Use of calibration gases in the U.S. acid rain program

The United States Acid Rain Program continuous emission monitors (CEMs) have been successful in producing quality-assured data 95% of the time, and in meeting a relative accuracy standard of less than or equal to 10.0% at over 99% of the CEMs in the program. One key reason for this high accuracy is the required use of high quality calibration gases in certification and quality assurance/quality control (QA/QC) tests. An annual QA audit helps ensure high quality calibration gases. A third party purchases gases from gas vendors. An Environmental Protection Agency (EPA) laboratory analyzes the gases and compares the results with the tag value on the cylinder. The results are posted on an EPA website. This allows purchasers of calibration gases to buy gases from vendors producing the most accurate gases. Over time, we believe it also results in better accuracy from all gas vendors. Because of a change in SO₂ quantification methodology, SO₂ emissions were underreported by approximately 2% between 1989 and 1996. EPA, the National Institute for Standards and Technology and calibration gas vendors collaborated to produce a correction policy and a standard correction form to be used by affected electric utility plants. Calibration gas cylinder tag values were required to be corrected by 1 January, 1997. In the future, it is possible that cleaner, more varied sources will be regulated for greenhouse effect, ozone and toxic emissions control. This will probably require more accurate CEMs, lower calibration gas concentrations, and a broader menu of gas mixtures. Received: 23 December 1999 Accepted: 12 December 2000     

Mass spectrometry in the U.S. space program: Past, present, and future

Recent years have witnessed significant progress on the miniaturization of mass spectrometers for a variety of field applications. This article describes the development and application of mass spectrometry (MS) instrumentation to support of goals of the U.S. space program. Its main focus is on the two most common space-related applications of MS: studying the composition of planetary atmospheres and monitoring air quality on manned space missions. Both sets of applications present special requirements in terms of analytical performance (sensitivity, selectivity, speed, etc.), logistical considerations (space, weight, and power requirements), and deployment in perhaps the harshest of all possible environments (space). The MS instruments deployed on the Pioneer Venus and Mars Viking Lander missions are reviewed for the purposes of illustrating the unique features of the sample introduction systems, mass analyzers, and vacuum systems, and for presenting their specifications which are impressive even by today's standards. The various approaches for monitoring volatile organic compounds (VOCs) in cabin atmospheres are also reviewed. In the past, ground-based GC/MS instruments have been used to identify and quantify VOCs in archival samples collected during the Mercury, Apollo, Skylab, Space Shuttle, and Mir missions. Some of the data from the more recent missions are provided to illustrate the composition data obtained and to underscore the need for instrumentation to perform such monitoring in situ. Lastly, the development of two emerging technologies, Direct Sampling Ion Trap Mass Spectrometry (DSITMS) and GC/Ion Mobility Spectrometry (GC/IMS), will be discussed to illustrate their potential utility for future missions.     

Analytical performance is improved by regular participation in proficiency testing: an analysis of data from the Aquacheck proficiency testing scheme

Analysis of historical data from the Aquacheck proficiency testing scheme demonstrates improvement in the performance of participants correlated to the frequency of participation. Analysis of the spread of results returned by all participants, defined by the percentage relative standard deviation (RSD) and the performance (Z) scores awarded to the individual participants, indicates that the overall performance for the group of participants is consistent. However, when the frequency of participation is analysed, it can be clearly seen that those laboratories who participated in the majority of the distributions available reported 10–15% more acceptable (Z-scores between +2 and ?2) results than those labs who took part with a greatly reduced frequency. When ‘more difficult’ analytes are considered, those laboratories who participated in greater than 75% of available rounds reported up to 30% more acceptable results than those laboratories who participated in 25% or fewer, of the available rounds.     

Methodology for the U.S. Food and Drug Administration's radionuclides in foods program

The U.S. Food and Drug Administration (FDA) is responsible for the wholesomeness of the nation's food supply. The FDA modified its food monitoring program in January, 1973, to include radioactive isotopes. The methodology used to perform, analyses on these food products are taken from the standerd setting societies such as the AOAC International, American Society for Testing Materials and American Public Health Association Standard Methods. In addition, methods not tested by these societies are taken from the literature or from Department of Energy manuals such as the Health and Safety Laboratory and also from Environmental Protection Agency, Public Health Service, and Food and Agricultural Organization manuals. These include the methods for long-lived radionuclides such as tritium, strontium-90, cesium-137 and plutonium. Also, the short-lived radionuclides such as iodine-131, radiocesium, radiocerium and radioruthenium. In addition, they include the natural occurring radionuclides such as radium and uranium isotopes. The activity concentrations of gamma-emitters such as radiocesium, iodine-131 and radioruthenium are determined by gamma-ray spectrometry. This is done using intrinsic germanium detectors with the appropriate hardware and software. The alpha and “pure” beta-emitters are determined by various radiochemical methods and techniques. The radiochemical methodology and equipment used in analyzing these radionuclides are described and discussed. Also, the methodology and equipment for the gamma-emitters are described in more detail in this paper. In addition, the limits of detection for the methods used will be discussed.     

