Urine dry reagent strip “error” rates using different reading methods

 The need for “quality” in near patient testing (NPT) has been acknowledged since the mid 1980s. The commonest biochemical NPT device is the dry reagent strip or “dipstick” for urinalysis. Dipsticks may be read in three ways, against the color chart printed along the side of the bottle, using a benchreader (the color chart printed on a flat card) or using an electronic reader. This report uses the results of a urinalysis quality assurance (QA) program, over 1998, to evaluate the “error” rates which occur using the three different reading methods. The QA samples are buffered aqueous solutions which are “spiked” to give concentrations midway between two color blocks for each analyte. Results are scored as ±1 if a color block adjacent to the target value, ±2 for results two color blocks (defined as “error”) and ±3 for results three color blocks (defined as “gross error”) from the target value. Analysis of the results show that the error rates are similar reading visually by either method, but greatly reduced when read electronically. Some persisting errors when using the electronic reader are explained by observation studies. The study highlights the value of a urinalysis QA program for NPT urinalysis in understanding the error rates of this simple but ubiquitous test. Received: 10 July 2000 / Accepted: 10 July 2000     

Assessment of uncertainty in calibration of a gas mass flowmeter

 A primary calibration system was set up in Rafael some years ago, based on volumetric flow rate. The primary standard measures volumetric flow by means of the volume change of a dual piston over a specific time interval. This system serves to calibrate secondary standards of the thermal mass flowmeter type. Calibration procedures were prepared and validated. The paper describes the tests and calibration procedure conducted for the uncertainty assessment, the different components contributing to the measurement uncertainties, and the formulas involved with volumetric flow fates and with thermal mass flowmeters. Received: 10 July 1999 / Accepted: 15 February 2000     

The EC4 European Register for Clinical Chemists in relation to quality aspects

 The European Register for Clinical Chemists is founded and guarded by the European Communities Confederation of Clinical Chemistry (EC4). This register fits the current mind set of harmonization and globalization of occupations within the European Community. But in addition it enables and serves the continuing quest for quality assessment and improvement within the field of laboratory medicine. The content and position of clinical chemists in the European Union is described and the European Register outlined. Received: 10 July 2000 / Accepted: 20 July 2000     

Analysis of long-term distributions of calibration parameters and calibration intervals for an atomic absorption spectrophotometer

 A combination of "black box" and "calendar-time" methods for the determination of calibration intervals of an analytical measuring instrument is discussed. Since the methods require information on the distributions of the calibration parameters, such information is described for an atomic absorption spectrophotometer, as an example. The hypotheses on the normal distribution of the calibration parameters are tested using the ω²-criterion and accepted at 0.90–0.95 levels of confidence. Corresponding control charts are designed for indication of warning and action limits of the calibration parameters, and diagnoses of outliers in further calibrations. Control charts indicate also when the calibration should be done according to the full program of the equipment manufacturer. Received: 15 April 2000 / Accepted: 24 July 2000     

Voltammetric trace analysis of DNA and RNA

A voltammetric determination of DNA/RNA is described. The new aspect is the use of the extracellular endonuclease Serratia marcescens in the sample preparation. Using this enzyme it is possible to determine DNA/RNA with a detection limit of 2–5 pg/mL. This satisfies the requirements of the WHO and the FDA. Received: 16 May 2000 / Revised: 21 July 2000 / Accepted: 23 July 2000     

Percolation in alkyl polyglycoside microemulsions

Mixtures of oil, water, alkyl polyglycosides and long-chain alcohols form almost-temperature-invariant microemulsions. The phase behaviour depends on the content of cosurfactant, usually long-chain alcohols. We show that the system C_8/10G_1.5/octane/water/octanol exhibits cosurfactant-induced percolation phenomena. The percolation transition from an electrically conducting oil-in-water microemulsion to an electrically non-conducting water-in-oil microemulsion with increasing cosurfactant content is observed by measurements of electrical conductivity and time-resolved electric birefringence. The field-off relaxation time yields information on the internal length scale. The scaling behaviour of field-off relaxation times and Kerr constants with respect to the percolation point leads to insight into the influence of cosurfactant on phase behaviour. Received: 27 July 1999/Accepted: 8 February 2000     

Symmetry-adapted integrals over many-electron basis functions and operators

We consider integrals over symmetry-adapted basis functions that involve the coordinates of more than one electron. We focus on basis functions that can be written as products of one-electron functions and (say) a two-electron function. We show first that the two-electron parts of the basis functions can be absorbed into the operator, resulting in an integral over only one-electron basis functions, but a more complicated many-electron operator. We then prove a general formula for expressing such integrals in terms of symmetry-distinct integrals only. Received: 16 June 2000 / Accepted: 10 July 2000 / Published online: 19 January 2001     

Separation of gallium and indium from ores matrix by sorption on Amberlite XAD-2 coated with PAN

