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Flame Atomic Absorption Spectroscopy (FAAS) and the Operation of the Pyc Unicam SP 9 Series AAS ACTIVATING THE INSTRUMENT (refer to panel schematic) 1. Turn on the instrument with the on/off switch. 2. D2 energy switch should be in sample position (i.e. out). (D2 = deuterium background correction lamp) 3. The FES /AAS switch should be set to AAS (i.e. out). (FES = flame emission spectrophotometry; AAS = atomic absorption spectrophotometry) 4. The BC switch and D2 Lamp switch should be off (i.e. out). (BC = background correction mode) 5. Set the damping switch to 0.1 sec (tentative position). 6. AUTOZERO switch will be used in conjunction with calibration. 7. The gain control should be turned down for now. 8. The scale expansion control will have no effect in our tests. 9. The curvature control must be turned fully counterclockwise. 10. Set the CONC / ABS switch to absorbance position (i.e. out). PREPARATION OF LAMPS FOR USE 1. The alignment of the hollow cathode lamps will be demonstrated in lab. 2. Please sure the appropriate HCL is installed and check the turret position. The power supply for desired lamp should be set to either the current indicated in the chart inside the door or the maximum current indicated on the lamp label whichever is lower. This option is important for a multielement, use the “ma” current stated on the HCL. This procedure extends the HCL life. 3. Use the dial at the top of the instrument to set the desired wavelength in the window marked "nm" (the wavelengths are listed inside the door 4. Set the bandpass to 1 nm (tentative position; may change to increase or decrease sensitivity) 5. Turn up the gain control until the energy meter starts to climb, then slowly move the wavelength setting up and down to '9peak" the wavelength. If the energy moves toward the 100 mark, turn down the gain and continue to adjust the wavelength until you are satisfied that you have settled on the peak of your desired wavelength. Set the energy in the blue region. 6. Set the damping to 2.0 sec. 1 FLAME IGNITION Note: There is a slight (very slight) chance of explosion during the lighting of the flame. If the instructions here are followed, the gas interlocks and microprocessors in the machine should prohibit that undesirable occurrence from taking place. 1. To prevent a backflash, check that there is water in the plastic trap on the left side of the machine. To remove toxic gases, check to see that the fume hood over the burner is turned on. 2. Turn on the air source and set to 30 psi. 3. Turn on the main acetylene valve and adjust the regulator to about 12 psi. 4. The PRESSURE SENSOR lamp should be out. If it is on, get help. 5. Press the AIR / FUEL CHECK switch. If the PRESSURE SENSOR lamp goes out, increase the fuel pressure slightly. Release the MR/FUEL CHECK switch. 6. Press and hold the AIR / FUEL CHECK switch and confirm that the air flow meter reads 26 to 33 mm and adjust the fuel flow rate to 20 mm. 7. At this time the START switch should be illuminated. Press the START switch for a few seconds until the flame ignites. TAKING MEASUREMENTS MAKING A CALIBRATION CURVE The readouts from this AA all come by way of the SP 9 microcomputer, which sits to the right of the AAS. This computer will come on when the main power to the instrument is turned on. To use the instrument in any manner requires some simple programming of the computer (really just hitting a few keys). I. Set the INT / FIT / AREA switch to INT (integrate). 2. Push the PARAM switch. Notice the red light, which came “on” on the panel. Keep pushing the PARAM switch until the light above TIME is on. Enter a time of 4 seconds by pushing the 4 on the keypad. Then push the LOAD key. 3. Set the ABS / CONC switch on the main console to ABS (i.e. out). Make sure the red light above the letters ” on "con the computer is out. If it is on, press the conc button on the computer to turn it off. 4. Aspirate double distilled water and press the AUTOZERO button on the main console. 5. Aspirate a standard or sample. Pressing the RUN button will cause the meter to read out the absorbance, averaged over a 4 second period. 6. Use standards to collect absorbance versus concentration data so that a calibration curve can be plotted over the region of interest (i.e. the region where you expect your data to be) 2 USING THE SYSTEM WITH THE CALIBTATION CURVE HELD IN THE COMPUTER The computer allows the use of sets of calibration standards in certain fixed ratios. We will use internal calibration program #2 which requires a blank (double distilled or ultrapure water) and two standards in a 5:10 ratio. The blank should be a reagent or matrix blank. [What is ppm? mg / L? mg / mL?] For example, if we were measuring unknowns in the 4 mg / L range, we might choose standards of 5 mg / L and 10. mg / L. If we expected our samples to be below 1 mg / L, we might choose standards of 0.5 mg / L and 1.0 mg / L. In any case, we must tell the computer what we are doing and then carry out the calibration in a very set pattern of steps. 1. Set the ABS / CONC switch on the main console to CONC. 2. Select TIME. Set to 4 sec. Press LOAD key. 3. Select STD. Press CLEAR. Set to the concentration of the highest standard to be used (e.g. 10.00 mg / L). Press the LOAD key 4. Select PROG. Set to 2. Press the LOAD key. Proceed as follows: 5. Aspirate a blank solution and press AUTOZERO on the main console. 6. Press the CONC key on the computer. 7. Aspirate the 1st standard (5 mg / L in this example), press the STD key, press the number 1 key and initiate the calibration by pressing the RUN key. 8. Aspirate the second standard (here, 10 mg / L), press the STD key, press the number 2 key, and calibrate by pushing the RUN key. 9. Aspirating a sample and pushing the RUN key will cause the concentration of the sample to be displayed and printed. 10. Repeat step 9 for all samples. SHUTTING OFF THE SYSTEM 1. Push the FLAME OFF button and shut off the air and fuel regulators. 2. Turn the lamp power supplies off. 3. Turn off the main machine power. 4. Cover the instrument with the plastic cover, otherwise dirt and dust will eventually clog the aspirator. 3
"AAS Pye Unicam SP9"