Spectrophotometers. Manufacturers, model range, main characteristics and cost. Spectrophotometer - how it works What does a spectrophotometer measure?

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.

Photometric studies are carried out using photocolorimeters and spectrophotometers. Measurement of the optical density of the standard and test colored solutions is always carried out in relation to the reference solution (zero solution). As a reference solution, you can use a part of the test solution containing all the added components, except for the reagent that forms a colored compound with a certain substance. If the reference solution remains colorless and, therefore, does not absorb rays in the visible region of the spectrum, then distilled water can be used as a reference solution.

Let us consider the design and principle of operation of photometric instruments using the example of the photoelectric concentration colorimeter KFK-2 and the spectrophotometer SF-46.

Single-beam photometer KFK-2 is designed for measuring transmittance, optical density and concentration of colored solutions, scattering suspensions, emulsions and colloidal solutions in the spectral region of 315-980 nm. Transmittance measurement limits 100-5% (D = 0-1.3). The basic absolute error of transmittance measurement is 1%.

The basic optical diagram of the KFK-2 photocolorimeter is shown in Fig. 2.2.

Light from a small-sized halogen lamp (1) passes sequentially through a system of lenses, heat-protective (2), neutral (3), selected color (4) filters, a cuvette with a solution (5), hits the plate (6), which divides the light flux into two: 10% of the light is directed to the photodiode when measuring in the spectral region 590-540 nm) and 90% to the photocell (when measuring in the spectral region 315-540 nm).

The characteristics of the filters are presented in table. 2.1.

Photoelectric photometer KFK-3 is intended for measuring the transmittance and optical density of transparent liquid solutions and transparent solid samples, as well as for measuring the rate of change in the optical density of a substance and determining the concentration of a substance in solutions after preliminary calibration of the photometer. The basic optical diagram of the KFK-3 photometer is shown in Fig. 2.3.

The lamp filament (1) is represented by a condenser (2) in the plane of the diaphragm D1 (0.8 x 4.0), filling the diaphragm slit with light. Next, diaphragm D1 is represented by a concave diffraction grating (4) and a concave mirror (5) in the plane of the same slit diaphragm D 2 (0.8 x 4.0). The diffraction grating (6) and the mirror create a stretched spectrum pattern in the plane of the diaphragm D2. By rotating the diffraction grating around an axis parallel to the grating lines, radiation of any wavelength from 315 to 990 nm is isolated through the diaphragm slit D2. The lens (7, 8) creates a weakly luminous beam of light in the cuvette compartment and forms an enlarged image of the slit D 2 in front of the lens (10). The lens (10) converges the light beam on the receiver (11) in the form of a uniformly illuminated circle of light. To reduce the influence of scattered light in the ultraviolet region of the spectrum, a light filter (3) is installed behind the D1 diaphragm, which operates in the circuit during measurements in the spectral region of 315-400 nm, and then is automatically removed. Rectangular cuvettes (9) are installed in the cuvette compartment (between objective 7, 8 and lens 10).

The photometer is intended for use in agriculture, medicine, water supply enterprises, metallurgical, chemical, food industries and other areas. The measurement limits for transmittance are 0.1-100%, optical density is 0-3%.

The SF-46 spectrophotometer is designed for measuring the spectral transmittance of liquid and solid substances in the spectral region from 190-1100 nm.

The SF-46 spectrophotometer is a stationary device designed for use in laboratory premises, without increased risk of electric shock.

The measurement range of spectral transmittances is from 1 to 100%.

The absolute measurement error does not exceed 1%, and the standard deviation of transmission does not exceed 0.1%.

The operation of the SF-46 spectrophotometer is based on the principle of measuring the ratio of two light fluxes: the flux passing through the test sample, and the flux incident on the test sample (or passing through the control sample).

The light beam from the illuminator enters the monochromator through the incoming slit and is decomposed into a spectrum by a diffraction grating. The control and test samples are alternately introduced into the monochromatic radiation flow coming from the exit slit into the cuvette compartment. The radiation passed through the sample reaches the cathode of the photocell in the receiving and amplifying unit. Electrical signals on a resistor included in the anode circuit of a photocell are proportional to the radiation fluxes incident on the photocathode.

A DC amplifier with a gain close to unity ensures transmission of signals to the input of a microprocessor system (MPS), which, at the operator’s command, alternately measures and stores voltages UT, U 0 And U, proportional to the dark current of the photocell, the flux passing through the sample under study. After measurement, the MPS calculates the transmittance of the sample under study using the formula

In the mode of determining the optical density of a sample, the MPS will calculate the optical density according to the formula

The value of the measured value is displayed on a digital photometric display.

In Fig. 2.4 shows a block diagram, and Fig. 2.5 - optical diagram of the SF-46 spectrophotometer.

Radiation from the source (1 or G) falls on a mirror capacitor (2), which directs it to a flat rotating mirror (3) and gives an image of the radiation source in the plane of the lens (4), located near the entrance slit (5) of the monochromator.

