《美国FDA农残分析手册》（第一卷英文版）Chapter 3 Multiclass MRMS.pdf_大学文库

Pesticide Analytical Manual Vol. I SECTION 301 301: MULTICLASS MRMS: CONCEPT AND APPLICATION Pesticide multiresidue methods (MRMs) are capable of simultaneously determin- ing more than one residue in a single analysis; this multiresidue capability is provided by a glC or HPLC determinative step that separates residues from one another before detection. The mRM concept is raised to a higher dimension when a single extract is examined with more than one chromatographic determinative step, each provid overage of residues in a different class, e. g, chlorinated hydrocarbons, organophosphates, and carbamates, PAM I refers to these broad scope methods as"multiclass MRMs. A multiclass MRM is potentially capable of determining any residue extracted by its extraction step; PAM I multiclass MRMs extract residues with organic solvents known to remove most nonionic residues from food commodities. each determi- native step in a multiclass MRM provides coverage for a particular group of resi- dues in the extract, and each cleanup step is designed to purify the extract suffi- ciently to permit accurate determination. A multiclass MRM scheme can be ex- panded continually as new technologies are developed and adapted This introductory section presents a recommended approach to application of multiclass MRMs and background information with which any analyst using such methods should be familiar 301 A: RECOMMENDED APPLICATON OF MULTICLASS MRMS Whenever a sample of unknown pesticide treatment history is analyzed, and no residue(s)is targeted, a multiclass MRM should be used to provide the broadest coverage of potential residues; Figure 301-a displays the recommended multiclass MRM for each commodity category. The more detailed scheme provided with each method(Figures 302-a, 303-a, 304-adirects the user to recommended module(s) for particular commodities. The user may choose as many or as few of these modules as time and resources permit; once residues are extracted, each determinative step extends coverage of the analysis to additional compounds Follow these directions to maximize coverage of residues without sacrificing quan- titative accuracy For broadest coverage of potential residues, examine the uncleaned extract by determinative steps that are sufficiently selective to permit residue identification and quantitation in the presence of co-extractives Following determination by selective determinative steps, clean up the extract as needed to permit additional determinations; these may in- clude determinative steps designed for specific groups of residues(e.g from Chapter 4 methods) When a peak appears in the chromatogram of the extract, use the fol- owing PAM I tables to tentatively identify the residue and to choose the additional analyses needed for optimum identification, quantitation, and/ or confirmation: 1)PESTDATA (Appendix I). Compare GLC relative retention time(rrt of the residue to lists of rrts on several common glc columns 301-1

Pesticide Analytical Manual Vol. I SECTION 301 301–1 Transmittal No. 94-1 (1/94) Form FDA 2905a (6/92) 301: MULTICLASS MRMS: CONCEPT AND APPLICATION Pesticide multiresidue methods (MRMs) are capable of simultaneously determining more than one residue in a single analysis; this multiresidue capability is provided by a GLC or HPLC determinative step that separates residues from one another before detection. The MRM concept is raised to a higher dimension when a single extract is examined with more than one chromatographic determinative step, each providing coverage of residues in a different class, e.g., chlorinated hydrocarbons, organophosphates, and carbamates. PAM I refers to these broad scope methods as “multiclass MRMs.” A multiclass MRM is potentially capable of determining any residue extracted by its extraction step; PAM I multiclass MRMs extract residues with organic solvents known to remove most nonionic residues from food commodities. Each determinative step in a multiclass MRM provides coverage for a particular group of residues in the extract, and each cleanup step is designed to purify the extract sufficiently to permit accurate determination. A multiclass MRM scheme can be expanded continually as new technologies are developed and adapted. This introductory section presents a recommended approach to application of multiclass MRMs and background information with which any analyst using such methods should be familiar. 301 A: RECOMMENDED APPLICATION OF MULTICLASS MRMS Whenever a sample of unknown pesticide treatment history is analyzed, and no residue(s) is targeted, a multiclass MRM should be used to provide the broadest coverage of potential residues; Figure 301-a displays the recommended multiclass MRM for each commodity category. The more detailed scheme provided with each method (Figures 302-a, 303-a, 304-a) directs the user to recommended module(s) for particular commodities. The user may choose as many or as few of these modules as time and resources permit; once residues are extracted, each determinative step extends coverage of the analysis to additional compounds. Follow these directions to maximize coverage of residues without sacrificing quantitative accuracy: • For broadest coverage of potential residues, examine the uncleaned extract by determinative steps that are sufficiently selective to permit residue identification and quantitation in the presence of co-extractives. • Following determination by selective determinative steps, clean up the extract as needed to permit additional determinations; these may include determinative steps designed for specific groups of residues (e.g., from Chapter 4 methods). • When a peak appears in the chromatogram of the extract, use the following PAM I tables to tentatively identify the residue and to choose the additional analyses needed for optimum identification, quantitation, and/ or confirmation: 1) PESTDATA (Appendix I). Compare GLC relative retention time (rrt) of the residue to lists of rrts on several common GLC columns

