Separation of niobium(V) and tantalum(V) by capillary electrophoresis with chemiluminescence detection

First investigation of polyoxoniobate and polyoxotantalate aqueous speciation by capillary zone electrophoresis

Aqueous solutions of hexaniobate (H_xNb₆O₁₉^x−8, 0 ≤ x ≤ 3) and hexatantalate ions (H_xTa₆O₁₉^x−8, 0 ≤ x ≤ 3) have been probed by capillary zone electrophoresis (CE) for the first time.

High throughput methods for analyzing transition metals in proteins on a microgram scale

Transition metals are among the most common ligands that contribute to the biochemical and physiological properties of proteins. In the course of structural proteomic projects, the detection of transition metal cofactors prior to the determination of a high-resolution structure is extremely beneficial. This information can be used to select tractable targets from the proteomic pipeline because the presence of a metal often improves protein stability and can be used to help solve the phasing problem in x-ray crystallography. Recombinant proteins are often purified with substoichiometric amounts of metal loaded, so additional metal may be needed to obtain the homogeneous protein solution crucial for structural analysis. Furthermore, identifying a metal cofactor provides a clue about the nature of the biological role of an unclassified protein and can be applied with structural data in the assignation of a putative function. Many of the existing methods for transition metal analysis of purified proteins have limitations, which include a requirement for a large quantity of protein or a reliance on equipment with a prohibitive cost.The authors have developed two simple high throughput methods for identifying metalloproteins on a microgram scale. Each of the techniques has distinct advantages and can be applied to address divergent experimental goals. The first method, based on simple luminescence and colorimetric reactions, is fast, cheap, and semiquantitative. The second method, which employs HPLC separation, is accurate and affords unambiguous metal identification.

An evaluation of the experimental approaches to detection of small ions in CE

This review points out some important trends in the development of the detection techniques for small ions in CE. On the basis of selected literature references it briefly discusses some general requirements on detection techniques in CE. Various optical measurements, mass spectrometric approaches and electrochemical detection techniques are dealt with. Some specific features of microchip CE separation and detection are pointed out and possibilities of dual detection are mentioned. The principal parameters of the above detection techniques are then briefly compared.

Electrochemical and optical detectors for capillary and chip separations

In separations in capillaries or on chips, the most predominant detectors outside of the field of proteomics are electrochemical (EC) and optical. These detectors operate in the μM to pM range on nL peak volumes with ms time resolution. The driving forces for improvement are different for the two classes of detectors.With EC detectors, there are two limitations that the field is trying to overcome. One is the ever-present surface of the electrode which, while often advantageous for its catalytic or adsorptive properties, is also frequently responsible for changes in sensitivity over time. The other is the decoupling of the electrical systems that operate electrokinetic separations from the system operating the detector.With optical detectors, there are similarly a small number of important limitations. One is the need to bring the portability (size, weight and power requirements) of the detection system into the range of EC detectors. The other is broadening and simplifying the applications of fluorescence detection, as it almost always involves derivatization.Limitations aside, the ability to make detector electrodes and focused laser beams of the order of 1 μm in size, and the rapid time response of both detectors has vaulted capillary and chip separations to the forefront of small sample, fast, low mass-detection limit analysis.

Determination of phenothiazines in pharmaceutical formulations and human urine using capillary electrophoresis with chemiluminescence detection

A CE instrument coupled with chemiluminescence (CL) detection was designed for the determination of promethazine hydrochloride (PTH) and promazine hydrochloride (PMH) in real samples. An important enhancement of the CL emission of luminol with potassium ferricyanide was observed in the presence of these phenothiazines; so this system was selected for their detection after CE separation. Parameters affecting the electrophoretic separation were optimized in a univariate way, while those affecting CL detection were optimized by means of a multivariate approach based on the use of experimental designs. Chemometrics was also employed for the study of the robustness of the factors influencing the postcolumn CL detection. The method allows the separation of the phenothiazines in less than 4 min, achieving LODs of 80 ng/mL for PMH and 334 ng/mL for PTH, using sample injection by gravity. Electrokinetic injection was used to obtain lower LODs for the determination of the compounds in biological samples. The applicability of the CE-CL method was illustrated in the determination of PTH in pharmaceutical formulations and in the analysis of PMH in human urine, using a previous SPE procedure, achieving an LOD of 1 ng/mL and recoveries higher than 85%.

