TABLE OF CONTENTS The second part of the principle of correct sampling requires that the integrity of the sample be preserved. Carelessness and lack of training are the main reasons this fails in practice. As we have illustrated, collecting representative samples consistently requires correct use of the proper sampling equipment. We have also seen how easily these efforts can be neutralized if the property of interest changes somehow as the sample is taken or as nonsampling activities such as transfer, transport, storage, or particle size reduction take place. The best resource to help with protocols, tools, and containers that will ensure preserving the sample integrity is a chemist. Many sample-handling errors have associated chemical issues, and chemists are well versed in sample handling from their lab experience. Gy identifies several categories of sample-handling errors, some of which we have addressed in previous examples. In this discussion, we put them into three groups for simplicity:
contamination,
loss, and
unintentional mistakes or intentional tampering.
Sample contamination occurs when extraneous material or molecules are added to the sample after the sample is taken but before the chemical or physical analysis. This very common problem occurs with solids, liquids, and gases. One simple source of contamination occurs because the sampling tool or sampling equipment is not cleaned. Material from one batch or even from another product is left in the equipment and becomes mixed with material in the next sample. It is ludicrous for production personnel to sample solids day in...