Metrology in service of society: the role of proficiency testing

A sound system of competent measurements, underpinned by standards and accreditation, is an essential component of the infrastructure of any modern society. Proficiency Testing is an indispensible tool for developing and maintaining this infrastructure. It is used to verify compliance with standards, for ongoing monitoring of laboratory performance, for demonstration of competence, and for evaluating the performance of measurement procedures; it is used to indicate performance problems that might not be detected otherwise; and it is used as a tool for education and self-improvement. The new International Standard, ISO/IEC 17043, contains requirements and recommendations to make optimal use of this important tool.     

Establishment of proficiency testing programs in the Philippines

Accreditation and Quality Assurance - In order to improve the competitiveness of Philippine food products in the global market, the Department of Science and Technology—Food and Nutrition...     

The practice of proficiency testing in China

This paper briefly summarises the current situation for proficiency testing (PT) in China, outlines the policy for PT of China’s national accreditation committee for laboratories (CNACL), and exemplifies activities of the CNACL’s metal working group. Received: 9 December 2000 Accepted: 14 December 2000     

Economy of proficiency testing: reference versus consensus values

Many proficiency tests are operated with a consensus value derived from the participants’ results. Apart from technical issues, one of the reasons often mentioned is that proficiency tests operated with consensus values would be cheaper than those using reference values obtained from a priori characterisation measurements. The economy of a proficiency test must of course be balanced by the need of the participants, and the quality of the comparison in general. The proficiency tests selected in this study had both a reference value and a consensus value, one of which was used for assessing the performance of the participating laboratories. In this work, both a technical and an economical assessment of how the comparisons were operated is made. From the evaluation, it follows that usually the use of consensus values does not necessarily reduce the costs of a proficiency test. However, frequently it may be observed that the quality of the assessment of the laboratories is better with a reference value. Received: 11 October 2000 Accepted: 3 January 2001     

Experiences from the assessment of proficiency testing providers

Following a pilot project in 2001–2002, UKAS accredited nine PT providers. During the course of the pilot and at subsequent surveillance visits, UKAS has gained experience in assessing organisations against the criteria detailed within ISO/IEC Guide 43-1:1997 and ILAC G13:2000. This article explores some of the key aspects that arose during the pilot and how UKAS has accommodated the addition of the accreditation of PT providers in to its range of services.Presented at the Eurachem PT Workshop September 2005, Portorož, Slovenia     

Regulatory aspects of proficiency testing: experience from the water sector

Proficiency tests in the regulated sector have requirements different from other areas. Repeated unsuccessful participation can lead to the economic ruin of a laboratory. This is illustrated at the water analyses sector in Germany as an example. Collusion and falsification have to be avoided. A special and uniform evaluation technique is necessary that includes the possibility of a common evaluation of different concentration levels and considers the skewed distribution of data. A suitable approach is published in a new German DIN standard (DIN 38402-45). The assessment of the values and the laboratories as a whole also needs special attention. A concept to do this with as few injustices as possible was developed in an inter-state working group in Germany.

     

Regulatory aspects of proficiency testing: experience from the water sector

Proficiency tests in the regulated sector have requirements different from other areas. Repeated unsuccessful participation can lead to the economic ruin of a laboratory. This is illustrated at the water analyses sector in Germany as an example. Collusion and falsification have to be avoided. A special and uniform evaluation technique is necessary that includes the possibility of a common evaluation of different concentration levels and considers the skewed distribution of data. A suitable approach is published in a new German DIN standard (DIN 38402-45). The assessment of the values and the laboratories as a whole also needs special attention. A concept to do this with as few injustices as possible was developed in an inter-state working group in Germany.     

