4 things to know about two new analytical methods
Did you know that sulfuric acid is produced and consumed more than any other chemical in the world? It’s true! Sulfuric acid is also one of the oldest known industrial chemicals. That’s because this strong inorganic acid has qualities that make it very useful for a large number of industries, including fertilizers, inorganic chemical manufacturing, petroleum refining, pharmaceuticals, soaps and detergents, textiles, pulp and paper, metals, car batteries, and pigments and dyes.
However, determining impurities in sulfuric acid comes with its share of challenges. Here are four things to know about identifying sulfuric acid:
1. Trace impurities in sulfuric acid matter
Trace ionic impurities in concentrated sulfuric acid can have a direct impact on the yield and reliability of chemical and semiconductor material processes, such as water cleaning.
2. Determining impurities is no cake walk
The determination of anionic impurities in concentrated acids has been an analytical challenge for years. Why? The titration method is cumbersome, tedious and uses hazardous chemicals.
3. Ion chromatography (IC) is a promising alternative, but presents challenges for sulfuric acid
IC is a promising alternative technique to determine low levels of anionic impurities. However, while low concentrations of contaminating anions in weaker acids such as hydrofluoric acid and phosphoric acid can be determined using online ion-exclusion sample preparation, that approach cannot be used for a strong acid like sulfuric acid. In sulfuric acid, the high concentration of sulfate limits the amount that can be injected into the anion-exchange column, thus limiting method sensitivity.
4. Two methods offer a fresh approach to determining impurities in sulfuric acid
In recent work by a team at Thermo Fisher Scientific, two experts borrow knowledge from determining anionic contamination in another strong acid, nitric acid. The team developed a similar approach for sulfuric acid whereby the concentrated sulfuric acid sample is diluted, and a volume that has been empirically determined to avoid overloading a high-capacity column is injected. Here’s a breakdown of the two methods:
- Method 1 uses a Thermo Scientific™ Dionex™ IonPac™ AS19 column with a hydroxide eluent to accurately determine fluoride, chloride, bromide, nitrite, and nitrate. This method is ideal for separating a wide range of inorganic anions with high sensitivity.
- Method 2 uses a Thermo Scientific™ Dionex™ IonPac™ AS23-4μm column with a carbonate/bicarbonate eluent to determine phosphate. The carbonate eluent is ideal for determining phosphate in sulfuric acid because it elutes before sulfate.
The team published the two methods and evaluated key performance parameters (including response linearity for each analyte, limits of detection, and accuracy) in a new application note.
To learn more about the methods and the team’s findings, read the application note.