High-Resolution Microcoil ¹ H-NMR for Mass-Limited, Nanoliter-Volume Samples

Abstract

1800" to 2000'C. The sarnples stayed at that temperature for 10 to 20 m n before belng quenched by the cuttng off of power to the furnace. The quench rate was measured to be -500'C per second The samples were subsequently decompressed at a rate of 2 to 3 GPaihour. 17. NMR spectra descrlbed here were collected with a Varan Unity spectrometer operating at 9 L T was a MAS probe from Doty Scentfic (Coumba, SC), wlth 3.5-mm rotors commonly splnning at 9.3 kHz (unless otherwise specifed). To make 27AI analyss as straightforward as possible, a small tip angle ( i n I 6 ) was used in all cases. ' "a and "Al NMR was done w t h the use of delay tmes on the order of 1 s, wlth a spectral band width of 2 MHz. For2"S1 NMR. a smaller spectral band width was used because of the mited chemical shft range in Si; however much longer delay tlmes were used (70 s) because o i the possibility of havng long relaxaton tlmesfor Si speces even w t h a small paramagnetic dopant (Gd20,) [A. Abragam. Principles of Nuclear Magnetism (Oxford Unv. Press, New York, 1961)). We subtracted a 27Al background from the probe by colectng data on an empty rotor under condtions identical to those under whlch the glass samples were run. There was no probe background ~n the 23Na and 23S1 spectra; however, the Si3N, rotors gave a characteristc resonance at -L8.8 ppm relative to tetramethyl silane at 0 ppm with spinnlng sdebands in the sllcon NMR Thls was used as an internal chemical shift cabratlon for '%i NMR. To reference the chemcal sh~ft of ' % l a and "AI, a liquid sample of 1 M NaC (0 ppm) and 1 M ACI, (0 ppm) was run before each spectrum, respectvely. 18. We prepared the ?9S~enriched Ab5,NTS5, by fusing sto~chometr~c amounts of 92%-abeed 29Si0, glass (Cambridge Isotope Laboratory. Andover, MA) with sodium carbonate (Na,CO,), alumnum oxlde (A120s). and 0.1 weght percent gadolnium oxide (Gd20,) at 1200'C for 2 hours. Glass was formed upon removal of the Pt crucble containing the mixed iqud components from the furnace. We did not chemically analyze the sample because of the expense of labeled material and the proven nature of the synthesis process. Gd20s was added to shorten the spin-lattlce relaation time of SI. This sample. along wlth unlabeled glass made under the same conditions, was then sealed In Pt capsules for use in the hlgh-pressure multl-anvl quenchng descrlbed in (76).

Development of a Functionalized Xenon Biosensor

“…This does not necessitate the acquisition of a functionalized xenon spectrum. Here we introduce a method, Figure 8a, that measures changes in the Figure 8b shows the application of the indirect assay (n = 5) to a solution containing 1.5 mM of peptide-derivatized cryptophane-A cage (17). The decrease in the integrated intensity of the solution peak by 60% reflects the presence the cryptophane-bound xenon.…”

“…Steady progress is being made to incorporate NMR analysis into high-throughput and combinatorial chemistry applications. [13][14][15][16][17][18] Utilization of conventional NMR for high-throughput biosensor applications may be limited by the intrinsically low sensitivity and the complexity of spectra obtained from biomolecules and mixtures. Laser-polarization 19 of 129 Xe offers an increase in signal-tonoise by several orders of magnitude relative to the equilibrium nuclear-spin polarizations measured in normal NMR experiments.…”

An optimised detector for in-situ high-resolution NMR in microfluidic devices

“…As is well known, miniaturised NMR detectors benefit from a favorable scaling of mass sensitivity (the absolute number of spins required for a detectable signal) with probe volume [13]. This had led to flow probes with very high sensitivity based on micro-solenoid coils wound around glass capillaries.…”

Structural shimming for high-resolution nuclear magnetic resonance spectroscopy in lab-on-a-chip devices

“…Micro-fabricated receiver structures can be directly integrated into lab-on-achip devices, and systems with limits of detection as low as 0.025 nmol · s 1/2 have been reported in the literature 5 . Different detector geometries and microfabrication strategies for microfluidic NMR have been described, including solenoids [6][7][8] , planar spirals [9][10][11][12] , and microslots/micro striplines [13][14][15][16] . While these approaches yield similar sensitivity for a given probe volume, resolution in the vicinity of 0.01 ppm has only been achieved with very simple, linear fluidic geometries (capillar- ies).…”