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Spectrophotometer in laboratory

1. What is spectrophotometer?
    1.1. Definition of spectrophotometer
    1.2. Spectrophotometer application
2. Spectrophotometer working principle
3. Spectrophotometer parts and functions
4. Types of spectrophotometer
    4.1. VIS spectrophotometer
    4.2. UV-VIS spectrophotometer
    4.3. Infrared spectrophotometer
    4.4. Fluorescence spectrophotometer
    4.5. Atomic absorption spectrophotometer
5. Spectrophotometer specifications
    5.1. Double beam spectrophotometer
    5.2. Flame atomic absorption spectrometer
    5.3. Fluorescence spectrophotometer
    5.4. Handheld spectrometer
6. How to use spectrophotometer?
7. Precautions for using spectrophotometer
8. How to buy spectrophotometer?

What is spectrophotometer?

Definition of spectrophotometer

Spectrophotometer, also known as spectrometer , is a scientific instrument that decomposes light of complex composition into spectral lines. The measurement range generally includes the wavelength range of 380 ~ 780 nm in the visible region and the wavelength range of 200 ~ 380 nm in the ultraviolet region. Different light sources have their emission spectra, so different light emitters can be used as the light source of the instrument. The emission spectrum of tungsten lamp: tungsten light source issued by the 380 ~ 780 nm wavelength spectrum of light through the refraction of the trigonal prism, can be obtained by the red, orange, yellow, green, blue, indigo, violet continuous chromatography; the chromatography can be used as a visible spectrophotometer light source.

Spectrophotometer application

Spectrometer is a kind of analytical instrument with wide applications. Its application areas involve laboratory analysis, pharmaceutical, medical and health, chemical and chemical, environmental protection, geology, machinery, metallurgy, petroleum, food, biology, materials, metrology science, agriculture, forestry, fisheries, and other fields of scientific research, teaching, and other aspects, used for qualitative analysis, purity check, structural analysis, complex composition and determination of stability constants, reaction kinetics research, etc.

Spectrophotometer working principle

The basic principle of spectrophotometer is that substances produce the effect of light absorption under the irradiation of light, and the absorption of light by substances is selective. Various different substances have their own absorption spectrum. Therefore, different wavelengths of monochromatic light through the solution when its light energy will be absorbed to different degrees, the degree of light energy is absorbed and the concentration of the substance has a certain proportional relationship, that is, in line with Beale's law:
From the above equation, we can see that, T is the transmittance, I0 is the incident light intensity, I is the transmitted light intensity, A is the extinction value (absorbance), ε is the absorption coefficient, b is the optical path length of the solution, and c is the concentration of the solution. From the above equation, it can be seen that when the incident light, absorption coefficient and solution thickness are certain, the transmittance is varied according to the concentration of the solution.

Spectrophotometer parts and functions

Spectrometer is a highly used instrument in the laboratory, in terms of its basic structure, are composed of five basic parts, which is light source, monochromator, absorption cell, detector and data system.
1. Spectrophotometer light source
Two types of lamps are used as light sources for spectrophotometers, heavy hydrogen lamps for measurements in the ultraviolet band and tungsten lamps for measurements in the visible and near-infrared bands.

2.spectrophotometer monochromator
Spectrophotometer spectrometer spectroscope’s role is to extract monochromatic light from the light source (white light), spectrometer filter type, prism type, and grating type (diffraction grating) several.
* Filter
Available filter picks out a single wavelength of light. Filters can also be used in combination with diffraction gratings to filter out stray light
* Prisms
Can scatter light in the spectral range of 175-2,700 nm. The degree of scattering depends on the wavelength.
* Diffraction grating
Scattering is available over all wavelengths, and a wide range of wavelengths can be obtained with diffraction gratings. In addition, a constant spectrum can be obtained with a constant slit width.

3.Spectrophotometer absorption cell
The container in which the sample is placed is called a "cell", and there are two types of cells: glass and quartz. Glass cells are used for measurements in the visible wavelengths above 340 nm because the light in the ultraviolet wavelengths below 340 nm is difficult to pass through the glass cell. On the contrary, although quartz cells allow light of all wavelengths in the UV and visible bands to pass through, they are mainly used for measurements in the UV band due to their high price.