The radiation passing through the entrance slit falls on a concave diffraction grating (6) with a variable pitch and a curved line. The grating is made on a spherical surface, therefore, in addition to dispersing properties, it has the property of focusing the spectrum. The use of a variable pitch and a curved groove significantly reduces the aberration distortion of the concave diffraction grating and makes it possible to obtain high quality spectrum over the entire operating spectral range.

The diffraction beam is focused in the plane of the output slit (7) of the monochromator, located above the entrance slit (5). Scanning is carried out by rotating the diffraction grating, while monochromatic radiation of different wavelengths passes through the exit slit (7) and lens (8), a control or test sample, lens (9) and, using a rotating mirror (10), hits the photosensitive layer of one of the photocells (11 or 12).

To ensure the operation of the spectrophotometer in a wide spectral range, two photocells and two radiation sources of a continuous spectrum are used.

An antimony-cesium photocell with a quartz glass window is used for measurements in the spectral region from 186 to 700 nm, and an oxygen-cesium photocell for measurements in the spectral region from 600 to 1100 nm. The wavelength at which one should switch from measurements with one photocell to measurements with another photocell is indicated in the passport.

The design of spectrophotometers and their characteristics can vary significantly depending on the manufacturer and the tasks for which the device is designed. However, the basic design elements of all devices are similar. These are a light source, a monochromator, a cuvette compartment with a sample and a recording detector. Mercury or halogen lamps are most often used as a light source. A monochromator is a device for selecting a narrow part of it (1-2 nm) from the entire emitted spectrum. Monochromators can be built on the basis of light-separating prisms or on the basis of a diffraction grating. Also, some devices may additionally use sets of light filters. The cuvette compartment can be equipped with mechanisms for thermostatting, mixing, and adding substances directly during the measurement process. For studies of small volumes of substances, cellless technology can be used, when the sample is held due to the forces of surface tension of the liquid.

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

The rotating reflector (2) directs the flow of light energy from one of the sources (1 or 3), through the optical system (4) to the entrance slit (5) of the monochromator. From the output of the monochromator, a monochromatic flow of light energy with a certain wavelength λ arrives through the slit (9). Setting the required wavelength is most often done by changing the angle of incidence of the polychromatic flux of light energy relative to the plane of the dispersing element (7). The optical system (10) forms the light flux in such a way that, with the minimum permissible volume of the test solution and repeated installation of the cuvette (11) in the cuvette compartment, the geometry of the flow does not change.

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.

MAIN UNITS OF THE SPECTROPHOTOMETER

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 200 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.

Cuvettes

As you know, the sample under study is placed in special attachments. They are different for each type of sample. For solids, these are special clamps, and for spectral measurements of liquid samples, special containers made of quartz glass, so-called cuvettes, are used.

Most spectrophotometers use standard cuvettes that are designed to be placed in a way that allows the light beam to travel horizontally. The main disadvantage of such cuvettes is that only a small part of the sample (about 10%) is illuminated by the measuring light. If the sample is of high value or is available in small volumes, microcuvettes or ultramicrocuvettes with a volume of 50 or even 2.5 µl can be used. Very small volume cuvettes exhibit capillary properties and problems arise with the formation of air bubbles, which requires degassing. Finally, it is difficult to remove the sample from such cuvettes. Standard cuvettes have external dimensions: 12.5 12.5 45 mm, and internal ones - 10 10 mm. Cuvettes with a smaller internal volume, produced by one manufacturer, have the same external size as the standard ones, but the internal one, for example, 10 1.25 mm.

DISPERSING ELEMENT

In spectrophotometers, prisms and diffraction gratings are most often used as a dispersing element.

A diffraction grating is a technologically more complex product than a prism. Most of the gratings currently used are made by burning and holographic copying and are plates with a large number of parallel lines - up to several hundred per millimeter.

The main advantage of using a prism in a spectrophotometer is its low cost.

The advantage of diffraction gratings is that they provide linear dispersion of light over the entire range of the visible and UV spectra. A negative aspect of using diffraction gratings is their high cost in comparison with prisms and filters.

One of the most important characteristics of monochromators is the bandwidth, expressed in units of wavelengths - nanometers.

If interference filters provide a transmission width in the range of 6-20 nm, then prisms and diffraction gratings provide a narrower band - less than 5 nm, and therefore greater “purity” (monochrome) of the light incident on the cuvette with the sample. Bandwidth is one of the most important characteristics of a spectrophotometer. A decrease in the bandwidth entails an increase in the resolution of the spectrophotometer - a significant characteristic of the quality of spectrophotometric instruments.

MONOCHROMATERS

The operation of spectral devices - spectrophotometers - is based on the fact that in some physical systems the conditions for the passage of light are different. Such systems are called dispersive. Typically a prism or diffraction grating is used as a dispersing element. Devices that make it possible to separate polychromatic light into a monochromatic emission spectrum are called monochromators.

Functional diagram of a monochromator with a prism.

