Freezer spikes

To fortify a sample, the label from a fortification sampling vial was removed and secured to the pre-labeled sample jar. Spike vials were individually shaken before use. The cap was discarded, the contents of the vial were poured into the sample jar and then the vial was dropped into the sample. The sample jar was capped with a Tefion-lined lid, hand shaken to mix, placed in a Kapak bag and sealed. Jars were placed immediately in storage freezers. In all cases, quality control samples were transported and stored with their corresponding field plot samples throughout sample handling and shipment to the analytical facility. 

When you place it in the freezer, it will often form spikes, sometimes as long as an inch. Why The surface of the water first becomes covered in ice, growing from the outside edge in, until only a small hole is left in the middle. Ice takes up more space than water, so as more ice forms underneath, the water that s left has nowhere to go and it s forced up through the hole. 

One function of the QC sample (or validation samples as they are sometimes called when used during the validation phase) is to mimic the study sample. Therefore, the therapeutic drug is spiked into a neat sample matrix, and not into a diluted or otherwise modified matrix. The QCs should be stored preferably along with the samples in the same freezer or at least in a comparable freezer. Documentation of freezer conditions will be critical to provide evidence that the conditions of samples and QCs are similar. 

Sample Stability. Experiments demonstrating sufficient stability of the analyte in the sample matrix must be included in prestudy validation. Such experiments should mimic as closely as possible the conditions under which study samples will be collected, stored, and processed. Assessment should include bench-top stability, refrigerator stability, whole-blood stability, freeze-thaw stability, and long-term freezer stability. Stability samples can be prepared by spiking the analyte reference at high and low concentrations into the sample matrix. 

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