Spectrophotometers. Manufacturers, model range, main characteristics and cost. Spectrophotometers Spectrophotometer types

In the modern world, the study of substances, substances and various types of radiation is extremely important for further technological developments. High-precision analysis of an object allows you to collect data about it that cannot be obtained by traditional metrological means. For such purposes, a spectrometer is used in various fields. This is a device with which you can determine the characteristics of color coatings, light emissions and the elemental composition of solid materials.

Spectrometry tasks

The general purpose of a spectrometer is an analysis tool that gives an idea of various substances and individual parameters of condensed matter. And the target object can be radiation, liquid, solids and even molecules.

Each spectrometer can work with specific elements or media, and in limited frequency ranges. There are universal models with enhanced performance characteristics, but working with such equipment requires special mechanical manipulations.

What are universal and specialized spectrometers used for? The former are suitable for generating parameters of serial pulses using a frequency comb, while the latter are used for narrow tasks associated with similar measurements under certain conditions. For example, if you periodically need to fix the light range on the work site.

Today, quantum models of spectrometers have also become widespread, which are used in flow scanning of materials, monitoring a wide range of different substances and environments at high speed.

Optical slit of the device

The main operating components of the spectrometer are the entrance slit and the diffraction grating. The slit serves to transmit and visualize radiation entering the device analyzer through a special cavity. It determines the light flux that is sent to the optical region of the detector. The input circuit can have different widths, depending on the general purpose of the spectrometer; this range is from 5 to 800 µm, on average. The height of the gap in the standard version is 1 mm.

Spectrometer diffraction grating

An equally important element is the diffraction grating of the spectrometer. This is the component that generates ranges of light wavelengths and also affects the resolution of the detector. In practice, this grating will determine the glare angle and frequency of light streaks.

There are holographic and threaded gratings. The difference between them is determined by the configuration of the distribution of laser beams on the photosensitive layer and the general spectral characteristics.

Types of spectrometers

Among the wide variety of these devices, the following varieties can be distinguished:

Gloss meter. This is a spectrometer focused on measuring brightness. It is used in cases where this parameter is a qualitative characteristic.
Spectrophotometer. Using this device, the spectral composition is analyzed by determining the length of electromagnetic radiation in the optical range. The output data is presented in the form of photometry and can be used for printing control.
Colorimeter. In this case we are talking about a type of color spectrometer. This is a device for measuring the intensity and temperature of shades, adjusted to a reference color scale.
Exposure meter. Determines exposure in photography and cinematography.
Spectroradiometer. This device is based on an optical system that accumulates spectra and counts them. First, information about the spectrum is recorded by scanning, and then this data is converted into an electrical signal.
Brightness meter. A device that determines the brightness of light sources.
The device provides information about the illumination.

Devices can perform each of these functions separately, or they can combine several operations. Multifunctional industrial spectrometers are capable of working with light, paints and other working media in the context of studying various parameters.

Portable and stationary devices

This classification largely determines the division according to technical, structural and communication characteristics. Portable (mobile, pocket) devices look like small testers or multimeters. These are compact devices that can be used to control colors on surfaces with complex geometries, where the use of stationary equipment is impossible. Moreover, despite their small size, devices of this type effectively cope with the analysis of various coatings, regardless of texture and degree of grain.

A stationary spectrometer is a more functional device, equipped with powerful optical elements and data processing tools. As a rule, it has its own microprocessor with a system for visual presentation of the recorded spectra. The user can operate the equipment's own LCD display and keyboard.

Operating principle of light spectrometers

The spectrometer operates as follows:

At the first stage, the device records and accumulates light spectra, after which the information is digitized by the signal with further analysis in a special program.
Processing of the primary light flux occurs in the optical fiber as it passes through a narrow aperture.
Next, the scattered light is directed into the already mentioned diffraction grating, which scatters the flow at different angles.
At the final stage, the photons recorded by the detector are converted into an electrical signal, which is processed in a computer.

