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2025
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Determination of fatty acid content in hulled rice by fully automated potentiometric titration
1. Introduction
Grain fatty acid value is a quantitative indicator of the amount of free fatty acids in grains. The result is expressed as the amount of potassium hydroxide required to neutralize the free fatty acids in 100g of grain sample. Its change reflects the degree of quality deterioration commonly observed in rice and corn. In the national standard for grain storage judgment rules, it serves as an indicator of the suitability for storage of rice and corn. According to Appendix A of GB/T 20569 Rice Storage Quality Judgment Rules, the fatty acid value of dehulled rice was determined using the JH-T6 fully automatic potentiometric titration method from Shanghai Jiahang. This method is simple, time-saving, and labor-saving, and avoids subjective errors caused by manual endpoint determination, making it the preferred choice for detecting fatty acid values in grains.
2. Instruments and Equipment
2.1 Instruments
JH-T6 potentiometric titrator, composite pH electrode.
2.2 Reagents
Potassium hydroxide titrant (0.1 mol/L)
3 Experimental Methods
3.1 Experimental Procedures
Preparation:
(1) Calibrate the pH electrode using buffer solutions with pH values of 4.01, 6.86, and 9.18.
(2) Process the sample according to the operating procedure in Appendix A, A4 of GB/T 20569-2006. Take approximately 10g of the prepared sample, accurate to 0.01g, and add it to a titration cup. Add 50ml of anhydrous ethanol using a pipette. Seal the cup with sealing film, stir magnetically for 30min, let it stand for 1-2 minutes, place folded filter paper on a glass funnel, discard the first few drops of filtrate, collect more than 2.5ml of filtrate, and place it in a titration cup. Cover and set aside. Test:
Take 25 ml of the prepared filtrate, add 50 ml of distilled water, and titrate to the endpoint with potassium hydroxide-ethanol solution (0.05 mol/L).
3.2 Parameter Settings
4. Results and Discussion
4.1 Experimental Results
Calculation formula:
In the formula:
V1 is the volume of titrant consumed by the sample;
V0 is the volume of titrant consumed by the blank; c is the concentration of the potassium hydroxide titrant;
50 is the volume of anhydrous ethanol used for sample extraction;
25 is the volume of the extract used for titration;
100 is the mass converted to 100g of dry sample;
m is the mass of the sample weighed.
4.2 Spectrum
4.3 Conclusion
The JH-T6 fully automatic potentiometric titrator showed good repeatability in determining the fatty acid content of hulled rice, with all results falling within the standard range. It also avoided errors caused by color indicators. This instrument fully meets the requirements for determining the fatty acid value of rice.
References
[1] GB/T 20569 Rules for Judging the Storage Quality of Rice [S].
Keyword:
automated potentiometric titration
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