Appendix III. Amendments to the Procedural Manual

AMENDMENTS TO THE GUIDELINES FOR THE INCLUSION OF SPECIFIC PROVISIONS IN CODEX STANDARDS AND RELATED TEXTS

1. AMENDMENT TO THE GENERAL CRITERIA FOR THE SELECTION OF METHODS OF ANALYSIS USING THE CRITERIA APPROACH

In the case of Codex Type II and Type III methods, method criteria may be identified and values quantified for incorporation into the appropriate Codex commodity standard. Method criteria which are developed will include the criteria in section Methods of Analysis, paragraph © above together with other appropriate criteria, e.g., recovery factors.”

2. WORKING INSTRUCTIONS FOR THE IMPLEMENTATION OF THE CRITERIA APPROACH IN CODEX

(for inclusion at the end of the Principles for the Establishment of Codex Methods of Analysis after the above General Criteria)

Any Codex Commodity Committee may continue to propose an appropriate method of analysis for determining the chemical entity, or develop a set of criteria to which a method used for the determination must comply. In some cases a Codex Commodity Committee may find it easier to recommend a specific method and request the Codex Committee on Methods of Analysis and Sampling (CCMAS) to “convert” that method into appropriate criteria. The Criteria will then be considered by the CCMAS for endorsement and will, after the endorsement, form part of the commodity standard replacing the recommended method of analysis. If a Codex Commodity Committee wishes to develop the criteria by itself rather than allowing the CCMAS to do so, it should follow instructions given for the development of specific criteria as outlined below. These criteria must be approved for the determination in question.

However, the primary responsibility for supplying methods of analysis and criteria resides with the Commodity Committee. If the Commodity Committee fails to provide a method of analysis or criteria despite numerous requests, then the CCMAS may supply an appropriate method and “convert” that method into appropriate criteria.

The minimum “approved” Codex analytical characteristics will include the following numeric criteria as well as the general criteria for methods laid down in the Analytical Terminology for Codex Use (see page 66):

• precision (within and between laboratories, but generated from collaborative trial data rather than measurement uncertainty considerations)

• recovery

• selectivity (interference effects etc.)

• applicability (matrix, concentration range and preference given to ‘general’ methods)

• detection/determination limits if appropriate for the determination being considered

• linearity

CCMAS will generate the data corresponding to the above criteria.

Conversion of Specific Methods of Analysis to Method Criteria by the CCMAS

When a Codex Commodity Committee submits a Type II or Type III method to CCMAS for endorsement, it should also submit information on the criteria listed below to enable the CCMAS to convert it into suitable generalized analytical characteristics:

• accuracy

• applicability (matrix, concentration range and preference given to ‘general’ methods)

• detection limit

• determination limit

• precision; repeatability intra-laboratory (within laboratory), reproducibility inter-laboratory (within laboratory and between laboratories), but generated from collaborative trial data rather than measurement uncertainty considerations

• recovery

• selectivity

• sensitivity

• linearity

These terms are defined in the Analytical Terminology for Codex Use (see page 66), as are other terms of importance.

The CCMAS will assess the actual analytical performance of the method which has been determined in its validation. This will take account of the appropriate precision characteristics obtained in collaborative trials which may have been carried out on the method together with results from other development work carried out during the course of the method development. The set of criteria that are developed will form part of the report of the CCMAS and will be inserted in the appropriate Codex Commodity Standard.

In addition, the CCMAS will identify numeric values for the criteria for which it would wish such methods to comply.

Assessment of the Acceptability of the Precision Characteristics of a Method of Analysis

The calculated repeatability and reproducibility values can be compared with existing methods and a comparison made. If these are satisfactory then the method can be used as a validated method. If there is no method with which to compare the precision parameters then theoretical repeatability and reproducibility values can be calculated from the Horwitz equation. (M. Thompson, Analyst, 2000, 125, 385-386).

Additions to ANALYTICAL TERMINOLOGY FOR CODEX USE^[117]

Terms to Be Used in the Criteria Approach

a) Detection Limit

The detection limit is conventionally defined as field blank + 3s, where s is the standard deviation of the field blank value signal (IUPAC definition).

However, an alternative definition which overcomes most of the objections to the above approach (i.e. the high variability at the limit of measurement can never be overcome) is to base it on the rounded value of the reproducibility relative standard deviation when it goes out of control (where 3 s_R = 100%; s_R = 33%, rounded to 50% because of the high variability). Such a value is directly related to the analyte and to the measurement system and is not based on the local measurement system.

b) Determination limit

As for detection limit except that 6s or 10s is required rather than 3s.

However, an alternative definition that corresponds to that proposed for the detection limit is to use s_R = 25%. This value does not differ much from that assigned to the detection limit because the upper limit of the detection limit merges indistinguishably into the lower limit of the determination limit.

c) Recovery

Proportion of the amount of analyte present or added to the test material which is extracted and presented for measurement.

d) Selectivity

Selectivity is the extent to which a method can determine particular analyte(s) in mixtures or matrices without interferences from other components.

Selectivity is the recommended term in analytical chemistry to express the extent to which a particular method can determine analyte(s) in the presence of interferences from other components. Selectivity can be graded. The use of the term specificity for the same concept is to be discouraged as this often leads to confusion.

e) Linearity

The ability of a method of analysis, within a certain range, to provide an instrumental response or results proportional to the quality of analyte to be determined in the laboratory sample. This proportionality is expressed by an a priori defined mathematical expression. The linearity limits are the experimental limits of concentrations between which a linear calibration model can be applied with a known confidence level (generally taken to be equal to 1%).

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ADDITION TO APPENDIX TO THE PROCEDURAL MANUAL: GENERAL DECISIONS OF THE COMMISSION

MEASURES TO FACILITATE CONSENSUS

The Codex Alimentarius Commission, desiring that every effort should be made to reach agreement on the adoption or amendment of standards by consensus, recommends the following measures to facilitate consensus:

• Refraining from submitting proposals in the step process where the scientific basis is not well established on current data and, where necessary, carry out further studies in order to clarify controversial issues;

• Providing for thorough discussions and documentation of the issues at meetings of the committees concerned;

• Organizing informal meetings of the parties concerned where disagreements arise, provided that the objectives of any such meetings are clearly defined by the Committee concerned and that participation is open to all interest delegations and observers in order to preserve transparency;

• Redefining, where possible, the scope of the subject matter being considered for the elaboration of standards in order to cut out issues on which consensus could not be reached;

• Providing that matters are not progressed from step to step until all relevant concerns are taken into account and adequate compromises worked out;

• Emphasizing to Committees and their Chairpersons that matters should not be passed on to the Commission until such time as consensus has been achieved at the technical level;

• Facilitating the increased involvement and participation of developing countries.

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TERMS OF REFERENCE OF CODEX COMMITTEES AND TASK FORCES

Amend the name and terms of reference of the Codex Committee on Meat and poultry Hygiene to read as follows:

CODEX COMMITTEE ON MEAT HYGIENE (CX-723)

To elaborate world-wide standards and/or codes of practice as appropriate for meat hygiene.