spektrofotometreja

Spectrophotometers are analytical instruments that measure the amount of light a sample absorbs or transmits at specific wavelengths. They are widely used to determine the concentration of solutes in solution, based on the principle that absorbance is related to concentration through the Beer-Lambert law.

A typical spectrophotometer consists of a light source, a wavelength-selecting element (monochromator or filters), a sample holder (cuvette), and a photodetector with signal-processing electronics. In many designs a reference beam and a measurement beam allow compensation for source fluctuations. The instrument converts the detected light intensity into a numerical value, usually called absorbance or transmittance.

There are two main configurations: single-beam and double-beam. The most common range for routine analyses is the ultraviolet to visible (UV–Vis) region, roughly 190–1100 nm. There are also instruments specialized for infrared or other spectral regions. Samples are typically placed in cuvettes made of quartz or fused silica when UV light is involved, or glass or plastic for visible light.

Operation and data interpretation rely on proper calibration. A blank (solvent or buffer) sets the baseline, and standards with known concentrations establish a calibration curve. The resulting absorbance can be translated into concentration using the Beer-Lambert law, with factors such as path length and molar absorptivity.

Applications span chemistry, biochemistry, environmental analysis, clinical diagnostics, pharmaceuticals, and food quality control. Spectrophotometry is used for concentration determinations, enzyme kinetics, reaction monitoring, and quality assurance, while acknowledging limitations from sample color, turbidity, or interfering substances.