Introduction to the Theory and Practice of Sampling

by Kim H. Esbensen

IM Publications Open, Chichester, UK

Review by Gary Ritchie, MS
Principal Consultant, GER COMPLIANCE
Council for Near Infrared Spectroscopy News Editor
QC/QA GMP Remediation, Training, Audits, Data Analytics, Chemometric/Spectroscopy Remote Analysis
Former Director of Operations and Regulatory Affairs Analyst for Dynalabs, LLC, St Louis, MO, USA
Former Director of Scientific Affairs for Infratrac, Silver Spring, MD, USA
Former Scientific Fellow for Process Analytical Technology (PAT) with the United States Pharmacopeia (USP)
International expert in multivariate spectroscopic analysis, pharmaceutical analysis, Good Manufacturing Practices compliance, laboratory management, design, quality, and process analytical technology using spectroscopic methods and multivariate analysis

How to read this book?

The reader is encouraged to read the first two chapters, followed by Chapters 22–24, and only then continuing from Chapter 3. In this fashion the reader is promised guaranteed optimal conditions with which to achieve all the promised learning goals. Having read the book in the manner recommended above, I have the following comments.

Does this book work as intended?

I thoroughly enjoyed the conversational style in which the book is written. I imagine that I could very well be listening to Pierre Gy himself as he presents his Theory of Sampling for the very first time. If the author intended for the reader to experience an introduction to the TOS as if he/she was the first to ever hear it, the book has achieved its objective well.

What is good?

Far from being a conventional cut and dry textbook, the informal and didactic style adopted allows the student-reader to learn at an easy and suitable pace. I followed the recommendation on how to read the book; I read the first two chapters, followed by Chapters 23–25, and only then continuing from Chapter 3; again. This works well because once read in this manner, a self-paced cadence for further instruction and insight into the references provided was easily achieved.

There is a vast amount of additional text offered in the book (directly clickable sidebars),which can at first make it somewhat difficult to determine what is essential versus what is more for extra information. However as one moves along, these sidebars prove to be important locations for necessary reinforcement and references for further reading. The main text provides much scientific insight and color and additionalities as well, but it is precisely this mix that gives the reader-student the sense of discovering the TOS for the very first time.

General assessment

The take away lesson from this book is clear, and very unsettling.

“...hidden economic losses due to faulty decisions based on faulty analytical results due to non-representative sampling.”

These words should give every analytical chemist pause for concern. After all, we have been taught and we believe that our analytical results are based on a sample that must be representative, for why else are we testing it? And then, when/if the result fails the acceptance criteria, we are told, after a proper investigation, to test it again. It has become the focus of discussions: just what is a sample really and what is it representative of? This delves right into the realm of the Theory of Sampling (TOS). While analytical testing is in and of itself a science rooted in the natural sciences and mathematics, here now comes the TOS that teaches us that homogeneity of the aliquot isn’t the goal, but representativity of the primary sample (and all sub-samples hereof) is, and that sample size matters and sampling error goes beyond conventional statistics. It is all about the sampling process, and here the book’s strongpoint is that all major points made can easily be understood within the framework of TOS’ six fundamental sampling principles and four sampling unit operations.

In Introduction to the Theory and Practice of Sampling, by Professor Esbensen, with contributions from several well-known and respected experts on the subject, the TOS is presented in an easy, comprehensible style that is assessible to everyone at all academic levels that allows readers, students and practitioners to learn very quickly a fundamental fact of nature that can no longer afford to be unknown or ignored: homogeneous materials do not exist in the real world; every material in technology and industry is heterogeneous. Hence, the flaw in our current thinking and practice of treating “analytical grab samples” as if they always are homogeneous and representative, turns out to be the single biggest source of economic loss to most of the modern world’s industrial endeavors.

I recommend this book to all newcomers to TOS, but especially also to those who want to go beyond the TOS basics and further explore its numerous literature sidebars and background references. For in depth coverage of the quantitative nature of sampling theory and practice, this is the place to start. I feel the opportunity to review this book is an extension, and culmination, of my role when as a scientist at the United States Pharmacopeia about ten years ago, as the perfect time and place to get the TOS in front of the key committee members who would go onto incorporate the Theory of Sampling into the United States Drug Compendium.

Buy a copy of the book