分光光度计Spectrophotometry

主要部件：光源（氘灯提供紫外光、钨灯或卤钨灯提供可见光）、单色器（光栅或棱镜把复合光分成单色光）、样品池（可见区用玻璃，紫外区用石英比色皿）、检测器（光电倍增管或光电二极管阵列）和数据处理系统。测量吸光度 A = −lg(I/I₀) = εbc，ε 为摩尔吸光系数，b 为光程（通常 1 cm），c 为浓度。双光束仪器同时测量参比和样品，可消除光源波动。

The main parts are a light source (a deuterium lamp for UV and a tungsten or tungsten-halogen lamp for visible), a monochromator (grating or prism) that selects one wavelength, a sample cell (glass for the visible, quartz for the UV), a detector (photomultiplier or photodiode array) and a data system. Absorbance A = −log(I/I₀) = εbc, with molar absorptivity ε, path length b (usually 1 cm) and concentration c. Double-beam instruments measure reference and sample together, cancelling source drift.

1940 年美国贝克曼公司推出 DU 型紫外-可见分光光度计，用石英棱镜实现了紫外区的精确测量，把以前需要数周的维生素 A 等分析缩短到几分钟，被誉为“改变化学的仪器”。此前比色分析主要依靠目视比较颜色深浅。

In 1940 Beckman launched the DU UV–visible spectrophotometer, whose quartz prism allowed precise measurement in the ultraviolet; analyses such as vitamin A that had taken weeks now took minutes, and it has been called the instrument that changed chemistry. Before it, colorimetry relied on comparing colours by eye.

测定金属离子（如邻二氮菲-Fe²⁺ 法测铁、二苯碳酰二肼法测 Cr⁶⁺）、蛋白质（280 nm 或考马斯亮蓝法）和核酸（260 nm，A₂₆₀/A₂₈₀ 判断纯度）浓度，酶动力学（NADH 340 nm），水质分析（氨氮、总磷、COD），药物含量测定，以及反应动力学研究。

It determines metal ions (iron with 1,10-phenanthroline, Cr⁶⁺ with diphenylcarbazide), proteins (at 280 nm or by Coomassie dye), nucleic acids (at 260 nm, with A₂₆₀/A₂₈₀ indicating purity), enzyme kinetics (NADH at 340 nm), water-quality parameters (ammonia, total phosphorus, COD), drug content and reaction kinetics.