How does a light spectrometer work with software? Via a USB port, the device transmits electrons to a computer, which interpolates the signal. In the simplest models, graphs are performed with the distribution of spectra by wavelength. More complex equipment additionally performs calibration and carries out numerous spectral operations based on the obtained data, etc.

Operating principle of a paint spectrometer

Instruments are commonly used to accurately determine shades on textured and structured surfaces. How does a paint spectrometer work? The optical system directly receives the data, after which the information is analyzed and processed in the aperture attachments. Most of these devices are equipped with pulsed xenon lamps, which record spectra with wavelengths from 360 to 740 nm on average. The output is a graph with colorimetric values.

Conclusion

Spectrometers, despite the complexity of their design, have a wide range of applications. They are used in scientific research, when monitoring products in factories, in construction when assessing the quality of a structure, as well as in agriculture and the domestic sphere. The point is that a spectrometer is an instrument that monitors characteristics that can be important to each person depending on the circumstances. Light analysis, for example, will make it possible to organize comfortable lighting both in enterprises and at home. Working with paint, in turn, will allow both the average motorist to select the optimal paint and varnish mixture for body repair, and the cladding manufacturer to successfully produce a material with the texture specified by the designer.

Application

Spectrophotometers can operate in a variety of wavelength ranges, from ultraviolet to infrared. Depending on this, the devices have different purposes.

Purpose

The main purpose of spectrophotometers in the printing industry is to accurately linearize and calibrate printing processes. Spectrophotometers from GretagMacbeth, X-Rite, Techkon, Konica-Minolta and other manufacturers provide the ability to perform spot and automated measurements to create high-quality ICC profiles.

Design

The figures show two main diagrams of spectrophotometers that measure the spectral aperture reflectance of a given object relative to a working standard with a known spectral characteristic:

The sample to be measured is illuminated with monochromatic light.

Structural diagrams

There are two schemes for constructing spectrophotometers: a spectrophotometer in the form of a wedge-shaped plate and using a heterodyne scheme for receiving light radiation.

In the form of a wedge-shaped plate

Spectrophotometer in the form of a wedge-shaped plate

The spectrophotometer (Fig. 1) is made in the form of a wedge-shaped plate, on one of the surfaces of which a thin, partially transmitting layer is applied, and on the other surface a reflective coating is applied, partially transmitting light radiation.

The operating principle of the spectrophotometer is based on recording the interference fringes of a standing light wave by projecting an image of a system of interference fringes onto photosensitive rulers. At the same time, the signal processing method differs from traditional Fourier spectroscopy only in that signals of spatial rather than temporal frequency are converted. The spectrophotometer has high noise immunity to incoherent light radiation.

Heterodyne circuit

Heterodyne circuit for receiving light radiation.

To do this, the spectrophotometer is equipped with a second laser with a radiation frequency that differs from the first by the frequency of the light beat (Fig. 2). In this case, interference fringes with almost the same period d are formed from the radiation of the second laser, and light beats appear on a thin layer, like on a mixer. The resulting electrical signals are recorded and subjected to a two-dimensional Fourier transform.

Light filters

The following filters can be used in printing:

POL - polarizing filter. Used to obtain a tentative spectrum after the paint has cured.
D65 - used to simulate the D65 radiation source.
UV-cut is used to measure the optical densities of papers that use fluorescent optical brighteners.
No - designation of the absence of a light filter. Typically, clear glass is used to protect the speccrophotometer from dust.

Radiation sources

The main sources of radiation are:

A(incandescent light, 2856 K);
WITH(indirect sunlight, 6774 K);
D(daylight, 5000 K);
D65(daylight, 6500 K);
F11(narrow range fluorescent radiation corresponding to the Philips TL84 tube);
and so on.

Optical design

Measurement Geometry

45/0 (the sample is illuminated by one or more light beams, the axes of which form an angle 45±5° relative to the normal to the sample surface).
0/45 10°).
D/0(the sample is illuminated diffusely using an integrating sphere. The integrating sphere can have any diameter, provided that the total area of the holes does not exceed 10 % internal reflective surface of the sphere).
0/D(the sample is illuminated by a light beam, the axis of which makes an angle of no more than 10°. The reflected flux is collected using an integrating sphere).

