An Investigation into the Suitability of Bismuth as an Alternative to Gold‐Amalgam as a Working Electrode for the In Situ Determination of Chemical Redox Species in the Natural Environment

The suitability of the bismuth film working electrode was investigated as an alternative to the gold‐amalgam electrode used in solid state microelectrodes for in situ voltammetric analysis of redox chemistry in the natural environment (e.g., lakes, oceans, sedimentary pore waters). Chemical redox species measurable with the Au‐amalgam include O₂, H₂S, S , S₂O , Fe²⁺, Fe³⁺, Mn²⁺, I^?. Bismuth was electrochemically deposited to form a solid film analogous to the Au‐amalgam on a polished gold disk electrode. The useable potential window of the Bi‐film was found to be narrower than that of the Au‐amalgam, precluding the detection of dissolved O₂, I^? and S₂O , whose redox potentials fall outside the Bi‐film's range. The Bi‐film was able to detect free H₂S/HS^? and total sulfide (AVS), but not Fe²⁺ or Mn²⁺. The Bi‐film was less sensitive to low levels of total sulfide (<10 μM) than the Au‐amalgam; however, the Bi‐film was able to accurately quantify very high concentrations of sulfide (at least 15 mM), with a linear response up to an order of magnitude higher than that of the Au‐amalgam. Thus the Bi‐film appears to have limited application as an alternative to the Au‐amalgam microelectrode for in situ analysis of redox species in natural waters.     

Novel Xylan Gels Prepared from Oat Spelts

Gels and pastes are used in many areas including application in the cosmetic, pharmaceutical and medical industries. A xylan derivative with pasty consistency was prepared in addition to the synthesis of xylan ethers and esters. The water content of the gel can be widely varied. The gel is formed although the xylan contains no cross-linking group. The hydrophobic and hydrophilic nature of the xylan gel can be adjusted by modifying the xylan. All of the gels can be dried using different methods (air drying, solvent exchange as well as freeze drying) and the dried gels can again disperse in water. The gels were characterised by porosity measurements (mercury intrusion), dynamic vapour sorption (DVS), scanning electron microscopy (SEM) and dispersion stability investigation respectively.     

海水入侵危险程度的非线性映射分析

海水入侵是我国沿海地区出现的一典型资源与环境问题.作者选用地质、气候、地理环境和人为因素等四类指标来反映海水入侵存在的风险,采用非线性映射分析将高维空间问题转化为低维空间问题.根据离差极小、最大欧氏距离等原理提出了海水入侵风险阈值求解方法与海水入侵风险判定方法,使存在海水入侵风险的区域可被及时、准确地判定出来.实例分析表明,该方法使分析结果真实、准确,为沿海地区海水入侵风险管理开辟了一条新途径.     

Direct injection of seawater for the analysis of nitroaromatic explosives and their degradation products by micellar electrokinetic chromatography

Practical considerations for the injection and separation of nitroaromatic explosives in seawater sample matrices are discussed. The use of high surfactant concentrations and long electrokinetic injections allows for improved detection limits. Sensitivity was enhanced by two mechanisms, improved stacking at the detector-side of the sample plug and desorption of analyte from the capillary wall by surfactant-containing BGE from the inlet side of the sample plug. Calculated limits of detection (S/N = 3) for analytes prepared in pure seawater were 70–800 ppb with injection times varying from 5 to 100 s.     

On-site determination of polynuclear aromatic hydrocarbons in seawater by stir bar sorptive extraction (SBSE) and thermal desorption GC-MS

The identification and quantification of semi-volatile contaminants dissolved in water is currently done in laboratory after a sampling step. This procedure is not satisfactory first because risks of samples contamination and analytes losses remain, in particular when these are present in ultra-trace concentrations, and secondly because procedures are time-consuming. The coupling of the stir bar sorptive extraction (SBSE), a new device of extraction technique, and a new generation of gas chromatography mass spectrometry (GC-MS), the field apparatus EM 640 S from Bruker, could be an answer to the challenge of on-site analysis. This analytical system was used to analyze 24 PAHs, among them 15 EPA priority pollutants. It was shown that this coupling led to encouraging results with LODs around the sub-ppt level for most of the compounds and R.S.D. included between 1 and 48%. The existence of competition phenomena between the various analytes inside the absorbent phase was demonstrated with the release (up to 80%) of light compounds. This result shows the necessity to work on the kinetic domain rather than on the thermodynamic equilibrium that is influenced by nature and concentration of other compounds. The matrix effects were also studied through the comparative analysis of ultrapure water, artificial and natural seawaters spiked with PAHs and the influence of ionic strength and particulate organic matter was investigated.     

