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.     

An alternative statistical approach for interlaboratory comparison data evaluation

Interlaboratory comparisons are an essential component of method validation, laboratory proficiency and equivalency evaluation, and standard reference material certification. The reliability of the results from interlaboratory comparison largely depends upon analyzing the data with appropriate statistical methods. Intercomparison data are often found to be non-normally distributed as a result of sample heterogeneity, uneven laboratory variance, and methodology bias. The statistical methods that require data normality are inappropriate for analyzing such skewed data. Instead of using data transformation or non-parametric methods, an alternative method which sets aside the assumption of data normality is utilized in the certification of new National Institute of Standards and Technology (NIST) Ocean Sediment Standard Reference Material (SRM-4357). It first determines the best-fit distribution for the data, then calculates appropriate distributional mean and tolerance limits, and finally estimates the uncertainties for the derived statistics by bootstrap analysis. The method was applied to evaluate the data from the SRM intercomparison, and revealed homogeneity for natural radionuclides and inhomogeneity for anthropogenic radionuclides in the SRM. It was found that the data of natural radionuclides in the SRM are normally distributed. In contrast, the data of anthropogenic radionuclides, such as ⁹⁰Sr, ¹³⁷Cs, ²³⁸Pu, and ^(239+240)Pu, are best fitted by Weibull distributions. The difference on data distributions for the two types of radionuclides is believed to be related to "hot" particles in the SRM. By determining the best-fit data distribution and applying bootstrap analysis, more reliable and realistic massic activity (Bq·kg^-1) for anthropogenic radionuclides were certified in comparison to those obtained using data transformation and nonparametric methods. Although the developed method is computationally intensive, it provides a straightforward, rigorous procedure for computing the statistics that would otherwise be difficult to obtain when the data distribution form is complicated. With the help of advanced personal computers and use of the DataPlot software from NIST, this method becomes very practical and has enhanced interlaboratory comparison data studies and certification of the NIST standard reference materials.     

Quality management in wastewater treatment plants

A quality management system has been designed for process analyses in wastewater plants. The quality management concept consists of a quality manual, quality control charts used together with certified reference materials, and proficiency testing. Certified reference materials have been used to eliminate basic analytical errors. Proficiency testing has been conducted by VKI, the Reference Laboratory for Environmental Chemistry, subcontracted by the Danish Environmental Protection Agency. In the first proficiency test the analytical quality was comparable in general to the quality of routine environmental laboratories. One of the simplified analytical systems resulted, however, in a low recovery of nitrate in wastewater. The COD results reported in the proficiency test were slightly higher than the theoretical values.     

Accelerator mass spectrometry: ultra-sensitive analysis for global science

Accelerator mass spectrometry (AMS) is the analytical technique of choice for the detection of long-lived radionuclides that cannot be practically analysed with decay counting or conventional mass spectrometry. AMS has been used for the analysis of ¹⁴C, ¹⁰Be, ³⁶Cl and other cosmogenic radionuclides in archaeology, geology and environmental science. In addition, the ultrasensitivity of AMS is being applied in biomedicine to study the exposure of human tissues to chemicals and biomolecules at attomole levels. AMS is also being considered for the detection of anthropogenic radionuclides, such as ¹²⁹I and ²³⁶U, in environmental samples for the verification of the nuclear non-proliferation agreements. The state of the art of AMS is reviewed with examples from some recent applications.     

Sedimentation process in Ariake Bay using NAA and gamma-spectrometry

In order to assess the effect of marine and terrestrial environmental change in the last decades on the sedimentation environment in Ariake Bay, we collected three sediment cores. The concentrations of natural and anthropogenic radionuclides, major elements, and rare-earth elements were measured using gamma-spectrometry and neutron activation analysis. Vertical distributions of both radionuclides and sedimentation rates, determined using Cs-137 and Pb-210_ex dating methods, varied significantly among the sites.     

Lognormal distribution of natural radionuclides in freshwater sediments and coal-ash repositories

The distribution of natural radionuclides,⁴⁰K,²²⁶Ra, and²³²Th, in freshwater sediments and in coal-fired power-plant ash repositories has been tested for lognormality. Thereafter, lognormality for natural radionuclide concentration frequency distribution was accepted with a high probability. The lognormal natural radionuclide distribution in sediments and coal-ash indicated single population groups. The anthropogenic modifications of the natural radionuclide concentrations in the environment are indicated. The adsorbed dose rates, in mGy y^–1, in air from gamma field of the natural radionuclides were calculated.     

