most concentrated benzene stream and a very pure nitrogen product, but the energy use was greater than the other processes. For liquid systems counter-current operation could produce the purest product, but regenerant requirements were high. With slightly lower purity requirements HFA reduced solvent usage and increased the concentration of the concentrated waste stream. For the liquid system all processes used approximately 3% or less of the energy that would be required for evaporation.     

Determination of Size Distribution of Nano-particles by Capillary Zone Electrophoresis

A new method was developed for the determination of the size distribution of nano-particles by capillary zone electrophoresis (CZE). Scattering effect of nanoparticles was studied. This method for the determination of size distribution was statistical.     

Determination of aristolochic acid by capillary zone electrophoresis

A simple and rapid capillary zone electrophoresis (CZE) method for the determination of aristolochic acid (AA) in dietary supplements and selected herbs is described. A clear separation of AA from other sample constituents was achieved within 5 minutes without any sample clean up. A mixture of 20 mM-morpholinethanesulphonic acid+10 mM-BisTrisPropane+0.2% hydroxyethylcelullose in 10% methanol serves as a background electrolyte. The linearity, accuracy, intra-assay and detection limit of the developed method are 200–6000 ng/mL, 95–103%, 3.5%, and 50 ng/ml, respectively. Ease of use, sufficient sensitivity and low running cost are the most important attributes of the CZE method. The proposed CZE method was compared with HPLC.     

Simultaneous determination of sulfamethoxazole and trimethoprim in human plasma by capillary zone electrophoresis

A capillary electrophoretic method for the simultaneous determination of sulfamethoxazole and trimethoprim in plasma was developed. Sulfamethoxazole and trimethoprim extracted from human plasma with ethyl acetate were analyzed at 20 kV and 25 degrees C using 15 mm phosphate buffer (pH 6.2) as the electrolyte. The detection was by UV at 220 nm. The run time was 8.0 min and the limit of quantification was 10.00 microg/mL for sulfamethoxazole and 2.00 microg/mL for trimethoprim. The recovery was >99% for both compounds. This method enabled the detection of sulfamethoxazole and trimethoprim in plasma of patients after oral ingestion of their combined formulation. The present simple and rapid method is applicable to drug monitoring in immunocompromised patients who are taking the combined formulation of these compounds for the treatment or prophylaxis of Pneumocystis carinii pneumonia.