Effect of eluent on the ionization efficiency of flavonoids by ion spray, atmospheric pressure chemical ionization, and atmospheric pressure photoionization mass spectrometry.

The effect of nine different eluent compositions on the ionization efficiency of five flavonoids was studied using ion spray (IS), atmospheric pressure chemical ionization (APCI), and the novel atmospheric pressure photoionization (APPI), in positive and negative ion modes. The eluent composition had a great effect on the ionization efficiency, and the optimal ionization conditions were achieved in positive ion IS and APCI using 0.4% formic acid (pH 2.3) as a buffer, and in negative ion IS and APCI using ammonium acetate buffer adjusted to pH 4.0. For APPI work, the eluent of choice appeared to be a mixture of organic solvent and 5 mM aqueous ammonium acetate. The limits of detection (LODs) were determined in scan mode for the analytes by liquid chromatography/mass spectrometry using IS, APCI and APPI interfaces. The results show that negative ion IS with an eluent system consisting of acidic ammonium acetate buffer provides the best conditions for detection of flavonoids in mass spectrometry mode, their LODs being between 0.8 and 13 microM for an injection volume of 20 microl.     

Chiral analysis of biogenic D,L-amino acids derivatized by N-fluorenylmethoxycarbonyl-L-alanyl N-carboxyanhydride using high-performance liquid chromatography

Nineteen biogenic D,L-amino acids are derivatized with highly reactive N-fluorenylmethoxycarbonyl-L-alanyl N-carboxyanhydride. Using a 0.5M borate buffer at pH 7.5 and acetone, the derivatization of amino acids is completed in 5 min at room temperature. Some of the resulting diastereomeric N-protected dipeptides are successfully separated on an octylsilica stationary phase using 100mM acetate buffer (pH 4.4) and acetonitrile as the eluent.     

Reversed-phase partition high-pressure liquid chromatography of trace amounts of inorganic and organic mercury with silver diethyldithiocarbamate

Inorganic and organic mercury diethyldithiocarbamates have been separated by reversedphase partition high-pressure liquid chromatography. The mercury chelates were formed by an exchange reaction with silver diethyldithiocarbamate in chloroform, in the presence of acetate buffer (pH 5.0). The inorganic and organic mercury chelates in the extract were separated within 30 min on a 3.9 x 300 mm mu-Bondapak C(18) column. EDTA (10(-4)M) in methanol-water mixture (78:22 v v ) was used as eluent at a flow-rate of 0.5 ml min .     

Chiral CE of aromatic amino acids by ligand-exchange with zinc(II)-L-lysine complex

A novel method of chiral ligand-exchange CE was developed with either L- or D-lysine (Lys) as a chiral ligand and zinc(II) as a central ion. This type of chiral complexes was explored for the first time to efficiently separate either individual pairs of or mixed aromatic amino acid enantiomers. Using a running buffer of 5 mM ammonium acetate, 100 mM boric acid, 3 mM ZnSO(4) x 7H(2)O and 6 mM L-Lys at pH 7.6, unlabeled D,L-tryptophan, D,L-phenylalanine, and D,L-tyrosine were well separated, giving a chiral resolution of up to 7.09. The best separation was obtained at a Lys-to-zinc ratio of 2:1, zinc concentration of 2-4 mM and running buffer pH 7.6. The buffer pH was determined to have a strong influence on resolution, while buffer composition and concentration impacted on both the resolution and peak shape. Boric acid with some ammonium acetate was an adoptable buffer system, and some additives like ethylene diamine tetraacetic acid capable of destroying the complex should be avoided. Fine-tuning of the chiral resolution and elution order was achieved by regulating the ratio of L-Lys to D-Lys; i.e. the resolution increased from zero to its highest value as the ratio ascended from 1:0 to 1:infinitive, and L-isomers eluted before or after D-isomers in excessive D- or L-Lys, respectively.     

Retention,enantioselectivity and enantiomeric elution order of propranolol and its ester derivatives on an alpha1-acid glycoprotein-bonded column

Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an ₁-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.     

Meso-四(对-磺基苯基)卟啉光度法测定螺旋藻中的痕量锌

在pH=4．5的乙酸-乙酸钠缓冲介质中，锌和meso-四-（对磺基苯基）卟啉生成1：l的黄色配合物，λmax=421nm，ε=4.34×105L·mol-1·cm-1。该法可不经分离直接测定螺旋藻中的锌,结果满意。     

High performance liquid chromatographic analysis of tetroxoprim and sulphadiazine in serum and urine.