Global comparability of analytical results

 Global decisions made on the basis of chemical analytical results need global comparability. The concept of traceability is important and necessary but not sufficient to achieve global comparability, especially for routine analysis in environmental protection, health care and public safety. Sometimes comparability is only determined by the method. In this case validated methods have to be known and recognized internationally. In addition, a minimum level of proficiency of the personnel producing analytical results has to be guaranteed. Finally, a system of measures designed to build up trust is needed for worldwide acceptance of analytical results. The method of self-declaration by the supplier of chemical analytical services has the advantage of presenting specific responsibility and gaining a good reputation. Additional methods should be employed. The evaluation of reference materials by specific quality criteria is mentioned as an example. Received: 1 July 1998 · Accepted: 20 July 1998     

Development of a proficiency testing scheme for a limited number of participants in the field of natural water analysis

A proficiency testing (PT) scheme was developed for a limited number of analytical laboratories participating in the analysis of natural water in Israel. Three fit-for-intended-use reference materials (RMs) were prepared for a pilot PT from natural water: RM-blank and two in-house reference materials (IHRMs) with seven analytes fortified to achieve different levels of analyte concentrations. The measurands for the PT participants were the traceable spike values certified in the IHRMs, i.e., added mass concentrations of the analytes. The RM-blank and IHRMs were found to be homogeneous and stable over 11 days, the time necessary for the experimental part of the PT. The RMs were distributed to the PT participants as unknown test items similar to routine samples. The test results were evaluated using their deviations from the IHRM-certified values. Eight Israeli laboratories took part in the interlaboratory comparison. Individual laboratory performance and metrological compatibility of the PT results of the participants, as a local group of laboratories, were evaluated for every analyte.     

Monitoring of radioactivity in NW Irish Sea water using a stationary underwater gamma-ray spectrometer with satellite data transmission

Summary An underground laboratory for low-level gamma- and beta-spectrometry has been constructed at IAEA-MEL, Monaco, for the analysis of environmental radionuclides. The laboratory is situated at a depth of 35 m water equivalent underground and equipped with 4, large volume HPGe detectors placed in a common lead shield with anti-cosmic plastic scintillator shielding. There is also an anti-Compton gamma-spectrometer, comprized of an HPGe detector and NaI(Tl) shielding, and finally, a Quantulus liquid scintillation spectrometer. The performance of the gamma-spectrometers with different shielding settings/adjustments are discussed, as well as their possible applications in the analysis of natural and anthropogenic radionuclides in the marine environment.     

IAEA-MEL’s underground counting laboratory (CAVE) for the analysis of radionuclides in the environment at very low-levels

Summary An underground laboratory for low-level gamma- and beta-spectrometry has been constructed at IAEA-MEL, Monaco, for the analysis of environmental radionuclides. The laboratory is situated at a depth of 35 m water equivalent underground and equipped with 4, large volume HPGe detectors placed in a common lead shield with anti-cosmic plastic scintillator shielding. There is also an anti-Compton gamma-spectrometer, comprized of an HPGe detector and NaI(Tl) shielding, and finally, a Quantulus liquid scintillation spectrometer. The performance of the gamma-spectrometers with different shielding settings/adjustments are discussed, as well as their possible applications in the analysis of natural and anthropogenic radionuclides in the marine environment.     

专题研讨课教学法在分析化学课程中的实践

以2012、2013和2014级药学专业学生为研究对象,在分析化学课程教学中开设“分析测试的质量保证”专题研讨课。通过课堂汇报、问卷调查和研讨总结及体会报告的方式对教学效果进行评价。结果表明,该教学法有利于培养学生的逻辑思维能力,自主学习能力,以及发现问题、分析问题和解决问题等多方面的能力,起到了提高教学质量的效果。     

