TNI Logo The NELAC Institute

Standard Interpretation



SIR #: 251
Standard: 2009 TNI
Section: V1M2, Section 5.6.4.2 (d)


REQUEST:

Assuming that we have a working definition for reagents, does the word "prepared" in 5.6.4.2(d) refer only to standards or all three (standards, reference materials and reagents)? Assuming the latter, see the discussion below for the actual question). Please contact Chandra at the secondary email in this request if any clarification is needed.

Prepared reagents are readily defined as reagents that are prepared in the lab by modifying (diluting, mixing, etc.) one or more precursor reagents or standards. However there is some ambiguity concerning the term "container".

Suppose I make 200 ml of a reagent stock, say the Ammonium Molybdate reagent used in total phosphorus analysis that is stored in a lab refrigerator. Every time we perform a TP run, a small amount of this reagent is poured into a second container, a removable, plastic reagent well that is part of our discrete analyzer's autosampler. At the end of the day, this reagent is not completely used up, and to minimize waste, we cap the removable plastic well and store it in the refrigerator overnight. It is refilled the following day for the next day's analysis.

Since the reagent stock was prepared only once, it would be assigned a single, unique serial number. The mere act of pouring some of this reagent into a second container should not (logically) require one to generate a second serial number.

To summarize the question, is only one unique serial number needed for each contiguous preparation, regardless of the number of containers in which the reagent might be stored? i.e., Is this description of unique identifiers for prepared reagents consistent with the meaning and intent of 5.6.4.2 (d)?

TNI FINAL RESPONSE:

(Quality Systems Expert Committee and NELAP AC, 9-23-15)

The use of the reagent at analysis requires that all data necessary for the historical reconstruction of the data be available (see 4.13.3 f). Somewhere with the analytical batch, reference must be made to the unique serial number of this reagent. A new serial number need not be created due to the act of pouring the reagent from one container to another. The unique serial number is created at a point in time when the reagent, standard or material is made in the lab. If no changes are made, then a new number need not be created.

The act of removing the container from its specific location on the instrument requires that the container be labeled with the reagent's unique identifier in order to comply with the traceability requirement of 5.6.4.2 c.