User manual Bruker DPX200 NMR spectrometer

Transcription

1 User manual Bruker DPX200 NMR spectrometer Insert the NMR tube in the spinner in such a way that the bottom of the tube reaches the grey disc at the bottom of the spinnerholder. Make sure that the NMR tubes are clean on the outside in order to prevent the inside of the probe from getting filthy. Spinner On/Off Lift On/Off Lock Gain Spinning Rate Done Z Z 2 Z 3 Fine A Draainknop Figure 1 BSMS keyboard Activate the lift with the Lift on/off button (see Figure 1) and wait until you can hear a strong airflow. Insert the spinner with the sample into the shaft of the magnet and press Lift on/off again, the tube will now be transported into the magnet. Wait until the sign down switches from red to green and then turn on the spinner by pressing Spinner on/off. By pressing spinning rate (Figure 1) the spinning frequency can be checked; it should read 18Hz. In order to open a new dataset you type edc in the command line of the xwinnmr window (Figure 3). A dialoguebox appears in which you can enter the name and number of the measurement (Figure 2). Choose an appropriate name (e.g. your login name, which is a unique name), and then enter a sequential number in the field expno. In the field procno it should generally read 1. After the edc command has been given by clicking save all experimental parameters of the old dataset, in which you gave the edc command, will be taken over in the new measurement. Most convenient is to always use the same name and have the expno increase by 1 for every new experiment. In this way back-ups are easily made and spectra are easy to retrieve. 1

2 Figure 2 edc window Now the spectrometer has to be locked on the deuterium signal of the solvent. Enter Lock (or l) in the command line of the xwinnmr window (Figure 3). Figure 3 Xwinnmr window A list with solvents appears in which you have to select the solvent you are using. The spectrometer will now fully automatically lock onto the solvent deuterium signal. Below in the command line after a while the message check lock shift finished appears which means the spectrometer has succesfully locked. Next the spectrometer needs to be shimmed. First you need to activate the lock window by selecting lock [lockdisp] in the drop-down menu windows. (See Figure 4) 2

3 Figure 4 Lock window Press the Z button (Figure 1) and turn the turning knob A until the lock signal (in the lock display) ceases to move upward. If the lock signal runs out of the window press lock gain and turn back knob A until the lock signal is back in the middle of the lock display. Now press Z 2 and again turn knob A until the lock signal ceases to to move upward. The same procedure needs to be carried out for Z 3 and then iteratively Z, Z 2 and Z 3 need to be adjusted until no more improvement of the lock signal is observed. If the signal does not respond or only a little you could try switching of te fine mode to see if the response improves (for Z 3 this is usually necessary). It s important to thoroughly shim the spectrometer in order to get an optimal measurement. If the lock signal shows a lot of noise and does not respond to changing Z, Z 2 and Z 3 a standard shimfile with standard shimming parameters can be loaded. This is done by entering rsh inverseprobe in the xwinnmr command line. After having loaded the shimfile the spectrometer can be further shimmed as described above. 3

4 Figure 5 edpar window In order to manually alter the acquisition parameters the dialogue box for the acquisition parameters (Figure 5) needs to be activated by typing eda in the command line. In this dialogue box all the acquisition parameters can be entered. Explanation of the most important parameters; PULSPROG In this field the NMR pulse program used is indicated. Usually it should read zg. The pulse program will be activated when zg is entered in the command line. AQ_mod Shows the acquisition mode (usually qsim, which is a quadrature detection method). TD Here the amount of data points for the FID (free induction decay) is entered. Typically 16k is entered here. NS Number of scans. This should be dividable by 4. DS Number of dummy scans. These are used to reach an equilibrium in the sample before starting the actual measurement. D array Array containing the values for d1-d31. These are delays the pulse program uses. D1 is the relaxation delay. P array Array containing the values for p1-p31. These are pulse lengths the pulse program uses. P1 is the 90 o pulse. SW, SWH Sweepwidth of the spectrum. SW is given in ppm. SWH is the sweepwidth in Hertz. AQ Acquisition time (seconds). NUC1 O1 PROSOL In this field the nucleus to be measured is indicated. (Usually H). This is the offset frequency in Hz (O1) or in ppm (O1P). O1 is in the middle of the spectrum. Example: If O1P is 5 ppm and the Sweepwidth (SW) is 12 ppm the spectrum will range from 1 to 11 ppm. This should be set to true. The software will adjust the pulse length and power to the specifications of the probe. 4

5 Close the acquisition parameter dialogue box by clicking save. Now the receiver gain has to be determined. The receiver gain function adjusts the amplitude of the FID before it is sent to the digitizer. An optimal amplitude must be found as to have a maximal FID amplitude without overloading the digitizer. (Overloading the digitizer could lead to artefacts in the spectrum). The most convenient way to determine the receiver gain is by typing rga (receiver gain automatic) in the command line. The receiver gain is adjusted automatically and after a few pulses the message rga finished appears. Now the measurement can be started by typing zg in the command line. The measurement is started and the expected measuring time is displayed below the command line. To see the progress of the measurement the FID and the experiment counter can be viewed in the acquisition mode. This acquisition mode can be activated by selecting acquire at the top of the xwinnmr window or by typing a in the command line. After the measurement is completed the size si of the processed dataset has to be checked. This is done by typing si in the command line. The value for si should be half of TD; si=1/2*td. The spectrum can now be viewed by typing ft (Fourier transform) in the command line. The spectrum is now shown but it usually is still out of phase. A Figure 6 Phase window In order to correct the phase of the spectrum you have to activate the phase window (see Figure 6, click phase ). In the phase window first you need to click biggest. A dotted line will appear in the spectrum which indicates the biggest peak. (Figure 6A) Then by clicking PH0 and by dragging the mouse across the PH0 button the phase of the biggest peak can be adjusted. Subsequently with PH1 the phase of peaks far away 5

6 from the biggest peak can be adjusted in a similar manner. After having adjusted the phase press return. In the dialogue box that now appears choose save&return. Further manipulations as well as printing the spectra can be done behind a workstation at the department. In order to take the sample out of the spectrometer first switch off the lock function and the spinner on the console and then activate the lift. After having taken out the sample switch off the lift and place the spinner back in the spinnerholder. The commands in a nutshell: -press lift on/off -Insert the spinner with the NMR tube in the shaft of the magnet and press lift on/off again. -type l or lock in the command line -select the solvent from the solvent list -shim the spectrometer by iteratively adjusting Z, Z 2 and Z 3. -type eda and insert or adjust the acquisition parameters -type rga to adjust the receiver gain. -type zg to start the measurement -after having checked si (command: si) enter ft to obtain the spectrum -Adjust the phase by click/dragging the PH0 and PH1 buttons in the phase window. -switch off the lock function and the spinner and then activate the lift to take out the sample. -switch off the lift and put the spinner back. Standard parameters If you want to start from scratch with the standard parameters you can use the rpar command to load a standard parameter file. To do this type rpar anorstd1h ( 1 H measurement) or rpar anorstd13c ( 13 C measurement) in the command line. 6