The tungsten lamp has a long life of 1200 h. The tungsten lamp consists of a tungsten filament, emitting a visible spectral range between 330-900 nm. It uses plastic and glass cuvettes and a tungsten halogen light source. This device determines the absorbance or transmittance for the fluids and even solutions. The hydrogen lamp emits continuous or discontinuous spectral UV- light ranging between 200-450 nm. It uses cuvettes made of quartz and hydrogen or deuterium lamps as a light source. A photocell detects the amount of light transmitted or absorbed and gives the reading on the display meter.īased on Light Wavelength Ultraviolet spectrophotometer One beam of light passes from the test sample to the photocell, and the other passes from the reference sample to another photocell. Its mechanism is more or less similar to a single beam spectrophotometer but differs because the dual mirrors divide a single beam of light into two. One falls onto the reference sample and the other onto the test sample. In this, a fraction of light coming from the monochromator device parts into two beams. A photocell detects the portion of light transmitted or absorbed and gives the reading on the display meter. The focusing convex lens transmits light of a particular wavelength from the sample to the photocell detector. The diaphragm ensures 100% transmittance and allows the light to fall onto the monochromator device.Ī dispersion medium or monochromator device allows the transmittance of a single source of light onto the focusing convex lens. A beam of light from the light source falls onto the collimator convex lens and moves to the diaphragm. In this, a fraction of light from the diverging devices is wholly passed from the sample solution. Finally, an internal circuit inside a spectrophotometer gives out a final output on a digital meter.A photocell detector converts the light energy into electrical energy, and an amplifier transmits this electrical signal to the internal circuit. The focusing convex lens will pass a fraction of the monochromatic light source from the sample solution to the photocell detector.Then, the monochromator will produce a single source of light that falls onto the focusing wavelength selector.Firstly, a light source falls onto the monochromator (Dispersion device).MechanismĪ spectrophotometer includes the following sequential events: Absorbance is a non-dimensional quantity whose value ranges between 0-1. The amount of light transmitted from the solution is inversely proportional to the absorption of light.Īs the absorbance of the medium increases, the transmittance of light through the solution decreases and vice versa. According to Beer-Lambert law, the absorbance is equal to the given mathematical expression:Ĭ= Concentration of the absorbing material The spectrophotometer principle depends upon the Beer-Lambert law, which states that a beam of light incidents on the homogenous solution, reflects some fraction of incident light, absorbs some light and transmits the remaining light through the solution.īoth Beer and Lambert have given their own theories on the absorption of radiation. Its basic theory concludes that each chemical compound transmits or absorbs certain light according to its relative wavelength. Spectrophotometry is a science which deals with the study of light intensity absorbed or transmitted by the different solutions once a ray of light moves through the test sample. This device contains several components like a light source, collimator, monochromator, cuvette, light detector, and digital meter. The spectrophotometer refers to an instrument that measures the absorbance of the test sample at a specific wavelength by measuring the amount of light transmitted by the sample. This post discusses the definition, principle, types, components and applications of the applications. The amount of light transmitted or absorbed can be calculated by the readings obtained in a digital meter of a spectrophotometer. The process of calibrating the device commonly is called zeroing of the spectrophotometer. The spectrophotometer must be calibrated before taking the readings of the test sample by putting a cuvette holding a control solution.
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