A miniaturized and integrated galvanic cell for the potentiometric measurement of ions in biological liquids

A procedure for an all-plastic electrochemical cell comprising miniaturized planar indicator and reference electrodes is described. All electrodes are based on conducting polymers, are fully integrated, and contain no internal electrolyte. The reference microsensors were deposited via electrochemical polymerization from a water solution containing the monomer 3,4-ethylenedioxythiophene (EDOT) or 1-methylpyrrole (MPy) and a biochemical buffer 3-(N-morpholino) propanesulfonic acid [MOPS], 2-(N-morpholino) ethanesulfonic acid [MES], or 2-hydroxy-5-sulfobenzoic acid [SSA]). Ion-sensitive microelectrodes were prepared by the deposition of the ion-sensitive membrane solution (Ca²⁺, K⁺, and Cl⁻) directly onto the mediating poly-EDOT (PEDOT), PEDOT–SSA, PEDOT–MES, PEDOT–MOPS, or poly-MPy–MOPS layers.     

Element assessment in whole blood, serum and urine of three Italian healthy sub-populations by INAA

This research, that is a framework of a big project regarding the knowledge of human metabolism in patients affected by renal disease, is aimed to assess the levels of some selected essential (Co, Fe, K, Na, Rb, Se and Zn) and non-essential elements (Br Cr, Cs, Hg, Ni and Sb) in different biological matrices such as whole blood, serum and urine, of three Italian sub-populations.The analytical methodology involved is the Instrumental Neutron Activation Analysis (INAA), a primary analytical technique: the samples (totally 144) were irradiated in the Triga nuclear reactor at the R.C.-Casaccia ENEA for 12 h at a neutron flux of 2.6 × 10¹² n × cm^{− 2} × s^{− 1}.The results show a similar distribution for essential elements whereas quite different for non-essential elements. The statistical treatment has evidenced no differences among the samples grouping the subpopulations into unique one. In this way, the levels found can be considered “reference values” in the investigated matrices.     

Computer-aided design of formulated products

Formulated products represent a particular class of complex chemical products, and their design is typically based on experience and extensive experimentation. Although still at an early stage, and despite that their potential is not fully accessed and not fully used by the industry, computer-aided design (CAD) methods and tools offer many possibilities in the design of formulated products. The CAD methodology based on computerized models enables the formulation chemists to speed up the design process, without completely replacing experiments.In this work, we summarize previous studies in the field and present important elements of the CAD framework, emphasizing estimation methods for key target properties, link to specifications, and finally, some case studies will illustrate how the CAD framework can be used in practice for formulated products.     

Traceability without uncertainty: current situation in the pharmaceutical industry

The current situation in the pharmaceutical industry is discussed, when the traceability of measurement (analytical) results to certified values of pharmacopoeial reference standards is required, without evaluating their uncertainties. It is shown that the evaluation of measurement uncertainty is necessary for understanding the level of confidence of the analytical results and their comparability, particularly during preparation and characterisation of the reference standards.Papers published in this section do not necessarily reflect the opinion of the Editors, the Editorial Board and the Publisher. Apart from exceptional circumstances, they are not submitted to the usual referee procedure and go essentially unaltered.     

Certification of reference materials and accreditation of reference material producers: Questionable terminology leads to confusion

In the view of the Deutscher Kalibrierdienst (DKD) , a certifying body for reference materials can be considered to be a calibration laboratory. Therefore, accreditation of calibration laboratories in accordance with ISO/IEC 17025 is the most appropriate way to establish confidence in certificates for reference materials. If necessary, the criteria of ISO/IEC 17025 can be tailored to specific cases. There is no need to provide any new kind of reference-material specific accreditation. However, in view of the variety of reference materials and the practice existing in other countries, accreditation of testing laboratories and product certification bodies may optionally be acceptable as long as the same stringent principles with respect to traceability and measurement uncertainty are applied. Such accreditations but not accreditations of reference material producers (ISO Guide 34) are also covered by existing international mutual recognition arrangements (MRA).     

A Quality Assurance Study for the Analysis of Hydrocarbons in Sediments

Abstract

Two exercises (MEDCAL I and II) were conducted in our Department during November 1984 and October 1986, with participants from the Mediterranean region, for testing the IOC Manual for the determination of petroleum hydrocarbons in sediments (IOC, Manuals and Guides, No. 11).

The gas chromatographic analysis of the saturated hydrocarbon fraction provided, at the best, a precision of 60% (relative standard deviation RSD) for n-alkanes (mean conc. 0.89 μg/g) and 56 % for the unresolved complex mixture (UCM) (mean conc. 16μg/g). The CPI and the pristane/phytane ratio provided better results (13% RSD). The aromatic fractions, analysed by UV-fluorescence, yielded in total a mean concentration of 10μg/g of chrysene equivalents with a 49% RSD.

The extraction-partition step was confirmed to be the main source of error in the analysis because when the results were corrected for recoveries, the RSD were reduced to 17, 30 and 6% for n-alkanes, UCM and total aromatics, respectively. Our reference intra-laboratory precision was, respectively, 18, 14 and 14%.     

Recent development of non-faradaic potentiometry

Non-faradaic potentiometry has been plagued by a great many fundamental errors and a lack of conceptualization. Of greatest concern is the second Nernst equation hiatus. Potentiometry may be generally classified as faradaic and non-faradaic. The former deals with the redox reactions using the Nernst equation to explain the potential origin. The latter deals with the non-redox reactions using the Boltzmann and modified Boltzmann equations to explain the origin of electrode potential. Redox faradaic potentiometry has been well described in the textbooks. However, non-faradaic potentiometry has been almost completely neglected in the literature. Many well-known electrodes, such as the pH glass electrode, common reference electrodes, and ion selective electrodes (ISE) have been mistakenly interpreted as redox reactions or ion exchange reactions. New theories and experimental results show their mechanisms to be non-faradaic in nature. Furthermore, the reaction mechanisms for ISE have been confused in textbooks with redox reactions and the Nernst equation. The ISE potentials originating from adsorption of ions or charged particles based on surface charge density will be explained using the double and counterion triple layers concept. The new counterion triple layer concept may be applied to the potential development of sensors. The reason for a new concept, theory, or mechanism is to better explain the phenomena. Examples will be given of how our new concept explains the capacitor, counterion triple layer, surface adsorbed layers interactions, and the interface structure. We will also discuss the new sensor development based on the new adsorption concept. For the first time a new type of Ag/AgCl reference electrode for non-faradaic potentiometry will be presented, one without a liquid junction and with a Pt wire instead of a salt bridge. They will help open up a new horizon for electrochemical sensor research and may be used under unusual conditions, such as high temperature and high pressure, stirring, etc.     

开发面向分析化学的复杂方程绘图求解软件

化学平衡的精确解析会涉及复杂方程的求解,而分析化学专业人员通常不完全具备相关算法和编程知识。所以,尽管当前硬件发达、编程语言丰富,精确解析仍然难以在分析化学课程中大规模推广。为此,基于Matlab语言,开发了具有针对性的方程求解软件。该软件以简洁的界面、直观的图像和自然的人机交互,实现方程的高效求解;对用户的编程要求非常低。期望通过这种方式,显著降低化学平衡精确解析中的软件使用成本,从而为大规模推广提供进一步的支持。本文介绍了该软件的基本原理和主要特点;通过3个复杂化学平衡实例,详细说明软件的使用方法以及注意事项。另外提供Android系统版本,免费使用。