- entrance slot; 2-lens forming a parallel flow of light energy; 3-prism; 4 - lens directing the energy flow to the screen; 5 - screen; 6 - exit slot

The slit (1), onto which the polychromatic flow of light energy falls, is located in the focal plane of the lens (2). This part of the device is called a collimator. A parallel stream of light energy emerging from the lens (2) falls on the prism (3). Due to dispersion (due to the dependence of the refractive index on wavelength), light of different wavelengths leaves the prism at different angles. If a screen (5) is placed in the focal plane of the objective lens (4), the lens will focus parallel energy flows for different wavelengths in different places on the screen. By rotating the prism (3), you can scan through the slit (6) monochromatic energy flows in the entire radiation spectrum. Often, a diffraction grating is used as a dispersing element, which is a glass or metal plate on which parallel identical strokes are applied, located at exactly the same distances from each other. The figure shows a diffraction grating consisting of alternating slits parallel to each other of the same width b, located at the same distance a from each other. The sum (a+b) is the period of this structure and is called the lattice constant d.

Functional diagram of a monochromator with a diffraction grating.

- entrance slot; 2 - lens that forms a parallel flow of light energy; 3 - diffraction grating; 4 - lens directing the energy flow to the screen; 5 - screen; 6 - exit slot

Through the entrance slit (1), the polychromatic flow of light energy by the objective lens (2) is transformed into a parallel flow that passes through the slits of the diffraction grating (3). At each point on the screen (5), located in the focal plane of the objective lens (4), those rays will be collected that before the lens were parallel to each other and propagated at a certain angle Q to the direction of the incident wave. Therefore, the illumination at point P on the screen (5) is determined by the result of the interference of secondary waves propagating both from different parts of the same slit and from different slits. There is a direction in which, propagating, secondary waves from all slits will arrive at point P in one phase and strengthen each other, and another - when the waves are out of phase and weaken each other. Thus, alternating light and dark stripes are observed on the screen. The condition for the formation of maxima from a diffraction grating, that is, when waves reinforce each other during interference, is observed when the path difference is equal to an integer number of waves. The dependence of the formation of maxima of various wavelengths on the angle Q of the diffraction grating is expressed by the formula: d*sinQ = k - 1, where k = 0, 1, 2.

If light of different wavelengths is incident on the grating, then the maxima for different wavelengths are located at different angles Q to the original direction of light propagation. Therefore, a diffraction grating decomposes polychromatic light into a diffraction spectrum and is used as a dispersive device.

Spectrophotometers are modern equipment designed to study the properties of substances or objects by analyzing the spectrum of the optical range of electromagnetic radiation passed through a sample or reflected from it. Simply put, spectrophotometers compare the flow of light initially directed at the sample being studied with the flow of light transmitted through or reflected from the sample. For research, the widest possible range of wavelengths is scanned - from 160 nm (ultraviolet region) to 3300 nm (infrared region), which allows you to obtain maximum information about the substance.

Spectrophotometric methods are based on the fact that each substance has its own spectral properties, characteristic only of it. In this case, the state of aggregation, temperature, and interaction of the sample with other substances, for example, in a mixture or chemical compound, do not matter. With the help of spectrophotometers, qualitative and quantitative studies are possible.

More complex and more expensive than conventional photocolorimeters, but they are more accurate and allow solving more complex problems. The great advantage of spectrophotometers is the ability to draw conclusions about the composition of a substance, the presence and amount of impurities, while photocolorimeters work only with already known solutions. For example, it is impossible to determine the counterfeit of red wine using magenta using a photocolorimeter, since the color of the solution of magenta salts is identical to the color of natural wine. But the spectrophotometer will easily detect and identify the atypical spectrum of foreign impurities.

Spectrophotometer device

Spectrophotometers of all types consist of the following main components:
- Light source;
- monochromator;
- optical elements that direct the light flux: glass, prisms, mirrors, light guides, etc.;
- compartment for the substance being studied, solid or liquid;
- photodetector;
- signal amplifier.

As a light source, conventional tungsten lamps operating in the visible and infrared spectrum, deuterium lamps for the UV range, and combined halogen-deuterium lamps with a range from ultraviolet to infrared are used.

A monochromator uses prisms or diffraction gratings that emit radiation of a certain wavelength, usually with an accuracy of ±10 nm (precision laboratory instruments allow analysis with an accuracy of ±2 nm).

The compartment for the substance being studied can be adapted for one or several samples, as well as for operational flow analysis.
Photodetectors record the level of light flux passing through the sample under study. The results can be displayed in different forms, depending on the purpose of the device and the choice of the type of study. As a rule, spectrophotometers are equipped with several types of photodetectors in order to record radiation in different regions of the spectrum. For example, antimony-cesium is capable of detecting radiation with a wavelength from 186 to 700 nm, and a semiconductor based on PbS - from 700 to 1800 nm.

The most modern spectrophotometers are equipped with a photodiode array with built-in sensors for each wavelength range. All sensors convert light signals into electrical signals simultaneously, allowing specialized microcontrollers to display test results almost instantly. (Conventional spectrophotometers process signals for different wavelengths sequentially.) The resolution of the device depends on how many photodiode sensors the device is equipped with. Spectrophotometers with a photodiode array make it possible to conduct operational analyzes directly in production and at the time of a chemical reaction, analyzing the state of the reaction products.

In the next article we will talk about the operating principle of spectrophotometers, places of their application and features of selecting suitable equipment for the laboratory.