Pesticide Analytical Manual Vol. I SECTION 301 for the first clue to residue identity Review method behavior infor mation for additional clues about which potential candidate(s) be- haves in the same way as the residue. Inject solutions of appropriate reference standard(s) for comparison to the residue peak If retention times of residue and reference standard match. use PESTDATA information on the chemicals molecular formula and its rrts on other columns as a guide to selecting other determina- tions that will provide confirmatory evidence. If additional analyses are needed, choose appropriate other methods from PESTDATA listings of recoveries, Index to Methods, and tables related to spe- cific methods. below PESTDATA ITts are for GLC systems only. Retention times from the HPLC determinative steps of Sections 401, 403, and 404 are included in the tables that accompany those methods. Use those tables to tentatively identify residues found 2)Index to Methods. Use this summary as a guide to other method(s) available for a tentatively identified residue. Review method tables, below for additional details. 3) Tables 302, 303, 304, 401, 402, 403, and 404. When a residue is tentatively identified, review method tables for details about special situations that may diminish recoveries, opportunities to improve recoveries, need for particular determinative step(s), etc. Decide what additional analyses are necessary based on this information When tabulated information about behavior of the tentatively identified residue indicates that the method used provided only incomplete rece ery, re-analyze the commodity with another method capable of complete recovery of the residue (The analyst should be aware that all data in PAM I tables reflect the best information available but do not guarantee that results will be iden tical in every situation. Data have been collected for 30 years from many sources, including original method development studies, recovery stud- ies by FDA laboratories, recovery studies by pesticide registrants and/or their contract laboratories. and collaborative and validation studies con- ducted under the auspices of AOAC International. Particular results with or without sample present, through complete methods or through individual procedures of a method, and with or without use of lauric acid adsorption value for Florisil column weight adjustment.) When the method used has not been previously validated for the resi- due/ commodity combination, develop the necessary validation data. Inherent in this approach to residue analysis is the acknowledgment that multiclass MRM is quantitatively valid for all residues it is capable of detectin Thus, re-analysis by other method(s) is required when a residue(s) is identified by a method known to be incapable of confirmatory identification and/or quantita- tive accuracy. Demonstration of method validity for any residue/ commodity com- bination that orted is the responsibility of the analyst using the method. 301-3

Pesticide Analytical Manual Vol. I SECTION 301 301–3 Transmittal No. 94-1 (1/94) Form FDA 2905a (6/92) for the first clue to residue identity. Review method behavior information for additional clues about which potential candidate(s) behaves in the same way as the residue. Inject solutions of appropriate reference standard(s) for comparison to the residue peak. If retention times of residue and reference standard match, use PESTDATA information on the chemical’s molecular formula and its rrts on other columns as a guide to selecting other determinations that will provide confirmatory evidence. If additional analyses are needed, choose appropriate other methods from PESTDATA listings of recoveries, Index to Methods, and tables related to specific methods, below. PESTDATA rrts are for GLC systems only. Retention times from the HPLC determinative steps of Sections 401, 403, and 404 are included in the tables that accompany those methods. Use those tables to tentatively identify residues found. 2) Index to Methods. Use this summary as a guide to other method(s) available for a tentatively identified residue. Review method tables, below, for additional details. 3) Tables 302, 303, 304, 401, 402, 403, and 404. When a residue is tentatively identified, review method tables for details about special situations that may diminish recoveries, opportunities to improve recoveries, need for particular determinative step(s), etc. Decide what additional analyses are necessary based on this information. • When tabulated information about behavior of the tentatively identified residue indicates that the method used provided only incomplete recovery, re-analyze the commodity with another method capable of complete recovery of the residue. (The analyst should be aware that all data in PAM I tables reflect the best information available but do not guarantee that results will be identical in every situation. Data have been collected for 30 years from many sources, including original method development studies, recovery studies by FDA laboratories, recovery studies by pesticide registrants and/or their contract laboratories, and collaborative and validation studies conducted under the auspices of AOAC International. Particular results may represent many analyses or only one, may have been performed with or without sample present, through complete methods or through individual procedures of a method, and with or without use of lauric acid adsorption value for Florisil column weight adjustment.) • When the method used has not been previously validated for the residue/commodity combination, develop the necessary validation data. Inherent in this approach to residue analysis is the acknowledgment that no multiclass MRM is quantitatively valid for all residues it is capable of detecting. Thus, re-analysis by other method(s) is required when a residue(s) is identified by a method known to be incapable of confirmatory identification and/or quantitative accuracy. Demonstration of method validity for any residue/commodity combination that is reported is the responsibility of the analyst using the method

