Double-Beam Spectrophotometer
The illustration below shows a diagram of a scanning, double-beam spectrophotometer. A chopper directs the source’s radiation, using a transparent window to pass radiation to the sample and a mirror to reflect […]
Image and Video Exchange
Get a look at images, photos, videos, and animations that encompass many facets of teaching and learning about analytical chemistry.
Single-Beam Spectrophotometer
The illustration here shows a diagram of a single-beam spectrophotometer that uses a monochromator to select the wavelength. The analyst manually selects the wavelength by adjusting the wavelength dial. Battery-operated, hand-held single-beam spectrophotometers […]
Filter Photometer
The illustration below is a diagram of a simple filter photometer, which uses an absorption filter (shown here) or interference filter to isolate a band of radiation. The analyst either inserts a removable filter […]
Limitation to Beer’s Law
Beer’s law suggests that a calibration curve is a straight line with a y-intercept of zero and a slope of εb. In many cases a calibration curve deviates from this ideal behavior, as […]
Beer’s Law
Absorbance is the more common unit for expressing the attenuation of radiation because it is a linear function of the analyte’s concentration. When monochromatic electromagnetic radiation passes through an infinitesimally thin layer of […]
Transmittance
As light passes through a sample, its power decreases as some of it is absorbed. This attenuation of radiation is described quantitatively T = PT/Po where T is transmittance and PT and Po are, […]
Atomic Spectra
The energy of ultraviolet and visible electromagnetic radiation is sufficient to cause a change in an atom’s valence electron configuration. Sodium, for example, has a single valence electron in its 3s atomic […]
Infrared Spectra
The illustration here shows two electronic energy levels (E0 and E1), each with five vibrational energy levels (ν0–ν4). Absorption of ultraviolet and visible radiation leads to a change in the analyte’s electronic energy […]
Photomultiplier Detector
A photomultiplier contains a photosensitive surface that absorbs radiation in the ultraviolet, visible, or near IR, producing an electrical current proportional to the number of photons reaching the photomultiplier. As shown here, […]
Wavelength Selection Using an Interferometer
An interferometer provides an alternative approach for wavelength selection. Instead of filtering or dispersing the electromagnetic radiation, an interferometer allows source radiation of all wavelengths to reach the detector simultaneously, as illustrated […]
Wavelength Selection Using a Monochromator
An absorption filter has one significant limitation—because a filter has a fixed nominal wavelength, if you need to make measurements at two different wavelengths, then you need to use two different filters. A […]
Wavelength Selection Using an Absorption Filter
The simplest method for isolating a narrow band of radiation is to use an absorption filter, which work by selectively absorbing radiation from one or more regions of the electromagnetic spectrum. A […]