Quantitative determination of tetroxoprim and sulphadiazine in serum and urine was performed using reversed phase high performance liquid chromatography. Protein precipitation using 10% perchloric acid was utilized for purification of serum samples while urine samples were diluted prior to analysis. The mobile phase consisted of triethylammonium acetate buffer (85%), acetonitrile (12%) and methanol (3%), with a final pH of 4.2. The eluent was monitored at 280 nm. Benzoic acid was used as an internal standard. Standardization, validation and application of the method is described.     

Complexation of antibacterial quinolonic acid and cinolonic derivatives with Zn(II) and Al(III): application to their determination in human urine

Nalidixic acid, 7-hydroxymethylnalidixic acid, oxolinic acid, pipemidic acid and cinoxacine form complexes with zinc(II) in the presence of acetate buffer of pH 5.5 and oxolinic acid, pipemidic acid and cinoxacine form complexes with aluminium(III) in the presence of chloroacetate buffer of pH 3.0. In all cases, an enhancement of the fluorescence emission was observed. Fluorimetric studies on the spectral characteristics of the complexes were performed. A 1:1 stoichiometry for all the complexes was established. The association constants were calculated, by using the changes in the fluorescence of all antibacterials, that occurred when the complexes were formed. The fluorescence reactions were used to develop methods for the determination of all of the above compounds, showing a higher sensitivity than in the absence of the cationic ions. The methods were satisfactorily applied to the determination of these compounds in urine.     

螯合树脂在线富集火焰原子吸收法测定痕量铅和镉

在pH=4.88的乙酸-乙酸钠缓冲溶液中,用螯合离子交换树脂富集铅和镉,以1.50mol/L HNO3作洗脱液,火焰原子吸收法测定洗脱液中痕量铅和镉。该方法对铅和镉的线性范围分别是4.0～80.0μg/L和2.0～30.0μg/L,检出限分别为1.3μg/L和0.7μg/L。该方法用于地表水中痕量铅和镉的测定,分析结果满意。     

On-line preconcentration and determination of Zn in natural water samples employing a styrene-divinylbenzene functionalized resin and flame atomic absorption spectrometry.

In this work, flame atomic absorption spectrometry (FAAS) was used as a detector for the determination of zinc in natural water samples with a flow-injection system coupled to solid-phase extraction (SPE). In order to promote the on-line preconcentration of zinc from samples a minicolumn packed with 35 mg of a styrene-divinylbenzene resin functionalized with (S)-2-[hydroxy-bis(4-vinylphenyl)methyl]pyrrolidine-1-carboxylic acid ethyl esther was utilized. The system operation was based on Zn(II) ion retention at pH 9.5 +/- 0.5 in such a minicolumn with analyte elution, at the back flush mode, with 1 mol L(-1) HCl directly to the FAAS nebulizer. The influence of the chemical (sample pH, buffer concentration, HCl eluent concentration and effect of the ionic strength) and flow (sample and eluent flow rates and preconcentration time) parameters that could affect the performance of the system were investigated as well as the possible interferents. At the optimum conditions, for 2 min of preconcentration time (9.9 ml of sample volume), the developed methodology presented a detection limit of 1.1 microg L(-1), a RSD of 3.5% at 10 microg L(-1) and an analytical throughput of 24 h(-1). Whereas, for 4 min of the preconcentration time (19.8 ml of sample volume) a detection limit of 0.98 microg L(-1), a RSD of 6.5% at 5 microg L(-1) and a sampling frequency of 13 h(-1) are reported.     

A Comparison and Clinical Applications of Ammonium Acetate and Phosphate Based Mobile Phases for the Separation of Catecholamines on Reversed Phase Columns

Abstract

A novel ion paired high performance liquid chromatographic system on reversed phase columns with ammonium acetate buffer as eluent is described for the separation of catecholamines. The advantages of using ammonium acetate buffer have been systematically studied and compared with the more widely employed phosphate buffer. The applicability of the method was demonstrated by analysis of catecholamines in clinical specimens.     

