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Pharma, healthcare and body care · TD-NMR

Water in raw materials and formulations

Free versus bound water and hydration state of excipients, actives and finished products, including hygroscopic materials that are hard to handle.

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What it tells you

Not only how much water, but in which state

Water in a solid is not all the same. Some is tightly bound to the material, some is loosely held, and some moves almost freely. These states behave differently: free water drives hydrolysis, caking and poor flow, while bound water can be harmless. A measurement that separates them says more about stability than the total water content alone.

Stacked bars showing the share of tightly bound, loosely bound and free water as the water content of a sample increases
States of water in a material at increasing water content. Schematic illustration, not measured data.
Typical samples

Where it is used

  • Excipients such as celluloses, starches and sugars
  • Hygroscopic active ingredients
  • Granules, blends and tablets
  • Freeze-dried products
  • Capsule shells, gelatin and plant-based

Typical tasks are checking incoming materials, following moisture uptake at different humidities, choosing packaging, and relating the state of the water to stability or mechanical properties such as the softening of a capsule shell.

How it works

Different mobility, different signal

The signals of water in different states fade at different speeds, so one measurement separates them. A calibration for the material turns the signals into amounts. Powders in closed glass vials can often be measured through the glass, so hygroscopic materials stay sealed.

A powder in a closed vial is measured through the glass and gives separate results for free and bound water
Measuring water in a powder through its vial. Schematic illustration.
Why time-domain NMR

What it adds

  • Non-destructive, with little or no sample preparation
  • Hygroscopic materials can stay in their closed container
  • Shows the state of the water, not only the total
  • The same sample can be followed during humidity studies
Good to know

Points that matter in practice

  • Karl Fischer titration remains the reference for the total water content and for trace water, and it is the natural reference for the calibration
  • How water is divided into states is partly a matter of the model used. Validate it against another property that matters to you
  • Very low water contents and very small samples limit what can be measured
  • Paramagnetic impurities shorten relaxation times, and the sample temperature must be controlled
  • Calibrate for each material, because the signal per unit of water depends on it
How MSY Consulting helps

From your materials to a routine method

Send or bring representative samples. MSY Consulting runs feasibility measurements, plans the calibration against your reference method, and trains your team until the measurement is part of your routine.

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Contact

Let's talk about your application

Send an email describing your instrument and your application, and you will get a reply.

contact@msyconsulting.eu

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