Draft radioanalytical water and soil performance testing: Uncertainty acceptance criteria derived from historical mixed-analyte performance evaluation program results

Radioanalytical performance testing programs provide radioassay laboratories, regulators and the public performance-based evidence that measurement capabilities are in control. Performance acceptance criteria that combine aspects of measurements difference from a known value and the associated combined uncertainty establishes a quantitative statement of statistical confidence. However, there is need for a reasonable upper limit of the reported measurement uncertainty. Evaluation of thousands of historical U.S. DOE Mixed-Analyte Performance Evaluation Program measurement results for 17 radionuclides in soil and water samples provides predictive expectations for future measurement results and a statistical basis for establishing reasonable upper limits for reported measurement uncertainties for performance evaluation programs.     

Discussion on classification and performance evaluation of diversified testing procedures

Accreditation and Quality Assurance - More and more testing procedures with different principles are being developed covering both quantitative and qualitative analyses. To ensure the reliability...     

Information system and qualifying criteria for proficiency testing schemes

Since October 1998 the European Commission has financed a concerted action on Information System and Qualifying Criteria for Proficiency Testing Schemes within the 4th framework program. As a major result of this project EPTIS, the European Information System on Proficiency Testing Schemes which is available on the Internet since March 2000, is presented in this paper. Today EPTIS contains comprehensive information on approximately 640 proficiency testing schemes from 16 European countries providing information on the state of the art in proficiency testing in Europe. Finally some possible approaches for interlinkages and recognition of proficiency testing schemes are discussed.     

Sythesis of methylthiomaleimides for the preparation of pyridazines and related comopounds

New functionalized maleimides (3‐methylthio‐2,5‐dioxo‐1H‐pyrroles) were obtained by the reaction of ketene dithioacetals with nitromethane or the reaction of nitro ketene dithioacetal with active methylene compounds in the presence of the appropriate base in dimethyl sulfoxide followed by treatment with methanol. These nakeunudes reacted with various nucleophilic reagents such as election‐rich aromatic and heteroaromatic compounds like dialkylanilines, aminophenols, indoles, indolizines, and cyalazines to give the corresponding 3‐aryl‐ or heteroaryl‐ 1H‐pyrole‐2,5‐diones. Styryl and merocyanie dyes, and polycyclic pyridazine‐diones as chemiluminophors and succinimides were also obtained from these maleimides with good results.     

The preparation and utilization of performance evaluation soils for evaluating radioassay laboratories engaged in site remediation work

Site remediation projects dealing with uranium, thorium or radium require the services of a radioassay laboratory during the site characterization, remediation and final site survey/verification phases. In the U.S., regulatory agencies and industry guidelines recommend that the remediation contractor conduct an external laboratory QC program to ensure the quality of the analytical results. The commercial availability of certified natural soil matrices is extremely limited not only by nuclide and nuclide concentration but also by soil type. In most cases, the applicability of these materials for an external QC program is questionable since the chemical constituents of the certified soil may not be representative of the remediation soil type. Also, such materials are typically only suitable as single blind performance evaluation (PE) samples. The Yankee Atomic Environmental Laboratory (YAEL) has characterized soil materials from several uranium mining and milling sites for use in two laboratory PE programs. The site specific PE materials were prepared in accordance with their intended use and quality performance requirements. One PE material was dried, pulverized to a particle size of approximately 10 microns and homogeneously blended. The second PE material (total of 1,024 kg) was methodically field blended and aliquoted to produce 1,000 separate homogeneous 1 kg samples. Both PE materials were characterized for radionuclide concentration and heterogeneity or sample distribution. A summary of the characterization studies of the different PE materials as well as the quality performance criteria developed for evaluating the laboratory's performance and the advantages and disadvantages of using each PE material will be discussed and summarized.     

Tandem oxime formation—epoxide ring opening sequences for the preparation of oxazines related to the trichodermamides

A mild and straightforward method for the preparation of 4H-5,6-dihydro-1,2-oxazines from keto-epoxides via cyclisation of the intermediate oximes is reported, as is a preparative route to 3-amino-7,8-dimethoxychromen-2-one; these procedures were then employed to prepare a novel analogue of trichodermamide natural products.     

Detection methods and performance criteria for genetically modified organisms

Detection methods for genetically modified organisms (GMOs) are necessary for many applications, from seed purity assessment to compliance of food labeling in several countries. Numerous analytical methods are currently used or under development to support these needs. The currently used methods are bioassays and protein- and DNA-based detection protocols. To avoid discrepancy of results between such largely different methods and, for instance, the potential resulting legal actions, compatibility of the methods is urgently needed. Performance criteria of methods allow evaluation against a common standard. The more-common performance criteria for detection methods are precision, accuracy, sensitivity, and specificity, which together specifically address other terms used to describe the performance of a method, such as applicability, selectivity, calibration, trueness, precision, recovery, operating range, limit of quantitation, limit of detection, and ruggedness. Performance criteria should provide objective tools to accept or reject specific methods, to validate them, to ensure compatibility between validated methods, and be used on a routine basis to reject data outside an acceptable range of variability. When selecting a method of detection, it is also important to consider its applicability, its field of applications, and its limitations, by including factors such as its ability to detect the target analyte in a given matrix, the duration of the analyses, its cost effectiveness, and the necessary sample sizes for testing. Thus, the current GMO detection methods should be evaluated against a common set of performance criteria.     