Modification of basic measurement geometries

To eliminate the specular component of high-gloss materials, the light receiver is placed at an angle of 8° to the normal, and a gloss trap is installed opposite it, symmetrically relative to the normal. Light that does not hit the sample at an angle of 8° (due to the glare trap) is not reflected specularly in the direction of the receiver, therefore, the flux reflected by the sample consists only of diffuse light. In this case, the measurement geometry becomes D/8. If the mirror component is enabled, then the designation for this is D/8:i(trap closed). If disabled, the measurement geometry is indicated D/8:e(trap is open).

Specification

Spectral resolution- the minimum wavelength step, the signals at the edges of which can still be distinguished on the spectrum. Typically, the step by which the wavelength changes is 10 nm, which makes it possible to measure the spectrum of any radiation with a high degree of accuracy. More accurate spectrophotometers used for research purposes can measure the spectrum in narrower intervals of 5 nm and 1 nm, but the accuracy will be excessive when used in printing.

Spectral range This is the range within which the spectrophotometer can operate. For most cases in printing, the spectrum of light radiation is assessed in the visible wavelength range from 380 to 730 nm. For some cases, it may be necessary to evaluate the ultraviolet and infrared components of radiation. Spectrophotometers measure only the emission spectrum. All other characteristics are considered based on spectral data.

Inter-device consistency- this is the spread of measured values of the same sample, measured using a reference and test device.

Repeatability determines the accuracy of measurements carried out by the same operators during several measurements with the same instruments of the same samples.

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Synonyms:

Spectrophotometers are designed to measure transmittance, optical density and concentration of substances in liquid samples and can be used in laboratories of various profiles.

The choice of instruments for carrying out spectrophotometric techniques is quite wide. The devices differ, first of all, in the spectral range (visible region of the spectrum or the region including UV), the spectral width of the slit, the accuracy and reproducibility of wavelength setting, the presence of scanning spectra, equipment, type of wavelength setting (manual or automatic - software), etc. .

Manufacturers of spectrophotometers and main models

Among the devices sold on the Russian market, the following models and manufacturers can be distinguished:

— (models B-1100, UV-1100, UV-1200, UV-3000, UV-3100, UV-3200, UV-6100). They are produced in China by order and under the control of the Russian company Industrial Environmental Laboratories.

— Spectrophotometers of the PE series(PE-5300VI, PE-5400VI, PE-5400UF). The devices are manufactured by the Russian company EKROSHIM.

— Spectrophotometer KFK-3-01(Concentration photoelectric photometer). This device is produced by the Zagorsk Optical-Mechanical Plant (ZOMZ) and is an improved model of KFK-3, which was used in almost any laboratory in the USSR.

— Spectrophotometer KFK-3KM produced by UNICO-SIS, Russia.

— Spectrophotometers SF-56 and SF-2000 for operation in the range of 190–1100 nm. The devices are manufactured by the Russian company OKB Spectr.

— Spectrophotometers UNICO(models 1201, 1205, 2100, 2800, 2802, 2802S, 2804, 2100UV). Manufacturer United Products & Instruments, Inc., USA, distributor in Russia - UNICO-SIS company

— LEKI spectrophotometers(models SS1104, SS1207, SS1207 UV, SS2107, SS2107UV, SS2109UV, SS2110UV). The devices are manufactured by MEDIORA, Finland, and the distributor in Russia is the Laboratory Equipment and Instruments company.

All of these devices are included in the register of measuring instruments and can be used in an accredited laboratory.

Technical characteristics and features of models

Below we will discuss the main technical characteristics, features and prices of the most popular spectrophotometer models.

Spectrophotometers B-1100 and UV-1100 Ecoview series

They have been produced since 2016 and replaced the discontinued spectrophotometers of the PE Promekolab series. Devices of the PE Promekolab series work in many laboratories and have proven themselves well. The Ecoview models that replaced them have improved technical characteristics and improved software.

