A step towards accreditation: A robustness test of etching process

abstract In the present study the robustness of the etching process used by our laboratory was assessed. Thestrategy followed was based on the procedure suggested by Youden. Critical factors for the process wereestimated using both Lenth's method and Dong's algorithm. The robustness test evidences that particularattention needs to be paid to the control of the etching solution's temperature.& 2015 Elsevier Ltd. All rights reserved. 1. IntroductionIn the framework of the general requirements for the compe-tence of testing and calibration laboratories, the ISO/IEC standard(2005) requires the validation of all non-standard methods. Forintegrated radon measurements, experimental methods usingNRPB/SSI type dosimeters and CR39 plastics (Intercast Europe,Italy) as detectors (SSNTD) can be applied: experimental detailsabout the laboratory-developed method followed in the presentwork are described elsewhere (Mishra et al., 2005; Orlando et al.,2002).The validation of a laboratory-developed method is performedto ensure that an analytical methodology is accurate, specific, re-producible and robust over the specified range that an analyte willbe analyzed. Some aspects of the quality assurance program forthe validation of the integrated radon measurements method werepreviously described (D’Alessandro et al., 2010). In this work theattention of the authors has been focused principally to therobustness evaluation of the etching process of plastic detectorswith the aim to study which factors influencing the final result.The robustness of an analytical procedure is a measure of itscapacity to remain unaffected by small, but deliberate variations inmethod parameters and provides an indication of its reliabilityduring normal usage. Robustness can be described as the ability toreproduce the analytical method in different laboratories or underdifferent circumstances without the occurrence of unexpecteddifferences in the obtained result.As well known heavy charged particles, impacting the plasticmaterial surface (SSNTD), cause an extensive ionization of thematerial that led to the creation of a damaged zone (latent track)along the particles ‘path (Nikezic and Yu, 2004).The etching process allows to visualize the latent tracks andafterward to count them by using optical systems. The perfor-mance of the etching process is strictly influenced by the chemicalcharacteristics, the concentration and temperature of the etchant(Hermsdorf et al., 2007). In our method, in order to have easilyContents lists available at ScienceDirectjournal homepage:www.elsevier.com/locate/apradiso