Abbe refractometer JH-2WAJ measuring oil application scheme

1. Preface

When light propagates between different substances, the ratio of the incidence Angle sine to the refraction Angle sine is a constant, which varies from substance to substance and is an inherent property of matter. Each homogeneous substance has a specific refractive index, and for a solution of a substance, the refractive index is related to the concentration, usually in a positive relationship.

Natural oils and fats are mixtures of mixed glycerides, and the glycerides contained in different sources of oils and fats have different corresponding refractive indices. The refractive index of a particular natural oil is a physical constant that changes when the quality of the oil changes, such as doping and rancidity. Moreover, the oil with high relative density has a high refractive index, and when the density decreases due to the increase of acidity, the refractive index decreases. Therefore, measuring the refractive index of oil is an important means to identify the composition and quality of oil.

2. Experiment preparation

2.1 Test equipment: JH-2WAJ Abbe refractometer of Shanghai Jiahang Instrument Co., LTD

JH-2WAJ Abbe refractometer has high precision optical system and stable structure, which can accurately measure the refractive index of grease and provide reliable data support for experiments. The operation interface design is simple and easy for the experimental personnel to quickly get started.

2.2 Experimental reagents

1) Soybean oil

2) Peanut oil

3) Corn oil

4) Rapeseed oil

5) Cottonseed oil

2.3 Reference Standards

"Animal and vegetable oil refraction index determination GB/ T5527-2010"

3. Experimental steps

3.1 Sample Test

The JH-2WAJ Abbe refractometer is connected with the constant temperature water bath, and the temperature is precisely controlled at 20℃. Calibrate the instrument with distilled water to ensure that the index of refraction shown by the instrument is 1.3330 to ensure the accuracy of the measurement.

Carefully separate the two prisms of the refractometer, use a clean straw to absorb a small amount (1-3 drops) of the sample, evenly drop on the fixed prism surface, and quickly close the prism. Wait a few minutes for the sample to fully reach the temperature of the prism, ensuring that the measurement results are not affected by temperature differences.

The spiral hand wheel of the prism is slowly adjusted so that the field of view is clearly divided into light and dark parts. Next, the compensator knob (dispersion handwheel) is turned to eliminate the iris phenomenon and make the dividing line clearly visible. Continue to fine-tune the spiral handwheel so that the dividing line is precisely aligned with the reticle.

Press the test button on the instrument, and the instrument will quickly display the refractive index of the sample. To ensure data reliability, reread the data immediately. At least two readings are taken for each sample and their arithmetic mean is calculated.

After each measurement, use a special cleaning solution and a clean soft cloth to carefully clean and completely dry the two prisms. Then the sample is measured for a second time, and finally the average of the two test results is taken as the final refractive index of the sample.

4. Results and discussion

4.1 Test Interface

The test interface of the JH-2WAJ Abbe refractometer visually displays the measured parameters, including the current temperature, the measured refractive index value, etc. The experimental personnel can obtain the data clearly on the interface, which is convenient for recording and analysis.

4.2 Experimental Results

4.3 Discussion

Refractive index is one of the key parameters to measure the purity of edible oil. In general, the refractive index of fatty acids increases with the increase of molecular weight and unsaturation. For example, short-chain saturated fatty acid esters have a lower refractive index, while oils with a high unsaturated acid content, such as flaxseed oil, have a higher refractive index. In the edible oil quality control and quality inspection industry, refractive index detection is an important must-check item. Using the JH-2WAJ Abbe refractometer, you can quickly detect the quality of oil and oil, and can also be used for quick inspection of fake and shoddy products. For example, in the market supervision of the industrial and commercial system, the content of other oils (such as sunflower oil) in peanut oil can be detected to maintain market order and consumer rights and interests.