Experimental evaluation of different precision criteria applicable to microbiological counting methods

The dispersion of microbiological counting measurements, when repeating the analysis on the same material both within a laboratory (repeatability) and between laboratories (reproducibility) can be characterized by the organization of interlaboratory studies, where several sets of identical test materials are sent to several laboratories. Using the example of data generated by an interlaboratory study on enumeration of Listeria monocytogenes in foods by the standardized reference method (colony-count technique), 2 types of robust estimators of reproducibility standard deviations, based on the median, were examined, in comparison with the classical estimators, based on the mean. Experimental evaluation indicated that the 3 approaches gave consistent results for most of the combinations. The usual log10 transformation of the enumeration results was also questioned before these calculations were conducted.     

Theoretical considerations on the performance of electrochemical flow-through detectors

A survey of the equations on the limiting current in electrochemical flow-through cells is presented. For voltammetric detectors, a generalized equation for the limiting current is given. The conditions to be considered in designing an electrochemical flow-through detector for optimal signal-to-noise ratios are outlined for tubular, thin-layer, wall-jet and disk electrodes.     

A new synthetic method for the preparation of protonated-NHCs and related compounds

Protonated versions of N-heterocyclic carbenes (NHC,H⁺) are classically prepared by closing the ring through the introduction of the CH⁺ fragment. Here we report a totally different synthetic approach, which can be viewed as the addition of a 1,3-diazaallyl anion to a compound featuring two leaving groups (hereafter named “di-electrophile”). Using 1,3- and 1,4-dibromides, six- and seven-membered NHC,H⁺s have been prepared in good yields. Similarly, with 1,3,2-dioxathiolane-2,2-dioxide as a di-electrophile, imidazolidinium salts were obtained. To illustrate its broad scope of application, this synthetic route has been expanded to the preparation of protonated cyclic amino alkyl carbenes (CAACs) and amino thio carbenes, using 1-aza-allyl and 1,3-azathio-allyl anions, respectively.     

Quality criteria for the detection of analytes in test samples with special reference to anabolic agents and related compounds

In order to create a system for qualitative analysis, in which well defined limits of ambiguity can be set, criteria have been formulated for application to the identification method(s) used. Criteria are presented for separation techniques (thin-layer chromatography, gas chromatography, high-performance liquid chromatography) and for spectrometric methods (ultraviolet-visible spectroscopy via diode array, mass spectrometry, infrared spectroscopy), as well as general considerations for the whole procedure.     

Design, preparation and testing of suitable probe-receptors for RNA biosensing

Absolute measurements of a given RNA in a cheap, easy, rapid and reproducible manner using biosensors technology could overcome many of the operative and analytical limits of conventional molecular biology methods. To this end, an integrated approach for the design, synthesis, and connection of RNA probes to the transducing surface of a microgravimetric biosensor has been developed. Suitable probes to be used as the bioreceptors in RNA biosensor were successfully designed by using a purposely developed computational method whose selection criteria are based on the accessibility of target region to probe, on pairing stability of probe-target duplex and on the uniqueness of selected targets over all known expressed sequences from a genome data base. Automated chemical synthesis of selected probes was performed and the oligonucleotides produced were covalently conjugated to the sensing surface of a quartz microbalance. The microgravimetric sensor was tested in a flow chamber by measuring the variation of resonance frequency due to the binding of synthetic target substrates. Specific dose dependent binding was observed. Furthermore, the binding of a transcribed full-length mRNA substrate was successfully monitored under similar conditions.     

Thermo-oxidation of lactam polymers related to the conditions of their preparation by hydrolytic polymerization

Due to side reactions, polymers (prepared by hydrolytic polymerization under the same conditions) of 7, 9 and 13-membered lactams differ in the number of macromolecules, in the content of acid and basic groups, and also in the ratio of basic and primary amine groups. Due to the different extents of secondary reactions which are temperature-dependent, the polymers contain different concentrations of structures which accelerate or retard thermo-oxidation. At polymerization temperatures below 250°, the reaction time has no effect on the subsequent oxidation of the polymer.     

A comparison of performance statistics for proficiency testing programmes

Recently, ISO issued a new document on statistical methods for use in proficiency-testing schemes. The document presented a number of new performance statistics that involve the use of measurement uncertainties of the participants’ results and/or the assigned values for the performance evaluation. Making use of the Monte Carlo simulation technique, this paper attempts to compare selected performance statistics of different approaches. In addition, the simulation programme was extended to study the effect of multi-modality in participants’ results on the performance evaluation when different performance statistics were applied.