Picotrace system: Temperature programs

The temperature programs are set up, selected, started, and stopped using buttons on the front panel of the controller box. The programs described below have been put in to the system, so all you have to do is select and start them.

This illustration shows the front panel of the controller box. The box stores and runs temperature programs for the hot plate, and it displays the temperature of the hot plate or, if you press the select button 7, the sample vessel temperature. To write a program, you will have to use the the displays and buttons described below shown in red text. Don't try to write a program without learning how.

Temperature programs all assume the hood is turned off, the sash is half open, and the rectangular Teflon jacket and wind breaks are in place. Note, condensed acid vapors may cause damage to the digestion vessel block. The hold instructions in the programs below keep the blocks hot until you come along and turn them off. This avoids condensation, which might occur if they cooled to room temperature without removing the vessels. The moral is to keep the vessel block warm until you are ready to process the samples. You must, however, process them quickly; don't digest samples just so they can hang out in the expensive equipment forever!

Cleaning program: #1

This program is set up to clean the sample vessels if the chance of cross contamination is large. New vessels and vessels used to dissolve mineral separates (e.g., zircon) should probably be cleaned prior to use.

1. Turn the control box on.
2. After it boots, press the prog button #4 until "1" is shown in display #2.
3. Press the start/stop button #5, then the big green start button. The program should commence running.
4. Be sure the thermocouple on the white wire is in one of the block thermocouple wells.

Dissolution program: #2

This program is set up to dissolve samples containing radiation damaged zircon that can be dissolved in four days.

1. Turn the control box on.
2. After it boots, press the prog button #4 until "2" is shown in display #2.
3. Press the start/stop button #5, then the big green start button. The program should commence running.
4. Be sure the thermocouple on the white wire is in one of the block thermocouple wells.

Evaporation program: #4

This program is set up to evaporate the samples to dryness overnight, without boiling or hydrated salt decrepitation. Temperature in the digestion vessels ramps slowly toward the boiling temperature. Boiling should not actually be reached for 50% HF (108°C) or HNO3 (120°C), especially considering the dissolved salts in most of the vessels. Evaporation is usually complete overnight.

1. Turn the control box on.
2. After it boots, press the prog button #4 until "4" is shown in display #2.
3. Press the start/stop button #5, then the big green start button. The program should commence running.
4. Be sure the thermocouple on the white wire is in one of the block thermocouple wells.

Note: I have noticed considerable loss of the Re internal standard from the blank solutions (not from the dissolved rock solutions) at vessel evaporation temperatures of 120°C (hot plate ~150°C). Re is probably lost as a volatile fluoride. There seems to be no discernable Re loss at a digestion vessel temperature of 105°C. To generally avoid loss of potentially volatile trace elements, we now add internal standards during the last dissolution step (program below) and evaporate at the lowest effective temperature.

Final solution program: #5

This program puts the residual salts back into solution for analysis.

1. Turn the control box on.
2. After it boots, press the prog button #4 until "5" is shown in display #2.
3. Press the start/stop button #5, then the big green start button. The program should commence running.
4. Be sure the thermocouple on the white wire is in one of the block thermocouple wells.