What acid should be added to the oil and grease sample to adjust the pH?

To adjust the pH of an oil and grease sample, sulfuric acid (H2SO4) is often the preferred choice. This strong acid serves the purpose effectively due to its ability to rapidly lower the pH of the sample. It is particularly useful in analytical laboratories where precise control over pH is necessary before proceeding with further testing or analysis.

H2SO4 also has a high acidity and can be used in smaller quantities, making it efficient in terms of its effectiveness at adjusting pH levels. In many environmental analyses, maintaining an appropriate pH is crucial for preserving the integrity of the sample and ensuring accurate results in subsequent testing phases.

While hydrochloric acid (HCl) could also lower pH, H2SO4 is generally favored in protocols related to oil and grease because of its properties and efficiency. Sodium hydroxide (NaOH) would be inappropriate for this context since it is a base, which serves to raise pH rather than lower it. Acetic acid, being a weak acid, may not provide the strong pH adjustment needed for precise control in this situation.