Determination of Anion Content in Sulfuric Acid, Hydrochloric Acid, and Nitric Acid by Ion Chromatography

This application note introduces the determination of anion content in concentrated sulfuric acid, hydrochloric acid, and nitric acid using Wayeal ion chromatography. The traditional chemical volumetric method for determining impurity ions in concentrated acids is not only time-consuming and less reliable, but also increasingly inadequate for the quality control of high-purity sulfuric, hydrochloric, and nitric acids. Moreover, due to the highly corrosive nature of sulfuric, hydrochloric, and nitric acids, they pose significant hazards to both operators and the environment. Therefore, it is necessary to establish a convenient, sensitive, and reliable instrumental analysis method. Ion chromatography is a preferred method for determining inorganic anions. This application establishes a direct injection method for analyzing anions in sulfuric acid, hydrochloric acid, and nitric acid reagents, with optimized chromatographic conditions. This application has established a direct injection method for the analysis of anions in sulfuric acid, hydrochloric acid, and nitric acid reagents, with optimized chromatographic conditions. It determines impurity ions in 98% concentrated sulfuric acid, 37% hydrochloric acid, and 68% concentrated nitric acid, showing good peak shape, response, and resolution for the impurity ions, thereby meeting the testing requirements.

Keywords: Ion chromatography, Concentrated Hydrochloric Acid, Concentrated Sulfuric Acid, Concentrated Nitric Acid.

1. Instruments and Reagents

1.1 Configuration List of Ion Chromatography

Table 1 Configuration List of Ion Chromatography

1.2 Reagents Standards

Table 2 Table List of Reagents and Standards

1.3 Experimental Materials and Auxiliary Equipment

0.45μm Syringe filter (preloaded/cartridge type)

Disposable syringe (5mL)

2. Experiment Method

2.1 Sample Pre-treatment

Weigh appropriate amounts of 98% sulfuric acid, 37% hydrochloric acid, and 68% nitric acid samples separately into volumetric flasks. Dilute each with ultrapure water by a factor of 200 and make up to a final volume of 100mL. After filtration through a 0.45μm aqueous syringe filter, the samples are ready for instrumental analysis.

2.2 Experiment Conditions

Chromatographic Conditions for Anion Analysis

3. Experiment Result

3.1 Standards Chromatogram

The determination of anions in all samples was completed within 45 minutes, with satisfactory peak shape, signal response, and resolution, meeting the requirements of the experimental analysis.

Fig 1 Overlay Chromatogram of Mixed Standard Calibration Curves

3.2 Linear Range

Take an appropriate amount of each ion standard solution to prepare the calibration curve. The linear range is 0.02–2mg/L. The deviation between the linear detection results and the known concentrations is less than the maximum allowable deviation, with R² above 0.999, indicating good linearity for all components.

Table 3 Linear Range Table for Each Ion

Fig 2 Linearity Results for Each Ion

3.3 Sample Analysis

3.3.1 Analysis of 98% Sulfuric Acid Sample

Test Chromatogram of 98% Sulfuric Acid Sample Diluted 200-Fold

Partially Magnified Test Chromatogram of 98% Sulfuric Acid Sample Diluted 200-Fold

3.3.2 Analysis of 68% Nitric Acid Sample

Test Chromatogram of 68% Nitric Acid Sample Diluted 200-Fold

Partially Magnified Test Spectrum of 68% Nitric Acid Sample Diluted 200-Fold

3.3.3 Analysis of 37% Hydrochloric Acid Sample

Test Chromatogram of 37% Hydrochloric Acid Sample Diluted 200-Fold

Partially Magnified Test Spectrum of 37% Hydrochloric Acid Sample Diluted 200-Fold

3.4 Sample Analysis Results

Based on the data, it can be concluded that at low dilution factors, the method exhibits good chromatographic peak shapes, with linear correlation coefficients all greater than 0.999. The sample contents are as follows (Note: ND indicates not detected, and "—" indicates content overload at the current dilution factor, making quantification impossible).

4. Conclusion

This sample analysis employed Wayeal ion chromatograph to determine anion content in sulfuric acid and nitric acid. This method maintains precise monitoring of quality control requirements even at low dilution factors. Testing ensures acid compounds comply with established standards, enhancing product purity and stability while preventing impurities from affecting downstream applications. It also evaluates residual levels of raw materials, intermediates, or byproducts during production, aiding in process optimization and yield improvement.