The quest for comparability: Calibration 2000

 Most efforts in quality control have been focussed on the reduction of intralaboratory variation and the assessment of interlaboratory variation. Over the last few years, the importance of bias in interlaboratory variation and intralaboratory shifts has become clear. Small shifts can sometimes have a large impact on the number of treated patients, particularly in assays where cut off values are used. For example in cholesterol, HDL-cholesterol, HbA1c and TSH assays. There is an obvious need for adequate calibration material. However, the process of development of international primary reference materials and reference methods takes time, and even if reference materials exist and are used by in vitro diagnostics manufacturers, there still remains significant and clinically relevant interlaboratory variance and intralaboratory shifts, as is seen, e.g. in protein chemistry. The harmonization of inter laboratory and intralaboratory results needs an impulse from professional organizations to convince individual laboratories of the importance and significance of bias. This applies to all subdisciplines of laboratory medicine. On the occasion of the 25th anniversary of the Foundation for External Quality Assessment (SKZL), a large interdisciplinary harmonization project called Calibration 2000 was launched in The Netherlands The strategy and first results are reported in this paper. The project aims at harmonization of laboratory data of several disciplines, using secondary calibration materials, leading to common reference ranges throughout The Netherlands. Received: 15 April 2000 · Accepted: 15 April 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     

Proficiency testing schemes for therapeutics and toxicology

 This report addresses the proposition: current proficiency testing (PT) schemes for therapeutics and toxicology can easily engender complacency. The proposition was based on the premise that there are substantial between-laboratory differences and objectives in the supply of services for the measurement of drugs, as a result of which it is difficult to design PT schemes which adequately cover the requirements of all laboratories. Thus, acceptable performance in a PT scheme may lead participants to consider that they have tested their procedures more rigorously than is the case. Four areas, validity of the PT scheme, PT material, frequency of testing and acceptance criteria are examined. Received: 15 April 2000 · Accepted: 15 April 2000     

Global trends in quality specifications: a report from the Stockholm Conference

 In Stockholm a conference entitled: "Strategies to Set Global Quality Specifications in Laboratory Medicine" was held in April 1999. The primary aim in organizing the Conference was to provide a vehicle for reaching consensus on global quality specifications in laboratory medicine. This objective was achieved and a lively constructive debate, after the presentations were complete, led to agreement on the principles laid down in the Consensus Statement. The International Federation of Clinical Chemistry (IFCC), the International Union of Pure and Applied Chemistry (IUPAC) and the World Health Organization (WHO) kindly sponsored the Conference but it must be noted that the Consensus Statement reflects the views of the presenters and registrants who participated in the Conference and does not necessarily represent those of the sponsoring bodies. This paper reports on the standardization efforts so far, the Stockholm Consensus Conference, the ISO uncertainty concept and the consensus reality. A hierarchy of quality specifications in laboratory medicine was defined and agreed on. Received: 15 April 2000 · Accepted: 15 April 2000     

Quality assurance in immunogenetics and histocompatibility: experience with EFI Accreditation

 The European Federation for Immunogenetics (EFI) has its own standards for histocompatibility testing. Compared with EN 45001 and ISO Standards, EFI Standards are more detailed, actually stating "what to do" in the laboratory. The decision of Eurotransplant that all its organ transplantation programmes must be EFI-accredited by the year 2000, illustrates the importance of the these standards. It took us 11 months to prepare the EFI questionnaire, describing the main features of our laboratory and how they complied with EFI Standards. After approval of this file, inspection was performed by a team of two peers who routinely worked in an EFI-accredited tissue typing laboratory. The pre-analytical, analytical and post-analytical phases were inspected during a one day visit. Furthermore, a checklist was reviewed against the laboratory's documentation system. Within 1 month of reception of the inspection report, we were expected to send a reply listing the corrective actions taken. Upon acknowledgement of the latter, EFI Accreditation was granted, for 1 year. We feel that detailed standards, specifically designed for a certain type of laboratory, offer many advantages. Received: 15 April 2000 · Accepted: 15 April 2000     

