Double beam UV visible spectrophotometer with two beams of monochromatic light, two cuvette. It also has two types: one is the two beams of monochromatic light, two cuvettes, two photoelectric converter; the other is a two beams of monochromatic light, two cuvettes, a photoelectric converter. At present, double beam UV two photoelectric converter visible spectrophotometer instrument is rare, especially high-grade double beam UV visible spectrophotometer is a photoelectric converter device. Double beam UV these two types of visible spectrophotometer using a photoelectric converter is basically the photomultiplier tube (PMT).
(1) the two beams of monochromatic light, two cuvettes, two photoelectric converter
The use of two photomultiplier tube double beam UV visible spectrophotometer, can affect the fluctuation of light source, partially offset by a stray light, electrical noise, so measuring the time accuracy good. However, the structure is more complex, the price is more expensive. At the same time, because of the photomultiplier tube spectral response characteristics may not be fully matched, so, when the spectral scan large measurement errors, in general do not have this kind of double beam UV visible spectrophotometer to scan. In addition, because of a beam of light into two beams, so the energy of each beam is low, signal to noise ratio than the single beam UV visible spectrophotometer is good. At present, China's market on 1880, 8500, UV/FL-I type instrument belongs to this kind of double beam UV visible spectrophotometer.
(2) the two beams of monochromatic light, two cuvettes, a photoelectric converter
Ago, the domestic and foreign top grade double beam UV VIS spectrophotometer are basically two beams, two colorimetric III, a photoelectric converter apparatus. For example, Lambda950, Lambdt, Cary6000 America, Cary500. Cary5, UV-2550PC. UV-310IPC. U-3400 UV-2450PC. of Japan, and China's TU-1901, TU-1900, UV-2100, UV-765, SP-2500UV etc.. This kind of double beam UV visible spectrophotometer was mostly advanced technical index. Since there are two beam of light, the influence of light source fluctuation, stray light, electronics noise can partially offset, so the stray light, photometric noise is very small. Therefore, the double beam UV Spectrophotometry in this type of visible spectrophotometer of good accuracy. This is the biggest advantage of double beam ultraviolet a photoelectric converter visible spectrophotometer.
But this instrument a beam of monochromatic light is split into two beams, so the energy of each beam is reduced by half. Therefore, the signal to noise ratio than the single beam UV VIS spectrophotometer, high. But the structure is complex, the price is more expensive. But because the two beams of light path of noise may cancel each other out, so the sensitivity is still good.
At present, the international on the UV visible spectrophotometer Dan Guangshu and double beam quality problems, there are significant differences. One view is that the dual beam instrument is good, because the two beams can offset part of stray light shaft noise, offset in part due to the effect of light source fluctuation on the stability of instrument, which can improve the reliability of ultraviolet visible spectrophotometer instrument. America PE company holds this view. Another view is that the single beam instrument, because with the development of computer, many single beam instrument shortcomings can be used to make up for the computer software; a single beam of light energy is double beam intensity, the SNR is high, the instrument sensitivity is higher; the structure of a single beam is relatively simple, the price is cheaper. The early launch of ultraviolet visible spectrophotometer commercial instruments USA Beck-man company holds this view. China's current production of ultraviolet visible spectrophotometer, single beam more than double beam. However, most of our country's science and technology workers think is better than that of the single beam double beam.
Atomic absorption spectrophotometer has Dan Guangshu, double beam, however, from the instrumentation point of view, the advantages and disadvantages of it and violet visible spectrophotometer different. Because the UV visible spectrophotometer is a precision 6 analysis tools (relative error of up to 1%), and the atomic absorption spectrophotometer is a relative measurement instrument (relative error sometimes up to 10% or more).