With multi-analyte methods the probability exists or is statistically likely that at least one test result in each run will be out of limits. Thus, an out of limit test result does not necessarily mean there is an error and assignable cause for the result.

The laboratory's approach should be balanced: avoiding unproductive corrective actions for statistically random events, yet not so broad as to ignore correctible, non-random errors. The laboratory's approach may take into consideration the fact that for some multi-analyte methods, some analytes behave better than others (i.e. exhibiting less variance and/or higher mean recovery) and that an analyte's variance may increase as the concentration of the analyte decreases.

The approach should also include an examination to assure that analytes react independently, meaning that the analyte chemistry is independent. For example in metals, the results of some metals are dependent on the interference component of other metals, like iron interferes with certain metals. 

The approach should also group analytes with similar chemical structure that react similarly in the chemical processing. An example of this is low molecular weight ketones that tend to be lost in the sample preparation process or organic acids that may be poor performers in certain extraction processes.

There are several approaches that could be taken to set limits and to take into account the probability of an out of control result in multi-analyte methods.  One approach would be to assign the analytes to groups that have similar analytical characteristics. Then the quality control and control charting procedure can be designed to track each of these groups.

Another approach that could be taken is to set limits that take into the account the probability that an out of control result will be encountered, such as the approach set forth for environmental testing laboratories in the 2003 NELAC Standard (Appendix D, section D.1.1.2.1.e).

Appendix B Food Micro, section 2.1.1 states “records shall be kept to include…… date opened…” Does the date opened have to be kept as a record?

The date opened is included on the label and is not always stored in a lab notebook or electronic record. Thus, when the label is discarded, the record of the date opened is discarded. Does the date opened have to be maintained as a record?

How often must the temperature uniformity of freezers and refrigerators be verified? What is a practical approach to determining temperature uniformity?

As stated in Table 2. Refrigerators and freezers must have the temperature verified daily.

As stated in Table 1, refrigerators and freezers must have the accuracy of the temperature sensing system, uniformity and stability of temperature calibrated at installation (or initial use) and annually.

Any device which minimizes errors from actions such as opening the door could be used. For example, thermocouples could by used. They can be placed in the refrigerator or freezer, the door closed with the leads protruding, and all of them checked by connecting each lead to the meter without opening the door until finished and they can be removed. 

The AOAC Appendix A (Equipment) Table 3 includes a requirement (nine occurrences) to sanitize equipment. In the pesticide residue field, many sanitizing agents cause interferences with the LC and GC instruments. Also, the equipment does not need to be sanitized as it does for microbiological work.

Table 2 includes multiple requirements to verify sterility and one to verify microbial density. These requirements are of importance only for micro labs and are not relevant to chemical tests.

The following note is related to Appendix A: Equipment

The requirements for microbiological methods imply that 30 data points is the minimum number acceptable, but it is not stated explicitly.

Is the minimum number 30, or do we have some latitude (e.g. 20 - 50)?

The recommendation to use 30 data points is based on the specification for calculating Measurement Uncertainty and is applicable to quantitative methods. 30 data points should provide sufficient information on the variability of a quantitative method to permit a decision on method performance and its fitness for purpose.

The lab must document and justify its decisions as to how many data points to use. The use of fewer than 30 data points should not be routine but may be justified under special circumstances. In this case, as more data is collected the charts should be updated/recalculated to reflect a minimum of 30 points.

Fewer data points (10-15) would be appropriate for verifying qualitative methods. Again, the lab must document its justification for how many data points are used.

In Appendix B: Food Microbiology part 6. Standards for Laboratory Grade Water under Weekly testing (or with use): the Standard reads >1.0 megohoms-cm resistance at 25oC.  The units for resistance are ohms however in the Standard the units are megohm-cm which are units of resistivity.

Does the >1.0 in the Standard refer to resistance or resistivity?

6. Standards for Laboratory Grade Water
Only water that has been treated to be free from traces of dissolved metal, bactericidal, and inhibitory compounds should be used to prepare culture media, reagents, and dilution blanks [reference: Standard Methods for the Examination of Dairy Products (SMEDP, 16th Ed.) and Standard Methods for the Examination of Water and Wastewater (SMEWW, 20th Ed.)]. Inhibitor-free water is referred to as microbiologically suitable (MS) water.

Question: Appendix B, 6.0 includes a requirement for annual testing for toxicity. The specifics of this requirement are unclear. Some labs have interpreted this to require acute water toxicity testing, which is not the intent. Please reference the section of the SMEDP and SMEWW that pertains to the toxicity requirement.

The correct references for “Test for Toxicity” under “Annual Testing” are:

SMEDP, 17th edition, Section 4.041 Dilution Water Toxicity Test

SMEWW, 21st edition, Section 9020 B. Intralaboratory Quality Control Guidelines

Original Question
Appendix B, Section 4  states that all batches of media... shall be traceable to autoclave records which shall show.. time into autoclave, time at desired temperature and time out of autoclave.... 

Thus, the question is that for those autoclaves (typically smaller table top sized units) which lack a tempscribe, (or other temperature recording device), other than noting the timer setting, what records can  / must the laboratory produce in order to demonstrate that it is meeting the requirements of this particular clause?

5.9

Does ALACC section 5.9 require the laboratory to take the same Quality Control Sample through all steps in quantitative and qualitative analyses, or is an appropriate step-specific QCS allowed even if it is not the same one all the way through the analysis?

Although it is ideal to take the same Quality Control Sample through all steps, ALACC does recognize that for some methods this may not be possible.

In such cases, the lab is expected to explain the reason the same sample can not be used and do the best it can do. The lab must clearly identify the steps in the method that differ between the control sample and routine sample and have written justification/explanation how the lab knows and is able to verify the process is in control. It is imperative that the lab does have controls in all the steps so that the entire analytical process is monitored.