BASIC RULES OF USAGE, OLIS DSM-20 CD Management The instrument is currently managed by the Analytical Biophysics Core Facility.

Transcription

1 Olis DSM-20 instructrions and rules p. 1 BASIC RULES OF USAGE, OLIS DSM-20 CD Management The instrument is currently managed by the Analytical Biophysics Core Facility. Signup On a first-come, first-served basis for approved users. Signup is online via the scheduling website: Please be courteous and do not sign up for more than two days in a row without making special arrangements. Usage fees This instrument currently has no formal usage fees. However, each laboratory may be asked to purchase nitrogen tanks periodically, depending upon how many hours of usage are logged by members of the lab. Currently, one nitrogen tank lasts about 50 hrs of instrument time and costs about $100. Use of cells See sheet on cells. We have a basic set of cells for common usage, but repeat users and users with special applications will want to buy their own. Damage to instrument The CD is not a toy and can be severely damaged if used improperly. Users who, through negligence, damage the CD (for example due to ozone damage caused by nitrogen flow failure) will pay for repairs. In the case of damage to optics by ozone, be aware that this may run in the $10,000 range. THE USER IS ALWAYS RESPONSIBLE FOR ENSURING NITROGEN FLOW

2 Olis DSM-20 instructrions and rules p. 2 THROUGH THE INSTRUMENT WHILE THE LAMP IS OPERATING. THERE IS NEVER, REPEAT NEVER, AN EXCUSE FOR NITROGEN FLOW FAILURE ON YOUR WATCH.

3 Olis DSM-20 instructrions and rules p. 3 OLIS DSM-20 CD STARTUP 1. Purge the system with nitrogen for 15 minutes. Start a flow of at least 8 lpm (liters per minute) nitrogen gas through the lamp, monochromator and sample chambers. Refer to separate instructions on managing nitrogen flow and its importance. At least 8 lpm ABSOLUTELY MUST be kept up AT ALL TIMES during CD operation, as well as 15 min before lamp firing and after shutoff. 2. Make sure the main power strip switch is off, so that the computer and other electronic devices do not get damaged by power surges when the lamp is fired. 3. Turn on the lamp cooling box (gray box behind computer monitor). 4. Press the power button for the lamp power supply. 5. Press and hold the ignite button on the lamp power supply, until the lamp ignites. This should take no more than 2 to 3 seconds. You will know the lamp has ignited when the blue light on top of the lamp chamber comes on. Initial lamp wattage after firing will be about 135 watts. Over 5 minutes or so, this will rise to ~150 watts and then stabilize. 6. Turn on the main power strip switch. This will automatically turn on the computer monitor, instrument controller, the PEM, the sample chamber peltier controller, and the sample chamber peltier cooling box. It will also allow the computer to be started. If you are using the autotitrator, turn on the titrator power strip as well. 7. Turn on the computer, and open the Global Works program. 8. Select the Data Collection tab, and double click on DSM-20. The spectrophotometer will now initialize and calibrate. 9. Once lamp power has stabilized at about 150 watts, measure and RECORD IN THE LOG BOOK the PMT HV values at 200 nm with no cell or cell holder in place, and with 8-10 lpm nitrogen flow. This is how we monitor the health of the lamp and optics. Under the Live Display tab, set current wavelength to 200 nm, and click on Live Mode (MAKING SURE THAT THE SAMPLE CHAMBER LID IS CLOSED--see the Five Commandments). The instrument should then automatically set the PMT HV to maintain appropriate current in the PMT, based on how much light is impinging upon the PMT. Record PMT HV values for both red and blue PMTs. 10. Let the spectrophotometer warm up about 60 minutes. The spectrophotometer can be used immediately, but we have found that the baseline dichroism may still drift by several millidegrees during the first minutes following startup. If you do not wait for about 60 min, you may find that this drift affects accurate baseline subtraction. OLIS DSM-20 CD SHUTDOWN 1. Turn off the lamp power supply. This will shut the lampitself off. You will now need to leave the lamp cooling box and nitrogen on for 15 minutes (see step 5)

4 Olis DSM-20 instructrions and rules p Make sure all data files are saved (assuming you want to save them), exit the Global Works Program, and shut down the computer. 3. Turn off the main power strip. This will shut down the computer monitor, instrument controller, the PEM, the sample chamber peltier controller, and the sample chamber peltier cooling box. If you are using the autotitrator, shut off the titrator power strip at this time as well. 4. If you are using any of the common cells, make sure they are cleaned and stored with 25% ethanol/ 1 M HCl solution in them minutes after the lamp was shut off, turn off the nitrogen flow, and switch off the lamp cooling box.

5 Olis DSM-20 instructrions and rules p. 5 Five Commandments of the DSM 20 CD 1. Thou shalt not operate the CD without at least 8 liters per minute nitrogen flow through all chambers. 2. Thou shalt be vigilant, periodically monitoring the nitrogen flow, tank pressure, and tank fill level to make sure that commandment 1 is not violated. 3. Thou shalt not ignite the lamp while any other components (computer, monitor, temperature and instrument controllers, in particular) are on. 4. Thou shalt not steal the CD cells, and shalt place the CD cells in cleaning solution when finished with them. 5. Thou shalt not open the sample compartment while in live mode, and shalt leave the lid on at all times except when directly removing or replacing a sample. LIQUID N2 TANKS AND THE OLIS DSM-20 CD: NEVER EVER EVER EVER EVER RUN THE CD WITHOUT NITROGEN GAS FLOW!

