SepNMR Detail
Plumbing Scheme
Using the plumbing scheme detailed in Figure 1, the SepNMR system accomplishes the isolation, concentration and solvent exchange of trace components in mixtures. Valve 1 set to load diverting flow to waste when no peak of interest is observed in the first dimension of chromatography. Valve 1 is switched to inject when the desired peak is detected in the first dimension with the material being directed into the sample loop on Valve 1. After the peak is captured in the loop, it is moved to the trap by switching Valve 1 back to load, Valve 2 to to load using pump C. Pump C output is directed through a flow splitter where a low flow stream pushes the sample from the loop and is combined and mixed with a high flow stream and loaded onto the the trap on Valve 2. This scenario can be repeated (we've done it 4 times with good recovery) to accumulate even lower abundance material from mixtures. Once sufficient material is accumulated the sample is eluted from the trap by setting Valve 2 and the external valveto inject intruducing a stream of gas (He) to dry the trap removing residual solvent. Finally, the sample is eluted from the trap with pump D and Valve 2 set to inject and the external valve to load. The sample elutes out of Valve 2, port 4.
Figure 1
Efficient Peak Trapping
In order to capture the of the sample from the loop on Valve 1 on the trap on Valve 2, the organic content of the peak collected in the sample loop must be reduced. This is accomplished by using Pump C filled with 100% D2O with a split flow delivery. The computer controlled splitter valve of the MS4 allows for precise and reproducible dilutions of the collected peak in the loop. The high flow portion is delivered into the mixing station (see Figure 1) and the low flow pushes the captured peak from the first chromatographic dimension. Figure 2 shows the mixing profile of several splitter valve settings. These data were generated by loading the sample loop with a fixed amount of a test compound and monitoring the UV post split flow recombination and mixing (see Figure 1). The figure shows the degree of sample dilution from least peak dilution to most peak dilution: light blue (R1), magenta (R2), green (R3) and dark blue (R4).
Figure 2
The loop elution profile affected by flow rate, split ratio and loop volume. The flow split ratio can be modified by either changing the relative flow resistance between the high and low flow sides (change the length and/or tubing diameter) or by adjusting the setting of the flow splitter (see figure 1).
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