Cheng Jieke

Reversed-phase HPLC determination of some noble metals as their thiazolylazoresorcinol chelates.

The first use of 4-(2-thiazolylazo)resorcinol (TAR) as a chelating reagent in the reversed-phase HPLC separation and determination of Os, Rh and Ru is reported. A precolumn derivatization method is used, followed by separation on an octadecyl-bonded silica stationary phase with a methanol-water mobile phase. The coloured complexes of Os, Rh, and Ru are completely separated within 8 min with a 60:40 v/v methanol-water mixture (pH 4.0, tetrabutylammonium as counter-ion). The detection limits for Rh, Ru and Os at 550 nm are 5, 6 and 17 ng/ml respectively. Recoveries of 94-102% have been obtained for these trace noble metals in analysis of anode slime.

Separation mechanism exploration on metal-MBTAE-salicylic acid mixed ligand complexes by reversed-phase high performance liquid chromatography

The separation and determination of platinum metal and co-existing metal complexes by reversed-phase high performance liquid chromatography (HPLC) with 2-(6-methyl-2-benzothiazolylazo)-5-diethylamino phenol (MBTAE) as a precolumn derivatizing reagent is presented. The separation mechanism of these complexes was investigated by combining spectrophotometry with HPLC while salicylic acid was contained in the mobile phase. The results show that most platinum metal ions, Co(II) and Cu(II) can form ternary mixed ligand complexes with MBTAE and salicylic acid. The relationship of the retention behavior of complexes and the surface tension of the mobile phase (gamma), the column temperature (T), and the composition and space configuration of complexes was also investigated. Some possible configurations of complexes are also proposed. These may all be illustrated well from the viewpoint of solvophobic theory. These method allowed the prediction of the composition and structure of metal complexes by utilizing HPLC.

Determination of total rare earth elements, thorium and chromium with 2-(2-arsenophenylazo)-1,8-dihydroxy-7-(2,6-dibromo-4-fluorophenylazo) naphthalene-3,6-disulphonic acid by reversed-phase ion-pair liquid chromatography

Abstract The retention behaviour of the complexes of rare earth elements, thorium and chromium with 2-(2- arsenophenylazo)-1,8-dihydroxy-7-(2,6-dibromo-4-fluorophenylazo)naphthalene-3,6-disulphonic acid was studied. Precolumn derivatization was used. The stationary phase was ODS-bonded silica and the mobile phase was methanol-water-tetrabutylammonium bromide. The detection limits are 2 ng ml−1 for total rare earths, 2.5 ng ml−1 for thorium and 10 ng ml−1 for chromium. The tolerance of foreign ions is very high. The method can be applied satisfactorily to ore samples and rocks.

Comparison of Four Carbon Fiber Electrodes in Microfluidic Chip Integrated With Electrochemical Detector

Abstract A microchip electrophoresis system with integrated amperometric detector was developed. Using 0.02 M Tris-HCl (pH = 8) as buffer, at the detection potential of 0.6 V ( vs . Ag/AgCl), dopamine (DA) and isoprenaline (IP) were detected by chip-CE with end-column amperometric detection using a carbon fiber microelectrode (CFME), a carbon fiber nanoelectrode (CFNE), a carbon fiber microelectrode modified by single-walled carbon nanotubes (SWNTs-CFME), and a carbon fiber microdisc electrode (CFMDE). The resolution of DA and IP are 0.64, 1.06, 0.61 and 1.22, and the sensitivity of DA ( S / N = 3) are 1.7 × 10 −7 , 5.9 × 10 −8 , 2.3 × 10 −8 , and 5.3 × 10 −7 , respectively. As the CFNE had high resolution and sensitivity, the nanoelectrode-based microchip CE system was successfully applied to the determination of DA in cultured rat pheochromocytoma (PC12) cells, and the average content of DA in an individual PC12 cell was 0.57 ± 0.07 fmol ( n = 5), which was in good agreement with that reported in the literatures.

Synthesis of meso-tetra-(2-chloro-4-sulfophenyl) prophyrin and spectrophotometric determination of trace amounts of cadmium

Synthesis of a new high sensitive water soluble chromogenic reagent meso-tetra-(2-chloro-4-sulfophenyl) prophyrin and the conditions for the reaction of this reagent with cadmium (I) were studied. The apparent molar absorption coefficient at 434 nm is 5.20×105 L·mol−1·cm−1. The method has been applied to the determination of 5.0×10−9 (content by weight) Cadmium (I) in honey.

Separation of DNA fragments by cross-linked polymer coating capillary electrophoresis with non-gel sieving matrix

A new type of flush/fill equipment driven by high-pressure (1MPa) nitrogen gas for filling the capillary is demonstrated. High-viscous and microlitre grade volume solution can be filled into a capillary by means of this equipment. The capillary coated by cross-linked polyacrylamide and filled with “interpenetrating polymer networks” non-gels sieving matrix (0.8% hydroxyethyl cellulose, 10% sucrose in 1×TBE buffer) was applied for separating DNA fragments. All 11 fragments of Ø174/Hae III DNA were successfully separated. The man-made circle plasmid from E. coli were separated and detected.

Kinetic Characteristic of Photooxidation of Cypermethrin by Organic Peroxy Radical

The kinetic characteristic of photolysis of cypermethrin (CPM) sensitized by acetophenone (AP) and the effect of probe substance 2,6-Di-tert-butyl-4-methylphenol and tetralin is studied in this report. It showed that the photolysis rate of CPM increases slightly with the increase of AP concentration; photolysis rate of CPM has no relationship with [CPM] itself; The more dipolar moment the solvent has, the more the interaction between radical and solvent has, and the slower the photolysis of CPM is. The addition of radical probe substance confirms that ROO·is more than RO·. The steady-state concentration of ROO·is about 10−8 mol·L−1.

Amperometric detection of histamine and amino acid neurotransmitters in capillary electrophoresis with copper microelectrodes

Copper microelectrodes were used in microvoltammetry to detect histamine and several amino acid neurotransmitters. High sensitivity was obtained through the use of copper microelectrodes, and detection limits of 50 nmol/L and 90 nmol/L were obtained for histamine and histidine, respectively. Furthermore, histamine and several amino acids neurotransmitters were firstly separated and detected by capillary electrophoresis with amperometric detection on copper microelectrodes. Mass limits of 490 amol and 440 amol were achieved for histamine and histidines, respectively, by using this mothod.

Separation of Co(II), Ni(II) and Pd(II) with 2-(5-nitro-2-pyridylazo)-5-dimethylaminobenzoic acid by high-performance liquid chromatography

Summary2-(5-Nitro-2-pyridylazo)-5-dimethylaminobenzoic acid has been found to be a suitable precolumn derivatization reagent for the separation of Co, Ni and Pd. The detection limit for Pd at 665 nm is 0.64 ppb; the linear calibration range is 8–400 ppb.

Synthesis of tin(IV) vanadopyrophosphate as a novel stationary phase for high-performance liquid chromatography and its application to amino acid analysis

The preparation and ion-exchange properties of a novel microcrystalline ion exchanger, tin(IV) vanadopyrophosphate (SVPP), were studied. The exchanger has a high ion-exchange capacity (3.17 mequiv g–1), and its chemical and thermal stabilities are excellent. It was used as a stationary phase for the high-performance ion-exchange chromatographic separation of amino acids. Optimum conditions for high-performance liquid chromatography were investigated. Five amino acids were separated rapidly on a short SVPP column.