Separation of enantiomers by capillary electrophoresis using pentosan polysulfate

Pentosan polysulfate, a semisynthetic polysaccharide, was employed as a chiral run buffer additive in capillary electrophoresis. Twenty-eight racemic analytes were resolved. The separations were successful only at low pH when the analytes were significantly protonated. This suggests that ionic interactions were the dominant associative interactions between the anionic pentosan polysulfate and the positively charged analytes. Compared to other linear, carbohydrate-based chiral selectors (i.e., chondroitin sulfates, heparin and dextran sulfate) pentosan polysulfate has some characteristics common of anionic polysaccharides; yet it has several differences in its structure and properties which account for its unusual enantioselectivity. The effects of pH, concentration of phosphate buffer, concentration of pentosan polysulfate and the type and concentration of organic modifier on the enantiomeric separations were investigated. The optimization of these separations were dependent on the nature of the analytes and could be achieved by the proper choice of experimental conditions.     

Salt effects in anion exchange displacement chromatography: Comparison of pentosan polysulfate and dextran sulfate displacers

Summary Experimental studies were carried out to investigate the utility of pentosan polysulfate as a low molecular weight polyelectrolyte displacer for the purification of proteins in anion-exchange displacement systems. In addition, the influence of mobile phase salt concentration on displacer efficacy, protein-protein resolution, and displacement development were studied for several anionic displacers. It was found that while large polyelectrolytes (50 kd dextran sulfate) were efficient displacers for a wide range of salt concentrations, relatively small polyelectrolytes (3 kd pentosan polysulfate) were seen to act as an efficient displacer only under conditions of high salt micro-environments. In addition, for proteins exhibiting similar affinities, zone mixing at the protein-protein boundary was found to be quite sensitive to the salt concentration. Finally, displacement chromatography was successfully implemented for the separation of proteins from milk whey.     

The role of statistics in quality assurance

Summary The quality of data, which is to say its accuracy, must be known whenever it is to be used for purposes of decision. This is only possible as it is produced by a valid analytical system operating in a state of statistical control. A quality assurance program should be established, consisting of quality control of the analytical system and quality assessment of the data that are produced. Data quality objectives should be established for every measurement situation and the accuracy attained must be within these limits. Ideally, the attained accuracy should exceed the required accuracy by a factor of three, at a minimum. The estimation of attained accuracy is best made using reliable reference materials. When they are not available, spikes may be used with lesser confidence. No matter what estimation techniques are used, decisions must be made on the basis of statistical tests of significance. The evaluation of accuracy is a continuing operation and facilitated by the use of appropriate control charts. The paper discusses the above described concepts and summarizes the techniques most useful for evaluating the accuracy of analytical data.

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Die Rolle der Statistik in der Qualitätssicherung

     

External quality assurance programmes in medical laboratories

 Medical laboratories have a long tradition of external quality assessment. Starting from pure quality control of laboratory performances, most schemes have evolved to a powerful tool for improving quality of clinical outcome of results. External quality assurance in medical laboratories not only includes laboratory performance evaluation, but also evaluation of method performance, post-marked vigilance, training and help. In the future, the quality of programmes must further be improved by accreditation of schemes and by using electronic data interchange. Received: 9 December 2000 Accepted: 14 December 2000     

Use of reference materials in coastal monitoring quality assurance

The NOAA National Status and Trends (NS&T) Program determines the current status of, and changes over time in the environmental health of U.S estuarine and coastal waters. Concentrations of organic and inorganic contaminants are determined in bivalves, bottom-dwelling fish and sediments. The quality of the analytical data generated by the NS&T Program is over-seen by the performance-based Quality Assurance Project, which is designed to document sampling protocols, analytical procedures, and laboratory performance, and to reduce intralaboratory and interlaboratory variation. All NS&T cooperating laboratories are required to participate in yearly intercomparison exercises. The analysis of reference materials, such as the National Research Council of Canada's Certified Reference Materials (CRMs) and National Institute of Standards and Technology's (NIST) Standard Reference Materials (SRMs), and of control materials, is required. Because of the need for marine matrix reference materials and standards, NOAA contributed to the production of eight NIST SRMs and seven internal standard solutions. Analytical data from all control materials and all matrix reference materials are reported to the Program office.     

EC initiatives for quality assurance training in analytical chemistry

Quality in the analytical laboratory is essential nowadays, must prove to meet the needs of customers, attract their confidence (and that of others who make use of the results), and represent value for money. There are innumerable areas where the results of chemical analysis are important (e.g., in the determination of the quality of manufactured products, in support of health and safety, in establishing environmental legislation, and in forensic science). However, although the concept of quality control and quality assurance is well understood by modern laboratories (whether commercial or with national responsibilities) –which are often accredited in various analytical sectors – there is an enormous gap in the transfer of knowledge to smaller laboratories. Training actions are therefore urgently needed, especially for analysts working in routine laboratories. This article describes two initiatives carried out under the umbrella of the EC Standards, Measurements and Testing Programme.     

