Applicability of capillary zone electrophoresis to study metal complexation in solution

The stability constants of the proton and metal complexes of basic α-amino acids, arginine, lysine, and ornithine, have been collected and critically evaluated on the basis of the considerations of the factors affecting the stability constant determinations, such as experimental methods, conditions of measurements, purity of reactants, calibration of the apparatus, and methods of calculation. In the presence of the side chain basic group, metal complex formation normally occurs through the glycine-like mode of coordination by the amino acids with the side chain group protonated, and deprolonation from the complexes often occurs in basic solution. The collected stability constants were evaluated as ‘recommended’, ‘tentative’, ‘informative’, ‘doubtful’, or ‘rejected’ according to the above criteria. The thermodynamic parameters reported for a limited number of complexes have also been collected and evaluated.

Application and optimization of capillary zone electrophoresis in vitamin analysis

Presdented is a review of the stability constants for metal complexes with thiocyanate ion. The literature data presented is critically discussed and recommended values, where warranted, listed from the many studies cited.

Synthesis, spectral, thermal, potentiometric and antimicrobial studies of transition metal complexes of tridentate ligand

Critical Evaluation of Stability Constants for Nucleotide Complexes With Protons and Metal Ions and the Accompanying Enthalpy ChangesSeries Title: Critical Evaluation of Stability Constants of Metal Complexes in Solution.

The stability constants of a series of internal metal complexes derived from 8-hydroxyquinoline, salicylaldehyde, and acetylacetone have been determined by means of an electrometric method. A quantitative treatment of the chelation of 8-hydroxyquinoline, based on the theory of step equilibria, is given and the modifications required for dealing with the other substances investigated are indicated. Two important facts emerge from this survey : (1) The order of the metals (as regards stability of their complexes) is substantially the same for each of the three chelating substances studied. (2) The order of the stability of the complexes derived from the three chelating substances is independent of the nature of the coordinating metal, the 8-hydroxyquinoline complex of a metal being more stable than its acetylacetone complex which in turn is more stable than its salicylaldehyde complex. Measurements were made of the stability constants in water-dioxan mixtures and the effect of changing the proportions of the two components in the solvent mixture was studied in several instances. The values of stability constants of internal metal complexes in water-dioxan mixtures are greater than those in water. It is shown that insolubility of internal metal complexes is not, in general, a criterion of their relative stability. The possible significance of stability-constants in chemotherapy, biochemistry, and analytical chemistry is briefly discussed.

Article Determination of Stability Constants of Metal Complexes by Polarographic Methods - A Review was published on December 1, 1986 in the journal Reviews in Analytical Chemistry (volume 8, issue 4).

Critical Survey of Stability Constants of Complexes of Glycine Series Title: Critical Evaluation of Stability Constants of Metal Complexes in Solution

Article Critical evaluation of equilibrium constants in solution. Stability constants of metal complexes was published on January 1, 1977 in the journal Pure and Applied Chemistry (volume 49, issue 1).

Application of capillary zone electrophoresis to the analysis and to a stability study of cephalosporins

Metallothioneins (MTs) from various eukaryotic species were subjected to capillary zone electrophoresis (CZE) performed under the following conditions: Capillary: untreated polyimide-clad fused silica 75 (im I.D. × 94 cm; Loading and Running Voltage: 30 kV; Electrode Buffer: 50 mM Tris-HCI pH 9.1; Sample Buffer: 10 mM Tris-HCI pH 9.1; Sample Volume: 250 μl; Detection: UV absorbance at 214 nm; Loading Method: electrokinetic migration; Loading Times: 1–6 seconds. Complete separation of MT-1 and MT-2 isoforms was achieved in less than 6 min. Using a rabbit liver Cd, Zn-MT standard (0.5 mg/ml), a linear relationship was found to exist between the voltage used to load the MT sample and the integrated peak area of the individual MT isoforms. Similarly, the integrated peak area of the separated MT isoforms was a linear function of the time used to load the sample. These findings suggest that with appropriate standardization CZE is capable of both qualitative and quantitative determinations of MT isoforms. In CZE, the concentration of MT in solution determines the limit of sensitivity. MT could be accurately detected at a concentration as low as 10 μg/ml. CZE was applied to assess thermal and proteolytic degradation of rabbit liver MT. CZE represents a rapid analytical technique for the characterization of MT isoforms that requires very little sample yet provides excellent resolution of individual MT isoforms.

Determination of deamidated isoforms of human insulin using capillary electrophoresis.

The application of capillary zone electrophoresis (CZE) to the separation and determination of creatinine in human urine with photodiode array detection was described. Optimum conditions for the separation were established. The effect of pH of the background buffer on the existence state of creatinine was investigated. Photodiode array detection permitted the rapid identification of creatinine in the samples analysed. By selecting 234 nm as monitoring wavelength, the interference from urea in urine was eliminated. By selecting a suitable pH, the interferences from other substances in urine were also eliminated. The linear range, detection limit, precision and recovery of the method were investigated.

Nanoparticles are a potential source and carrier of nutrients and pollutants in aquatic ecosystems, yet the stability of nanoparticles in environmental conditions is poorly known. Here, we studied volcanic ash nanoparticles by simultaneous application of capillary zone electrophoresis and laser diffraction for determination of size, zeta-potential and long-term aggregation stability. Results show that volcanic ash nanoparticles remained stable for at least 28 days. Stability increases from pH 5.5 to 8.5. Zeta-potentials are − 56 mV at pH 7.2 and − 64 mV at pH 8.5. Findings imply that volcanic ash nanoparticles have a high potential for long-range transport of nutrient and toxic elements in surface waters. Moreover, the developed method allows direct conversion of electropherograms into particle size distributions.

The possibilities and applications of capillary electrophoresis (CE) as an analytical technique for plant secondary metabolites are reviewed. Applications of both capillary zone electrophoresis and micellar electrokinetic capillary chromatography for this purpose are described. CE is compared with high pressure liquid chromato‐graphy (HPLC) as an analytical technique, and the advantages and criticisms of CE are described. The effects of the applied voltage, capillary temperature, electrolyte concentration and nature (complexing or non‐complexing buffers), buffer pH, micelle concentration and nature (sodium dodecyl sulphate or cetyltrimethylammonium bromide and the addition of organic modifiers to the running buffer (organic solvents, cyclodextrins, urea, cholate) on the parameters of separation and resolution of different secondary metabolites are discussed. The applications of CE to the analysis of flavonoid aglycones and glycosides, phenolic acids, quinones, coumarins, alkaloids, capsacinoids, glucosinolates, polyamines, monoterpenes, diterpenes, phytoecdysteroids, cardiac glycosides and saponins are shown. It is concluded that CE is a very promising analytical technique in the analysis of plant secondary metabolites, and it will become an indispensable tool, together with HPLC and gas liquid chromatography, in phytochemical laboratories since these techniques are in many ways complementary, and problems that are difficult to solve by HPLC can often be solved using CE.