GR Scientific MicroTAN - Atmospheric Oxygen Titrator
Oils continually react with atmospheric oxygen to produce organic oxidation products that are acidic in nature. At ambient temperature, this reaction is very slow and has little effect upon oil conditions. At the elevated temperatures that exist within an operating engine, reaction rates are much higher. Elevated operating temperatures can generate high levels of weak organic acids. They cause increased oil viscosity and can deposit as lacquers on hot surfaces.
Total Acid Number or TAN is the measure of both th...
Total Acid Number or TAN is the measure of both the weak organic and strong inorganic acids present in oil. It is applicable to gearbox, gas engine, gas turbine and hydraulic lubricants. It is an important quality measurement of crude oil. The TAN value indicates to the crude oil refinery the potential of corrosion problems. Total Acid Number is an analytical test to determine the deterioration of lubricants. The more acidic a lubricant is, the further its degradation has proceeded. Theoretically, the Total Acid Number (TAN) is the amount of potassium hydroxide in milligrams that is needed to neutralize the acids in one gram of oil. TAN value can be measured by potentiometric titration. The sample is dissolved in toluene and propanol with a little water and titrated with alcoholic potassium hydroxide. A glass electrode and reference electrode is immersed in the sample and connected to the instrument. The meter reading (in millivolts) is plotted against the volume of titrant. The end point is taken at the distinct inflection of the resulting titration curve corresponding to the basic pH 11 buffer solution.
Installation
Install the instrument, titration stand and electrode in accordance with pages 6-9 of the User manual.
(Note: The only difference is the use of a single, micro combination electrode in place of an electrode pair. This electrode, by its very construction, should be handled carefully).
Load the titrant reagent, KOH 0.1mol/l in 2-propanol, into the syringe using the Manual Activation instructions on page 12.
Calibration
Pour 25ml of pH 11 buffer into the micro titration vessel.
Place vessel onto the titration stand and immerse the electrode.
(Note: the electrode is designed to ensure correction positioning in the vessel).
From the Main Menu, select Calibration and follow the instructions on the display.
At the end point, the system will be calibrated.
(Note: this should be done on a daily basis to ensure system performance).
Cleaning and conditioning electrode
After measuring the aqueous buffer, rinse the electrode tip with water.
Stand in beaker of water for 2 minutes.
Before performing blank procedure, rinse electrode with 2-propanol.
Stand in beaker of titration solvent for 2 minutes.
Blot dry before use with soft tissue.
Blank determination
This procedure is carried out when the instrument is used for the first time and for every new batch of titration solvent.
Measure 25ml of titration solvent into the titration vessel. Add stirrer bar.
Place vessel on titration stand.
From Main Menu, select Analyze.
Select Blank.
Follow instructions on page 14 of manual.
Start titration.
Once the titration is finished, select ‘Accept result’ to store Blank value in system memory.
Remove vessel from stand. Discard titrated ‘Blank’ into waste solvent container.
Wash electrode tip with 2-propanol.
Stand in beaker of water for 2 minutes.
Stand in beaker of titration solvent for 2 minutes to recondition ready for non-aqueous sample analysis.
TAN analysis
Introduce 1.0 ml of sample into titration vessel using graduated gas tight syringe.
Add 25ml of titration solvent and stirrer bar.
From Main Menu, select Analyze.
Select TAN < 0.1 for all samples (to ensure optimum titre and sample result).
Key in sample weight of 0.875g.
Start titration.
At the end point of the analysis, the TAN value (in mg KOH/g sample) will be displayed.
Clean and recondition electrode for next analysis/storage
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