HPLC tools, today, are widely used across multiple sectors for different purposes. High Performance Liquid Chromatography was introduced in 1980s for analyzing, identifying & separating chemical compounds of complex nature. These days, HPLC is used in industries such as pharmaceutical, environmental, food, drink and energy, and for research and development. The HPLC instrument consists of many different parts such as pumps, autosamplers, integrator, column, injector and a HPLC detector. Each of the HPLC components comes in different sizes and varieties. Let’s take a look at the different types of detectors available –
- Refractive Index (RI) detectors – These types of HPLC accessories measure the capability of sample molecules to bend or refract light. Now, the property for each molecule or compound is called its refractive index. Usually in the RI detectors light proceeds through a bi-modular flow-cell to a photodetector. One channel of the flow-cell directs the mobile phase passing via the column while the other directs only the mobile phase. Next, the detection occurs when the light is bent due to samples eluting from the column, and this is read as a disparity between the two channels.
- Fluorescent detectors – Using these detectors one can measure the ability of a compound to absorb then re-emit light at specific wavelengths. Each compound has a characteristic fluorescence. The excitation source passes via the flow-cell to a photodetector while a monochromatic measures the emission wavelengths. The fluorescent detectors have the sensitivity limit of 10-9 to 10-11 gm/ml.
- Light-Scattering (LS) Detectors – When a source emits a parallel beam of light which strikes particles in solution, some light is reflected, absorbed, transmitted, or scattered. Two forms of LS detection may be used to measure the two latter occurrences namely Nephelometry & Turbidimetry.
- Ultra-Violet (UV) detectors – These detectors measure the ability of a sample to absorb light. This can be accomplished at one or several wavelengths such as fixed, variable, and diode array. The UV detectors have a sensitivity to approximately 10-8 or 10 -9 gm/ml.
- Electrochemical detectors – These are also some of the most widely used detectors. They measure compounds which undergo oxidation or reduction reactions. Electrochemical detectors have sensitivity of 10-12 to 10-13 gm/ml.
- Radiochemical detectors – Further, the radiochemical detection includes the use of radio-labeled material, usually tritium (3H) or carbon-14 (14C). This operates by detection of fluorescence associated with beta-particle ionization, and it is most popular in metabolite research. Now the radiochemical detectors are sub-divided into two detector types namely Homogeneous & Heterogeneous. These types of detectors have the sensitivity limit up to 10-9 to 10-10 gm/ml.
These were some of the most common used HPLC detectors. There are many more to explore. While buying HPLC kits, one must be absolutely careful! You must purchase accessories such as the HPLC Lamp from established HPLC parts suppliers.