A fluorometer is a sophisticated instrument designed to measure the fluorescence emitted by a sample after it has been excited by a specific wavelength of light. This device is crucial in various scientific fields, including biochemistry, environmental monitoring, and medical diagnostics, where it helps quantify the presence and concentration of fluorescent molecules, known as fluorophores.

Principle of Operation

Fluorescence occurs when a substance absorbs light at one wavelength and re-emits it at a longer wavelength. A fluorometer typically consists of several key components:

• Light Source: Often a xenon lamp or laser that provides the excitation light.
• Monochromators or Filters: These select the specific wavelengths of light used for excitation and emission. Filter fluorometers use optical filters, while spectrofluorometers employ monochromators for greater flexibility in wavelength selection.
• Sample Holder (Cuvet): This is where the sample is placed for analysis. It must be made from materials that do not fluoresce at the wavelengths being used.
• Detector: Commonly a photomultiplier tube (PMT) or charge-coupled device (CCD), which measures the intensity of the emitted fluorescence.

Types of Fluorometers

There are two main types of fluorometers:

• Filter Fluorometers: These are generally less expensive and use fixed optical filters to select excitation and emission wavelengths. They are simpler but offer lower sensitivity and resolution compared to spectrofluorometers.
• Spectrofluorometers: These use monochromators to select wavelengths, allowing for greater flexibility and sensitivity. They can be tuned to a wide range of wavelengths, making them suitable for more complex analyses.

Applications

Fluorometers are widely used in:

• Biological Research: For quantifying nucleic acids and proteins in samples, often at very low concentrations (down to parts per trillion).
• Environmental Monitoring: To detect pollutants or monitor biological processes in ecosystems.
• Medical Diagnostics: In assays that require high sensitivity for detecting specific biomolecules.
• Industrial Applications: Such as quality control in pharmaceuticals and food products.