The proof of analytical chemical education lies in proficiency testing: A proficiency testing programme in polytechnic academia and vocational colleges in The Netherlands

Participation in proficiency testing schemes (PT-schemes) is an important way to prove and to improve the skills of analytical chemical students. It gives valuable information on the professional capabilities of the students and is thus an important step in the training of laboratory engineers and technicians. In the programme described three types of samples are offered to the students: chemical, environmental and clinical samples. A guiding protocol presents instructions to the participating student groups. Standard operating procedures are available, but the students are also free to select their own method. The results are methodologically and statistically judged by professional PT-organisers and are presented in the customary way: the dataset, the mean (consensus) value of all participants and the Z-scores. The final presentation of the results takes place in an annual symposium where awards are presented to the best performing student groups, and a lecture programme is presented with subjects in the area of quality assurance and quality control. A selection of results from the KILO/PT/1998–1999 and the KILO/PT/1999–2000 programme is presented.     

The proof of analytical chemical education lies in proficiency testing: a proficiency testing programme in polytechnic academia and vocational colleges in The Netherlands

Participation in proficiency testing schemes (PT-schemes) is an important way to prove and to improve the skills of analytical chemical students. It gives valuable information on the professional capabilities of the students and is thus an important step in the training of laboratory engineers and technicians. In the programme described three types of samples are offered to the students: chemical, environmental and clinical samples. A guiding protocol presents instructions to the participating student groups. Standard operating procedures are available, but the students are also free to select their own method. The results are methodologically and statistically judged by professional PT-organisers and are presented in the customary way: the dataset, the mean (consensus) value of all participants and the Z-scores. The final presentation of the results takes place in an annual symposium where awards are presented to the best performing student groups, and a lecture programme is presented with subjects in the area of quality assurance and quality control. A selection of results from the KILO/PT/1998-1999 and the KILO/PT/1999-2000 programme is presented.     

The role of proficiency testing in method validation

The general principle of using data collected during proficiency testing (PT) for the additional purpose of assessing method performance is discussed. Particular attention is paid to the similarities and differences in conduct of traditional interlaboratory method performance studies and proficiency testing. Recommendations are made for implementing PT-based method performance studies, including statistical assessment of the data. It is concluded that, properly implemented, PT-based method performance study provides essentially equivalent information to that obtained from traditional collaborative study and may be used in appraising candidate methods with a view to their adoption as standard methods.     

Education in analytical chemistry in the U.S.S.R.

Analytical Chemistry is taught at over 600 schools of higher education in the U.S.S.R. Contents of general and special courses are described in this article. The main problems and objectives of education at universities are mentioned.     

Application of a new AMIQAS computer program for integrated quality control, method evaluation and proficiency testing

Summary The computer program AMI - Quality Assessment Scheme (AMIQAS) was designed to give easy statistical management of analytical data in relation to method evaluation, internal quality control and proficiency testing. The program is designed in accordance with the recommendation of the ISO 5725 guideline and other official recommendations. The program consists of a database, test for outliers, statistics and graphs for evaluation of an analytical method for chemical, biological and environmental analysis, different control charts to be used in day-to-day internal quality control (Shewhart charts and z-charts). Finally the program has facilities to perform proficiency testing (also called external quality control) and produce the relevant evaluation reports for the documentation of method performance and quality control of results of measurements. The present paper demonstrates the applicability of the AMIQAS program for integrated method evaluation, internal quality control and proficiency testing using the determination of the concentration of lead in human whole blood as the numerical example.     

Evaluation of the use of consensus values in proficiency testing programmes

Proficiency testing (PT) is an essential tool used by laboratory accreditation bodies to assess the competency of laboratories. Because of limited resources of PT providers or for other reasons, the assigned reference value used in the calculation of z-score values has usually been derived from some sort of consensus value obtained by central tendency estimators such as the arithmetic mean or robust mean. However, if the assigned reference value deviates significantly from the ‘true value’ of the analyte in the test material, laboratories’ performance will be evaluated incorrectly. This paper evaluates the use of consensus values in proficiency testing programmes using the Monte Carlo simulation technique. The results indicated that the deviation of the assigned value from the true value could be as large as 40%, depending on the parameters of the proficiency testing programmes under investigation such as sample homogeneity, number of participant laboratories, concentration level, method precision and laboratory bias. To study how these parameters affect the degree of discrepancy between the consensus value and the true value, a fractional factorial design was also applied. The findings indicate that the number of participating laboratories and the distribution of laboratory bias were the prime two factors affecting the deviation of the consensus value from the true value.