Determination of Sugar Components in Oilseed Crops by Ion Chromatography

This study employs ion chromatography to determine the contents of fructose, glucose, sucrose, stachyose, and raffinose in oilseed crops. The author utilized a Wayeal ion chromatograph equipped with an amperometric detector, using a self-prepared NaOH and water solution as the eluent. This method features simple pretreatment, excellent recovery, and high sensitivity, making it suitable for the determination of fructose, glucose, sucrose, stachyose, and raffinose contents in oilseeds as specified in the standard.

Keywords: Oilseeds, ion chromatography, sugars.

1. Instruments and Reagents

1.1 Configuration List of Ion Chromatography

Table 1 Instrument Configuration List

1.2 Reagents and Standard Solutions

Table 2 Table of Reagents and Standards

1.3 Experiment Material and Auxiliary Equipment

Filtration setup

Ultrasonic cleaner

Analytical Balance (0.0001g precision)

Disposable syringe (2mL)

Aqueous syringe filter (0.22μm)

Ultrapure water, with a resistivity of 18.2 MΩ·cm (25°C)

2. Experiment Method

2.1 Solution Preparation

2.1.1 Zinc acetate solution (1mol/L): Weigh 21.9g of zinc acetate, add 3mL of glacial acetic acid, dissolve and dilute to 100mL with water.

2.1.2 Potassium ferrocyanide solution (1 mol/L): Weigh 10.6g of potassium ferrocyanide, dissolve and dilute to 100mL with water.

2.1.3 Sodium hydroxide solution (200mmol/L): Measure 10.5mL of 50% sodium hydroxide solution, dilute to 1000mL with pre-degassed water, and protect with nitrogen gas.

2.2 Sample Pretreatment

2.2.1 Sample extraction

Weigh 5g of the sample (accurate to 0.1mg), place it in a 50mL centrifuge tube with stopper, add 25mL of petroleum ether, vortex for 1min, centrifuge at 2000r/min for 5min, and discard the upper layer of petroleum ether. Repeat the above steps twice. Evaporate the residual petroleum ether in a 60°C water bath. Transfer the sample to a 150 mL conical flask (previously brought to constant weight) using a glass rod. Rinse the centrifuge tube twice with 50 mL of water, and combine the rinsings into the conical flask. Slowly add 5mL of zinc acetate solution and 5mL of potassium ferrocyanide solution, respectively. Then, add water until the total mass of the solution is approximately 100g (accurate to 1mg). After stirring at room temperature for 30 minutes, filter the solution through qualitative rapid filter paper. Further filter the filtrate through a 0.22μm syringe filter to obtain the test sample. Simultaneously, perform a blank test.

2.3 Experiment Conditions

2.3.1 Chromatography Conditions

Mobile phase: A: 200mM NaOH; B: water; C: 20mM NaOH

Flow rate: 0.4mL/min

Operating time: 65min

Column temperature: 30°C

Detection zone temperature: 30°C

Detector: Gold electrode, sugars, quadruple potential

Injection volume: 10μL

Table 3 Gradient Elution

3. Experiment Result

3.1 Standard Chromatogram

The separation of five sugars was completed within 20 minutes, with all peaks exhibiting good shape, no tailing phenomena, and all compounds showing excellent response, meeting the requirements for experimental determination.

Fig 1 Chromatogram of 5 Sugars (0.5mg/L)

Table 4 System Suitability Results

3.2 Linear Range

Take an appropriate amount of the mixed standard solution, and perform serial dilution to prepare a series of concentrations for constructing the standard curve. The linear range is 0.05–20mg/L. The deviation between the linear detection results and the known concentrations is less than the maximum allowable deviation. The R² values range from 0.99985 to 1.00000, indicating excellent linearity for all components.

Table 5 Linear Range Table for Each Compound

Fig 2 Linear Results for Five Sugars

3.3 Precision

The soybean sample solution was extracted according to section 2.2.1 and analyzed under the instrument conditions specified in section 2.3.1 with six consecutive injections. The results are shown in the table below. The relative standard deviations (RSDs) of the five sugars in the soybean sample were all within 1%. The sample detection is reliable, and the method demonstrates good precision.

Table 3 Precision Results of Soybean Samples

Fig 3 Overlaid Chromatograms of Four Sugars Precision in Soybeans

3.4 Sample Test Result

3.4.1 Moisture Detection

Take the soybean and sesame samples to be tested, and determine the moisture content in the samples according to GB/T 14489.1. The results are shown in the table below.

Table 4 Sample Moisture Results

3.4.2 Sample Testing

Take the soybean and sesame samples to be tested, extract the sample solutions according to section 2.2.1, and perform injection analysis under the instrument conditions specified in section 2.3.1. The sample test results are shown in the table below. The detection of soybean and sesame samples is reliable, and the results are satisfactory.

Table 5 Sample Test Result

Fig 4 Test Chromatogram of Soybean Sample Diluted 200-Fold

Fig 5 Test Chromatogram of Sesame Sample Diluted 100-Fold

4. Conclusion

This method utilizes a Wayeal ion chromatography IC6300 series system equipped with an amperometric detector to establish an ion chromatographic method for the determination of fructose, glucose, sucrose, stachyose, and raffinose in oilseeds. The samples were processed through pretreatment, separated via an ion chromatography column, and quantified using the external standard method, enabling qualitative and quantitative analysis of fructose, glucose, sucrose, stachyose, and raffinose in oilseeds. The data indicate that all chromatographic peaks exhibit excellent shape without tailing, the sensitivity meets national standard requirements, and the linear correlation coefficients all exceed 0.999. This demonstrates that the method, coupled with Wanyeal's ion chromatography system, fulfills the routine qualitative and quantitative detection requirements for the target samples.