NMR的冷冻探针

Apart from DNP the development of CryoProbes™ delivered the single largest increase in NMR sensitivity in the last few decades. This jump in sensitivity enables scientists to observe sample amounts that were considered too small only a few years ago.

Bruker BioSpin offers two product lines of cryogenic probe technologies: one based on a closed cycle helium cryocooler (CryoProbe), the other on an open cycle liquid nitrogen cooling system (CryoProbe Prodigy). While the detection coil temperature is considerably lower for the first case, the working principle is identical for both:

• The transmit/receive coils as well as the tuning and matching circuits are maintained at a very low temperature in order to reduce the noise contributions resulting from the random thermal motion of electrons in the conductors (Johnson-Nyquist noise). The resistivity of pure metals decreases further with lower temperature, which additionally reduces the noise. Preamplifier, filters and transmit-receive-switch are also cooled in order to improve the noise figure of the electronic components.
  
  
• The reduced noise contribution by probe and electronics yields a signal-to-noise-ratio enhancement of up to a factor of five for a CryoProbe and two to three for a CryoProbe Prodigy compared to an equivalent room temperature probe. This can easily translate into an order of magnitude higher throughput.

For both platforms automatic cool-down, warm-up and timer features are controlled by the CryoPlatform resp. The Prodigy Control Unit and the associated CryoPanel™ software. The one button operation of cool-down and warm-up are completed in ~4 hours for the CryoPlatform. For the Prodigy platform the corresponding durations are ~2 hours. A timer feature enables the execution of these functions at any predefined time, whether or not the user is attending. Once in the cold state a Cryoprobe can be used just like a conventional probe. The cooling systems control all functions and guarantee excellent stability during both short and long term experiments.

尽管距离冷冻探针的冷区只有大约一毫米，但样品在周围的用户定义温度下稳定，或者取决于探针选项，在-40°C和 +135°C之间的温度下。冷冻探针中的样品处理与室温高分辨率探针相同。所有低温探针都可以配备ATM-UNIT，以自动调整和匹配所有探针通道。对于自动样品，更改Bruker Biospin提供了不同的解决方案，从高通量筛选，隔夜自动化到多用户开放访问（SampleJet，SampleXpress，Samplecase）。对于流量方法，冷冻探针与BEST™流入量配件兼容，也可以与LC-NMR结合使用。使用Cryofit™，可以将冷冻探针从管操作转换为流量方法。