水中易释放氰化物能力验证样品的研制及应用

根据国家地表水环境质量监测网监测任务要求和环境监测的实际需要,制备了水中易释放氰化物能力验证样品。通过均匀性、稳定性检验以及量值一致性评价,研制的样品均匀性良好,在3℃~6℃冷藏避光保存条件下1年内稳定,样品配制值与多家实验室协作测定结果一致。探讨了样品在能力验证活动中的应用,共有来自全国11个省的32家实验室参加了水中易释放氰化物的能力验证计划,实验室满意率在80%以上,实验室结果出现有问题或不满意主要是由于样品前处理以及检测过程质量控制不当导致的。经检测及实验室反馈的数据验证,该能力验证样品能够应用于能力验证活动。     

Proficiency test exercise on the determination of natural levels of radionuclides in mushroom reference material

The results from a proficiency test exercise for the determination of natural levels of radionuclides in mushroom reference material carried out by laboratories in six different countries are discussed. These laboratories submitted data on seven radionuclides, namely ¹³⁴Cs, ¹³⁷Cs, ⁴⁰K, ⁹⁰Sr, ²⁴¹Am, ²²⁶Ra, and ²¹⁰Po. However, only the data received for three of these radionuclides could be statistically evaluated to obtain consensus mean values and confidence intervals (at a significance level of 0.05). The contents of ¹³⁴Cs, ¹³⁷Cs and ⁴⁰K were quantified as 4.4, 2,899 and 1,136 Bq/kg, respectively.     

Bias analysis of proficiency testing programme results

A proficiency testing programme might involve a great number of participating laboratories coming from different countries or regions, and normally they analysed the same test materials using their own routine analytical methods. Hence, the results of a proficiency testing programme may contain valuable information which could serve purposes other than just performance evaluation. This study attempted to extract information from the results of a proficiency testing programme for the purposes of educating the participating laboratories as suggested by ISO/IEC 17043. The “bias analysis” approach introduced in this study was based on the statistical model of measurement and the nature of bias in chemical analysis. With this approach, the participating laboratories could estimate the bias associated with different settings of experimental conditions according to the statistics of subset distribution of the reported results from the participating laboratories. This would be useful for them to review the analytical procedures they used and modify their methods if needed. The approach was applied to the analysis of data obtained from a number of past proficiency testing programmes, and the findings were discussed in this paper.     

An anion exchange technique for separation of Na and K for neutron activation analysis of W-Ti alloy

Anthropogenic radioactivity is being measured in near-real time by an international monitoring system designed to verify the Comprehensive Nuclear Test Ban Treaty. Airborne radioactivity measurements are conducted in-situ by stations that are linked to a central data processing and analysis facility. Aerosols are separated by high-volume air sampling with high-efficiency particulate filters. Radio-xenon is separated from other gases through cryogenic methods. Gamma-spectrometry is performed by high purity germanium detectors and the raw spectral data is immediately transmitted to the central facility via Internet, satellite, or modem. These highly sensitive sensors, combined with the automated data processing at the central facility, result in a system capable of measuring environmental radioactivity on the microbeequerel scale where the data is available to scientists within minutes of the field measurement. During the past year, anthropogenic radioactivity has been measured at approximately half of the stations in the current network. Sources of these measured radionuclides include nuclear power plant emissions, Chernobyl resuspension, and isotope production facilities. The ability to thoroughly characterize site-specific radionuclides, which contribute to the radioactivity of the ambient environment, will be necessary to reduce the number of false positive events. This is especially true of anthropogenic radionuclides that could lead to ambiguous analysis.     

Environmental contamination by technologically enhanced naturally occurring radioactive material - TENORM: A case study of phosphogypsum

Summary In the last decades considerable attention has been given to technologically enhanced natural occurring radioactive material (TENORM). Within this frame, of particular concern is the phosphate fertilizer industry, located in Cubat?o, S?o Paulo State, Southwest Brazil. This industry is responsible for the production of 69 million tons of phosphogypsum waste, which is stockpiled in the surrounding environment. This waste concentrates radionuclides of the natural series originally present in the phosphate rocks used as raw material. This study aims to evaluate the environmental impact of such activities in the sediments of the estuarine system. Contents of natural radionuclides from thorium and uranium series were measured in sediments from Cubat?o estuarine system, using high-resolution gamma-spectrometry. U and Th were determined by instrumental neutron activation analysis (INAA). It was observed that U and Th concentration is higher in the rivers close to the phosphogypsum piles, at least five points were identified as being affected by anthropogenic factors.     

