This Application Note summarizes a series of test measurements performed with an OMNIS KF Titrator and Karl Fischer reagents Aquagent® Complet 5 and Methanol Fast from Scharlau.
Three series of titer determinations using various water standards were carried out. The results obtained using different water standards were found to lie in a similar range. The reproducibility of the results was determined to be very good.
Using an OMNIS titration system from Metrohm and the Scharlau Karl Fischer reagents, titer determinations can be carried out quickly without any decline in the reproducibility of results.
AQ00151000 – Aquagent® Complet 5
AQ00111000 – Aquagent® Methanol Fast
Three different water standards have been used for the tests performed in this study:
- Water standard with a water content of approximately 10.0 mg/g («water standard 10»)
- Sodium tartrate dihydrate with a water content of approximately 15.7%
- Deionized water
A 10-fold titer determination was carried out with both water standards and the deionized water.
The sample sizes were varied for water standard 10 (between 0.5 g and 4.0 g) as well as for the sodium tartrate dihydrate (between 0.077 g and 0.114 g). A constant sample size of 25 μg was used for the deionized water.
The water standard 10 was added with a glass syringe. To add the sodium tartrate dihydrate, a weighing boat (6.2412.000) was used. The deionized water was injected into the titration cell with a microliter syringe.
The following table shows the results of three titer determination series using using Aquagent® Complet 5 and Methanol Fast reagents from Scharlau.
Table 1. Results of the titer determination series (n = 10) with three water standards.
| Standard | Titer in mg/mL | s(abs) in mg/mL | s(rel) in % |
|---|---|---|---|
| 1 | 5.3936 | 0.02248 | 0.09 |
| 2 | 5.3781 | 0.00485 | 0.16 |
| 3 | 5.3459 | 0.00873 | 0.42 |
The titer determinations were both fast and reproducible. The relative standard deviations were very low, especially for the water standard 10 and the sodium tartrate dihydrate.
Methanol Fast contains additives to accelerate the titration, therefore it is recommended to use the method parameters suitable for two-component reagents (Table 2).
Table 2. List of suitable method parameters for two-component reagents in OMNIS.
| Parameter | Value |
|---|---|
| Dynamics | 300 mV |
| Max. rate | max |
| Min. volume increment | min |
| Ipol | 50 μA |
| EP | 250 mV |
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