HIGH-RESOLUTION MICROCOIL H-1-NMR FOR MASS-LIMITED, NANOLITER-VOLUME SAMPLES

High-resolution, proton nuclear magnetic resonance (NMR) spectra of 5- nanoliter samples have been obtained with much higher mass sensitivity [signal-to-noise ratio (S/N) per micromole] than with traditional met hods. Arginine and sucrose show a mean sensitivity enhancement of 130 compared to 278-microliter samples run in a 5-millimeter tube in a con ventional, commercial probe. This can reduce data acquisition time by a factor of >16,000 or reduce the needed sample mass by a factor of ab out 130. A linewidth of 0.6 hertz was achieved on a 360-megahertz spec trometer by matching the magnetic susceptibility of the medium that su rrounds the detection cell to of the copper coil. For sucrose, the lim it of detection (defined at S/N = 3) was 19 nanograms (56 picomoles) f or a 1-minute data acquisition. This technique should prove useful wit h mass-limited samples and for use as a detector in capillary separati ons.