Why must HPLC solvents be degassed before use? A. To change their color B. To remove bubbles that affect system accuracy C. To cool them D. To increase pressure
The correct answer and explanation is:
Correct Answer: B. To remove bubbles that affect system accuracy
Explanation:
High-Performance Liquid Chromatography (HPLC) is a highly sensitive analytical technique used to separate, identify, and quantify compounds in a mixture. For optimal performance, the solvents used in HPLC—referred to as the mobile phase—must be carefully prepared. One essential preparation step is degassing, which involves removing dissolved gases such as oxygen, nitrogen, or carbon dioxide from the solvents.
The main reason for degassing HPLC solvents is to remove bubbles that can interfere with the accuracy and reliability of the system. If gases remain dissolved in the solvent, they can form air bubbles when the solvent is pumped through the system. These bubbles can cause several problems:
- Baseline noise and drift: Air bubbles in the flow cell of the detector can scatter light and cause erratic signals, leading to noisy or unstable baselines that reduce analytical accuracy.
- Flow disruption: Bubbles entering the pump can cause inconsistent flow rates or pressure fluctuations, which in turn affect the reproducibility of retention times and peak shapes.
- Damage to components: Repeated bubble formation can lead to cavitation in the pump or other mechanical wear, reducing the lifespan of sensitive components.
Degassing can be accomplished using various methods, including:
- Vacuum degassing, where the solvent is subjected to a vacuum to remove dissolved gases.
- Ultrasonication, where ultrasonic waves help release trapped gases.
- Helium sparging, where helium is bubbled through the solvent to displace and remove other gases.
To clarify the incorrect options:
- A. To change their color: HPLC solvents are not degassed to alter appearance.
- C. To cool them: Degassing does not primarily cool solvents.
- D. To increase pressure: Degassing has no role in increasing system pressure.
Thus, Option B is correct because degassing helps ensure accurate, consistent, and reliable HPLC performance.