Peculiarities:

Availability of color display

Spectral range (model B-1100), nm: from 315 to 1050;
Spectral range (model UV-1100), nm: from 200 to 1050;

The approximate price of the B-1100 spectrophotometer is RUB 75,000.00. , UV-1100 – 148,000.00 rub.

and UV-1200 Ecoview series

The devices differ from the B-1100 and UV-1100 models by improved characteristics and additional software functions. the presence of a large color touch screen, which is unique for devices of this class. The devices are also equipped with special stepper motors that reduce operating noise. As in the models of the previous series, the devices are equipped with a self-calibration system and do not require the use of special control filters.

Peculiarities:

Availability of a color touch display and an intuitive interface;
Transfer data to external storage device
Transferring calibration curves between samples of the same type
Possibility of saving measurement results in the device memory
Availability of an operator prompt system that facilitates operation of the device
Automatic (software) wavelength setting
Large cuvette compartment, allowing the use of cuvettes with an optical path length of up to 100 mm.
Automatic wavelength adjustment system (no need to control parting accuracy using light filters)
Availability of USB connector

Main technical characteristics:

Spectral range (), nm: from 315 to 1050;
Spectral range (model UV-1200), nm: from 190 to 1050;
Measurement range of spectral coefficients of directional transmittance,%: from 0.1 to 99;
Range of indications of spectral coefficients of directional transmittance, %: from 0 to 200;
Range of optical density readings, B: from -0.3 to 3.0;
Error in setting wavelengths, nm, no more than: ±1.0
Spectral slit width, nm: 4.0

The approximate price of the spectrophotometer B-1200 is 115,000.00 rubles, UV-1200 is 198,000.00 rubles.

PE series spectrophotometers

The Ekroskhim company (formerly Ekokhim) produces spectrophotometers PE-5300VI, PE-5400VI and PE-5400UF. The devices are designed for carrying out spectrophotometric techniques in the visible and UV regions of the spectrum. The devices have a registration certificate for a medical device (RU) and can be used in medical institutions.

Spectrophotometer PE-5300VI

The device has a manual setting of the wavelength with an accuracy of 2 nm, is designed for measurements in the visible region of the spectrum, in the basic configuration it is equipped with a three-position cuvette holder for standard KFK cuvettes (width 24 mm), using additional adapters (included in the delivery set) it is possible to work with European cuvettes type (width 10 mm). The large cuvette compartment allows you to work with cuvettes with an optical path length of up to 100 mm. It can be equipped with a cuvette holder for 4 cuvettes 10 mm wide (European standard) with an optical path length from 5 to 50 mm. Availability of a USB connector for connecting a PC.

Main technical characteristics:

Spectral range: 325-1000 nm.
Wavelength setting error, no more than: ±2 nm.
Reproducibility of wavelength setting, no more than: 1 nm.
Limits of permissible absolute error when measuring spectral coefficients of directional transmission, no more than: ±0.5%T.
Optical density measurement range: from 3.000 to 0.000;

The approximate price of the PE-5300VI spectrophotometer is RUB 75,000.00.

Spectrophotometer PE-5400VI and PE-5400UF

The devices have an automatic (software) setting of the wavelength with an accuracy of 1 nm, are designed for measurements in the visible and UV regions of the spectrum, as standard they are equipped with a four-position cuvette holder for standard KFK cuvettes (width 24 mm), when using additional adapters (included in delivery) It is possible to work with European-type cuvettes (width 10 mm). The large cuvette compartment allows you to work with cuvettes with an optical path length of up to 100 mm. It can be equipped with a cuvette holder for 6 cuvettes 10 mm thick with an optical path length from 5 to 50 mm.

The PE-5400 series devices provide the ability to scan the spectrum using special SC5400 software, supplied separately. Availability of a USB connector for connecting a PC.

Main technical characteristics:

Spectral range (for model PE-5400VI): 315-1000 nm.
Spectral range (for model PE-5400UF): 190-1000 nm.
Spectral slit width: 4 nm.
Wavelength setting error: no more than ±1 nm.
Wavelength setting reproducibility: ± 0.5 nm.
Limits of permissible absolute error when measuring spectral coefficients of directional transmittance, no more than: ±0.5%T (315-1000 nm) and ±1.0%T (190-315 nm).
Optical density measurement range: 3.000 to 0.000;
Directional transmittance measurement range: 0.0 to 100.0%.

