二水草酸锌脱水的热分解动力学研究

提出一种多升温速率-等温法确定机理函数g(α)的新方法;并用迭代的等转化率法求出较为可靠的活化能Ea;在Ea和g(α)的基础上计算出指前因子A.用该法对二水草酸锌（ZnC2O4•2H2O）脱水反应的热分解动力学三因子进行了求算,得出Ea为87.22 kJ•mol－1, A为4.2120×108～7.2328×108 s－1;以及随机成核和随后生长型机理函数Am（Avrami-Erofeer）,其积分形式g(α)=[－ln(1－α)] 1/m和微分形式f(α)=m(1－α)•[－ln(1－α)](1－1/m),调节因子m=1.85～2.00.     

Initial data truncation for multivariate output of discrete-event simulations using the Kalman filter

Data truncation is a commonly accepted method of dealing with initialization bias in discrete-event simulation. An algorithm for determining the appropriate initial-data truncation point for multivariate output is proposed. The technique entails averaging across independent replications and estimating a steady-state output model in a state-space framework. A Bayesian technique called Multiple Model Adaptive Estimation (MMAE) is applied to compute a time varying estimate of the output's steady-state mean vector. This MMAE implementation features the use, in paralle, of a bank of Kalman filters. Each filter is constructed under a different assumption concerning the output's steady-state mean vector. One of the filters assumes that the steady-state mean vector is accurately reflected by an estimate, called the assumed steady-state mean vector, taken from the last half of the simulation data. As the filters process the output through the effective transient, this particular filter becomes more likely (in a Bayesian sense) to be the best filter to represent the data and the MMAE mean estimator is influenced increasingly towards the assumed steady-state mean vector. The estimated truncation point is selected when a norm of the MMAE mean vector estimate is within a small tolerance of the assumed steady-state mean vector. A Monte Carlo analysis using data from simulations of open and closed queueing models is used to evaluate the technique. The evaluation criteria include the ability to construct accurate and reliable confidence regions for the mean response vector based on the truncated sequences.     

伏安型植物组织生物微电极的研究：混合不同植物组织碳糊微电极的研究

由于香蕉组织中含有的氧化酶能够生物催化氧化多巴胺，去甲肾上腺素，Ｌ－多巴等，大大地提高了植物组织电极的灵敏度；又由于茄子组织中所含有的氧化酶在催化氧化儿茶酚的同时，能有效地抑制抗坏血酸在电极上的反应，将上述两种植物组织混合制成电极，使其更适于神经递质的测定，线性范围：２．４×１０＾－６－－９．８×１０＾－４ｍｏｌ／Ｌ；检出下限３．２×１０＾－７ｍｏｌ／Ｌ。     

Synthesis of chitosan resin possessing 3,4-diamino benzoic acid moiety for the collection/concentration of arsenic and selenium in water samples and their measurement by inductively coupled plasma-mass spectrometry

A chitosan resin functionalized with 3,4-diamino benzoic acid (CCTS-DBA resin) was newly synthesized by using a cross-linked chitosan (CCTS) as base material. The adsorption behavior of trace amounts of elements on the CCTS-DBA resin was examined by the pretreatment with a mini-column and measurement of the elements by inductively coupled plasma-Mass spectrometry (ICP-MS). Arsenic(V) could be retained on the CCTS-DBA resin at pH 3 as an oxoanion of H₂AsO₄⁻. Selenium(VI) is strongly adsorbed at pH 2 and pH 3 as an oxoanion of SeO₄²⁻, while selenium(IV) as HSeO₃⁻ is adsorbed on the resin at pH 3. The sorption capacities are 82, 64, and 88 mg g⁻¹resin for As(V), Se(IV), and Se(VI), respectively. The effect of common anions and cations on the adsorption of As(V), Se(IV), and Se(VI) were studied; there was no interference from such anionic matrices as chloride, sulfate, phosphate, and nitrate up to 20 ppm, as well as from such artificial river water matrices as Na, K, Mg, and Ca after passing samples through the mini-column containing the resin. The CCTS-DBA resin was applied to the collection of arsenic and selenium species in bottled drinking water, tap water, and river water.     

An alternative interface for CE-ICP-MS cadmium speciation in metallothioneins based on volatile species generation

An alternative CE-ICP-MS interface based on volatile species generation (VSG) is here developed, evaluated and compared to the conventional sample introduction systems via nebulisation. For this purpose, the speciation of Cd-metallothioneins (MTs) in rabbit liver is taken as a model. Cd, bound to the different MT isoforms previously separated by CE, is transformed into volatile species at the exit of the capillary and on-line detected by ICP-MS. Optimum conditions for Cd VSG have been investigated in a flow injection device, using NaBH₄ as hydrogenation reagent in a HCl medium containing cobalt and thiourea as catalysts. Sample volume injected, CE separation voltage and reagents flows have been optimised. Analytical performance characteristics of the CE-VSG-ICP-(Q)MS coupling developed were evaluated, in terms of repeatability and linearity of response, using standard rabbit liver metallothionein isoforms (MT1 and MT2). Detection limits for Cd-MTs turned out to be almost one order of magnitude better than those derived from using a conventional Babington nebuliser-based interface. Compared to a MicroMist-based interface detection limits resulted to be similar, but the observed peak height was eight times higher using the VSG interface, indicating the enhanced analyte transport efficiency derived from VSG sample introduction systems.     

