Practice question

Label-free quantification avoiding dyes, radioisotopes or antibodies requires intrinsic chromophores. Infrared spectroscopy demands high concentration and drying, mass spectrometry needs ionization, extensive calibration and often tagging. Fluorescence sensitivity depends on quantum yield, environment, quenching and usually extrinsic labeling. Ultraviolet absorption at 280 nm for aromatic residues and 260 nm for nucleic acids offers sensitive, non-destructive, immediate measurement in microgram range using Beer-Lambert law and known molar absorptivities, recovering sample intact. Instruments are inexpensive and prevalent, making UV spectroscopy gold standard for routine rapid estimation in molecular biology, biochemistry and diagnostics laboratories.