The approximate price of the spectrophotometer PE-5400VI is 109,000.00 rubles, PE-5400UF is 167,000.00 rubles.

Spectrophotometer KFK-3-01-"ZOMZ" (photoelectric photometer)

The device is produced by one of the oldest enterprises in the optical industry, the Zagorsk Optical-Mechanical Plant. The plant was founded in 1935 and produced spectrophotocalorimeters KFK-2 and KFK-3, known to all chemists.

KFK-3-01 is a small-sized universal spectrophotometer designed for the analysis of liquid solutions using spectrophotometric techniques in the visible region of the spectrum.

The device is available in three versions: KFK-3-01-ZOMZ - basic model; KFK-3-02-ZOMZ - a device with a thermostated cuvette compartment; KFK-3-03-ZOMZ is a photometer with a flow cell with a pump and an external thermostat for sample preparation.

The device is equipped with a cuvette holder for installing cuvettes with an optical path length of 1-100 mm. KFK-3-ZOMZ photometers have a registration certificate for a medical device (RU) and can be used in medical practice.

Main technical characteristics:

Spectral range: 315-990 nm;
Wavelength setting error ±3 nm
Selectable spectral interval, nm, no more than: 5 nm;
Transmittance measurement range, %: 1-100
Optical density measurement range, B: 0-3
Concentration measurement range, units. conc. 0.001-9999
Transmission coefficient measurement error ±0.5%

The approximate price of the KFK-3-01-ZOMZ spectrophotometer is RUB 73,000.00.

Spectrophotometer KFK-3KM

The spectrophotometer operates in the visible region of the spectrum (325-1000 us), measures optical density, transmittance and concentration of solutions and is designed to implement a wide range of spectrophotometric techniques. The device is manufactured in Russia from imported components and has a bright and unusual design.

In terms of capabilities and main characteristics, it completely replaces FEC, KFK-2, KFK-3, KFK-5.

Peculiarities:

Ease of use, intuitive interface;
Connects to a computer via the RS-232C port (COM port) and works with specialized software.
Availability of a registration certificate for medical equipment (RU), the device can be used in medical institutions;
Convenient 10-digit keyboard;
Programming function for creating and saving calibration graphs;
Work with cuvettes from 5 to 100 mm of standard thickness (24 mm, standard cuvettes for KFK);
Availability of adapters for European standard cuvettes with a width of 10 mm;
Non-volatile memory for storing measurements.

Main technical characteristics:

Spectral range: 325-1000 nm
Spectral slit width: 5 nm
Wavelength setting error, no more than 2 nm
Repeatability of wavelength setting - 1nm
Transmittance (T) measurement range: 0-125%
Optical density measurement range (A): -0.1-2.5
Error in determining transmittance, no more than 1.0%T

The approximate price of the KFK-3-KM spectrophotometer is 80,000.00-85,000.00 rubles. The price of the device depends on the dollar exchange rate.

Having a general understanding of the principle of measuring absorption spectra, you can try to synthesize the simplest spectrophotometer. The diagram of such a device is shown in Fig. 1.1.19.

Rice. 1.1.19.

This spectrophotometer scheme is called single-beam. Here, to measure absorption in the same monochromatic beam, light must be passed alternately through a cuvette with a sample and a cuvette with a solvent (control).

Modern models of spectrophotometers are built on the two-beam principle. In this type of spectrophotometer, a monochromatic beam is periodically directed by a rotating mirror through two channels, one of which contains a cuvette with a sample, and the other a cuvette with a solvent. The beams pass through the sample and control in antiphase, and the difference in intensities is recorded by a photometric system, followed by automatic recording of the spectrum on a form in the coordinates:

Such spectrophotometers include a dual-beam recording device Specord M-40, equipped with a microcomputer, with a high degree of automation of measurement processes and the possibility of mathematical processing of results (Fig. 1.1.20).

