1. Purpose

Resolution is the ability of an NMR spectrometer to observe resonance lines that are very close together as separate lines. This ability is measured by the line-width at half-height, Δν_1/2, which is usually greater than the natural line-width. The experimental line-width Δν_1/2 is determined by the homogeneity of the magnetic field. The traditional test for ¹H NMR resolution is ortho-dichlorobenzene (ODCB) which gives an AA′BB′ pattern. Usually the eighth line from the left is used for resolution measurement. Although the manufacturers have abandoned this test as a standard routine on delivery of a new instrument, we feel that this test is still of great value and tells a lot about the performance of the instrument and the operator.

2. Literature

T. D. W. Claridge, High-Resolution NMR Techniques in Organic Chemistry, Pergamon, Oxford, 1999, 87–94.
V. W. Miner, W. W. Conover, The Shimming of High Resolution NMR Magnets, 1997, http://www.acornnmr.com.
C. Anklin, D. v. Ow, H. Ruegger, Standard Test Procedures for Supercon Systems, Spectrospin AG, Fällanden, 1988.

3. Pulse Scheme and Phase Cycle

Single-pulse proton NMR sequence and phase cycle

4. Acquisition

Time requirement: approx. 1 h, very dependent on the skill of the operator and the state of the system.

Sample: 10% ortho-dichlorobenzene in [D₆]acetone, degassed and sealed.