Behavior of Humic Acid as a Micellar Phase in Micellar Electrokinetic Chromatography (MEKC)

The possibility of humic acids acting as micellar phase in micellar electrokinetic chromatography was evaluated. We investigated the separation of naphthalene in capillary electrophoresis using various samples of humic acids as micellar phase under different pH conditions, concentrations of humic acid, and temperature. The humic acid samples studied were from different origins including peat, vermicompost and a commercial sample acquired from Aldrich. Methanol was used as a marker for the electroosmotic flow. The results indicate that the formation of micelle depends on the number and nature of the hydrophobic association sites in an aqueous humic acid solution and on the origin and concentration of the humic acid at a defined pH. At lower pH values, the possibility of the humic acid molecule forming pseudomicelles increases due to a combination of neutralized and dissociated charged sites.     

Capillary zone electrophoresis of cationic and anionic drugs in methanol

The actual mobilities and dissociation constants of acidic and basic pharmaceuticals were determined in methanol. Actual mobilities were derived from the dependence of the effective mobilities of the analytes on the pH of the methanolic background electrolyte solution (pH(MeOH)). The pKa values of the pharmaceuticals in methanol (pK(a,MeOH)) were calculated by non-linear curve fitting to the measured mobility values. It was found that the shift in pKa value (when compounds were transferred from water to methanol) increased with the acidity of the analyte. The average pKa shift for compounds exhibiting acidic properties in water was ca. 5.5 units, and the shift for basic compounds about 2 units. As was shown for a mixture of beta-blockers, the calculated actual mobilities and pKa values can be utilised in the optimisation of pH conditions for separation. The practical value of the method was illustrated by the analysis of urine samples.     

Capillary electrophoretic determination of lignin degradation products obtained by permanganate oxidation

A new capillary electrophoretic (CE) technique was developed for the separation of lignin degradation products after permanganate oxidation, yielding information about quality and quantity of various linkages in the lignin molecule. This CE method is a promising alternative to existing gas chromatographic (GC) methods. An advantage in comparison with GC is the short separation time and the fact that the oxidation products (aromatic acids) can be analyzed without derivatization. The selectivity and sensitivity of CE combined with UV detection is adequate and makes it suited for fast routine characterization of lignins. If necessary, the CE method can be coupled with electrospray ionization mass spectrometry in order to make a clear assignment of the peaks.     

Direct determination of gentamicin components by capillary electrophoresis with potential gradient detection

A simple and fast method was developed to determine non-UV active compounds directly without derivatization. The usefulness of the method was demonstrated by detecting the major components in aminoglycoside antibiotic mixtures using capillary zone electrophoresis with potential gradient detection. Under optimized separation conditions (0.2 mM cetyltrimethylammonium bromide (CTAB), 1 mM ammonium citrate, pH 3.5), gentamicin was separated into three major peaks (C1, C1a, and C2+C2a) within 15 min. This method showed better sensitivity than other capillary electrophoresis (CE) methods for determining underivatized gentamicin. The linear range was from 10 to 500 ppm. Because of its good repeatability and simplicity, this new method could be a good alternative for the current assays given by US Pharmacopoeia and European Pharmacopoeia.     

CZE separations of basic proteins at low pH in fused silica capillaries with surfaces modified by silane derivatization and/or adsorption of polar polymers

Mixtures of several basic proteins have been used to test CZE capillaries with surfaces modified by new pretreatment procedures; the performance obtained has been compared with that achieved using capillaries treated by procedures described in the literature. It has been shown that addition of non-ionic polyvinylalcohols (PVA) to CZE buffer solutions deactivates even bare, i.e. untreated, fused silica surfaces and renders them suitable for separations of basic proteins. The performance obtained from such surfaces was comparable with that of capillaries modified by the more elaborate procedures of etching, silanol derivatization, and/or adsorptive coating (again with polymers). A home-made device is described which enables derivatization and coating reactions to be performed on fused silica capillaries under an inert atmosphere, i.e. one free from oxygen and water.     

安培检测芯片毛细管电泳及其初步应用

An end-channel amperometric detector with a guide tube for working electrode was designed and integrated on a home-made glass microchip. The guide tube was directly patterned and fabricated at the end of the detection reservoir, which made the fixation and alignment of working electrode relatively easy. The fabrication was carried out in a two-step etching process. A 30 μm carbon fiber microdisk electrode and Pt cathode were also integrated onto the amperometric detector. The baseline separation of dopamine (DA), catechol (CA) and epinephrine (EP) was achieved within 80 s. Relative standard deviations of not more than 5.2% were obtained for both peak currents and migration times of DA and CA (n=5). Using standard adding method, DA in tLrine and plasma samples was detected. The recoveries were in the range of 83%—103%.     

配体交换毛细管区带电泳拆分未衍生化氨基酸

以铜（Ⅱ）-L-谷氨酸络合物为手性分离选择剂，对苯丙氨酸、酪氨酸和色氨酸3种非衍生芳香族氨基酸的手性对映体拆分进行了研究，建立了一种快速、简便拆分未衍生化的氨基酸对映体的配体交换毛细管电泳方法。在使用10mmol／L NH4AC（pH5．0），5mmol／L CuSO4和10mmol／L L-谷氨酸的条件下，成功地拆分了苯丙氨酸、酪氨酸手性对映体；色氨酸手性对映体也得到部分分离；考察了电泳缓冲液组成、pH值等影响分离效果的因素。     

Non-radioactive determination of PTH and dabsyl phosphoamino acids by capillary electrophoresis

Summary Capillary electrophoresis is a novel technique in the non-radioactive determination of phosphoamino acids. The main advantage of the method presented is the high selectivity and the ability to separate all phosphoamino acid derivatives. Non-radioactive determination of PTH or dabsyl phosphoamino acids by capillary electrophoresis provides a fast and simple screening procedure for all O-phosphorylated amino acids in protein and peptides in the low picomolar range.     

Background-free,fast protein staining in sodium dodecyl sulfate polyacrylamide gel using counterion dyes,zincon and ethyl violet

A background-free, fast protein staining method in polyacrylamide gel electrophoresis using an acidic dye, zincon (ZC) and a basic dye, ethyl violet (EV) is described. It is based on the counterion dye staining technique that employs two oppositely charged dyes to form an ion-pair complex in staining solution. The selective binding of free dye molecules to proteins in acidic solution produces bluish violet-colored bands. It is a rapid and end-point staining procedure, involving only fixing and staining steps that are completed in 1-1.5 h. The detection limit of this method is 8-15 ng of protein that is comparable to the sensitivity of the colloidal Coomassie Brilliant Blue G (CBBG) stain. Due to its sensitivity and speed, this stain may be more practical than any other dye-based stains for routine laboratory purposes.     

Micellar electrokinetic capillary chromatography using polymeric hollow fibers

Summary In this paper, polymeric hollow fibers prepared from pH-stable polypropylene were used as columns for micellar electrokinetic capillary chromatography (MECC). The electroosmotic flow (EOF) for polypropylene hollow fibers was evaluated in the pH range of 5.0–12.0. With untreated polypropylene hollow fibers a stabilized but enhanced EOF was achieved when SDS was used in the buffer, decreasing the separation window for uncharged substances in MECC to impractical levels. Uncharged acrylamide and charged 2-acryloylamido-2-methylpropane sulfonic acid surface modifications were used to lower the strength of the EOF, increase the separation window and prevent local overheating that could melt the column wall.