Speciation analysis of aluminium(III) in natural waters and biological fluids by complexing with various catechols followed by differential pulse voltammetry detection

The biological effects of aluminium have received much attention in recent years. Speciation of Al is of basic relevance as it concerns its reactivity and bioavailability. A differential pulse voltammetry (DPV) procedure is proposed for speciation analysis of Al(III) in natural waters and biological fluids using six catechols (L-dopa, dopamine, epinephrine, norepinephrine, caffeic acid and o-benzenediol) as electroactive ligands. The decrease of the DPV anodic peak current for each catechol ligand is linear with the increase of Al concentration. This speciation analysis idea is based on the measurement of the complexation capacity, namely, different affinities of Al(III) for catechols and organic ligands under two pH conditions. The labile monomeric Al fraction (mainly inorganic aluminium) is determined at pH 4.6, while the total monomeric Al fraction is determined at pH 8.5. The principle for Al(III) speciation analysis by an electrochemical method is discussed. This sensitive and simple fractionation method is successfully applied to the speciation analysis of Al in natural waters and the results agree well with those of Driscoll's method. The speciation analysis of Al in biological fluids is also explored and the results are compared with those obtained by ultrafiltration and dialysis. Compared with other speciation protocols the electrochemical method possesses some remarkable advantages: rapidity, high sensitivity, cheap instrumentation and a simple operation procedure.     

Analytical methodologies for aluminium speciation in environmental and biological samples--a review

It is recognized that aluminium (Al) is a potential environmental hazard. Acidic deposition has been linked to increased Al concentrations in natural waters. Elevated levels of Al might have serious consequences for biological communities. Of particular interest is the speciation of Al in aquatic environments, because Al toxicity depends on its forms and concentrations. In this paper, advances in analytical methodologies for Al speciation in environmental and biological samples during the past five years are reviewed. Concerns about the specific problems of Al speciation and highlights of some important methods are elucidated in sections devoted to hybrid techniques (HPLC or FPLC coupled with ET-AAS, ICP-AES, or ICP-MS), flow-injection analysis (FIA), nuclear magnetic resonance (27Al NMR), electrochemical analysis, and computer simulation. More than 130 references are cited.     

Preparation and characterization of aliphatic/aromatic copolyesters based on 1,4-cyclohexanedicarboxylic acid

A series of biodegradable aliphatic/aromatic copolyesters, poly(butylene terephthalate)-co-poly(butylene cyclohexanedicarboxylate)-b-poly(ethylene glycol) (PTCG), were prepared by a two-step melt polycondensation method and characterized by means of GPC, FTIR, NMR, DSC, TGA, etc. The effects of aliphatic ester content on the physical, mechanical and thermal properties, as well as in vitro and in vivo degradation behaviors were investigated. The decrease in mechanical strength was observed with an increase in poly(butylene cyclohexanedicarboxylate) (PBC) molar fraction. DSC results showed one melting point and two glass transition temperatures in all samples, and the melting temperature was found to go down gradually as more cyclohexanedicarboxylic acid (CHDA) was added. During the in vitro and in vivo degradation processes, erosion of the surface was dominant as evidenced by scanning electron microscopic observations. The copolyesters containing many CHDA units were featured by the higher water uptake and faster degradation due to much richer amorphous phase within them.     

Synthesis and Ionic Conductivity of Network Polymer Electrolytes with Internal Plasticizers

Network polymer electrolytes with free oligo(oxyethylene) chains as internal plasticizers were prepared by cross-linking poly(ethylene glycol) acrylates. The effects of salt concentration and properties of internal plasticizers on ionic conductivity were studied.     

Redox behaviour of cysteine in the presence of ammonium trioxovanadate(V)

The interaction of ammonium trioxovanadate(V) with cysteine in aqueous solution was studied by cyclic voltammetry and absorption spectroscopy techniques. In the absence of cysteine, the cyclic voltammogram (CV) of ammonium trioxovanadate(V) solution in 0.1 M phosphate buffer (pH 7) gave two peaks at -0.130 V (reversible) and -0.400 V (irreversible). These peaks (-0.130 V, -0.400 V) can be attributed to V(V)/V(IV) and V(IV)/V(III) redox processes, respectively. In the presence of cysteine at low scan rate (40 mV/s), the peak at -0.780 V, which is assigned to the irreversible reduction of free cystine, was observed. In addition, the reduction peak of the disulfidic anion S(2)(2-) was seen at -0.650 V. Under aerobic conditions, the peaks of the disulfidic anion S(2)(2-) and free cystine are well separated. From electronic spectra of ammonium trioxovanadate(V) and cysteine mixtures, LMCT transition associated with V(V)-cyteine complex was obtained at 743 nm. The stoichiometry (ML(2)) and stability constant (log beta(1:2)=6.67) of V(V)-cysteine complex were determined by means of mole ratio method.     

The practical synthesis of a novel and highly potent analogue of bryostatin

Macrocycle 1 is a new highly potent analogue of bryostatin 1, a promising anti-cancer agent currently in human clinical trials. In vitro, 1 displays picomolar affinity for PKC and exhibits over 100-fold greater potency than bryostatin 1 when tested against various human cancer cell lines. Macrocycle 1 can be generated in clinically required amounts by chemical synthesis in only 19 steps (LLS) and represents a new clinical lead for the treatment of cancer.     

A Novel Preprocessing Algorithm for Three-Way HPLC Data

Orthogonal signal correction (OSC) was a data preprocessing algorithm. It ensured that the filtered information was irrelevant to concentration data while using it to filter the noise from the original data. This paper extended the OSC application range from two-way data to three-way data. Two drug data sets, Enoxacin, Norfloxacin, Ciprofloxacin and Betamethasone, cortisone acetate, prednisone acetate, showed that the application of the OSC algorithm to three-way HPLC data was feasible and needed further research.     

超高效液相色谱-串联质谱法测定茶叶中游离氨基酸成分

建立了使用超高效液相色谱-串联质谱（UHPLC-MS/MS）高效、快速直接测定茶叶中游离氨基酸的方法。通过对质谱、色谱条件及氨基酸提取条件的优化，以含0.2%（体积分数）甲酸的5 mmol/L乙酸铵水溶液和甲醇为流动相进行梯度洗脱，在电喷雾离子（ESI）源正离子扫描模式下检测，通过UHPLC-MS/MS测定，共解析了茶叶中的20种氨基酸。结果表明，茶氨酸（Thea）、Arg、Asn和Asp在50~500 μg/L范围内线性关系良好，其他氨基酸在10~250 μg/L范围内线性关系良好，相关系数均大于0.99；加标回收率为92.3%~109.2%，相对标准偏差为2.00%~9.88%，检出限为0.001~0.011 mg/L，定量限为0.010~0.053 mg/L。该方法灵敏、准确，具有良好的重复性和稳定性，可有效检测出茶叶中的20种氨基酸及氨基类成分。