Cellulose based macromolecular chelator having pyrocatechol as an anchored ligand: synthesis and applications as metal extractant prior to their determination by flame atomic absorption spectrometry

Pyrocatechol is immobilized on cellulose via ---NH---CH₂---CH₂---NH---SO₂---C₆H₄---N=N--- linker and the resulting macromolecular chelator characterized by IR, TGA, CPMAS ¹³C NMR and elemental analyses. It has been used for enrichment of Cu(II), Zn(II), Fe(III), Ni(II), Co(II), Cd(II) and Pb(II) prior to their determination by flame atomic absorption spectrometry (FAAS). The pH ranges for quantitative sorption (98.0–99.4%) are 4.0–7.0, 5.0–6.0, 3.0–4.0, 5.0–7.0, 5.0–8.0, 7.0–8.0 and 4.0–5.0, respectively. The desorption was found quantitative with 0.5 mol dm⁻³ HCl/HNO₃ (for Pb). The sorption capacity of the matrix for the seven metal ions has been found in the range 85.3–186.2 μmol g⁻¹. The optimum flow rate of metal ion solution for quantitative sorption of metal onto pyrocatechol functionalized cellulose as determined by column method, is 2–6 cm³ min⁻¹, whereas for desorption it is 2–4 cm³ min⁻¹. The tolerance limits for NaCl, NaBr, NaI, NaNO₃, Na₂SO₄, Na₃PO_4, humic acid, EDTA, ascorbic acid, citric acid, sodium tartrate, Ca(II) and Mg(II) in the sorption of all the seven metal ions are reported. Ascorbic acid is tolerable up to 0.8 mmol dm⁻³ with Cu and Pb where as sodium tartrate does not interfere up to 0.6 mmol dm⁻³ with Pb. There is no interference of NaBr, NaCl and NaNO₃ up to a concentration of 0.5 mol dm⁻³, in the sorption of Cu(II), Cd(II) and Fe(III) on to the chelating cellulose matrix The preconcentration factors are between 75 and 300 and t_1/2 values ≤5 min for all the metal ions. Simultaneous sorption of Cu, Zn, Ni and Co is possible at pH 5.0 if their total concentration does not exceed lowest sorption capacity. The present matrix coupled with FAAS has been used to enrich and determine the seven metal ions in river and tap water samples (relative standard deviation (R.S.D.) 1.05–7.20%) and synthetic certified water sample SLRS-4 (NRC, Canada) with R.S.D. 2.03%. The cobalt present in pharmaceutical vitamin tablets was also preconcentrated on the modified cellulose and determined by FAAS (R.S.D. 1.87%).     

气相色谱-质谱法分析化妆品中16种香精香料

建立了用毛细管气相色谱质谱测定化妆品中16种香精香料的方法.样品用甲醇超声提取,经高速冷冻离心,清液经干燥脱水过0.5 μm滤膜过滤,直接注入气相色谱质谱进行分析.经过GC-MS分析,用选择离子和保留时间定性,外标法定量.16种香精香料的回收率为：82.3%～108.2%,精密度为（以相对标准偏差表示）：1.6%～4.7%,检出限均为10 mg/kg.该方法准确度和灵敏度高,样品用量少,前处理简单,可同时测定化妆品中16种香精香料.     

The Use of Proton Nuclear Magnetic Resonance Spectroscopy for the Determin- ation of pK a Values in Aqueous/Organic Solutions for Basic Analytes Employed in Column Characterisation Protocols

Proton nuclear magnetic spectroscopy has been used to measure pK _a values of two basic analytes in a range of aqueous/organic eluents. The results support the hypothesis that the poor correlation in terms of ion exchange capacity with values greater than pH 7 may be attributed to the difference in the ionisation of the silica surface and not differences in ionisation of the basic analytes under the differing chromatographic conditions (i.e. temperature, type and amount of modifier) employed in two commonly used HPLC stationary phase characterisation procedures (Tanaka and Snyder).     

