User manual EUTECH INSTRUMENTS AMMONIA GAS

[. . . ] Instruction Manual Ammonia Gas-sensing Electrode EUTECH INSTRUMENTS PTE LTD. AMMONIA GAS-SENSING ELECTRODE INSTRUCTION MANUAL GENERAL INSTRUCTIONS Introduction Eutech Instruments Ammonia Gas-Sensing Electrode is used to quickly, simply, accurately, and economically measure dissolved ammonia in aqueous solutions. It can also be used to measure the ammonium ion after conversion to ammonia or organic nitrogen from Kjeldahl digestion of the sample. The measurement is not affected by sample color or turbidity and samples do not need to be distilled. Interference from anions, cations, and dissolved species, other than volatile amines, do not occur. [. . . ] Lower the electrode tip into the solution. Adjust the meter to the concentration of the ammonia standard and fix the value in the memory according to the meter manufacturer's instructions after stabilization of the reading. For low level measurements, place the rinsed, dried electrodes into a solution containing 100 ml of distilled water and 1 ml of ISA. After stabilization, fix the blank value in the meter according to the meter manufacturer's instructions. Place 100 ml of the sample and 1 ml of ISA in a 150 ml beaker. Place the beaker on the magnetic stirrer and begin stirring. When the reading has stabilized, read the concentration directly from the meter display. The calibration should be checked every 2 hours. Assuming no change in ambient temperature, place the electrode tip in the first ammonia standard. After the reading has stabilized, compare it to the original reading in step 3 above. A reading differing by more than 0. 5 units or a change in ambient temperature will necessitate the repetition of steps 28 above. The meter should be re-calibrated daily. 5. 6. 7. 8. 9. 10. 11. Low Level Ammonia Determination (using a pH/mV meter) As the concentration of ammonia decreases, the rate of ammonia diffusion through the membrane is slow, the rate of equilibrium between the ammonium in the internal filling solution and ammonia is slow, and thus the response time increases. If the internal filling solution is diluted with ammoniafree distilled water (1:10), response at low levels can improve. Measurements can be speeded up by first placing the electrode tip in an ammonia-free pH 4 buffer, then into the sample. Always keep standards and samples covered. Work with large solution volumes to minimize surface-area-tovolume ratio, thereby avoiding ammonia absorption from air. Allow 5-10 minutes for a stable reading in the pH 4 buffer or a low-level solution. Use the following low level ammonia measurement procedure in the non-linear portion of the calibration curve. (See Figure 1. ) This procedure is used for ammonia samples containing less than 1. 0x10-5M ammonia. 7 Instruction Manual Ammonia Gas-sensing Electrode 1. Measure out 100 ml of a pH 4 buffer solution, add it to a 150 ml beaker, place the beaker on the magnetic stirrer, and begin stirring. Place the electrode tip in the solution for about 3 minutes. By serial dilution, prepare a 10-2M or 100 ppm ammonia standard by diluting the 0. 1M or 1, 000 ppm standard solution. [. . . ] See Sample Requirements and Interference. 14 Instruction Manual Ammonia Gas-sensing Electrode Technique Be sure that the electrode's limit of detection has not been exceeded. Be sure that the analysis method is clearly understood and is compatible with the sample. Reread the sections GENERAL PREPARATION and ELECTRODE CHARACTERISTICS. If trouble still persists, call Eutech Instruments Pte Ltd. [. . . ]