Determination of transition metal ions in tobacco as their 2-(2-quinolinylazo)-5-dimethylaminophenol derivatives using reversed-phase liquid chromatography with UV-VIS detection

This paper reports the utilization of solid-phase extraction and the reversed-phase high-performance liquid chromatography for the determination of six important transition metal ions: iron, cobalt, nickel, copper, zinc and manganese in tobacco with 2-(2-quinolinylazo)-5-dimethylaminophenol (QADMAP) as chelating reagent. Iron, cobalt, nickel, copper, zinc and manganese ions react with QADMAP to form colored chelates in the medium of acetic acid-sodium acetate buffer solution (pH 4.0). These chelates can be enriched by solid-phase extraction with Waters Sep-Pak-C18 cartridge, and eluted the retained chelates from cartridge with tetrahydrofuran. The chelates were separated on a Waters Nova-Pak-C18 column (150x3.9 mm, 5 microm) by gradient elution with methanol (containing 0.5% of acetic acid) and 0.05 mol/l pH 4.0 acetic acid-sodium acetate buffer solution as mobile phase at a flow-rate of 0.5 ml/min. The detection limits of iron, cobalt, nickel, copper, zinc and manganese are 10, 12, 8, 13, 17 and 22 ng/l, respectively. This method had been applied to the determination of iron, cobalt, nickel, copper, zinc and manganese in tobacco with good results.     

磷酸盐洗脱液再生IMAC-Cu蛋白质芯片

使用扫描电子显微镜（SEM）和蛋白质芯片检测系统考察了磷酸盐洗脱液pH值和竞争洗脱剂对IMAC-Cu蛋白质芯片再生的影响。 结果表明,随着磷酸盐洗脱液pH值降低,芯片所吸附的蛋白质越容易被去除,但对芯片表面化学结构的破坏也随之加剧。 在洗脱液中加入竞争洗脱剂乙二胺四乙酸（EDTA）或甘氨酸（Gly）可有效改善蛋白质的洗脱效果。 当磷酸盐洗脱液pH=6.5、竞争洗脱剂为0.02 mol/L EDTA、洗脱时间72 h时,芯片的再生效果最佳。     

HPLC determination of orthophosphate coexisting with large amounts of organophosphates in biological samples

A simple and accurate HPLC method for the determination of orthophosphate in the presence of large amounts of organophosphates is described. The method is based on the formation and separation of the molybdenum orthophosphate complex. In order to prevent the hydrolysis of organophosphates, the sample was deproteinized with silicotungstate in acetate buffer (pH 4.0) under ice-cooling and then treated with ammonium molybdate in maleate buffer (pH 7.0). The sample was injected onto Styragel 60 A column (5 mm ID x 100 mm) with 38% (v/v) acetonitrile containing 0.3 M sulfuric acid as eluent. Detection was at 310 nm. The method was applied to the determination of orthophosphate in liver, kidney, spleen and mouse blood.     

Synthesis and characterization of a novel cross-linking complex of beta-cyclodextrin-o-vanillin benzoylhydrazone and its selective spectrofluorimetric determination of trace amounts of zinc

A novel host inclusion complex of beta-cyclodextrin-o-vanillin benzoylhydrazone (beta-CDP-OVBH) was prepared and characterized by IR and 1H-NMR spectra. A highly selective and sensitive fluorescent determination of trace amounts of zinc was proposed based on the reaction between Zn(2+) and beta-CDP-OVBH in sodium hydroxide-ammonium acetate buffer medium of pH 8.3. The molar ratio of beta-CDP-OVBH to Zn(2+) was 1:1.The maximum excitation and emission wavelengths were 396 and 486 nm, respectively. The linear range of this method was 2.5-500 microg l(-1) with a detection limit of 0.60 microg l(-1). The effect of interferences in the determination of zinc was investigated, the results showed that the host reagent had a quite high identifying capacity on Zn(2+). This method was successfully applied to the determination of trace amounts of Zn(2+) in tea and human hairs.     

Isolation of metallothionein from cells derived from aggressive form of high-grade prostate carcinoma using paramagnetic antibody-modified microbeads off-line coupled with electrochemical and electrophoretic analysis

Prostate cancer with altered zinc(II) cell metabolism is the second most frequently diagnosed cancer in developed countries. The alterations of zinc(II) metabolism can influence metabolism of other metal ions and can also be associated with the expression and translation of metal-binding proteins including metallothioneins. The aim of this article was to optimize immunoseparation protocol based on paramagnetic beads conjugated with protein G for the isolation of metallothionein. Isolated metallothionein was determined by differential pulse voltammetry Brdicka reaction and SDS-PAGE. Optimal conditions: antigen-binding time - 60 min, temperature - 70°C, and buffer composition and pH - acetate buffer, pH 4.3, were determined. Under the optimized conditions, lysates from 22Rv1 prostate cancer cells treated with various concentrations of cadmium(II) and copper(II) ions were analyzed. We observed strong correlation in all experimental groups and all lysate types (r>0.83 at p<0.041) between metallothionein concentration related to viability and concentration of copper(II) ions and cadmium(II) ions in medium. Moreover, the results were compared with standard sample preparation as heat treatment and SDS-PAGE analysis.     

