The standard test methods for water content of crude oil samples by coulometric Karl Fischer titration, stipulate that the Karl Fischer anode reagent must be mixed in a 70:30 or 60:40 ratio with xylene to improve sample miscibility and reduce waxy deposits and asphaltines from dropping out thereby causing problems with the generator electrode. However this modification to the reagent, and subsequent addition of the oil samples being analysed, affects the resistance/capacitance of the titration vessel. When this resistance in the electrolysis cell is increased beyond certain limits the coulometer is unable to operate efficiently and provides an incorrect result, usually falsely high. Every coulometer has a maximum titration current and count rate, if the resistance in the cell is high, it cannot generate required current but it continues to count as if the required current was being generated. This produces an incorrect result.
For this reason, although in principle standardisation of a coulometer is not necessary since the water ‘titrated’ is a direct function of the coulombs of electricity consumed, the above mentioned Karl Fischer methods stipulate that the performance of the coulometer should be regularly monitored by injecting 10 microlitre of pure water. The suggested interval is after every 10 determinations and the result obtained should be 10,000 +/- 200 microgram. The reagent should be changed if the result is outside these limits, but more importantly we now have to ask ourselves – at what point did the Karl Fischer titrator start to give incorrect results? All we can be certain of is that when we last ran the water check it was still OK.
- What about the last 10 samples we have analysed since then?
- Can we assume that all of those results were correct?
- Can we afford to make that assumption?
The ACE control system (Automatically Compensated Errors) patented by GR Scientific overcomes this problem by ensuring that the electrolysis current produced by the coulometer and the count rate being displayed are always correctly synchronised regardless of changes to the electrolysis cell resistance.
This provides several advantages including reduction in reagent consumption, improved cost efficiency due to higher sample throughput, better conditions for personnel as their exposure to hazardous chemicals is reduced, but most importantly – the ACE control system guarantees correct results.
The patented ACE Control System is a standard feature which is only available on the Aquamax KF range of Karl Fischer titrators.
What features make an Aquamax-KF-Portable stand ahead of our competition?
The Aquamax KF body has the battery, a printer plus a keypad built in.
- 8 hours of continuous battery operation. Each Aquamax KF also has an in-car adapter so that even when out in the field and battery power runs flat, operators may still source power by plugging into a car power outlet.
- Aquamax KF has high speed thermal printer built-in where users may print out results anywhere. In addition, this titrator has a removable flash drive (memory stick) which can store all results for PC downloading via Results Manager software supplied free of charge.
- Full keypad for allows all parameters to be entered very easily, saving time when compared to other manufacturers of similar titrators.
- No Teflon electrode sleeves or grease required. The Aquamax KF has a unique Low Drift Cell design which is far easier to use and also more robust. The electrode locking system allows joints to be sealed completely, providing improved baseline stability.
- Truly Portable – The Aquamax KF has a carry handle on top, of the main body, making it easy to carry single-handed. The stainless steel cage around the titration vessel ensures protection whilst carrying. The built-in battery enables the instrument to be carried even while it’s working.
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