Spectronic 20
| External video | |
|---|---|
 “Introduction to Colorimetry“ (Spectronic 20), David Frank |
|
| “Absorbance Spectrophotometry Video 02, Function test for Spectronic 20+”, Robin Aiken |
|
| “Lab Protocol - Spec 200 (Unit 2 Spectrophotometry)“, Mark Garcia |
The Spectronic 20 is a single-beam spectrophotometer, designed to operate in the visible spectrum[1] across a wavelength range of 340 nm to 950 nm, with a spectral bandwidth of 20 nm.[2][3] Because it measures the transmittance or absorption of visible light through a solution,[4] it is sometimes referred to as a colorimeter. Developed by Bausch & Lomb and launched in 1953, the Spectronic 20 was the first low-cost grating-based UV-Vis spectrophotometer.[5] It rapidly became an industry standard[6] due to its low cost, durability and ease of use,[7] and has been referred to as an "iconic lab spectrophotometer".[8] Approximately 600,000 units were sold over its nearly 60 year production run. It has been the most widely used spectrophotometer worldwide.[1] Production was discontinued in 2011 when it was replaced by the Spectronic 200,[9] but over 300,000 instruments are believed to remain in use in chemistry laboratories in both commercial and educational settings around the world.
Early history
The product line was sold to Milton Roy in 1985. Milton Roy sold its instrument group to Life Sciences International, renamed Spectronic instruments, Inc. in 1995. Spectronics Instruments was purchased by Thermo Optekin 1997, renamed Spectronic-Unicam in 2001 and Thermo-Spectronic in 2002. In 2003 the product line was moved to Madison, WI and the brand renamed to Thermo Electron.[10]
With the merger of Thermo Electron and Fisher Scientific in 2006 the brand changed to Thermo Scientific, and remained such until the end of the production run.[11] Spectronic 20 instruments found in labs today may bear any of the Bausch and Lomb, Milton Roy, Spectronic, Thermo Electron or Thermo Scientific brands.[10]
Design
The original design of the Spectronic 20 utilized an analog dial[12] for readout of transmission from 100%T to 1%T (top scale),[2] 0A - 2A (lower scale). Using the original instrument requires manual setting of the wavelength[2] and making readings from a moving-needle analog display.[13] The Spectronic 20D (launched in 1985) and then 20D+ replaced the analog dial with a red LED readout, offering greater precision in the readout, if not greater accuracy in the actual reading. A side-by-side comparison of the features of the 20+ and 20D+ is available in the 2001 operating manual.[13] The meter and educator versions were discontinued in December 2010 and the 20D+ was discontinued at the end of 2011.
Replacement
The Spectronic 20 was replaced by the Spectronic 200 in the Thermo Scientific spectrophotometer product line in 2011.[9] The Spectronic 200 utilizes an array detector and digital control of the measured wavelength, while retaining the characteristic λ knob of the SPEC 20 for setting the wavelength. In addition to replicating the user modes of the Spec 20D+ (which it can emulate on a color LCD screen) the Spec 200 accommodates both test-tubes and square cuvettes without needing to install an adapter. Software modes described in the Spectronic 200's specifications include scanning, four wavelength simultaneous measurement and quantitative analysis with up to four standards,[14] in contrast to the SPEC 20D+ which offered only single point calibration.
Popular culture
The Spectronic 20 is apparently one of the few lab instruments to remain intact after the destruction of the laboratory in the movie Back to the Future.[7]
References
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External links
- Spectronic 20, ChemLab Images and instructions (from Dartmouth College)
- Manufacturer's SPEC 200 webpage (from current manufacturer)