Telematics applications in a laboratory cluster

 The laboratories of six hospitals in the Canton of Wallis in Switzerland have been connected to one central laboratory, using the same database, the same software applications for the laboratory, pathology and pharmacy, and the same office and administration software. Some instruments in "Point of Care" sites are online for result transmission and for telemaintenance. The physicians may order drugs, material for sampling, analyses for specified patients and may consult knowledge bases, the patient data base, results and reports in different formats (ASCII, HTML, PDF, JPG, GIF, ...) using browsers like Netscape or MS-Explorer. To guarantee privacy, the access is restricted and protected by user-name, password and firewall. This report describes conditions for a successful introduction and usage of quality management through laboratory telematics. Received: 15 April 2000 · Accepted: 15 April 2000     

Reference intervals of serum folate and vitamin B12 developed from data of healthy subjects

 In this study the reference intervals for folate and vitamin B₁₂ were estimated according to the National Committee for Clinical Laboratory Standards Approved Guideline C28-A and International Federation of Clinical Chemistry recommendations. The study included 155 women and 124 men between ages 18–40. The health status was confirmed by history, physical examination and a questionnaire. The central 95% reference intervals of serum folate and vitamin B12 for women, determined non-parametrically, were found to be 3.9–18.1 ng/ml and 101–666.7 pg/ml, respectively. The reference values of serum folate and vitamin B12 for men were also found to be 2,5–17.6 ng/ml and 100–699.57 pg/ml, respectively. We did not observe subclass differences between females and males. Received: 15 April 2000 · Accepted: 15 April 2000     

Total quality management in hematology

 Healthcare is changing and clinical laboratory testing must change with it. In no discipline is this change more profound than in hematology. The principles of total quality management (TQM) including continuous quality improvement, reengineering and strategic planning can facilitate these changes. In the past, hematology has often been exlcuded from these processes due to its many manual procedures and the degree of expertise and skill needed to perform the testing. As automated technology continues to evolve, hematology testing, like other testing, will become integrated into the core, clinical laboratory. We suggest TQM can, and should, guide the way. Received: 15 April 2000 · Accepted: 19 April 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     

Unitary perturbation theory: a generalization of two-by-two rotations

A generalization of the two-by-two rotation technique is proposed, permitting a whole row (column) of the matrix to be treated simultaneously. The method is based on the explicit analytical evaluation of the matrix exponent representing a symmetric combination of the individual rotations. Besides constructing the unitary transformation matrices, a new orthogonalization algorithm is also proposed. The resulting “unitary perturbation theory” and orthogonalization method may be useful in different areas. Received: 15 November 1999 / Accepted: 30 January 2000 / Published online: 19 April 2000     

Highly selective thiocyanate poly(vinyl chloride) membrane electrode based on a cadmium–Schiff’s base complex

A PVC membrane electrode based on a cadmium–salen (N,N′-bis-salicylidene-1,2ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity sequence with a preference for thiocyanate at pH 1.5–11.0. It has a linear response to thiocyanate from 1.0 × 10^–6 to 1.0 × 10^–1 mol L^–1 with a slope of 59.1 ± 0.2 mV per decade, and a detection limit of 7 × 10^–7 mol L^–1. This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample. Received: 1 December 2000 / Revised: 19 April 2001 / Accepted: 30 April 2001     

Determination of the fast fission yield of141Pr using neutron activation analysis

A method is described for the determination of the fission yield of¹⁴¹Pr. This method was developed to determine the fast fission yield of¹⁴¹Pr in the Mark III loading (enriched uranium with about 2% zirconium) of the fast fission breeder reactor, EBR-1. The burnup of the fuel sample was determined using the previously reported fission yield of¹³⁷Cs. Praseodymium was separated from uranium, plutonium and other fission products by a combination of precipitation and ion exchange stages. Thereafter,⁵⁵Mn was added to serve as an internal flux monitor and praseodymium determined by neutron activation analysis. A precision of ±2% was obtained. Presented at the 15th Annual Meeting of the American Chemical Society, Miami Beach, Florida (USA), April 1967.     