A review of the studies on environmental transport and speciation analysis of radionuclides in India

Department of Atomic Energy, India, has a systematic environmental monitoring program to ensure that the impact of radionuclides on human and environment is well within the limits, stipulated by the regulatory body. Concentrations of radionuclides are estimated in air, water, soil, sediment and biota in the environment around the power plant site on a regular basis. The environmental migration pattern and impact of radionuclides in the environment depends upon not only on the total concentration but the physico-chemical nature of radionuclide also. This paper presents a brief review of the studies of environmental transportation of radionuclides and influence of speciation with special reference to Indian conditions. A fairly good amount of results are available on the influence of speciation of radionuclides on the wet and dry deposition and preliminary results are available on the speciation analysis in dietary items, in soil and in ground water. Initial studies are concentrated on tritium, ¹³⁷Cs, Uranium, ⁹⁰Sr and their chemical analogues.     

First proficiency test for the determination of NORM in contaminated soil from the oil field

The Atomic Energy Commission of Syria (AECS), in cooperation with the Arabic Atomic Energy Agency (AAEA), has initiated the first proficiency test exercise for the determination of naturally occurring radioactive materials (NORM) in contaminated soil from the oil field. The soil sample was collected from one of the most highly radioactively contaminated lagoons with production water in the Syrian oil fields, which was then prepared, characterised and certified according to a standard procedure. Samples were dispatched to laboratories from eight Arab countries; Kuwait, Egypt, Yemen, Tunisia, Jordan, the Kingdom of Saudi Arabia, Libya and Syria. The results were evaluated using three statistical criteria; z-score, the U _test score and the relative bias. These statistical methods were used to evaluate the performance of each laboratory, in addition to the overall evaluation for each radionuclide. This evaluation has indicated that 57% and 86% of the results passed the criteria set for precision and accuracy applied for this test in relation to ²²⁶Ra and ²²⁸Ra, respectively. These two radionuclides are considered to be the most important radionuclides in the oil industry.     

The IAEA Proficiency Test on Evaluation of Methods for 90Sr Measurement in a Mineral Matrix; Preliminary Evaluation of Sources of Bias and Measurement Uncertainties

The results from numerous intercomparison exercises and proficiency tests indicate that the measurement of ⁹⁰Sr in solid environmental matrices poses a problem to many analysts. The causes of the observed scatter of analytical results are not well understood and therefore difficult to remedy. In order to assess the effect of various analytical operations and measurement routines on the quality of the ⁹⁰Sr data, the IAEA's Analytical Control Services have organised a proficiency test using a mineral sample spiked at three different levels with known amounts of ⁹⁰Sr. This proficiency test generated considerable interest from the radioanalytical community as a total of 192 sets of samples were distributed to 158 radioanalytical laboratories world-wide. The reported data were evaluated with respect to their relative bias against the reference value and with respect to their reported overall uncertainty. The major sources of bias leading to overestimated values are ineffective purification procedures, high background values and a lack of statistical control over background values. The major sources of bias leading to an underestimation are overestimated recovery factors in part due to failure to correct for stable Sr in the sample and possibly failure to correct for quenching in liquid scintillation counting. Preliminary results for a small randomly selected group of laboratories are presented.     

Distribution of some natural and anthropogenic radionuclides in Sudanese harbour sediments

The distribution of some natural and anthropogenic radionuclides (²²⁶Ra,²²⁸Ra,²¹⁰Po,⁴⁰K,¹³⁷Cs) in surface marine sediments from the harbours at Port Sudan and Sawakin on the Sudanese coast of the Red Sea has been investigated using α-spectrometry and direct high-resolution γ-spectrometry. The prime ams were to assess the levels of radioactivity and the influence of factors such as dredging and the organic matter content of the sediments on the distribution pattern of the radionuclides. The results have been evaluated and the leves indicate the absence of any possible enhancement by anthropogenic influx from the hinterland. The spatial distribution pattern is more heterogeneous in Sawakin harbour where some parts have recently been dredged and the sludge is removed to maintain the required depth. The data also show an insignificant relationship between the activity concentrations of all the radionuclides and the content of organic matter in the sediments.