Determination of rare earth elements in seawater by on-line column preconcentration inductively coupled plasma mass spectrometry

A home made column of commercially available iminodiacetate resin, Muromac A-1 (50–100 mesh) was used to concentrate rare earth elements (REEs) (15 elements: Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in seawater. An automated low pressure flow analysis method with on-line column preconcentration/inductively coupled plasma mass spectrometry (ICP-MS) is described for the determination of REEs in seawater. Sample solutions (adjusted to pH of 3.0) passed through the column. After washing the column with water, the adsorbed elements were subsequently eluted into the plasma with 0.7 M nitric acid. Calibration curves were accomplished by means of purified artificial seawater with a sample loading time of 120 s. Detection limits (DLs) of the on-line column preconcentration/ICP-MS by eight replicate operations were between 0.040 and 0.251 pg ml⁻¹ for REEs in the artificial seawater. The precision was less than 8.9% for REEs and one sample can be processed in 7 min using a 7 ml of sample. The proposed method was applied to determine REEs in coastal seawater of Hiroshima Bay, Japan.     

The Employ of Multiple Voltammetric Pulses for the Study of the Adsorption of Bipyridilium Pesticides in River Sediment

The multiple square‐wave voltammetry (MSWV) allied to gold microelectrode (Au‐ME) was used to establish an electroanalytical procedure for the determination of the paraquat and diquat pesticides in river sediment samples. For both pesticides, two reduction peaks, at around ?0.70 V (peak 1) and around ?1.00 V vs. Ag/AgCl 3.00 mol L^?1 (peak 2), with profile of the totally reversible redox process, were observed. The experimental and voltammetric conditions showed that the best conditions to reduce paraquat and diquat were a pH of 6.0, a frequency of 250 s^?1, a scan increment 2 mV, a square‐wave amplitude of 50 mV and pulse number of 8 pulses of potential in each step of staircase of potential. Under such conditions, the detection limit of 0.044 μg L^?1 (0.044 ppb) and 0.360 μg L^?1 (0.360 ppb ) for peak 1 and peak 2 of paraquat and 0.159 μg L^?1 (0.159 ppb) and 0.533 μg L^?1 (0.533 ppb) for peak 1 and peak 2 of diquat, respectively, were obtained. These results are an order of magnitude of about two less than those obtained and published in the literature. Also, the electroanalytical procedure proposed was applied for the determination of adsorption isotherms of pesticides on river sediments samples collected from Mogi‐Guaçu River in Sao Paulo State, Brazil. The experimental data were fitted using the Langmuir and Freundlich isotherms models; and the results indicated low intensities of adsorption process of the pesticides in the samples employed with distribution coefficients (K_d) lower 5.0, and paraquat showed slightly higher affinity than diquat in the sediments. The increase in organic matter and organic carbon leads to an increase in the K_d values, and consequently an increase in the organic matter constant (K_OM) organic carbon constant (K_OC) values. All results demonstrated that isotherms “L” type in the Giles classification were obtained, indicating that sediments have a medium affinity for the pesticides, and no strong competition from the solvent used (in this case Na₂SO₄) for adsorption sites occurs.     

Matrix Effects and Behaviors of Elements in Oxalic Acid Medium by Inductively Coupled Plasma Mass Spectrometry

Because of its high sensitivity, wide dynamic range and relative freedom from interferences, inductively coupled plasma mass spectrometry (ICP-MS) has been developed for the determination of trace and ultra-trace levels of elements in various fields1. Due…     

Cadmium speciation in Arabidopsis thaliana as a strategy to study metal accumulation system in plants

The strategy to identify cadmium deactivation mechanism in Arabidopsis thaliana has been developed using selective and sensitive hyphenated techniques. Cadmium concentrations, in main parts of the plant, were determined by ICP-MS and total amount was found as 0.43-0.44 μg g⁻¹ in leaves and 3.3-3.4 μg g⁻¹ in roots. Speciation of the metal complexes in cells was investigated by SEC-ICP-MS in order to estimate the accumulation process. Phytochelatins, desglycyl-phytochelatins and phytochelatins homologues lacking the N-terminal γ-linked glutamic acid were extracted from plant and were identified by RPLC-ESI-MS. Two-dimensional chromatography allowed to link the metal complexes separated by SEC with isoforms of phytochelatins analyzed by high resolution RPLC and confirm their significant responsibility for metal accumulation. The potential of the cadmium complexes speciation indicates that obtained results could be reliable source of knowledge to confirm the information coming from the well-known genomic sequence of Arabidopsis and to estimate the role of γ-glutamyl transpeptidase in metabolism of glutathione.     

Arsenic Speciation in Urine and Blood Reference Materials

Acute and chronic exposure to arsenic is a growing problem in the industrialized world. Arsenic is a potent carcinogen and toxin in humans. In the body, arsenic is metabolized to produce several species, including inorganic forms, such as trivalent (As^III) and pentavalent (As^V), and the methylated metabolites such as monomethylarsonic acid, (MMA^V), and dimethylarsinic acid (DMA^V), in addition to arsenobetaine (AsB) which is ingested and excreted from the body in the same form. Each of these species has been reported to possess a specific but different degree of toxicity. Thus, not only is the measurement of total As required, but also quantification of the individual metabolites is necessary to evaluate the toxicity and risk assessment of this element. There are a large number of reference materials that are used to validate methodology for the analysis of As in blood and urine, but they are limited to total As concentrations. In this study, the speciation of five arsenic metabolites is reported in blood and urine from commercial available control materials certified for total arsenic levels. The separation was performed with an anion exchange column using inductively coupled plasma mass spectrometry as a detector. Baseline separation was achieved for As^III, As^V, MMA^V, DMA^V, and AsB, allowing us to quantify all five species. Excellent agreement between the total arsenic levels and the sum of the speciated As levels was obtained.