6 Olis DSM-20 instructrions and rules p. 6 LEVEL of liquid nitrogen in the tank (EMPTY vs. FULL): Before starting, check the empty/full gauge on the top of the tank, to see how full the tank is. Some tanks have a vertical gauge with a yellow ring, while others have a needle gauge, as on a speedometer. Sometimes either type of gauge will stick and read a falsely high level of nitrogen--so tap the gauge several times before reading. If the tank is more than about a third full, you should be fine for whatever experiments you want to do for the day. If it is down around a quarter you are going to need to frequently monitor nitrogen pressure during your experiments (see below). You should also alert Will Anderson in thecordes lab that the tank is low so that another may be ordered. PRESSURE of nitrogen in the tank: The 180 liter tanks are equipped with a gauge on the side that reads the tank pressure (this is NOT the same thing as how full the tank is!). In order to maintain adequate flow to the machine, we maintain the tank pressure at 50 psi or higher. Some tanks will naturally build pressure above this over time and maintain it, while others build pressure more slowly and will have more trouble maintaining it. This varies from tank to tank. If the tank pressure is reading less than 50 psi, you need to turn on the pressure builder (see below) to get the pressure up high enough before you begin. You also need to monitor the tank pressure periodically during your work to make sure it is not falling below 50 psi. When a tank is starting to run low, it may have trouble maintaining pressure. To some extent this can be compensated with the pressure builder, but eventually this won't work, and if you can't keep the pressure up, you will need to shut the lamp off and quit until a new tank can be obtained (see below). FLOW of nitrogen to the CD: The green gas use valve on the tank is connected to the instrument (and to the flow gauge on the wall above the instrument) via a regulator and a length of copper tubing. The flow gauge on the instrument has three parts that allow separate regulation of flow to the lamp chamber, the monochromator chamber and the sample chamber. The lamp chamber and monochromator chamber are the most critical, while the sample chamber is less critical. The knobs marked "H" on each gauge can be used to separately adjust flow. However, I never touch these except perhaps to turn the sample chamber up or down relative to the other two. Instead, I regulate the overall flow by adjusting the tank regulator until I achieve the desired flow through the three compartments. This flow should be read at the center of the black balls on the gauges. A minimal flow of 8 lpm (liters of gas per minute) is required, and for very far uv work 16 lpm is recommended. Opening the green gas use valve a half-turn or so will start flow. The overall flow from the tank may then be adjusted by the metal regulator valve (which is a rotating cylindrical brass bar). If you rotate the bar clockwise the flow will increase.

7 Olis DSM-20 instructrions and rules p. 7 CELLS FOR THE OLIS DSM-20 CD Care and cleaning of common cells: Before and after use, standard cylindrical cells should be rinsed repeatedly with water and then ethanol using the vacuum cell washer at the rear of the Cordes lab. A clipped pasteur pipet can be used as an adaptor to fit the cell neck to the washer apparatus. Between uses we store cells filled with a solution of 1 M HCl in 25% ethanol, a bottle of which is kept on the prep bench. To avoid fingerprints etc, cells should not be handled with bare hands/fingers. Nor should the windows be rubbed with anything except Fisher lens paper. Otherwise they may get scratched. Never allow a cell to dry with a sample in it (this includes putting a cell with sample on a vacuum apparatus without immediate rinsing)! Reputable quartz cell suppliers: Hellma website: Starna website: 1. For the standard cylindrical cell holder: For standard cylindrical cells for the CD, we typically use Hellma #120-QS, in the pathlengths listed below. A set of cells in these sizes is available for general use, but you may be asked to replace a general use cell should you break it. If your lab is doing more than a few experiments, you should buy your own set. pathlength sample volume required 1 mm 280 ul 2 mm 560 ul 5 mm 1400 ul 10 mm 2800 ul 2. For the short-path cell holder: For short-path cylindrical cells for the CD, we typically use Hellma # QS. The pathlengths listed below are available from the Hellma website The Cordes lab has a 0.1 mm cell which may be used under special arrangement, but in general you will need to buy your own short-path cells. pathlength sample volume required 0.1 mm160 ul 0.2 mm170 ul 0.5 mm210 ul 1 mm 280 ul 5 mm 850 ul 3. For the titrator cell holder: This cell holder is like the cylindrical cell holder, but has a thicker back and also has a hole in the bottom where the titrator cell connects to its tubing. 1 mm autotitrator cells have an open neck at the top and a threaded neck at the bottom. We have one cell available for general use. If your lab is doing more than a few experiments, you should buy your own titrator cell. These can be obtained directly from Olis corporation, using Starna catalog #37-Q-1/Q844. They might also be obtainable directly from Starna.