The increasing demands of quality assurance in chemical testing

The chemical and microbiological testing community is going through a rather difficult period of change. Publication of ISO/IEC 17025 (General requirements for the competence of Calibration and Testing Laboratories, 1999) [1] is placing additional demands on testing laboratories to ensure traceability and estimate uncertainty in their measurements. At the same time, laboratories must remain mindful of the need to provide relevant, timely and economic services to their clients. International Accreditation New Zealand (IANZ) and its accredited laboratories are currently focussing on establishing realistic methods for ensuring traceability to national and international standards and estimating measurement uncertainty. To this end, IANZ recognizes that it has an important role in providing as much advice and assistance as possible, not only to its accredited chemical laboratories but also to all those contemplating accreditation in New Zealand.

Key requirements for introducing quality assurance in measurement laboratories

 The implementation of a quality assurance system is fraught with difficulties. However, these difficulties may be overcome if the laboratory uses suitable means to facilitate the process. It is necessary to mobilise the intelligence and energy of all members of the laboratory. In order to command adherence, the project must be shared, and this necessitates a major effort by all concerned. Communication is a major factor in obtaining the support of all parties. Six important steps must be distinguished: – Defining quality policy – Creating awareness, information, training – Creating a quality structure – Establishing a deadline for obtaining accreditation – Progressive implementation – Experimentation and validation. Even if the task of obtaining and maintaining accreditation remains difficult, it clearly promotes a minimum level of organisation and stepwise progress in quality assurance. The laboratory must keep improving its quality system, using European Standard EN 45001 as an effective management model. Received: 9 April 1997 · Accepted: 11 September 1997     

The role of Nordtest in testing and quality assurance

 This article describes on the idea behind Nordtest, the results of its activities and how Nordtest has influenced testing and quality assurance. By financing projects in the field of technical testing Nordtest has been able to utilise the best available Nordic knowledge and resources to respond to Nordic needs and has gained acceptance in all Nordic countries. During Nordtest's 25 years of operation its projects have resulted in over 500 test methods and over 350 technical reports that are widely used both within and outside the Nordic countries. Examples of some project results are given. Important issues in testing and quality assurance are expressed in Nordtest position papers. Nordtest's active participation in the European and global co-operation in testing and quality assurance is also described.     

Progress in the quality assurance of environmental trace organic analysis

An overview is given on the stepwise learning programmes undertaken to identify the main sources of error associated with the determination of the mandatory organic contaminants in the marine monitoring programmes. Details are given on the preparation and use of LRMs and CRMs to maintain analytical control and quantify the laboratory errors in relation to the measurement of changes in the environment.     

Sense and nonsense of quality assurance in an R&D environment

Quality has always been one of the key issues in laboratories in general and formal quality assurance (QA) in testing laboratories has gained popularity over the last decade. However, the implementation QA in research and development (R&;D) laboratories is still the domain of a few pioneers. We can even ask whether a QA system in research makes sense at all and if such a system really provides any added value? Difficulties with respect to the implementation of such a system are mainly associated with the nature of the research process itself. However, it is obvious that QA offers clear advantages in R&;D, if some critical success factors have been taken into account. An important issue is the selection of a good QA standard for R&;D. This is certainly not an easy task, since there are no specific standards. Fortunately, some useful international guides have been published recently.     

Utilization ofk o-factors for quality assurance in neutron activation analysis

Multielement certification analysis by instrumental neutron activation analysis requires simultaneous irradiation of several elemental comparator standards in order to ascertain traceability. Internal consistency of different comparators may be checked by calculation ofk _o-ratios, which show large deviations from unity in case of stoichiometric or other gross errors. Quality assurance based on the Analysis of Precision ofk _o-ratios from replicate analyses detects unexpected variability associated with inaccurate comparator standards. In two actual cases of cerification lack of statistical control amongk _o-ratios led to biased analytical results.     

Analytical quality assurance in the german food contamination monitoring programme

Summary The general and analytical strategy for a monitoring project for various chemical elements, nitrate and some halogenated organic compounds in milk, beef, pork, potatoes, lettuce, cabbage, apples and strawberries within the activities of official food control in the Federal Republic of Germany is outlined.

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Analytische Qualitätssicherung im Rahmen eines deutschen Programms zur Überwachung von Lebensmittelverunreinigungen