Validation enforcement methods

In contrast to the requirements for enforcement methods, validation of a previously collaboratively tested method, which is used to generate data, should be validated for new laboratory conditions. Also, where published methods are submitted, validation is required, when applied to the relevant sample matrix and laboratory conditions. 

The purpose of this article is to clarify the assessment of residue analytical methods in the context of Directive 91/414/EEC. After discussing the legal and historical background, requirements for enforcement methods as well as data generation methods are reviewed. Finally, an outlook over further developments in the assessment and validation of analytical methods is provided. 

The extent of validation of confirmatory techniques is currently under consideration. Qne approach is that the extent of validation may be smaller than for the enforcement method. In principle, validation in triplicate at the relevant concentration level (LOQ or MRL) is sufficient. In the case where an MRL is set for multiple crops, a single validation in all representative crop groups is sufficient. A confirmatory method for residues in air is not required if a corresponding method was submitted for the other sample matrices. This approach is realized in Germany. ... 

The enforcement method must be suitable for the determination of all compounds included in the residue definition in order to enable Member States to determine compliance with MRLs. It is not feasible to validate a method for all commodities if a wide range of MRLs are set. Therefore, a concept of crop groups was developed in SANCO/825/00. The following crop groups with representative crops are presented ... 

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. 

From the analytical point of view there is no essential difference between drinking water and groundwater. Therefore, it is sufficient if the enforcement method is validated only for either drinking water or groundwater. The LOQ for drinking water/ groundwater must be <0.1 qgL (EU drinking water limit). 

The majority of validation data required for analytical methods supporting authorization purposes are common to those described for enforcement methods (see Section 4). However, some of the requirements such as minimum cost and commonly available equipment do not apply to methods supporting pre-registration studies (e.g., the use of GC/MS/MS technology). 

The use of immunoassay methodology for residue trial analysis is in principle just as acceptable as for enforcement methods, provided that the method has been adequately validated. Because the validation of such methods requires a different approach, as opposed to chromatographic and spectrometric methods, some important points to be aware of in the use are explained in SANCO/3029/99. The authors do not go into detail on this subject here, since on the one hand very few methods have been submitted up to the present, and on the other it would go beyond the scope of this article. 

In contrast to the requirements for enforcement methods and to ensure sufficient quality of the generated data, validation data should be submitted for all types of crop samples to be analyzed. However, matrix comparability and a reduced validation data set may be considered where two or more very similar matrices are to be analyzed (e.g., cereal grain). A reduced sample set may also be acceptable (two levels, at least three determinations and an assessment of matrix interference) provided that the investigated samples belong to the same crop group as described in SANCO/825/00 (see also Section 4.2.1). 

The principles of validation of residue methods for food, water and soil are generally the same. However, not all procedures and requirements are identical. From the public s point of view, the information on residues in food is probably the most important task. Compared with the other two areas (water and soil), the food sector is characterized by the largest number of regulations and legal limits. Therefore, this overview of validation requirements of enforcement methods will focus on methods for pesticide residues in food. 

Until 1991, manufacturers seeking authorizations for pesticides had to fulfil country-specific requirements of validation of enforcement methods. The term enforcement method means analytical methods which are developed for post-registration control and monitoring purposes. The harmonization of these requirements was initiated with the European Economic Community (EEC) Council Directive 91/414/EEC and temporarily finalized with the Guidance Document on Residue Analytical Methods SANCO/825/00 rev. 6, dated 20 June 2000 [Santd et Protection des Consommateurs (SANCO)]. The evaluation of validation studies by the competent authority is conducted by comparison of these European Union (EU) requirements with the study results and most often without any practical experience of the method. Some details of this evaluation are discussed below. 

Enforcement methods provided by the manufacturer are not generally tested in the laboratories of the European regulatory authorities. Very often, proposed methods are evaluated by assessing the logic of proposed procedures and only for the completeness of validation data. For this theoretical review process, as much information as possible should be available. Recovery data from many validation experiments with different kinds of matrices and the resulting chromatograms of control and fortified samples provide the confidence needed by the referee. In the following sections, the most important aspects of this evaluation will be considered. 

Although we speak generally of validated methods , only the performance of a method applied to a particular range of materials (matrices) is reported. The possibility of matrix interferences or the efficiency of cleanup steps may vary with matrix type. For that reason, methods should be validated in all matrix types, which differ significantly. In the context of the validation of enforcement methods by applicants, significant difference is not a well defined term. To avoid any dispute about completeness of validation, five material types had been selected for crops, which usually... 

This validation typically requires samples with radiolabeled analytes. However, alternative approaches are proposed which involve (i) comparison with extraction of samples using a procedure which has been previously validated rigorously, (ii) comparison with extraction of samples by a very different technique or (iii) analysis of a certified reference material. Generally, this validation should be performed with samples containing analyte incurred by the route by which residues would normally be expected to arise. The simplest option (i) requires fully validated and documented enforcement methods provided by the manufacturer of a pesticide. 

In Europe, very different concepts of method validation are in use. The extent of validation depends upon legal requirements (e.g., for enforcement methods provided by the applicant), upon the required level of acceptance (e.g., for CEN methods) and upon national resources. Undoubtedly, the best method validation is performed with the help of inter-laboratory studies of performance, but such studies can be uneconomic, too slow to reach completion or restricted in scope. 

This enforcement method has been validated on the (raw agricultural commodities) (RAC) and processed parts of various crops. The method limit of quantitation (LOQ) was validated at 0.05 mg kg and the method limit of detection (LOD) was set at 0.01 mgkg for all of the crop matrices. The method flow chart is presented in Figure 1. 

The QPP has three laboratories the Environmental Chemistry Laboratory (ECL) in Bay St. Louis, MS, and the Analytical Chemistry Laboratory (ACL) and the Microbiology Laboratory at the Environmental Science Center, both at Fort Meade, MD. The ECL is heavily involved with method validation efforts. The ACL evaluates enforcement analytical methods for product chemistry to ensure that the ingredient statements on the label are accurate and evaluates residue analytical methods for... 

Enforcement method to undergo independent laboratory validation study... 

Full acceptance of HPLC/MS methods by the US EPA OPP as enforcement methods occurred between 1998 and 2001. For example, in 1998, the EPA OPP accepted HPLC/MS (without MS/MS) methods as primary enforcement methods, and high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) only was suitable for confirmatory methods. However, in 2001, HPLC/MS/MS methods also became acceptable for primary enforcement. Table 4 summarizes the types of methods that were validated by the EPA OPP method validation program, for both food tolerance enforcement methods and environmental chemistry methods. 

An analytical method must be properly validated if it is to be used at the national level for enforcement purposes. Validated methods stand on their own merits in contested legal actions in national courts. This situation has been recognized by all nations and international organizations. Initiatives to harmonize method validation criteria and approaches are currently being considered. 

The FDA was aware of the discrepancy between the attention validation got in the enforcement through inspection and the role it played in the CGMP regulations written down in the CFR. In 1996, the FDA proposed a revision to update the requirements on process and methods validation and to reflect current practice by incorporating guidance previously issued to industry [11]. The revision, however, drew heavy criticism from industry for several reason. The most prominent weaknesses with regard to validation were... 

In all tests, the chemical analysis of the samples is a crucial step. Modern chromatographic methods are applied, for example, HPLC, LC-MS-MS, or GC-MS and all methods must be carefully validated. This means that linearity, accuracy, precision, and selectivity must be proven. Validations are required for methods used during the development phase and also for monitoring after a marketing authorization is granted. Enforcement methods are intended for use by government laboratories to monitor product quality, worker exposure, or residues in food, feed, and the environment. 

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