Chapter 3. Small-volume NMR: Microprobes and Cryoprobes

NMR spectroscopy is not the most sensitive of analytical techniques, and increasing the sensitivity has been a goal since the inception of the method. The most common way to analyze samples by NMR is to study them in a 5 mm tube in a 5 mm probe. For very small quantities this is not the optimal approach. Natural products are typically reasonably soluble but only available in small quantities. Probes with smaller diameters enhance the mass sensitivity to a point where quantities of 1 nmol or less can be studied. The optimal approach for such samples is to use tubes and probes that are optimized for smaller volumes and to utilize probes where the rf coil and electronics have been cooled to very low temperatures to enhance the sensitivity. This chapter present the technology and applications of such probes.