Determination of arsenic species by capillary zone electrophoresis with large-volume field-amplified stacking injection

Determination of arsenic species by large-volume field amplified stacking injection-capillary zone electrophoresis (LV-FASI-CZE) is reported in this paper. Whole column injection was employed. The optimum buffer pH for the separation of weak acids was discussed. It was found that the optimum buffer to analyze the stacked arsenate (As(V)), monomethylarsonate (MMA), and dimethylarsinate (DMA) was 25 mm phosphate at pH 6.5. However, the optimum buffer to analyze the concentrated arsenite (As(III)) was 20 mm phosphate - 10 mm borate at pH 9.28. The limits of detection of the method developed were 0.026 mg/L for As(III), 0.023 mg/L for As(V), 0.043 mg/L for MMA, and 0.018 mg/L for DMA. An enrichment factor of 34-100 for several arsenic species was obtained. In the end, this method was applied to determine the arsenic concentration in the environmental reference materials to show the usefulness of the method developed.

Matrix-assisted laser desorption/ionization mass spectrometry using porous silicon and silica gel as matrix

Porous silicon powder and silica gel particles have been applied as inorganic matrices for the analysis of small molecules in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOFMS). In contrast to conventional MALDI-TOFMS, the signal interference of low-molecular analytes by the matrix has been eliminated. Almost no fragmentations of the analytes were observed. Effects of various factors, such as the particle and pore size, the suspending solution, and sample preparation procedures, on the intensity of mass spectra have been investigated. The pore structure of the inorganic matrix and penetration of the analytes into the pores must be optimized for effective desorption and ionization of the analytes. Matrices (DHB and HCCA) were covalently bound to silica gel for improvement of spectrum intensity. Copyright (C) 2001 John Wiley & Sons, Ltd.

Separation of enantiomers of drugs by capillary electrophoresis with permethyl-gamma-cyclodextrin as chiral solvating agent

High-throughput screening is a promising new approach in analytical chemistry. Within the framework of an extended screening program (The German-Chinese Drug Screening Program), the enantioseparation of 86 drugs was investigated by capillary zone electrophoresis in the presence of the chiral solvating agent (CSA) octakis-(2,3,6-tri-O-methyl)-gamma-cyclodextrin (TM-gamma-CD). By this means, 15 drugs could be separated into enantiomeric pairs. Approximate measures for the degree of interaction (migration retardation factor, R-m) and for the degree of enantiomer recognition (migration separation factors, alpha(m)) revealed intriguing patterns that were compared with those found for native gamma-cyclodextrin (gamma-CD). Although there is a distinct influence of the analyte structure on the electrophoretic data, interpretation remains difficult. Most remarkably, permethylation of gamma-CD leads neither to a higher affinity nor to better chiral recognition, in contrast to the findings with alpha-CD.

Direct determination of sialic acids in serum by capillary electrophoresis with UV detection

A novel method for the determination of N-acetylneuraminic acid (NANA) and N-glycolylneuraminic acid (NGNA) has been developed using high-performance capillary electrophoresis with UV detection at 195 nm, without pre or post-column derivatisation. The acids were separated in a 50-cm, fused-silica capillary (50 mu m i.d, 45.5-cm effective length) with Na2B4O7-Na2HPO4 buffer. The detection limit for NANA is a concentration of 9.6 x 10(-6) M or, in terms of mass: 3.879 x 10(-14) mol (39 fmol). This method is applicable to determination of NANA in normal human serum. The results were also compared with those of the colorimetrie method.

Transient state of chiral recognition in a binary mixture of cyclodextrins in capillary electrophoresis

The transient state (as the defined point where no enantioseparation is obtained in a dual chiral selector system) of chiral recognition of aminoglutethimide in a binary mixture of neutral cyclodextrins (CDs) was studied by capillary electrophoresis (CE). The following three dual selector systems were used: alpha-cyclodextrin (alpha-CD) and beta-cyclodextrin (beta-CD); alpha-CD and heptakis(di-O-methyl-beta-cyclodextrin) (DM-beta-CD); alpha-CD and heptakis(tri-O-methyl-beta-cyclodextrin) (TM-beta-CD). The S-(-) enantiomer of the analyte was more strongly retained in the presence of either alpha-CD or TM-beta-CD at pH 2.5, 100 mM phosphate buffer, while the R-(+) enantiomer was more strongly retained in the presence of either P-CD or DM-P-CD. In the more simple case, the elution order is invariably kept if the enantiomers have the same elution order in either one of the two hosts of the binary mixture. In contrast, the elution order may be switched by varying the concentration ratio of two hosts that produce opposite elution order for this particular analyte. In such a dual selector system, the enantioselectivity will disappear at the transient state at a certain ratio of host,:host, Moreover, the migration times of the two enantiomers with host, alone (diluted in buffer) is approximately equal to the migration times at the corresponding concentration of host, alone (diluted in buffer), where the ratio of concentrations of host,:host, is the same as in the binary mixture at the transient state. As found by nuclear magnetic resonance experiments, the analyte is forming a 1:1 complex with either one of the CDs applied. From this finding, a theoretical model based on the mobility difference of the two enantiomers was derived that was used to simulate the transient state. (C) 2000 Elsevier Science B.V. All rights reserved.