SECTION 301 Pesticide Analytical Manual Vol I 301 B: CAPABILITIES AND LIMITATIONS OF MRMS Several aspects of an MRM influence its scope as a multiclass method:(1)thor- oughness with which the extraction solvent and physical procedure are capable of extracting residues from the sample, (2)ability of subsequent cleanup techniques to remove sample co-extractives without removing residues, and() the number of different determinative steps used to examine the extract During method devel- opment, a researcher evaluates each step of a method and makes choices based on optimum performance. Subsequent interlaboratory validation verifies that the method produces accurate results when performed as written This edition of PAM I presents MRMs as a series of modules, in recognition of standard practices in laboratories required to analyze many different commodities for many different potential residues Modules presented within the same section in this manual were not necessarily developed at the same time or by the same researcher Module combinations that have undergone interlaboratory validation are listed and recommended, but analysts may find it necessary to combine other modules to meet a particular need. Any such combination must be supported by with one another for the whole method to be applied in a valid manner mpatible data that validate its use in the situation. Steps of an MRM must be ce This section provides background information to assist the analyst in making valid choices and avoiding potential pitfalls. Included here are discussions about the overall influence solvents have on method performance and important informa tion about each category of method modules(extraction, cleanup, and determina- tive steps). Analysts combining method modules must be aware of the following concerns and take precautions to ensure that only appropriate combinations are Influence of solvents on Methodology Choice of solvent(s) is among the most important decisions made by a researcher of the following considerations related to solvents used in individual modules. re developing an analytical method. Analysts using these methods must also be aw Availability of Pure Solvent. Solvent purity is essential to avoid potential interfer ences in the determinative step; impurities are usually concentrated during the evaporation steps included in most residue methods. Higher purity solvents invari- ably cost more, and it may be possible to use less expensive, lower purity materials 204) supports their acceptability ed by appropriate determinative step(s)(Section if a solvent reagent blank exa Detector Response to Solvent. GlC detectors used in residue determinations are sually selective for an element in the analyte molecule, so the final extract must not be dissolved in a solvent containing element(s) to which the detector(s)re- spond. For example, no trace of acetonitrile can be present when a nitrogen- selective detector is used, and no methylene chloride when a halogen-selective detector is used. HPLC detectors commonly used in residue determination pre- clude use of solvents that absorb UV light or fluoresce at the wavelength used during determination Solvents can adversely affect detectors in other ways, such as the deleterious but poorly defined effect acetonitrile has on electroconductivity detectors Transmittal No 94-1(1/94) Form FDA 2905a(6/92

301–4 Transmittal No. 94-1 (1/94) Form FDA 2905a (6/92) SECTION 301 Pesticide Analytical Manual Vol. I 301 B: CAPABILITIES AND LIMITATIONS OF MRMS Several aspects of an MRM influence its scope as a multiclass method: (1) thoroughness with which the extraction solvent and physical procedure are capable of extracting residues from the sample, (2) ability of subsequent cleanup techniques to remove sample co-extractives without removing residues, and (3) the number of different determinative steps used to examine the extract. During method development, a researcher evaluates each step of a method and makes choices based on optimum performance. Subsequent interlaboratory validation verifies that the method produces accurate results when performed as written. This edition of PAM I presents MRMs as a series of modules, in recognition of standard practices in laboratories required to analyze many different commodities for many different potential residues. Modules presented within the same section in this manual were not necessarily developed at the same time or by the same researcher. Module combinations that have undergone interlaboratory validation are listed and recommended, but analysts may find it necessary to combine other modules to meet a particular need. Any such combination must be supported by data that validate its use in the situation. Steps of an MRM must be compatible with one another for the whole method to be applied in a valid manner. This section provides background information to assist the analyst in making valid choices and avoiding potential pitfalls. Included here are discussions about the overall influence solvents have on method performance and important information about each category of method modules (extraction, cleanup, and determinative steps). Analysts combining method modules must be aware of the following concerns and take precautions to ensure that only appropriate combinations are used. Influence of Solvents on Methodology Choice of solvent(s) is among the most important decisions made by a researcher developing an analytical method. Analysts using these methods must also be aware of the following considerations related to solvents used in individual modules: Availability of Pure Solvent. Solvent purity is essential to avoid potential interferences in the determinative step; impurities are usually concentrated during the evaporation steps included in most residue methods. Higher purity solvents invariably cost more, and it may be possible to use less expensive, lower purity materials if a solvent reagent blank examined by appropriate determinative step(s) (Section 204) supports their acceptability. Detector Response to Solvent. GLC detectors used in residue determinations are usually selective for an element in the analyte molecule, so the final extract must not be dissolved in a solvent containing element(s) to which the detector(s) respond. For example, no trace of acetonitrile can be present when a nitrogenselective detector is used, and no methylene chloride when a halogen-selective detector is used. HPLC detectors commonly used in residue determination preclude use of solvents that absorb UV light or fluoresce at the wavelength used during determination. Solvents can adversely affect detectors in other ways, such as the deleterious but poorly defined effect acetonitrile has on electroconductivity detectors