污染肝素中多硫酸化硫酸软骨素的分步醋酸纤维素薄膜电泳分析

采用离子交换色谱法从污染肝素原料中分离出多硫酸化硫酸软骨素(OSCS),建立了分步醋酸纤维素薄膜电泳法分析污染肝素中OSCS含量的方法.结果表明,先以0.05 mol/L醋酸钡缓冲液(pH 5.0)电泳,再以0.15 mol/L醋酸锌缓冲液(pH 6.3)电泳,可以将肝素和OSCS完全分开,检出限为0.1 g/L; 通过灰度积分建立定量校准曲线,相关系数为0.9934,平均回收率为102.1%～106.1%; RSD为4.1%～6.0%.     

Spectrophotometric determination of zinc with 1-(2-pyridylmethylidene)-5-(salicylidene)thiocarbohydrazone

The absorbance of the yellow complex formed in pH 4.8 acetate buffer is measured at 410 nm in 40% (v/v) dimethylformamide. The molar absorptivity is 68 000 l mol^?1 cm^?1. The effect of interferences is discussed, and the method is applied to zinc in tap water and standard alloys.     

Comparative study of methods for evaluating the mobility of element species in contaminated soil and technogenic sand under batch and dynamic extraction

A comparative study of the batch and dynamic extraction methods used to evaluate the physicochemical “mobility” of element species in environmental samples was carried out using samples of contaminated soils and technogenic sands of the Dzhida Tungsten–Molybdenum Factory. In determining the total concentration of mobile species of Cu, Zn, Pb, Cd, Mn, and Mo, they were extracted with an acetate–ammonium buffer solution (pH 4.8) in the batch mode. Fractionation of the most mobile and environmentally relevant element species, that is, exchange and acid-soluble, was carried out in a dynamic extraction mode in a rotating coil column using calcium nitrate and acetic acid. Element concentrations in the initial samples and extracts were determined by inductively coupled plasma atomic emission spectrometry and mass spectrometry. It is shown that the concentrations of mobile species of Cd, Mn, and Mo, isolated with an acetate–ammonium buffer solution, correspond to the sum of these elements in the exchange and acid-soluble fractions, while the concentration of lead in the acetate–ammonium extract is 2–4 times higher. The convergence of the results of dynamic and batch extraction of copper and zinc depends on the type of sample: for sand, the results are in satisfactory agreement, while for soil, the concentration of copper and zinc in the acetate–ammonium extract is 2–4 times lower than their concentration in the exchange and acid-soluble forms. Nevertheless, the data obtained confirm that the conventional method of batch extraction with an acetate–ammonium buffer solution (pH 4.8) can be considered acceptable for the rapid assessment of the physicochemical mobility and potential bioavailability of elements in soil and technogenic sand. For a more detailed study of highly contaminated samples and the assessment of their danger to the environment, it is advisable to separate exchange and acid-soluble fractions.     

High-performance liquid chromatography of micelle-solubilized complexes-IV Reversed-phase ion-pair chromatography of metal-3,5-diBr-PADAP-Triton X-100 complexes

The micellar solubilization complex systems of V(V), Cu(II), Zr(IV), Pd(II), Fe(III), Ni(II) and Co(II) with 3,5-diBr-PADAP and Triton X-100 have been investigated by HPLC on an ODS (5 x 250 mm) column with a ternary eluent of methanol-acetone-acetone-water containing TBA(+) and acetate buffer (pH 3.0) at 600 or 572 nm wavelength for the detection of the complexes. An HPLC-spectrophotometric method for determination of seven metal ions has been developed. The peak height calibration curves are linear up to 50-100 mu/1, metal ion concentration. The relative standard deviations for the determination of 30.0 mu/1 metal ion were 0.9-1.6% and the detection limits (S/N = 3) were 1.1-3.6 mug/1.