Separation of drug enantiomers by capillary electrophoresis in the presence of neutral cyclodextrins

This is a selected review, highlighting our results obtained in an extended screening program ("The German-Chinese Drug Screening Program"), with a focus on a set of original data obtained with heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin(TM-beta-CD) as the chiral solvating agent (CSA). The enantioseparation of 86 drugs by capillary zone electrophoresis in the presence of this CSA was successful for 47 drugs. The migration separation factors (alpha(m)) and the migration retardation factors (R-m) were compared with those found for native beta-cyclodextrin (beta-CD). The patterns thus obtained were also compared with those observed for hexakis(2,3,6-tri-O-methyl)-alpha-CD (TM-alpha-CD) and octakis(2,3,6-tri-O-methyl)-gamma-CD (TM-gamma-CD), respectively. From the statistical data, it can be concluded that there is a remarkable influence of the analyte structure on the electrophoretic data. A substructure 4H was found in the analyte structure that has a significant influence on the analytes' behaviour. Thus, analytes bearing the substructure 4H do not only have a strong affinity to the CDs but also a high rate of success of chiral separation in all systems reviewed. In light of this, the different ring sizes of native cyclodextrins (alpha-, beta- and gamma-CD) readily explain their behaviour towards a limited test set of chiral drugs. Sterical considerations point to the significance of side-on-binding versus inclusion in the cavity of the host. In addition to the findings from the screening program, numerous references to the Literature are given. (C) 2000 Elsevier Science B.V. All rights reserved.

Capillary electrophoresis of urinary normal and modified nucleosides of cancer patients

This paper gives a capillary electrophoretic method for the separation of 15 urinary normal and modified nucleosides from cancer patients in less than 40 min. A 500 mmx50 mu m uncoated capillary column (437.5 mm to window) was used. The effects of the voltage and the sodium dodecyl sulfate (SDS) concentration in the buffer on the separation were studied. With reproducibilities of migration times better than 1.2% (R.S.D.) and determined concentrations better than 5-25%, depending on the concentrations of nucleosides in the urine, the analytical characteristics of the method were food. Using this developed method, the concentrations of 13 normal and modified nucleosides, extracted on a phenyl boronic acid affinity chromatography column, in 25 urines from patients of 14 kinds of cancer were determined. The levels (nmol/mol creatinine) of modified nucleosides in urines from cancer patients were increased as compared with those in normal urines. (C) 1998 Elsevier Science B.V.

Quantitative evaluation of the interaction between pUC19DNA and ovalbumin by capillary zone electrophoresis

Capillary zone electrophoresis (CZE) was used to study the interaction between pUC19DNA (pUC19) and ovalbumin (Ova). Samples containing pUC19 and Ova at various ratios were incubated at room temperature and were then separated by CZE with tris-acetate buffer at pH 7.2. Reduction in ultraviolet (UV) absorbance of pUC19 was due to the decrease of free pUC19 after binding to Ova. The binding constant of the interaction calculated from the Scatchard plot was (1.46+/-0.15) x 10(5) M-1. The use of polyacrylamide-coated capillary showed better effects than that of uncoated capillary. The results show that it is important to keep a constant ionic strength in the samples in order to obtain accurate quantitative data in binding assays by CZE.

Interaction between netropsin and double-stranded DNA in capillary zone electrophoresis and affinity capillary electrophoresis

Capillary zone electrophoresis (CZE) and affinity capillary electrophoresis (ACE) were applied to study the interaction between netropsin and a 14mer double-stranded DNA (dsDNA). The use of a polyacrylamide coated capillary can suppress the electroosmotic flow (EOF) and the adsorption of DNA onto the wall. Better analysis of the DNA was achieved in a coated capillary upon Tris-acetate. In CZE, the peak width broadened due to the affinity interaction between dsDNA and netropsin. In ACE, o-toluic acid, a negatively charged molecule was used as the indicator to monitor the changes of EOF when netropsin was added to the running buffer. The 14mer dsDNA showed different mobilities upon various concentrations of netropsin due to the affinity interaction between the dsDNA and netropsin. The binding constants of this interaction were (1.07 +/- 0.10) . 10(5) M-1 calculated from CZE and (4.75 +/- 0.30) . 10(4) M-1 from ACE using a Scatchard plot. The binding stoichiometry was 1:1 calculated from CZE which was superior to ACE in this study. (C) 2002 Elsevier Science B.V. All rights reserved.

Separation and detection of chlorpromazine hydrochloride and promethazine hydrochloride using electrochemiluminescence followed by capillary electrophoresis

Phenothiazine drugs, chlorpromazine hydrochloride (CPZ) and promethazine hydrochloride (PMZ), were determined with Ru(bpy)(3)(2+) electrochemiluminescene by the capillary electrophoresis (CE-ECL). It was found that both CPZ and PMZ could produce an intermediate that acted as coreactants to react with Ru(bpy)(3)(2+) to produce excited states which were capable of emitting light. This CE-ECL detection method had high sensitivity, good selectivity and reproducibility for CPZ and PMZ determination.

A solid-state dye-sensitized solar cell based on a novel ionic liquid gel and ZnO nanoparticles on a flexible polymer substrate

This paper describes a new strategy to make a full solid-state, flexible, dye-sensitized solar cell (DSSC) based on novel ionic liquid gel, organic dye, ZnO nanoparticles and carbon nanotube (CNT) thin film stamped onto a polyethylene terephthalate (PET) substrate. The CNTs serve both as the charge collector and as scaffolds for the growth of ZnO nanoparticles, where the black dye molecules are anchored.

Synthesis and characterization of (Zn,Cd)TiO3 by a modified sol-gel method

Ilmenite-type (Zn1-xCdx)TiO3 (0 <= x <= 0.15 and 0.8 <= x <= 1.0) was synthesized by a modified sol-gel route including the Pechini process via two-step heat treatments. The thermal stability of (Zn1-xCdx)TiO3 depended on the amount of cadmium content. The as-synthesized (Zn1-xCdx)TiO3 (0 <= x <= 0.15 and 0.8 <= x <= 1.0) showed higher thermal stability than that of ZnTiO3. The variation of the dielectric constant of all synthesized (Zn1-xCdx)TiO3 samples for all measurement frequencies showed a similar tendency.