2024-09-13
Determination of Sulfur Dioxide in Chenpi Samples by Ion Chromatography
Ion chromatography has always been a research hotspot for the detection of sulfur dioxide in Chinese herbal, with its simple operation, high sensitivity and wide linear range, which is of practical value for the control of sulfur dioxide residue in pharmaceuticals.
In this experiment, the steam distillation method and the ion chromatography will be used to determine the content of sulfur dioxide in Chenpi. Wayeal ion chromatograph with conductivity detector, and KOH eluent. The method is simple to handle, with good recovery and high sensitivity, and is suitable for the determination of sulfur dioxide in Chenpi.
Keywords: Chenpi, sulfur dioxide, ion chromatograph
1. Experiment
1.1 Instruments and Reagents
Ion Chromatography: IC6200 Series ion chromatography with conductivity detector
Autosampler: AS2800
Anion Chromatography Column: HS-5A-P2, 250MM x 4.6mm, Sulfate ions in water(1000mg/L)
30% H2O2 solution;
Concentrated Hydrochloric Acid: Guaranteed reagent
Disposable Syringes (2mL)
Water-based Syringe Filter (0.22μm)
Electronic Balance, 1/10,000
The experimental water is prepared by the Wayeal ultrapure water purifier with a conductivity of 18.2 MΩ·cm (25 ℃).
1.2 Working Conditions
Column Temperature: 35°C
Cell Temperature : 40°C
Eluent : 30Mm KOH isocratie elution
Flow Rate : 1.0 mL/min
Suppressor Current: 90mA
Injection Volume: 25μL
1.3 Schematic Diagram of Steam Distillation
1.4 Sample Pretreatment
Take appropriate amount of sample (accurate to 0.0001g) to bottle A (two-necked flask), add 50mL deionized water, shaking, so that the dispersion is uniform, then connected to the water vapor distillation flask C. 20mL of 3% hydrogen peroxide solution was absorbed in Bottle B. The lower end of the absorbing tube was inserted below the level of the absorbing solution. Add 5mL of hydrochloric acid along the wall of bottle A, quickly close the stopper, and begin distillation, keeping bottle C boiling and adjusting the distillation fire so that the effluent from the end of the absorber tube flows at a rate of about 2mL/min. Distill until the total volume of the solution in bottle B was about 95mL (30~40min), wash the tail pipe with water and transfer it to a volumetric flask, fix the volume to the scale, shake it well, let it stand for 1h, filtered through 0.22μm aqueous filter membrane, choose the appropriate dilution times, and test and analyze it on the machine.
2. Result and Discussion
2.1 Linearity Test
0.1mg/L, 0.2mg/L, 0.5mg/L, 1.0mg/L, 2.0mg/L, 3.0mg/L of standard working curves of were pipetted respectively, and you will get the multi-point overlap chromatography of the standard curve according to the 1.2 working conditions, as shown in Fig. 1, linear equations as shown in Table1, and the linear correlation coefficients of sulfate under this chromatographic condition is above 0.999, which is good linearity.
Fig1 Overlap Chromatogram of SO4 Standard Curve
Fig 2 Standard Curve of SO4
Table 1 Linear Equation of Standard curve
| No | Ions | Linear Equation | Correlation Coefficient R |
| 1 | So42- | y=14.32737x-0.76329 | 0.99926 |
2.2 Sample Testing
2.2.1 Sample Content Testing
The pre-treated samples were detected under the 1.2 working conditions. The sample chromatogram as shown in Fig. 3 and Fig. 4, the chromatographic peaks are symmetrical, with good separation and no other peaks, and the final content of sulfur dioxide in the sample as shown in Table 2.
Fig 3. Chromatogram of Sample 1
Fig 4. Chromatogram of Sample 2
Table 2 Sample Results Analysis
| Sample | Weighing Sample/g | Ions | Concentration(mg/L) | SO2 Content(g/kg) |
| Blank | / | SO42- | 0.272 | / |
| Sample 1 | 2.5551 | SO42- | 1.417 | 0.030 |
| Sample 2 | 2.2370 | SO42- | 0.920 | 0.019 |
2.2.2 Sample Repeatability Testing
Fig 4 Repeatability Chromatogram of Sample 1
Table 3 Repeatability Results of Sample 1
| Sample | Weighing Sample/g | Retention Time/min | Peak Area | Concentration mg/L |
| Sample 1 | 2.5551 | 12.307 | 19.615 | 1.422 |
| 12.290 | 19.627 | 1.423 | ||
| 12.267 | 19.327 | 1.402 | ||
| 12.250 | 19.632 | 1.424 | ||
| 12.230 | 19.380 | 1.406 | ||
| 12.247 | 19.640 | 1.424 | ||
| Average Value | 12.265 | 19.537 | 1.417 | |
| RSD% | 0.235 | 0.732 | 0.705 |
3. Conclusion
An ion chromatographic method was established for the determination of sulfur dioxide in Chenpi samples by using Wayeal IC6200 series ion chromatograph equipped with a conductivity detector. The samples were pre-treated and then separated by an ion chromatographic column and quantified by external standard method, which was able to qualitatively and quantitatively analyze the sulfur dioxide in Chenpi. The method is simple and easy to use, with good reproducibility, sensitivity and accuracy, which can be adopted for the determination of sulfur dioxide in Chenpi.
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