Determination of moisture content in glycerol by volumetric method

1. Preface

Glycerin has a strong hygroscopicity. Glycerin with an appropriate amount of moisture can play a role in moisturizing and nourishing the skin. Pure glycerin cannot be directly applied to the skin, as it may cause dry and cracked skin and burning pain. Therefore, it is particularly important to control the moisture content of glycerol.

The determination of glycerol moisture by using the Karl Fischer moisture titrator can quickly and accurately detect the content of glycerol, providing an accurate and efficient basis for the determination of glycerol moisture.

2 Instruments and equipment

2.1 Instruments

JH-V5 Karl Fischer moisture titrator (volumetric method), double platinum electrodes, 5mL titration unit.

2.2 Reagents

Karl Fischer titrant, ethanol solvent [Ethanol (90%-100%), containing 2-methylimidazole (1%-5%), liquefied sulfur dioxide (1%-5%)}

3 Experimental Methods

3.1 Experimental Procedures

Through the liquid discharge device of the moisture titrator, the residual liquid is removed. Then, 50mL of solvent ethanol is added to the titration cup, with the solvent covering the electrode. After setting the parameters, the instrument starts the pre-titration. When the instrument is in standby mode, click on the system injection and open the rubber stopper of the feeding port. Quickly add an appropriate amount of the sample (the amount of sample depends on the moisture content of the sample) (use the difference method to weigh the sample), immediately cover the rubber stopper, click "Start Measurement", and use Karl Fischer. Titrate with the titrant to the endpoint, input the sample weight, and calculate the moisture content of the sample.

3.2 Instrument Parameters

4 Results and Discussion

4.1 Experimental Results

Calculation formula:

In the formula:

X - represents the moisture content of the sample (%);

V1 - The volume (mL) of titration liquid consumed when titrating the sample; m - The weighing amount of the sample (g);

T - represents the concentration of the titrant (mg/mL).

4.2 Conclusion and Discussion

The moisture content of glycerol was determined by the JH-V5 Karl Fischer moisture titrator. The RSD value of the measured data was 1.96%, with good data repeatability. The instrument can automatically control the titration process, determine the endpoint, and calculate the results, reducing errors caused by humans. It has the characteristics of rapidity and simplicity.

References

[1]SN/T 0839.4-1999 Industrial Glycerol for Import and Export, Karl Determination of moisture content by Fischer method [S].