Specord M-40 spectrophotometer is designed to measure absorption spectra in a wide range of wavelengths

I (200-900 nm) or V (50.000-11.000 cm~ x). Wave number v

is the reciprocal of the wavelength R, i.e. measured in cm~ x.

If I is expressed in nm, then: The device uses two light sources - a deuterium lamp for the ultraviolet range 200-400 nm (50,000-25,000 cm"1) and an incandescent lamp for the visible and near-infrared region 400-900 nm (25,000-

11,000 cm" 1). The optics of the device are designed to operate in the entire specified range and are assembled using reflective (mirror) technology (flat mirrors, condensers, replicas, etc.).

In the ultraviolet region, the principle of double monochromatization of the radiation of a deuterium lamp is used. The diffractive double monochromator, consisting of a preliminary and main monochromator, provides high quality monochromatization of ultraviolet light and reduction of interfering scattered radiation. When scanning the spectrum in the visible region, a flat mirror-screen is introduced into the ray path of the preliminary monochromator, which blocks the rays of the hydrogen lamp and directs light from the incandescent lamp to the entrance slit of the main monochromator. Thus, only the main monochromator operates in the visible region.

The operating range of ultraviolet gratings in the preliminary and main monochromator (1302 lines/mm) is in the range of 54,000-28,000 cm"1, and the gratings of the visible range (651 lines/mm) are in the range of 31,000-11,000 cm"1. Switching of gratings from those operating in the ultraviolet region to those intended for the visible region occurs automatically at the wave number at=30.000 cm" 1. Both gratings belong to the first order gratings (see above), and to prevent light rays from spectra of higher orders from entering when working in the visible range, light filters are automatically introduced (when switching light filters, the spectrum sweep also automatically stops for a while).

The Specord M-40 spectrophotometer provides adjustment of the width of the slits. The input and output slits of the monochromator are rigidly connected to each other and controlled by stepper motors from a computer. Two slot control modes are possible:

- with a constant slit width when recording the entire spectrum,
- with a variable slit width, the value of which can change during spectrum recording.

The spectral width of the slit can be set by selecting fixed values from a set of slits from 10 cm"1 to 200 cm"1. The spectrum is scanned by wavelength in the Specord M-40 spectrophotometer using stepper motors, the operation of which is controlled by a microcomputer built into the device. Thus, the spectrum is measured point by point - precisely fixed wavelengths. The choice of slot width and pitch (number of points) is made depending on the characteristics of the object and the purpose of the study.

A monochromatic beam of a given spectral width (interval with a known ^Kpshstrum.) is modulated and then directed

Rice. 1.1.20.

1. Source of ultraviolet radiation - deuterium lamp; 2. Source of visible and infrared radiation - incandescent lamp; 3. Pre-monochromator collimator (concave mirror); 4. Incandescent lamp condenser (concave mirror); 5. Pre-monochromator diffraction grating; 6. Flat rotating mirror; 7.10. Entrance (7) and exit (10) slits of the main monochromator; 8. Collimators of the main monochromator (concave mirrors); 9. Diffraction grating of the main Ebert monochromator (a - replica for the ultraviolet region, b - replica for the visible and infrared region); 11. Modulator; 12. Concave toroidal mirrors; 13. A rotating mirror on the motor axis that alternately separates two beams; 14. Flat rotating mirror; 15. Cuvette with sample; 16. Cuvette with control; 17. Photomultiplier tube (PMT).

alternately using a rotating flat mirror with slits (13, Fig. 1.1.20) into the channel with the object or into the channel with the solvent (control). The object chamber is divided into two compartments. The large compartment is designed for working with transparent solutions, and the small one is for light-scattering objects.

The rays passing through the sample and control alternately, in antiphase, enter the photomultiplier, generating (if there is light absorption in the sample) an alternating photocurrent (Fig. 1.1.21). If the intensity of the rays is the same (the absorption of the two cells is the same), then the alternating photocurrent at the PMT output is 0.

