The electronic cigarette and vaping industries are expanding. In these products, the mixtures which are typically used are called e-juices, e-liquids, or e-fluids. In order to guarantee these e-liquids' qualities, it is necessary to test the most important quality parameters. Moisture or water content constitutes one important quality control parameter.
The determination of moisture or water content using Karl Fischer Titration (KFT) is a reliable, established technique. The selectivity, reliability, and speed of KFT make it advantageous when compared to different methods. Volumetric KFT is the chosen method for high water content samples, like e-liquids.
This article presents a system for the reliable, rapid determination of water content in E-liquids. This system is completely automated, which means it can perform all of the steps of the analysis - including sample determination, preparation, titer, and blank - all entirely unattended. The operator consequently only has to weigh the sample before placing the sealed sample vessels onto the system.
Method Description
Sample
E-liquids
Sample Preparation
No sample preparation is required.
Configuration
| . |
. |
| 814 USB Sample Processor |
2.814.0030 |
| 901 Titrando |
2.901.0010 |
| 802 Rod stirrer |
2.802.0010 |
| 800 Dosino, 3x |
2.800.0010 |
| Dosing unit 50 mL |
6.3032.250 |
| Dosing unit 10 mL |
6.3032.210 |
| Sample rack 24 x 75 mL |
6.2041.340 |
| Sample beaker 75 mL, 24x |
6.1432.210 |
| Karl Fischer equipment |
6.5610.020 |
| Double Pt-wire electrode for sample changer (fixed cable) |
6.0340.000 |
Solutions
| . |
. |
| Titrant |
Hydranal Composite 5 |
| Solvent |
Hydranal Methanol Rapid |
Parameters
| . |
. |
| Titration mode |
KFT Ipol |
| Stirring rate |
8 |
| I(pol) |
50 μA |
| EP at |
250 mV |
| Dynamics |
100 mV |
| Max. rate |
5 mL/min |
| Min. volume increment |
5 μL |
| Stop criterion |
Drift |
| Stop drift |
20 μL/min |
| Titration direction |
- |
| Extraction time |
30 s |
| Stop volume |
20 mL |
Results
| Sample (n = 3) |
Water content / % |
s(rel) / % |
| E-liquid 1 |
11.26 |
0.74 |
| E-liquid 2 |
60.29 |
0.67 |
| E-liquid 3 |
64.48 |
0.52 |
| E-liquid 4 |
54.82 |
0.37 |
Analysis
A 75 ml glass beaker is used to weigh roughly 0.1 g of the sample. This beaker is subsequently sealed using a foil cap and foil holder, before the beaker is put onto the system's rack.
The system is loaded with two beakers for the system preparation, three beakers for the blank determination, and three beakers for titer determination, followed by the samples. The foil cap is automatically punctured by the system, which also adds solvent and titrates to dryness with Hydranal Composite 5 of its own accord.
About Metrohm
Metrohm is one of the world’s most trusted manufacturers of high-precision instruments for chemical analysis. Metrohm was founded in 1943 by engineer Bertold Suhner in Herisau, Switzerland. Today, Metrohm is represented in 120 countries by subsidiaries and exclusive distributors. The global Metrohm Group also includes the Dutch companies Metrohm Applikon and Metrohm Autolab, manufacturers of online analyzers and instruments for electrochemical research, respectively. Recently, the Metrohm Group was joined by Metrohm Raman, a leading manufacturer of handheld Raman spectrometers.
Metrohm is the global market leader in analytical instruments for titration. Instruments for ion chromatography, voltammetry, conductivity, and stability measurement make the Metrohm portfolio for ion analysis complete. Instruments for Near-infrared and Raman spectroscopy are another, strongly growing segment of the Metrohm portfolio.
Metrohm is a problem solver, both in the laboratory and within the industrial process. To this end, the company offers their customers complete solutions, including dedicated analytical instrumentation as well as comprehensive application know-how. More than 30% of the company’s employees at the Metrohm international headquarters in Herisau work in R&D.
Metrohm has been owned 100% by the non-profit Metrohm Foundation since 1982. The Metrohm Foundation, which does not exert any influence on the company’s business operations, sponsors gifted students in the natural sciences, supports charitable and philanthropic purposes and, above all, ensures the independence of the company.
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