Factors Influencing the Selection of Spectrophotometer

1. Wavelength detection range and wavelength selection mode (manual search, automatic search, or scan)

2. Light Beams. The beam types are single beam, dual beam, or quasi-twin beam. A single beam is generally suitable for measuring absorbance at a given wavelength, does not allow for full-band spectral scanning, and requires a high degree of stability of the light source and detector. The dual-beam allows for automatic recording and fast full-beam scanning. It can eliminate the effects of light source instability, detector sensitivity variation, and other factors, especially suitable for structural analysis. The false double beam is also known as the proportional double beam. It has the advantage of being able to monitor errors caused by changes in light sources. The principle is that the light emitted by the same monochromator is divided into two beams, one reaching the detector directly and the other passing through the sample and reaching the other detector. However, the approach does not eliminate the effect of the reference ratio.

3. Light source. In the visible region, tungsten and halogen lamps are mainly used (320~2500nm); in the ultraviolet region, hydrogen and deuterium lamps are mainly used (180~375nm); xenon lamps can be used as light sources in both the UV and visible regions.

4. Sample holder. The simple sample holder is a push-pull quadruple cell holder, which can only measure one sample at a time, and the reference and sample are measured twice; the high-grade sample cell holder has two fixed cell holders, one for the sample channel and one for the reference channel, which can measure the absorbance values of the reference and sample at the same time.

5. Slits. Simple slits are generally of fixed-width mode, with slit widths of 2nm and 1.5nm; high-grade slits are all continuously adjustable, which can be adapted to the needs of high resolution.

6. Optical performance indicators. The optical performance of the level directly affects the accuracy of the measurement, which is a particularly important technical indicator of the grating. High-grade grating quality of the instrument is better, generally the best grating for concave, and large size of the concave grating corresponding to the number of grooves more, so in resolution and stray light indicators are better than the simple instrument.

7. Detector. The detector is a device that uses the photoelectric effect to convert the light signal through the solution into an electrical signal and amplify the electrical signal. Simple instruments generally use photodiodes; medium-grade instruments use silicon photodiodes; high-grade instruments detectors use high-sensitivity photomultiplier and infrared detectors.

8. Display. Simple instruments are mostly mechanical heads or digital tube displays without data processors; high-grade instruments have LCD-type displays or computer connections, and data processing can be done by the instruments themselves or by external computers.

9. Measurement modes. Simple instruments are mostly fixed-point (fixed wavelength) absorbance or transmittance measurement mode, basically can not carry out wavelength scan measurement; high-grade instruments have more measurement modes, can display transmittance, absorbance, concentration, direct reading, single beam, single point, and scanning can be.

10. Measuring accessories. An important aspect of the quality of the instrument is the availability of a wide range of ancillary measurement devices, such as polarization, integrating sphere, reflection, autosampler, chromatic analysis software, and thin-film accessories.

11. Measure the state of the sample. Visible and ultraviolet spectrophotometers generally measure liquid samples, while infrared spectrophotometers are generally capable of analyzing samples in various states (gas, liquid, solid).