Independent laboratory validation

Reproducibility in the context of Directive 96/46/EC is defined as a validation of the repeatability of recovery, from representative matrices at representative levels, by at least one laboratory, which is independent of the laboratory which initially validated the study. This independent laboratory may be within the same company, but may not be involved in the development of the method. This concept of independent laboratory validation (ILV) substitutes the conduct of interlaboratory trials (e.g., according to ISO 5725) because the resources are not available taking into consideration the high number of a.i., matrix types and concentration levels which must be validated in the registration procedure. 

The second requirement is that enforcement methods for food must be validated by an independent laboratory [independent laboratory validation (ILV)]. The sample set is identical with the general sample set (see Section 4.1). If the method is identical for all four crop groups (mentioned at the beginning of the section), it may be sufficient to perform the ILV for plant materials with a minimum of two matrices, one of them with a high water content. In the case of food of animal origin, the ILV should be performed with at least two of the matrices milk, egg, meat, and, if appropriate, fat. 

The prerequisite that the laboratory chosen to conduct the ILV trials must not be involved in the method development and/or in its subsequent use is not applicable for multi-methods. If the applicability of a multi-method is published in an official manual, an ILV is not obligatory for this particular a.i. ILV is always required for single methods. Communications between the chosen laboratory and the method developers must be reported, provided that these communications were required to carry out the analysis successfully. Also, any subsequent amendments or modifications to the original method must be reported. Furthermore, the ILV report must contain a statement as to the applicability of the method. In contrast, it is not necessary to confirm fhe resulfs of fhe enforcement methods for soil, water, body fluids, tissues, and air by an independent laboratory validation. 

To demonstrate the validity of an analytical method, data regarding working range/ calibration, recovery, repeatability, specificity and LOQ have to be provided for each relevant sample matrix. Most often these data have to be collected from several studies, e.g., from several validation reports of the developer of the method, the independent laboratory validation or the confirmatory method trials. If the intended use of a pesticide is not restricted to one matrix type and if residues are transferred via feedstuffs to animals and finally to foodstuffs of animal origin, up to 30 sets of the quality parameters described above are necessary for each analyte of the residue definition. Table 2 can be used as a checklist to monitor the completeness of required data. 

From time to time in older studies, the validity of the method was not tested with all commodity groups. Nevertheless, these studies can be used if the omitted matrix types are tested additionally in the independent laboratory validation. 

The workhorses in national monitoring programs are multi-residue methods. Any official method collection of any EU Member State contains at least one multi-residue method. For multi-analyte and/or multi-matrix methods, it is likely to be impractical to validate a method for all possible combinations of analyte, concentration and type of sample matrix that may be encountered in subsequent use of the method. Therefore, initial validation should incorporate as many of the target analytes and matrices as practicable. For practical reasons this validation and the evaluation of other methods with limited scope often cannot be conducted in inter-laboratory studies. Other concepts based on independent laboratory validation or validation in a single laboratory have been developed and can provide a practical and cost-effective alternative (or intermediate) approach. 

Enforcement method to undergo independent laboratory validation study... 

Lastly, a laboratory not involved in the development process must validate the method. The independent laboratory validation study, or ruggedness trial, ensures that analysts unfamiliar with the method can successfully perform the method. The method developer should, therefore, strive to make all procedures as straightforward as possible to aid reproducibility of the method. 

The author thanks the following scientists at DuPont Crop Protection and Battelle, Geneva Research Centres, for developing and validating some of the methods summarized in this article C.R. Powley for the soil method by HPLC/MS/MS J. J. Stry, SJ. Hill and PR Maliszewski for the water method by HPLC/MS/MS and K.M. Jernberg, B. Francon, M. Jetzer, C. Steiner, L. Dubey and H. Mattou for the independent laboratory validations of the Multiresidue Method 2 for crop samples. 

EPA did not receive any comments or suggestions on the test kit recognition process itself. With respect to existing test kits, EPA has determined that the NIST research is the equivalent of an independent laboratory validation of test kit performance. 

An independent laboratory validation (ILV) must be submitted for a primary method with monitoring purposes and used to determine residues in plants, plant products, foodstuff, and feedingstuff. The LOQ of the primary method shall be confirmed by the ELV, but at least the MRL. If validation data for the residue analytic method of an analyte in at least one of the commodities of the respective matrix group have been provided by an international official standardization body and if these data have been generated in more than one laboratory with the required LOQ, acceptable recovery, and acceptable relative standard deviation (RSD) data, no additional ELV is required [45]. 

Annex VI to Directive 91/414/EEC concerning the placing of plant protection products on the market. The section concerning residue analytical methods was not fully finalized when the Directive was first adopted. There were no provisions for methods to determine residues from a.i. and relevant metabolites in soil, water, and air. The criteria for foodstuffs partly proved to be not helpful for the practice of assessment (e.g., with regard to reproducibility, ISO 5725 requires validation in at least eight independent laboratories). 

