Specific method development issues

Studies conducted in the laboratory provide fundamental data on processes by which a pesticide is degraded and on its mobility. In combination with field observations, which integrate multiple processes, these data describe a pesticide s environmental fate. This section provides a discussion of several important specific analytical issues which should be considered in the design of environmental fate studies to ensure that the data generated address the needs of scientists and regulatory agencies for information on the environmental fate and environmental and ecological impacts of a pesticide to the fullest extent. 

As probabilistic exposure and risk assessment methods are developed and become more frequently used for environmental fate and effects assessment, OPP increasingly needs distributions of environmental fate values rather than single point estimates, and quantitation of error and uncertainty in measurements. Probabilistic models currently being developed by the OPP require distributions of environmental fate and effects parameters either by measurement, extrapolation or a combination of the two. The models predictions will allow regulators to base decisions on the likelihood and magnitude of exposure and effects for a range of conditions which vary both spatially and temporally, rather than in a specific environment under static conditions. This increased need for basic data on environmental fate may increase data collection and drive development of less costly and more precise analytical methods. 

Typically, the EPA requires monitoring for specific pesticides and degradates. Degradates which need to be identified are major degradates [residues present at levels 10 pg kg (ppb) or 10% of applied], are mobile in the environment or have 

Even before a method is developed for detecting the presence of a pesticide or pesticides in the environment, the level of sensitivity in the method that will be needed for fate and monitoring studies to adequately portray the behavior of the analytes in the environment must be assessed. For example, in surface water monitoring programs. 

The MDL and practical quantitation limit (PQL) should be appropriate for the objectives of the analysis. MDL refers to the minimum concentration of the compound of interest that can be measured and reported with a specified confidence (99% probability) that the concentration is above zero. The registrants must provide or develop an analytical method for water for the parent pesticide and its degradates that has an MDL of 0.01% of the label application rate (calculated as the average concentration in the top six inches of soil), or 0.05 pgL , whichever is lower. PQL refers to the lowest concentration at which the laboratory can confidently quantify the concentration of the compound of interest. The study authors must report all samples with concentrations above the MDL as detections, including those below the PQL in which the concentration cannot be quantified. In addition, the study authors must provide sample equations to demonstrate how the PQL was calculated. 

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H. Safety considerations. The Occupational Safety and Health Administration (OSHA), US Department of Labor, standard entitled Occupational Exposure to Hazardous Chemicals in Laboratories (29 CFR 1910.1450) makes it necessary to address safety issues in the SOP. The standard requires laboratories that use hazardous chemicals to maintain employee exposures at or below the permissible exposure limits specified for these chemicals in 29 CFR Part 1910, Subpart Z. Hazards associated with any specific chemicals used in a method must be addressed so that the user has the information needed to follow the Chemical Hygiene Plan for their laboratory. The method developer should limit the use of hazardous chemicals where feasible. The use of toxic and/or carcinogenic reagents should be avoided or eliminated as much as possible. Additionally, the cost of disposal is increasing and could impact the practicality of a method. Material Safety Data Sheets for the analyte(s) and any unusual or hazardous reagents should be provided for the user. 

Composition is an age-old idea in software specification and development any method must have clear rules about the outcome of combining designs, specifications, or code. Popular 00 methods do not address this issue in a meaningful way. Exceptions are Disco s composition of entire models [Kurth90], Syntropy s subtyping and viewpoints [Cook94], and OORAM s role-model synthesis [Reenskang95], Related work in non-00 approaches are plentiful Z, Unity, and so on. 

QA requires the efficient analysis of many samples to support routine production release and stability programs. Methods are typically established in the analytical development group. Efficiency and convenience issues, including the speed of media preparation and the relative convenience of data handling and documentation, are important here. While compliance is important in all aspects of the pharmaceutical industry, QA functions must approach compliance perfection. Depending upon the facility, the automated apparatus may be tailored to specific methods with fixed configurations. Dissolution methods may be routine enough that a custom system, optimized for productivity, may be justified. Compliance of USP and use of industry standard apparatus is important to maintain compatibility with other company laboratories or in the case contract laboratory services are required. 

The approaches and strategies presented in this chapter are intended to overcome these issues for CE methods. Recendy a more advanced approach toward chromatographic method development was introduced in pharmaceutical product development that also is beneficial for CE methods. In the advanced approach (i) the voice of the customer is captured, (ii) key process input variables are identified, (iii) critical to quality (CTQ) factors are determined, (iv) several method verification tests are installed, (v) proactive evaluation of method performance during development is performed, (vi) continuous customer involvement and focus is institutionalized, and (vii) method capability assessment (suitability to be applied for release testing against specification limits) is established. 

This chapter discusses method parameters from the robustness point of view, not from the analyte or the specific analysis point of view. Certain aspects will be named under different parts, if they have impact on multiple aspects and overlap with other chapters is unavoidable. The chapter is not a review (Chapter 9), but will give illustrative examples. It is intended to help during method development and is based on the current status of equipment. The strategies provided are not considered to be the only way to address the issues discussed. They are offered as examples (for more discussion see other related chapters in this book) of... 

Basic to the entire exercise is the issue of how much alternative fuel development can be reasonably expected over the next twenty years. Given the previous synfuel program parameters, sulfur output then depends on both the characteristics of the original fuel source and the specific method of processing. These also serve to determine the location of the sulfur output. 

Method-dependent measurements can be grouped by sector. For example, in the clinical fields there are cases where some higher order reference materials are required for IVD methods, such as for determination of glucose in human serum. It is also required of reference laboratories in specific measurement methods. These issues are now under the responsibility of JCTLM (Joint Committee on the Traceability of Laboratory Medicine of CCQM). CENAM has developed a reference material for glucose and cholesterol determination in human serum, and certified by IDMS, which is under review by JCTLM for the use by reference laboratories in any country applying a reference method. 

A second aspect of this method, which specifications alone would not have addressed, is the issue of sample preparation. The method-development chemist purposefully developed a sample preparation procedure that did not require a sample dilution step. Although this resulted in a 1000-ml sample flask, the development chemist thought the absence of a dilution step would be appreciated by the QC chemist who would be using the method. In the QC environment, however, the use of such a large sample flask was seen as a burdensome inconvenience. A 1000-ml volumetric sample flask made for slow sample preparation. Over 12 liters of sample diluent were needed to test... 

It is important to recognize that the various standardized methods developed for the analysis of water-based samples are not fail-proof. In this regard, the utility of specific methods and the reliability of test results are dependent upon the use of proper laboratory practices and understanding the limitations of a given method. This section is designed to illustrate some of the important issues in this area. 

The process of method validation (i.e., evaluation of the assay) affects the quality of the quantitative data directly [9 A Guide to Analytical Method Validation, Waters Corporation]. Through method validation, it is assured that the method developed is acceptable. Issues involved in the validation of a mass spectrometry method for quantitative analysis are similar to those in any other analytical technique. The validation involves undertaking a series of studies to demonstrate the limit of detection G OD) limit of quantitation (LOQ) linear range specificity within-day precision and accuracy and day-to-day precision and accuracy, specificity, and robustness of the method. All of these parameters must be determined with those commonly accepted good laboratory practices criteria that are applicable in the vafidation of analytical methods. 

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