The derivative spectrometer

The theory and performance are described of a small portable second derivative spectrometer, the d(2)spectrometer. The physical principles of the apparatus permit detection of gases by absorption spectrometry with sensitivities two or more orders of magnitude greater than is attainable by use of more conventional spectrometers. When the spectrometer is used with a readily portable absorption cell having a 7.72-m folded light path, some common air pollutants are detectable in concentrations of parts per 100 million or less. Other designs of absorption cell permit measurement of ammonia in blood or in expired air.