Capillary electrophoresis with chemiluminescence detection of rutin and chlorogenic acid based on its enhancing effect for the luminol-ferricyanide system

A capillary electrophoresis with chemiluminescence method has been developed for the determination of rutin and chlorogenic acid based on its enhancing effect on the luminol-ferricyanide system. Under the optimum conditions, the analytes could be separated within 5 min, and the detection limits of the proposed method were 0.22 microg/ml for rutin and 0.50 microg/ml for chlorogenic acid, respectively. The method was successfully applied to the analysis of rutin and chlorogenic acid in real samples.

On-line chemiluminescence determination protocatechuic aldehyde and protocatechuic acid in pharmaceutical preparations by capillary electrophoresis

Capillary electrophoresis (CE) with on-line direct chemiluminescence (CL) detection was first used in detecting protocatechuic aldehyde (PAH) and protocatechuic acid (PA) in their pharmaceutical preparations. It was found that the weak CL produced from the reaction of luminol with ferricyanide in an alkaline solution was strongly increased by PAH and PA which was separated by CE. Parameters affecting separation process and CL detection have been examined in detail. Under the optimum conditions, the baseline separation of PAH and PA was obtained within 6 min. The relative standard deviation (R.S.D.) for the analysis of PAH and PA was less than 1.1% for the migration time and 1.6% for the peak height. The detection limits (S/N=3) of PAH and PA were 7.0 x 10(-8)M and 5.0 x10(-8)M, respectively. The proposed method has been satisfactorily applied to the determination of PAH and PA in Salivia miltorrhrza pharmaceutical preparations.

Chemiluminescence determination of pharmacologically active compounds by capillary electrophoresis

A simple and rapid capillary electrophoresis with direct chemiluminescence method has been developed for the determination of five natural pharmacologically active compounds including rutin, protocatechuic aldehyde, chlorogenic acid, luteolin and protocatechuic acid. The luminol as a component of the separation electrolyte buffer was introduced at the head of the separation capillary. The separation of five compounds was carried out in a fused-silica capillary with 15.0 mmol/L tetraborate, 1.0 mmol/L SDS and 0.42 mmol/L luminol (pH 8.5). The analytes was determined by enhancing the chemiluminescence of luminol with 0.13 mmol/L K3Fe(CN)6 in 0.05 mol/L NaOH, which was introduced at the post-column stage. The voltage applied was 16 kV. Under the optimum conditions, the analytes were separated within 10 min. The excellent linearity was obtained over two to three orders of magnitude with a detection limit (signal:noise = 3) of 0.012-0.055 micromol/L for all five analytes. The method was successfully used in the analysis of pharmaceutical and biological samples, and the assay results were satisfactory.

Derivatization of inorganic ions in capillary electrophoresis

This review gives a short overview of the main approaches to the derivatization of inorganic ions in capillary electrophoresis (CE) with emphasis on the most recent works. Various derivatization procedures and detection methods are discussed. A brief account of their advantages and limitations is given. More specific areas such as microchip CE, simultaneous separation of anions and cations, and speciation analysis are also briefly discussed.

Ultrasensitive chemiluminescence detection in capillary electrophoresis

Capillary electrophoresis techniques offer high plate numbers and are highly suited for the efficient separations of a wide variety of chemical components in diverse matrices. Because of the small capillary and detection cell dimensions, together with the minute volumes of samples to be injected, sensitive detection schemes based on different physicochemical principles are being developed. One logical approach to increased sensitivity in capillary electrophoresis detection has been the development of chemiluminescence-based detectors. The development of on-line ultrasensitive chemiluminescence detection (referred to the concentration detection limit of nM order of magnitude or mass detection limit of amol order of magnitude) in capillary electrophoresis system is reviewed. The applications and limitations of the current detection methodology are briefly considered and future prospects for the development are discussed.