Proving Proficiency

Setting An established analytical method consisting of the extraction of a drag and its major metabolite from blood plasma and the subsequent HPLC quantitation was precisely described in a R D report, and was to be transferred to three new labs across international boundaries. (Cf. Section 4.32.) The originator supplied a small amount of drug standard and a number of vials containing frozen blood plasma with the two components in a fixed ratio, at concentrations termed lo, mid, and hi. The report provided for evaluations both in the untransformed (linear/linear depiction) 

In one new laboratory the insfrument configuration was reproduced as faithfully as possible The insfrument was similar but of a different make. 

An inadvertent, and at first sight trivial shift in conditions raised the extraction efficiency from the stated =85% to nearly 100% This together with the different model of detector (optical path ) caused 

Because two laboratories were involved, there was a certain risk that this foreign contract laboratory in the cmcial calibration run would, despite cross-validation,26 come up with results for the QC standards that were at odds with those in the primary laboratory this would necessitate explanations. 

In a multi-year, multi-laboratory situation it is unlikely that the amount of primary standard (PS) will suffice to cover all requests. The next best thing is to calibrate a larger amount of lower-quality secondary standard (SS) against the PS, and to repeat the calibration at specified intervals until both the PS and the SS have been consumed. In this way, consistency can be upheld until a new lot of PS has been prepared and cross-validated against the previous one. In practice, a working standard will be locally calibrated against the SS and be used for the daily method calibration runs. (See Section 4.32.) 

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We should perhaps make a few important points before going any further - the title of this chapter is highly ambitious We certainly cannot promise to turn you, the reader into expert interpreters in the time it takes you to read this section. Experience is essential and to become really proficient in this area, you need to critically examine literally thousands of spectra. However, be that as it may, by establishing some sound principles and cultivating a critical approach to the spectra you encounter, this book should prove useful in helping you along the way. 

Evaluations of various soil and sediment samplers have been reported [56, 57]. The sediment shovel proved highly practical, but was limited because small particles tend to be lost when the shovel is lifted [56]. A cryogenic sediment sampler was less convenient to use, but allowed the collection of almost undisturbed samples. Houba described a different device for the automatic subsampling of soil, sediment and plant material for proficiency testing [57]. In another study, Thoms showed that freeze-sampling collects representative sediment samples, whereas grab-sampling introduces a bias into the textural composition of the 120 mesh fraction, due to washout and elutriation of the finer fractions [58]. 

Extension into physical metrology is less obvious, but has no conceptual barrier. The direct approach could be applied if proficiency tests were conducted by a reference laboratory distributing to device producers, preparing lots of material measures and calibrants such as gage blocks, masses, or thermometers. Distribution of such material measures is already a feature of most measurement assurance programs in physical metrology. Use of the indirect approach would have units randomly selected from production and sent to a reference laboratory. This could prove, in some cases, more economical than direct proficiency testing of the producers of the devices. 

The proficiency test involves qualitative analysis qualitative analyses are sufficient to confirm the presence or prove the absence of CWC-related agents. 

The efficiency of a cleanup method depends on the type of background chemicals to be removed and the type of target chemicals to be recovered. This particular cleanup method proved to be effective for the organic liquid sample composition in the eighth proficiency test. 

In both the trial and official proficiency tests, the ROPs for sample preparation validated in the round-robin tests proved themselves useful methods to recover CWC-related chemicals spiked at trace level. The participating laboratories had prepared the samples following the ROPs, though sometimes with slight modifications. Many of the laboratories were also able to identify degradation products... 

It has already been pointed out that a great deal of intracellular biochemistry is based on cofactors, with these cofactors, in turn, often being derived from nucleotides. However, while this indirectly implies the proficiency of ancient RNA catalysts, it does not prove that such catalysts could have existed. Although there are, for example, protein dehydrogenases and esterases, there are no modem ribozymes with similar activities. Just as engineering a ribozyme self-replicase will be an experimental demonstration that life could have arose via RNA, so the production of artificial ribozymes will be a demonstration that a metabolically complex RNA world may once have existed. 

The same method, with only slight variations (acetonitrile from 10 to 7.5%, detection wavelength from 280 to 230 nm) was adopted for the analysis of illicit cocaine. Benzoylecgonine, cocaine, and cis- and fram-cinnamoylcocaine, obtained from samples taken from cocaine seizures, were separated. MEKC results correlated well with those from gas chromatography (GC), with similar RSD values, and with HPLC. These authors reported that MEKC methods also proved highly reliable for heroin and cocaine analysis in interlaboratory proficiency tests. 

Users will quickly construct mental rules as they operate the systan for the first time. The assimilated rules empower than to go on to proficiently operate unfamiliar parts of the appUcation using the conventions learned in more accustomed areas. To achieve this designers need to strive for consistency in user interface design. For example, if some screens contain buttons labelled Save and Close whilst others have Okay and Cancel for the same functions, this is likely to prove confusing and hinder rule development In fact one of the least technically challenging enhancements to a user interface is to simply ensure that material is labelled appropriately, that abbreviations and ambiguities are avoided and button captions reflect their true function. 

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