Rice. 1.1.21.

Otherwise, an alternating current occurs, which is amplified. The signal is processed and the measurement result (transmission

or optical density) is recorded on

spectrophotometer recorder form. The entire process of spectrum measurement and its reproduction is carried out under the control of a microcomputer built into the device. Computerization of the spectrophotometer makes it possible to use programs for optimal measurement and subsequent mathematical processing of the results, as well as storing the received information in the computer memory in constant readiness for processing.

In the calibration mode, the operator enters the normalized values assigned to a given calibration solution from the console, sequentially supplies calibration solutions to the cuvette compartment and carries out measurements.

In the analysis mode, the operator places a cuvette with the test solution in the cuvette compartment and carries out the measurement.

Rice. 3.31. Generalized block diagram of a single-channel colorimeter. 1 - source of light energy; 2 - diaphragm; 3 - optical system; 4 - bandpass filter; 5 - optical system; 6 - cuvette; 7 - photodetector; 8 - analog-to-digital converter; 9 - microcomputer; 10 - indicator; 11 - operator console;

12 - communication interface with an external computer and recording device

Rice. 3.32. Simplified optical design of a single-beam spectrophotometer. 1 - monochromator (source of monochromatic radiation of light energy at wavelength \\, 2 - cuvette with the test solution; 3 - detector (photodetector); Ф„ - incident flux of light energy; Ф - flux of light energy passing through the solution, absorbing part of the energy

Rice. 3.33. Generalized block diagram of a single-channel spectrophotometer.

1 - source of light energy (visible region);

2 - rotating reflector; 3 - source of light energy (ultraviolet region); 4 - optical system directing the energy flow to the entrance slit; 5 - entrance slot; 6 - optical system that forms a parallel flow of light energy;

7 - dispersing element (prism or diffraction grating); 8 - optical system directing the energy flow to the exit slit; 9 - exit slot; 10 - optical system that forms the energy flow passing through the cell; 11 - cuvette; 12 - photodetector; 13 - analog-to-digital converter; 14 - microcomputer; 15 - indicator;

16 - operator console; 17 - communication interface with an external computer and recording device

If the device does not have an automatic calibration mode, then the operator constructs a calibration graph of the dependence of optical density and normalized values assigned to calibration solutions.

Spectrophotometers

The main difference between a spectrophotometer and a photocolorimeter is the ability to pass a light flux of any required wavelength through the sample under study, to carry out photometric measurements by scanning (viewing) the entire wavelength range of not only visible (V1S) light - from 380 to 750 nm, but also near ultraviolet ( UV) - from 200 to 380 nm.

The latter circumstance does not exclude the feasibility of producing inexpensive spectrophotometers that do not have a source of ultraviolet radiation and operate only in the visible part of the optical wavelength range.

The purpose of the mentioned and very important mode of operation of spectrophotometers - scanning mode - is to construct a spectral absorption (absorption) curve and find peaks on it, as well as study interference processes and search for false peaks that lead to erroneous results in spectrophotometric studies.

The main components of a single beam spectrophotometer are shown in Fig. 3.32.

The principle of operation of the spectrophotometer. Polychromatic light from the source passes through a monochromator, which splits white light into color components. Monochromatic radiation with discrete intervals of several nanometers passes through that part of the device where the sample with the test sample is located.

Light source. The UV/VIS spectrophotometer (ultraviolet + visible light) has two light sources: for the visible part of the spectrum and an ultraviolet source - from 100 to 390 nm.

The source of visible light is a tungsten lamp, usually a halogen lamp, which produces a constant light flux in the range of 380-950 nm, being a stable and durable source of light energy with an average service life of more than 500 hours.

Hydrogen or deuterium lamps are used as a UV source. Ultraviolet lamps containing deuterium have a high emission intensity and a continuous spectrum in the range from 200 to 360 nm.

Design and principle of operation of the spectrophotometer

In Fig. Figure 3.33 shows a generalized block diagram of the spectrophotometer.

Let's consider the interaction and functional purpose of the elements of the structural diagram.