| Popis: |
A detailed analysis of phase-cycling procedures in COSY 2D NMR experiments is described. It is shown that a phase-cycling scheme, originally proposed by Rinaldi and Iverson (J. Magn. Reson. 92, 528, 1991) can be used to eliminate all longitudinal MQ artifacts of even order Δm = 0, ±2, ±4, etc., exactly. In addition, it is demonstrated that in rotation-sensitive experiments, designed to produce an N-type Δm = −1 peak, the odd-order multiple-quantum artifact Δm = +3 appears as a P-type peak. Thus rotation-sensitive COSY experiments can be used to discriminate against Δm = 0, ±2, ±3, and ±4 MQ artifacts. The theoretical results are confirmed experimentally, using a nominally isolated spin- 1 2 ensemble, which can be made to generate MQ artifacts as high as Δm = ±5. |