Each individual method collection comprises a large number of methods, which often have different validation statuses. For instance, the most important Swedish multi-residue method (based on ethyl acetate extraction, GPC and GC) is validated for many pesticides by four laboratories, but other methods are presented with singlelaboratory validation data. Some methods in the Dutch and German manuals were tested in inter-laboratory method validation studies, but others by an independent laboratory or in a single laboratory only. 

We used a rather simple protocol in our laboratory validation studies. Future studies should include other factors such as temperature effects, the effects of potential interfering substances on recovery and actual field trials. These field trials should be monitored by an independent method in which we have a high degree of confidence. 

The test material is chosen to fulfill the aims of the study. In a proficiency testing scheme or a method validation study, the test material is usually as near as possible to typical field samples. There is no advantage in competently analyzing an artificial sample if the same laboratory has difficulty with real samples. The organizing laboratory must know the composition of the test material, and must be sure that the analyte for which a quantity is to be measured is present in about the desired amount. For pure materials this is not a problem, but for natural test materials or complex matrix materials, the organizing laboratory may have to do some analyses before the samples can be sent out to the participants. If the value of the measurand is to be established by an independent laboratory before the study, then the identity requirement is also fulfilled when the measurand is stated. 

It is important that there is a low level of doubt about the identity of the compound being measured and a high level of certainty that the quantity determined is a true reflection of the amount actually present. To achieve this, confirmatory techniques usually employ complex separation procedures to isolate the compound of interest and require calibration procedures that involve adding known amounts of the compound to uncontaminated specimens of the material under analysis. As a final check on the validity of the method it is recommended that the method should be evaluated in a collaborative trial in a minimum of three independent laboratories against a standard reference material. 

Using a test set to determine the quality of predictions is a form of validation. The test set could be obtained, experimentally, in a variety of ways, for example 60 orange juices might be analysed in the first place, and then randomly divided into 30 for the training set and 30 for the test set. Alternatively, the test set could have been produced in an independent laboratory. 

Most Superfund data are obtained through the EPA Contract Laboratory Program (CLP). Data are produced by approximately one hundred independent laboratories and utilized by the ten EPA Regions. The results of the analyses are routinely reviewed and validated against standard criteria to assure that they are of known quality, applicable for their intended use, and legally admissible (8.9). 

To predict concentration profiles, it is desired to combine independent laboratory reaction rate data with empirical data on the hydrodynamics of the flow. The problem of interpreting laboratory reaction data to obtain rate expressions which are valid within the complex natural system is in itself a difficult task beyond the scope of this work it is here... 

Because the electronic nose is based upon the science of gas chromatography, odour measurements can be easily confirmed and validated by independent laboratory measurements taken on quality control samples. The ability to rapidly perform analytical measurements on odours of all kinds in real time will provide first responders with a cost effective new tool for identifying explosive, chemical, or biological threat odours. 

The AOAC PVM program is intended to provide a class of tested methods that have not been the subject of a full collaborative study. Through a less intensive process, the program provides a rapid enuy point for method,s that arc recognized by the AOAC at a level of validation for methods not otherwise evaluated. The distinguishing aspect of an AOAC PVM is that its performance has been checked in at least one other independent laboratory. It is expected that eventually most PVMs will undergo full interlaboratory collaborative studies and obtain OMA status. 

STX is now distributed worldwide by IAEA and is being used in collaborative trials of the PSTs receptor binding assay (RBA). Single laboratory validation of the RBA using new radiolabeled saxitoxins were presented at the Marine and Freshwater Toxins Analysis First Joint Symposium and AO AC Task Force Meeting in Baiona, Spain, in April 2005. The limit of quantitation of the microplate format assay " was found to be 1.2 pg STX equivalent/100 g shellfish (regulatory limit 80 pg/100 g), with an overall repeatability of 17.7% for shellfish extracts run by one analyst on 5 independent days, and a correlation r =. 98 with the mouse bioassay. 

This procedure was validated by collaborative study with independent laboratories. 

Imagine that you are working with one of the forensic science analytical testing companies and have just undertaken a piece of work at the request of the crown prosecution service. You have analysed a brown powder and found it to contain 70% of the controlled drug diamorphine (heroin). The counsel for the defence has requested that the sample be analysed by an independent laboratory of its choosing. The sample is reanalysed and there is a dispute in relation to the result because the defence analyst finds only 10% of the controlled drug diamorphine. You attend court and are asked to justify your results. Your lab has a rigorous quality assurance system that includes method validation, system suitability, and instrument qualification the defence lab does not. Your result is accepted as the correct value. 

It may happen that AH is not available for the buffer substance used in the kinetic studies moreover the thermodynamic quantity A//° is not precisely the correct quantity to use in Eq. (6-37) because it does not apply to the experimental solvent composition. Then the experimentalist can determine AH. The most direct method is to measure AH calorimetrically however, few laboratories Eire equipped for this measurement. An alternative approach is to measure K, under the kinetic conditions of temperature and solvent this can be done potentiometrically or by potentiometry combined with spectrophotometry. Then, from the slope of the plot of log K a against l/T, AH is calculated. Although this value is not thermodynamically defined (since it is based on the assumption that AH is temperature independent), it will be valid for the present purpose over the temperature range studied. 

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