Model experiments to test the use of a liquid membrane for separation and preconcentration of copper from natural water

The transfer and separation of Cu(II) ions across a bulk liquid membrane (BLM) containing pyridine-2-acetaldehyde benzoylhydrazone (2-APBH) as the mobile carrier dissolved in toluene has been investigated and optimised. The system was applied to the preconcentration of copper from natural waters prior to analysis by flame atomic absorption spectroscopy. The flux of copper across the membrane has been studied, and characterised as a function of analytical variables such as the carrier concentration, volume of organic phase, pH of feed and strip receiving solutions, stirring rate and temperature of solutions. The preconcentration yield at optimum conditions was 100.54±0.94%, even with a high saline matrix (30 g l⁻¹ NaCl), with good precision (1.49%). A preconcentration factor of approximately 18 times could be obtained. The detection limit of a blank sample was 0.24 μg l⁻¹ of Cu.The method was validated using a certified reference material (TMDA-62) and was applied successfully to the analysis of copper in two samples of seawater collected from the coast of Huelva (Spain). The relative errors were 2.42% for CRM and 0.48 and 3.66%, for seawaters (obtained between the results of the proposed and DPASV methods), respectively.     

石墨炉原子吸收光谱无标样分析法的研究：Ⅳ.实际样品的分析

以有机基体改进剂、管壁原子化、热解涂层石墨管、峰面积积分吸收信号、Ｄ２灯或Ｚｅｅｍａｎ效应扣除背景，有效地控制和消除了海水基体对Ｃｄ，Ｃｏ，Ｃｒ，ＣｕＭｎ，ＮｉＰｂ等元素的干扰。在此前提下，用ＧＦＡＡＳ无标样分析汉分析了实验海水样品中的痕量元素，与极谱法及间接火焰原子吸收法测得的结果相符，测得质控海水样品的结果与标准值亦很吻合，而且检出限和回收率都达达到要求。     

应用离子色谱离线螯合及ICP-MS测定海水中多种痕量元素

简要介绍如何构建和运用离子色谱离线螯合系统结合ICP-MS方法分析海水中的痕量元素.     

Chromium(III, VI) speciation analysis with preconcentration on a maleic acid-functionalized XAD sorbent

Chromium may exist in environmental waters as Cr(III) and Cr(IV), the latter being the toxic and carcinogenic form. Since atomic absorption spectrometry (AAS) and inductively coupled plasma atomic emission spectrometry can only yield information on total Cr concentration, a polymer resin bearing O,O-donor chelating groups such as the maleic acid-functionalized XAD(CO)CHCHCOOH resin was synthesized to selectively retain Cr(III) at pH 4.0-5.5. The dynamic breakthrough capacity of the resin for Cr(III) at pH 5.0 was 7.52 mg g⁻¹, and the preconcentration factor extended to 250-300. Chromium(III) in the presence of 250-fold Cr(VI)—which was not retained—could be effectively preconcentrated on the NH₄⁺-form of the resin and determined by AAS or diphenylcarbazide (DPC) spectrophotometry. When Cr(VI) was reduced to Cr(III) with Na₂SO₃ solution brought to pH 1 by the addition of 1 M H₂SO₄, and preconcentrated on the resin, total Cr could be determined. The developed method was validated with a blended coal sample CRM-1632. Since the adsorption behavior as a function of pH of possible interferent metal ions, e.g. Ni(II), Co(II), Cu(II), Cd(II), Zn(II), Pb(II) and Fe(III), was similar to that of Cr(III), selective elution of Cr(III) from the resin was realized using a mixture of 1 wt.% H₂O₂+1 M NH₃. The eluate containing Cr as chromate could be directly analyzed by diphenyl carbazide spectrophotometry without any adverse effect from the common interferents of this method, i.e. Fe(III), Cu(II) Hg(II), VO₃⁻, MoO₄²⁻ and WO₄²⁻. Various synthetic waste solutions typical of electroplating bath effluents containing Cr, Cu, Ni, Zn, Na, Ca, cyanide (and chemical oxidation demand (COD), achieved by glucose addition) were subjected to pretreatment procedures such as hypochlorite oxidation (of cyanide) and catalytic oxidation (of COD) with peroxodisulfate. Chromium determination gave satisfactory results. The combined column preconcentration—selective elution—diphenylcarbazide spectrophotometric determination was also successfully applied to the determination of Cr in artificial and real seawater.     

Cooperative Study of Precision and Accuracy on the Determinations of Around-Ppb Levels of Copper and Lead in Environmental Waters

The results of a series of inter-laboratory cross-check on the determinations of ppb and sub-ppb levels of copper and lead in environmental samples are described. Thirteen laboratories participated during a five-stage comparison. Seven analytical methods and two pre-concentration procedures were performed on certified and real samples. For controlled and blind standards at higher concentration levels (10 ppb or above) the data reported by different participants show good agreement for both elements regardless of the method chosen. However, for samples having lower concentrations (1-10 ppb level), the relative standard deviation (R.S.D.) and bias increased. A high degree of scattering on data were demonstrated for a deep ocean water at less than 1 ppb level. The results of the present study give direct comparison between different analytical methods, and also reflect the average aptitude of analytical laboratories in Taiwan on the measurements of copper and lead in environmental samples.