Particular and homogeneous solutions of time-independent wavepacket Schrödinger equations: calculations using a subset of eigenstates of undamped or damped Hamiltonians

A variety of causal, particular and homogeneous solutions to the time-independent wavepacket Schr?dinger equation have been considered as the basis for calculations using Chebychev expansions, finite-τ expansions obtained from a partial Fourier transform of the time-dependent Schr?dinger equation, and the distributed approximating functional (DAF) representation for the spectral density operator (SDO). All the approximations are made computationally robust and reliable by damping the discrete Hamiltonian matrix along the edges of the finite grid to facilitate the use of compact grids. The approximations are found to be completely well behaved at all values of the (continuous) scattering energy. It is found that the DAF–SDO provides a suitable alternative to Chebychev propagation. Received: 29 February 2000 / Accepted: 5 April 2000 / Published online: 18 August 2000     

Lipids ofOriganum tytthanthum

The composition of lipids and fatty acids from the above-ground part ofOriganum tytthanthum Gontsch. (Lamiaceae) is studied. Lipids from the air-dried plant material are enriched in glycolipids, essential fatty acids, and biologically active lipophilic substances. The free fatty acids include 15-methylhexadecanoic acid (0.5 % by GLC).Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 100–102, March–April, 2000.     

Microwave assisted extraction of organochlorine pesticides from sediments and its application to contaminated sediment samples

A method was established and optimized for rapid and reproducible analyses of 17 organochlorine pesticides in sediments employing microwave assisted extraction followed by gas chromatographic separation with mass spectrometric detection using a computer optimized temperature program. For optimization, 5 g portions of sediment were spiked with a standard solution of the 17 analytes in isooctane at ∼50 ng/g for each pesticide and extracted in a microwave oven for 30 min at 100 °C using three different solvents. The best recoveries between 74% and 99% (RSD = 1.0–10.2%) were obtained with tetrahydro furan. The time consuming and laborious clean-up using liquid/liquid-extraction and two column-chromatographic steps was replaced by a one step liquid/solid-extraction, showing the same or even better performance in terms of recovery and reproducibility. Calibration plots were linear for all analytes and MDLs were in the range from 2–9 ng/g. To show the environmental applicability, the method was employed for the analysis of naturally contaminated sediments from the Netherlands (SETOC 701). The results were compared with the results obtained in our lab with ultrasonic extraction and supercritical fluid extraction and corresponded well with the median of results obtained from different interlaboratory comparison studies. Received: 18 January 1998 / Revised: 30 March 1998 / Accepted: 2 April 1998     

Microwave assisted extraction of organochlorine pesticides from sediments and its application to contaminated sediment samples

A method was established and optimized for rapid and reproducible analyses of 17 organochlorine pesticides in sediments employing microwave assisted extraction followed by gas chromatographic separation with mass spectrometric detection using a computer optimized temperature program. For optimization, 5 g portions of sediment were spiked with a standard solution of the 17 analytes in isooctane at ∼50 ng/g for each pesticide and extracted in a microwave oven for 30 min at 100 °C using three different solvents. The best recoveries between 74% and 99% (RSD = 1.0–10.2%) were obtained with tetrahydro furan. The time consuming and laborious clean-up using liquid/liquid-extraction and two column-chromatographic steps was replaced by a one step liquid/solid-extraction, showing the same or even better performance in terms of recovery and reproducibility. Calibration plots were linear for all analytes and MDLs were in the range from 2–9 ng/g. To show the environmental applicability, the method was employed for the analysis of naturally contaminated sediments from the Netherlands (SETOC 701). The results were compared with the results obtained in our lab with ultrasonic extraction and supercritical fluid extraction and corresponded well with the median of results obtained from different interlaboratory comparison studies. Received: 18 January 1998 / Revised: 30 March 1998 / Accepted: 2 April 1998     