A chelating sorbent obtained by adsorption of 1-(2-pyridylazo)-2-naphthol (PAN) on Amberlite XAD-2 was used for the preconcentration of Ga and In. The analytical characteristics of the chelating sorbent were investigated and optimun sorption conditions for these metals under dynamic conditions were established. A peristaltic pump is used to adjust the flow rate of the solution. Elements are collected from the column by using a mixture adjusted to a pH range of 4–7 and 6–12 by ammonia or ammonium chloride for Ga and In, respectively. The procedure developed was applied to the analysis of different ores. Received: 10 July 2000 / Revised: 21 September 2000 / Accepted: 23 September 2000     

Novel Functional Fullerene Materials: Fullerenes as Energy Acceptors

Summary.  Fullerene derivatives exhibit absorption throughout the UV/Vis region up to 750 nm. This feature is important for easy excitation. Once excited, fullerenes may become both electron and energy acceptors. The distinction between these two pathways depends strongly on the partner involved (donor) and on the conditions employed (solvent, etc.). Received June 23, 2000. Accepted July 7, 2000     

Quality [r]evolution in diabetes care

 To implement the St. Vincent Declaration Action Programme, initiatives have been started in the quality development of diabetes care across Europe. The main elements of the quality development cycle implemented in our hospital were realized by the use of the software package ‘CamitPro’ and participation in ‘the DiabCare Q-net NL’ network. From 1997 to 1999, 955, 1468, and 1624 patients with diabetes mellitus type 2 were integrated in the DiabCare Q-net NL network by using ‘CamitPro’ software, respectively. These patients showed substantial improvement in all of the clinical measures monitored. In addition, there was a drop in HbA_1c level. From 1997 to 1999, an HbA_1c interval of 5.1%–8.3% (mean up to mean +4SD) was recorded for 66%, 76% and 81% of the patients, respectively. An extension of the use of the software to a pan-European level should markedly improve diabetes care throughout the community. Received: 10 July 2000 / Accepted: 10 July 2000     

A quantum chemical study of the mechanism of manganese catalase

The catalytic mechanism of manganese catalase has been studied using the Becke's three parameter hybrid method with the Lee, Yang and Parr correlation functional. On the basis of available experimental information on the geometric and electronic structure of the active manganese dimer complex, different possibilities were investigated. The mechanism finally suggested consists of eight steps. In the first steps, the first hydrogen peroxide becomes bound and its O–O bond is activated. This occurs in a spin-forbidden process found to be common in many biological processes where the O–O bond is cleaved, and two general rules are formulated for the requirements for a low activation energy in this type of reaction. As the O–O bond is cleaved a hydroxyl radical is initially formed in the overall rate-limiting step of the catalytic cycle. This radical is then immediately and irreversibly quenched in a strongly exothermic step. In the subsequent steps, the second hydrogen peroxide becomes bound and its two O–H bonds are broken, leading to the formation of an O₂ molecule, which is released. Parallels between the reversal of the present O–O cleavage mechanism in manganese catalase and the recently suggested O–O bond formation in photosystem II are drawn. Received: 12 July 2000 / Accepted: 12 July 2000 / Published online: 21 December 2000     

A computational model of the 5-HT3 receptor extracellular domain: search for ligand binding sites

A three-dimensional model of the 5-HT₃ receptor extarcellular domain has been derived on the basis of the nicotinic acetylcholine receptor model recently published by Tsigelny et al. Maximum complementarity between the position and characteristics of mutated residues putatively involved in ligand interaction and the pharmacophoric elements derived by the indirect approach applied on several series of 5-HT₃ ligands have been exploited to gain insights into the ligand binding modalities and to speculate on the mechanistic role of the structural components. The analysis of the three-dimensional model allows one to distinguish among amino acids that exert key roles in ligand interactions, subunit architecture, receptor assembly and receptor dynamics. For some of these, alternative roles with respect to the ones hypothesized by experimentalists are assigned. Different binding modalities for agonists and antagonists are highlighted, and residues which probably play a role in the transduction of binding into a change in conformational state of the receptor are suggested. Received: 27 July 2000 / Accepted: 15 September 2000 / Published online: 21 December 2000     

Rapid identification of carbendazim and linuron by adsorptive stripping on a carbon fiber ultramicroelectrode

A method is described for the identification of a mixture of carbendazim and linuron. It is based on adsorptive stripping voltammetry at a carbon fiber ultramicroelectrode. Conditions for the determination of carbendazim in a mixture were optimized and the method was applied to soil samples. It was compared to HPLC with spectrophotometric detection, where similar results were obtained. Received: 23 June 2000 / Revised: 19 July 2000 / Accepted: 23 July 2000     

Dual propagation inversion of truncated signals

Fourier transforms occur in a variety of chemical systems and processes. A few examples include obtaining spectral information from correlation functions, energy relaxation processes, spectral densities obtained from force autocorrelation functions, etc. In this article, a new functional transform, named the dual propagation inversion (DPI) is introduced. The DPI functional transform can be applied to a variety of problems in chemistry, such as Fourier transforms of time correlation functions, energy relaxation processes, rate theory, etc. The present illustrative application is to generating the frequency representation of a discrete, truncated time-domain signal. The DPI result is compared with the traditional Fourier transform applied to the same truncated time signal. For both noise-free and noise-corrupted time-truncated signals, the DPI spectrum is found to be more accurate, particularly as the signal is more severely truncated. In the DPI, the distributed-approximating-functional free propagator is used to propagate and denoise the signal simultaneously. Received: 30 January 2000 / Accepted: 6 July 2000 / Published online: 23 November 2000     