Synchronous fluorescence determination of DNA based on the interaction between methylene blue and DNA

The fluorescence intensity of methylene blue (MB) quenched by DNA in the pH range of 6.5-8.0 was studied with synchronous fluorescence technology. A novel method for detecting single-stranded and double-stranded DNA was developed. The decreased fluorescence intensity at 664 nm is in proportion to the concentration of DNA in the range of 0.28-11.0 μmol L⁻¹ for ctDNA, 0.14-8.25 μmol L⁻¹ for thermally denatured ctDNA and 0.28-8.25 μmol L⁻¹ for hsDNA. The detection limits (S/N = 3) are 0.11, 0.04 and 0.04 μmol L⁻¹, respectively. The method is rapid, selective, and the reagents are lower toxic. It has been used for the determination of DNA in synthetic samples with good satisfaction. In addition, the interaction modes between MB and ctDNA and the mechanism of the fluorescence quenching were also discussed in detail. The experimental results from absorption spectra and fluorescence polarization indicate that the possible interaction modes between MB and DNA are the electrostatic binding and the intercalation binding.     

Determination of Se(IV) in On‐Line System by Cathodic Stripping Voltammetry

A sensitive and selective on‐line voltammetric procedure for determination of traces of Se(IV) is presented. The pulsed potential accumulation was proposed for minimization of interferences of surface active substances and foreign ions. The calibration plot was linear from 1×10^?9 mol L^?1 to 4×10^?8 mol L^?1 for accumulation time of 180 s. The relative standard deviation was 6.1% (n=5) for a Se(IV) concentration of 1×10^?8 mol L^?1. The detection limit estimated from (3 σ) for an accumulation time of 180 s was about 4×10^?10 mol L^?1. The validation of the procedure proposed was made by a recovery tests for tap and river water samples.     

新型D-238树脂色层分离-ICP/AES法测定4N光学级La_2O_3中Co、Cr、Cu、Fe、Mn、Ni、Pb和V

本文采用新型D-238树脂,使待测元素与基体La分离。用6mol/L HNO_3解脱非稀土杂质,ICP-AES法同时测定4N光学级La_2O_3中8个痕量非稀土杂质。方法的检出限为0.2～2.8μg/g,相对标准偏差<8%。     

Trends in metal-binding and metalloprotein analysis

This review describes recent tendencies for metal-binding and metalloprotein analysis, emphasizing metal quantification in proteins through X-ray, atomic absorption, mass spectrometric techniques, and others. Hyphenated techniques such as capillary electrophoresis-synchrotron radiation X-ray fluorescence (CE-SRXRF), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), matrix-assisted laser desorption/ionisation-time-of-flight mass spectrometry (MALDI-TOF-MS), etc. are also presented. As protein separation techniques electrophoresis (mainly sodium dodecyl sulphate-polyacrylamide gel electrophoresis, SDS-PAGE), capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) are indicated, due to their inherent sensitivity, resolution and/or easy implementation. Latest challenges in metallomics are also commented.     

四溴荧光素荧光猝灭法测定司帕沙星

基于司帕沙星能够猝灭四溴荧光素的荧光且荧光猝灭程度与司帕沙星的量成正比，建立了一种测定微量司帕沙星的方法。在pH3．5的Clark—Lubs缓冲溶液中，四溴荧光素激发波长λex=485nm、发射波长λem=545nm，司帕沙星的质量浓度在0～2．0mg／L范围内符合比耳定律，方法检出限为42．7μg/L。已用于片剂及胶囊中司帕沙星的测定。6次平行测定回收率为93．8％～104．3％，相对标准偏差为1．1％～2．8％。     

Multicomponent analysis of fermentation growth media using the electronic tongue (ET)

A potentiometric electronic tongue (ET) consisting of eight cross-sensitive chemical sensors and a standard pH electrode has been applied for analysis of simulated fermentation solutions typical for fermentation processes with Aspergillus niger. The electronic tongue has been found capable of simultaneous determination of ammonium, citrate and oxalate in complex media with good precision (typical error within 8%). The system preserved high sensitivity to the targeted substances also in the presence of sodium azide, which is commonly used for suppressing microbial activity in real-world fermentation samples. Sensor performance was fast and reproducible which promises well for routine application of the electronic tongue for fermentation process monitoring.     

A new method to evaluate force constants from experimental spectral data

An iterative procedure is proposed to facilitate the determination of molecular vi-brational force constants from the experimental fundamental frequencies. Proper restrictions are introduced to the force constants based on physical considerations for getting reasonable results. The experimental data of Coriolis coupling coefficients and isotopic frequency shifts are utilized to reduce the uncertainty of the calculated force constants when they are available. A series of various kinds of molecules have been calculated by this method and the results are satisfactory.