Determination of selenium in soils by slurry-sampling graphite-furnace atomic-absorption spectrometry with polytetrafluoroethylene as silica modifier

A 6% slurry of polytetrafluoroethylene (PTFE) in 4% hydrofluoric acid and 1% nickel nitrate were used as modifiers for determination of selenium in soils by GF AAS. PTFE was used to remove silica from the soil sample, because this resulted in severe matrix effects. The temperature of fluorination, determined thermogravimetrically, was 600 °C. The yield of fluorination depends on the molar ratio of PTFE/silica, particle size, and the time and temperature of fluorination. The soil samples were pretreated with a small amount of concentrated hydrofluoric acid placed directly in the cup of autosampler. The results for the determination of selenium in the reference soil materials by means of the slurry-sampling technique and use of aqueous standards are in good agreement with the certified values. Received: 20 December 2000 / Revised: 3 April 2001 / Accepted: 5 April 2001     

Matrix interferences in the determination of trace elements in waste waters by inductively coupled plasma atomic emission spectrometry with ultrasonic nebulization

The use of inductively coupled plasma atomic emission spectrometry with ultrasonic nebulization (USN-ICP-AES) for determining Ag, Al, As, Ba, Bi, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Sb, Sr, V and Zn in complex matrices of Ca, Na, K and P in waste waters is described. Generally, depressions in the analyte emission intensity occur in the presence of concomitants. Matrix interferences can be minimized by increasing the operating power and lowering the carrier gas flow rate. However, the enhancement of the signal-to-background ratios (SBRs) shows an opposite trend. Therefore, routine analyses were performed at a compromise power setting of 1350 W, a carrier gas flow rate of 0.8 L min^–1 and an observation height of 14 mm above the load coil and using a matrix matched calibration procedure. Limits of detection (LODs) at chosen operating conditions were at μg L^–1 levels for most of the elements studied, including mercury when KBr is added to the analyte solution to enhance sensitivity. LODs were not significantly changed in the presence of matrix elements. Recoveries for the majority of added elements from spiked waste water samples are between 93 and 105% using a matrix matched calibration. Received: 13 January 2000 / Revised: 10 April 2000 / Accepted: 18 April 2000     

Ab initio molecular orbital study of Fe(CO) n (n = 1–3)

Geometry optimization was performed for the ground states of FeCO, Fe(CO)₂, and Fe(CO)₃ at various levels of ab initio calculations, and the bond lengths and dissociation energies obtained were in reasonable agreement with experimental results. The nature of bonding was studied for these molecules using a complete-active-space self-consistent-field method. From the Mulliken population analysis, it was found that the traditional donation and back donation mechanism is valid for these molecules, including Fe(CO)₃, which has a pyramidal structure. Received: 27 September 1999 / Accepted: 13 January 2000 / Published online: 19 April 2000     

Determination of trace amounts of gold and silver in high-purity iron and steel by electrothermal atomic absorption spectrometry after reductive coprecipitation

Trace amounts of gold and silver in high-purity iron or steel were preconcentrated by reductive coprecipitation with palladium using ascorbic acid, and determined by electrothermal atomic absorption spectrometry (ET-AAS). Both gold and silver could be simultaneously separated and sensitively determined in 10 metals (aluminum, cobalt, chromium, copper, iron, manganese, molybdenum, nickel, vanadium and zinc). Comparable values were obtained for gold and silver in reference materials (low alloy steel) by the proposed method and a non-separation method; good agreement was found between the analytical values by both methods and the certified values. The proposed method is easy, simple and not dependent on sample composition and content. Moreover, gold and silver in metal samples could be simultaneously separated together with selenium and tellurium. The detection limits for gold and silver (3 σ) are 0.003 μg g^–1 and 0.002 μg g^–1, respectively. Received: 3 February 2000 / Revised: 11 April 2000 / Accepted: 16 April 2000