A venom sample arriving at a laboratory carries a few lines of text. The most important of them may well be the one that looks least meaningful at first glance: the batch number. Without it, the material in your hands has no past; there is no way to ask which animals it came from, on which dates or under which conditions.
What is a batch and how is it defined?
A batch is a quantity of material processed under the same conditions and treated as a single unit. Where venom is concerned, a batch does not come from one animal; it is built up by accumulating small volumes taken from many individuals over a defined period.
What draws the boundary of a batch is this decision to pool. Once the collection window closes, the material takes on a single identity and is treated as a separate unit from then on. Material added later is not recorded under the same batch, because the definition of a batch rests on everything within it sharing the same processing history.
That definition also settles indirectly how large a batch will be. A long window yields a larger and more homogeneous unit, but the material collected first will have waited longer. A short window shortens the wait, yet produces many small batches, each needing its own analysis. The decision is made between these two costs.
The number itself is a technical choice. Coding that carries date, period and sequence information is common; what counts is not the form of the code but that the same number travels unchanged to the end of the chain.
Links in the chain
A batch's journey begins in the colony and ends with the shipping paperwork. The record produced at each step is linked to the next.
| Step | Record produced | Information it links to |
|---|---|---|
| Colony | Individual or group code, husbandry log | Species identity and origin |
| Material collection | Date, volume collected, person carrying out the work | Individual codes |
| Pooling | Opening of the batch number | Contributing groups |
| Stabilization | Cycle parameters, drying record | Batch number |
| Packaging | Number of containers, label information | Batch number |
| Analysis | Sample submission record, laboratory report | Batch number |
| Shipment | Invoice, transport paperwork, document file | Batch number |
This chain carries a hidden cost: writing a few lines at every step. What it buys in return is the ability to answer a question asked months or years later with documents. Form design is therefore the part of the job that looks easy yet decides the most: a form that is hard to complete becomes a form completed incompletely.
What the columns in the table have in common is that every row can be linked back to the one before it. When the number is left off at one link, the chain breaks and everything before that point disappears from view. The logbook system on the colony side was described in the article on closed-cycle breeding.
Forward and backward tracing
Traceability works in two directions and answers two different questions.
- Backward tracing: Setting out from a container of material in hand and going back in time. Which individuals did it come from, on which dates was it collected, under which conditions was it dried, and which report recorded its measurements?
- Forward tracing: Setting out from a batch and coming forward to the present. How many containers was this batch split into, which institutions was it sent to, and where is the remaining quantity held?
The first question usually comes from the buyer. When an institution wants to state the source of the material used in a study it is about to publish, or is looking for evidence in an internal audit, it needs a chain that can be read backwards. Having that chain established inside the facility means the request is met in hours rather than days.
The second question is generally asked when something has gone wrong. If a break in the cold chain is noticed during a shipment, or an unexpected result comes out of a measurement, every buyer who received part of the same batch has to be identified quickly. That identification depends on records being kept in searchable form.
In practice the weakest point is the packaging step. When a batch is split between several containers, the batch each container belongs to has to be written on it individually; packaging arrangements are covered in the article on packaging. Keeping the label on the secondary container legible is no minor detail either.
Which documents does the number appear on?
In the file reaching the buyer, the batch number is expected to appear in more than one place, written identically each time: on the container label, in the certificate of analysis, in the shipping paperwork and, where present, in the declaration of storage conditions. The order in which documents are read is set out in the article on certificates of analysis.
The safety data sheet stands apart in this list. The sheet belongs to the product rather than the batch and is cited by its version number, so no batch number is looked for on it. Knowing at goods-in that the two documents follow different logic saves needless correspondence. The details of our facility's documents are listed on the documents page.
Consistency between documents is checked as well. Matching the number on the label with the number on the certificate may look like a redundant confirmation, but it is the quickest verification made at goods-in. Where a mismatch appears, the supplier is asked before the material is taken into use; in most cases the cause is a simple typing error or an old printout that found its way into the file.
How long records are kept is likewise part of traceability. A record has to remain accessible for a certain period after the material concerned has gone out of use; otherwise a question arriving years later goes unanswered. The length of that period is set by regulation, by contract and by the institution's own policy.
The contact page can be used for requests concerning documents or records for a particular batch. Records are batch-specific; values belonging to one batch are not taken as valid for another.