Metrology in laboratory medicine – Reference measurement systems

 The medical laboratory must provide results of measurements that are comparable over space and time in order to aid medical diagnosis and therapy. Thus, metrological traceability, preferably to the SI, is necessary. The task is formidable due to the many disciplines involved, the high production rate, short request-to-report time, small sample volumes, microheterogeneity of many analytes, and complex matrices. The prerequisite reference measurement systems include definition of measurand, unit of measurement (when applicable), consecutive levels of measurement procedures and calibrators in a calibration hierarchy, international organizations, reference measurement laboratories, dedicated manufacturers, written standards and guides for the medical laboratory, production of reference materials, internal and external quality control schemes, and increasingly accreditation. The present availability of reference measurement procedures and primary calibrators is shown to be insufficient to obtain international comparability of all types of quantity in laboratory medicine. Received: 19 April 2000 / Accepted: 3 July 2000     

Quality assurance of qualitative analysis in the framework of the European project ’MEQUALAN’

 The European Commission has supported the G6MA-CT-2000–01012 project on ”Metrology of Qualitative Chemical Analysis” (MEQUALAN), which was developed during 2000–2002. The final result is a document produced by a group of scientists with expertise in different areas of chemical analysis, metrology and quality assurance. One important part of this document deals, therefore, with aspects involved in analytical quality assurance of qualitative analysis. This article shows the main conclusions reported in the document referring to the implementation of quality principles in qualitative analysis: traceability, reliability (uncertainty), validation, and internal/external quality control for qualitative methods. Received: 15 October 2002 Accepted: 20 October 2002 This paper is a summary of the Quality Assurance section included in the final report of the MEQUALAN project. The authors of this paper correspond to the members of the MEQUALAN Consortium. One of them (K.H.) does not fully agree with some parts of the text. Correspondence to A. Ríos     

Exploratory Analysis of Micrographic Teflon Images

 Some analytical techniques are able to produce images, making if possible to obtain a large amount of information. Working with images, the pixels can be treated like objects in a data matrix. In this way, a multi-way PCA of micrograph images was applied to the internal surface of a Teflon coil used for microwave sample digestion. This Teflon coil was used for 120 h and had been attacked with different acids. It was cut into 3 pieces (namely: initial, medium and central portions) in order to obtain 7 micrographs (2 for initial, 2 for medium and 3 for the central part). A micrograph of a piece from a new Teflon coil was used for comparison. With these 8 micrographs, it was possible to establish a three-dimensional arrangement. After multi-way PCA was applied to the Teflon surface images, was possible to group a great amount of information and to characterise different parts of this coil. Received March 3, 2000. Revision July 28, 2000.     

Chemical destabilization of crude oil based emulsions and asphaltene stabilized emulsions

A comparison of low and high molecular weight demulsifiers and their effect on both crude oil and asphaltene based water-in-oil emulsions is performed. Physical characteristics are given for crudes and for the chemicals. These parameters were then correlated with the demulsifier performance. Results indicate that a significant lowering of interfacial tension is required, but not sufficient for an efficient demulsification. Addition of the chemicals directly to the oil phase prior to emulsification, i.e., as inhibitors, increased the performance of the chemicals significantly. Received: 3 May 2000 Accepted: 10 July 2000     

Keeping the spotlight on quality from a distance

 Maintaining the quality of testing in remote locations can be demanding of laboratory resources in terms of daily visits to instruments and providing support outside of normal working hours. Recently technology and software solutions have appeared to reduce this burden for laboratory scientists dramatically. The AVL Auto QC unit, in conjunction with OMNILink software, allow laboratory staff to perform many quality control and maintenance procedures on instruments in wards and medical units from a PC in the central laboratory. Assessment of this technology and software in the Special Baby Care Unit at Bradford Royal Infirmary has demonstrated many benefits including reduction in ward visits, better support out of hours, regular quality control checks, and improved analytical quality. Received: 15 April 2000 · Accepted: 15 April 2000     

Kinetics and Mechanism of the Oxidation of 1,10-Phenanthroline by Diperiodatonickelate(IV)in Aqueous Alkaline Medium

Summary.  The title reaction was investigated in aqueous alkaline medium. A first order dependence on both [diperiodatonickelate(IV)] and [OH⁻] and an apparent fractional order in [1,10-Phenanthroline] was obtained. Addition of the reaction product has no effect on the reaction. The effects of dielectric constant, ionic strength, and temperature on the rate of the reaction were studied. A mechanism based on the experimental results is proposed, and the constants involved in the mechanism were evaluated. A good agreement between the observed and calculated rate constants at varying experimental conditions was obtained. Received May 26, 2000. Accepted (revised) July 27, 2000