Natural abundant 17 O NMR in a 1.5‐T Halbach magnet

We present mobile, low‐field 17 O NMR as a means for monitoring oxygen in liquids. Whereas oxygen is one of the most important elements, oxygen NMR is limited by a poor sensitivity related to low natural abundance and gyro‐magnetic ratio of the NMR active 17 O isotope. Here, we demonstrate 17 O NMR detection at a Larmor frequency of 8.74 MHz in a 1.5‐T Halbach neodymium magnet with a home‐built digital NMR instrument suitable for large‐scale production and in‐line monitoring applications. The proposed 17 O NMR sensor may be applied for direct, noninvasive measurements of water content in, for example, oil, manure, or food in automated quality or process control. Copyright © 2015 John Wiley & Sons, Ltd.