Hello! My name is Amanda Ranowsky, and I’ve just been hired at CSC Scientific. I’ve come fresh from completing my Master of Arts degree abroad, studying Publishing at Oxford Brookes University in the United Kingdom. I also have a BA in English from Christopher Newport University.
CSC Scientific Blog
Many accessing our web site ask questions such as:
“How does water content affect water activity?”
"How is water activity different from water content?”
”Can I convert from moisture to water activity?”
I previously commented on water activity and now hope to clarify the differences between water activity and moisture content. Given that both of these measurements deal with water connected to a material, we must first understand of water content in a product.
I am very excited about a new update to the CSC Digital Moisture Balance. To give you a perspective of why I’m excited about this Moisture Content Analyzer update, I thought you my be interested in the story of the transition from a classic mechanical moisture analyzer to the current highly robust and durable electronic instrument of today.
As you know the Karl Fischer Method of moisture analysis has a reputation of being water specific. The method works through the use of a special Karl Fischer Reagent.
As usual when we pose a question,like:
Should you use Coulometric or Volumetric Karl Fischer to measure moisture in your product?
We often get a the reaction, “So Who Cares?” We'll try to answer both questions.
Last week, as I was reflecting on a recent moisture content problem, I recalled our series “Loss-on Drying and Other Moisture Mysteries.” In that series I examined moisture chemistry in products. However, I did little to define moisture content.
The other day, I woke up with a lingering quandary: Are the concepts of
Moisture Content and Water Activity the same thing?
As usual, I’ve decided to take on the task of clarifying the difference. I hope I pull it off.
From the perspective of someone who supplies instruments that measure moisture content, water activity has not been a primary consideration. However, I believe that comparison and contrast of these important concepts will be useful.
“Why are my Moisture Test results inconsistent?”
That is an issue for many of you who test for moisture. We discussed the complexities and multiplicity of issues involved with moisture content determination in our “Loss-on Drying Moisture Analysis and other Moisture Mysteries” series.
In addition to intrinsic properties of test samples that may adversely affect moisture testing systems, automatic equipment parameter set-up, operator oversights and sample handling contribute to seemingly intractable moisture test result inaccuracies.
When People are first introduced to the Karl Fischer Moisture Determination Method, eyes glaze over and we can perceive a mental “Why did I ask?”
If you have any history with moisture analysis, you will have found, that for some applications, the Karl Fischer Titration Method is the best and sometimes the only way to get an accurate moisture measurement.
Just over six months ago, I began this journey explaining the simplest approach to measuring or determining moisture: Loss-on Drying. Little did I know how involved and esoteric it would become.
This voyage has taken me down mysterious paths through spooky theories, back to age-old chemistry concepts and into the vagaries of thermodynamics related to evaporation, vapor pressure, bound water and water activity. I have come full-circle; back to explaining Loss-on Drying -- a form of drying that I had assumed would be the simplest of all.
I thought the first four topics [evaporation, vapor pressure, bound moisture, water activity] were tough, complex, confounding and less-than-obvious. Drying -- defined as “the mass-transfer process of removing water (or other solute) by evaporation from a solid, semi solid or liquid” -- seemed easy.
As is often the case, reality makes “easy” a non-operative word. Such has turned out to be so with respect to the issue of drying.