Describe the three main detectors used in LC and their strengths and limitations.

Liquid Chromatography (LC) is a technique used to separate a mixture into its individual components. There are three main types of detectors used in LC: UV/Vis detectors, Refractive Index (RI) detectors, and Mass Spectrometry (MS) detectors.

1. UV/Vis Detectors: These detectors measure the absorbance of light by the sample at different wavelengths. They are most commonly used in LC because they are sensitive and provide good selectivity for compounds that absorb UV or visible light.

   Strengths:

   • High sensitivity for compounds that absorb light in the UV or visible range.
   • Can provide information about the structure of the compound based on its absorbance spectrum.

   Limitations:

   • Not all compounds absorb light in the UV or visible range, so this detector is not universal.
   • The presence of other compounds that absorb at the same wavelength can interfere with the detection of the compound of interest.

2. Refractive Index (RI) Detectors: These detectors measure the change in the refractive index of the eluent as the sample passes through it. They are often used for detecting compounds that do not absorb UV or visible light.

   Strengths:

   • Universal detection, as all compounds will change the refractive index of the eluent to some extent.
   • Non-destructive, meaning the sample can be recovered after detection.

   Limitations:

   • Less sensitive than UV/Vis detectors.
   • Changes in temperature or pressure can affect the refractive index, leading to baseline noise.

3. Mass Spectrometry (MS) Detectors: These detectors ionize the sample and then measure the mass-to-charge ratio of the ions. They are often used in combination with LC for the identification and quantification of compounds.

   Strengths:

   • High sensitivity and selectivity.
   • Can provide structural information about the compound based on its mass spectrum.

   Limitations:

   • More complex and expensive than other detectors.
   • Some compounds may not ionize well, leading to lower sensitivity.