4. Spectrophotometer detector
The role of the detector is to convert the transmitted light of the sample into an electrical signal. Optical semiconductors or various types of photomultiplier tubes can be used as detectors.
* Optical semiconductor
In the ultraviolet to near-infrared band with high speed, high sensitivity, and low noise characteristics. Photocells sensitive only to the visible wavelength band are used. Silicon photodiodes are a representative type of optical semiconductor.
* Photomultiplier
The combination of a photocell and an amplifier (about 10 times amplification) is sensitive to both UV and visible wavelengths, and the sensitivity can be adjusted substantially by adjusting the applied voltage.

Types of spectrophotometer

There are five main types of spectrophotometers:

1. VIS spectrophotometer

VIS spectrophotometer is used to measure the absorbance of the substance to be measured to visible light (400-760nm) and to perform quantitative analysis of the instrument, called a visible spectrophotometer. Bacterial cell density can be measured at 600nm.

2. UV-VIS spectrophotometer

UV-Vis spectrometer is an instrument used to measure the absorbance of a substance to be measured to visible light or UV light (200-760nm) and to quantify it. It can measure the concentration of nucleic acids and proteins, and can also measure bacterial cell density.
UV spectrophotometer can be divided into single-beam, pseudo-double-beam, and double-beam. Their uses are also different.
Single-beam: suitable for measuring absorbance or transmittance at a given wavelength, generally not for full-band spectral scanning, requiring a high stability of the light source and detector.
Double-beam: automatic recording, fast full-band scanning. Can eliminate the influence of light source instability, detector sensitivity changes and other factors, especially suitable for structural analysis. The instrument is complex and more expensive.
Pseudo dual-beam, also known as proportional dual-beam, is based on the principle that light from the same monochromator is split into two beams, with one beam reaching the detector directly and the other beam passing through the sample and reaching the other detector. The advantage of this instrument is that it can monitor the error caused by the variation of the light source, but it does not eliminate the effect caused by the reference ratio.

3. Infrared spectrophotometer

Infrared spectrophotometer in general refers to infrared spectra greater than 760 nm, which is the commonly used spectral region for the study of organic compounds and can analyze specimens in various states (gas, liquid, and solid). Infrared spectroscopy is characterized by rapidity, small sample size (a few micrograms - a few milligrams), high characterization (various substances have their specific infrared spectrograms), ability to analyze specimens in various states (gas, liquid, solid) and non-destruction of the sample.

4. Fluorescence spectrophotometer

Fluorescence spectrophotometer is an instrument used to scan the fluorescence spectrum emitted by the fluorescent markers in a liquid phase. It is used in scientific research, chemical industry, medicine, biochemistry, environmental protection, as well as clinical testing, food testing, teaching experiments, and other fields.
By measuring these parameters, not only can we do general quantitative analysis, but also can infer the conformational changes of molecules in various environments, to elucidate the relationship between molecular structure and function.

5. Atomic absorption spectrophotometer

The atomic absorption spectrophotometer performs elemental analysis of metals based on the absorption of characteristic radiation by the atomic vapor in the ground state of the substance. It is capable of sensitive and reliable determination of traces or traces of elements.

Spectrophotometer specifications

Double beam spectrophotometer

TypeUV-VIS spectrophotometer
Wavelength range 190-1100nm
Wavelength accuracy±0.3nm
Repeatability of wavelength 0.1nm
Spectral bandwidth 1.8nm
Color transmission ratio accuracy±0.003%T
Repeatability of color transmission ratio0.001%T
Color transmission ratio range 0.0-200%T
Absorbance range -0.30-3A
Concentration display range 0-1999
Baseline straightness±0.001A
Stray light0.05%T@220nm, 360nm
1. Double beam spectrophotometer equips with a large LCD (128×64) graphic liquid crystal display.
2. Spacious sample chamber can accommodate 5-100mm cuvettes.
3. Host can photometric detection, quantitative detection, can display.
4. Standard curve, can store 200 standard curves and 200 detection data.
5. With automatic wavelength calibration, automatic power off to maintain data under the wavelength of absorbance, transmittance, concentration testing.
6. Can be directly connected to a printer (optional) to print data or graphs.

Flame atomic absorption spectrometer

TypeAtomic absorption spectrophotometer
Optical system Large area 1800 lines/mm inscribed grating, fully enclosed optical system
Wavelength range 190-900nm, automatic wave peak search, one-key optical optimization function
Wavelength accuracy ≤0.15nm
Wavelength repeatability ±0.1nm
Burner head Full titanium burner head, 50mm or 100mm universal burner head
Characteristic concentration 0.015μg/mL/1% (Cu)
1. Flame atomic absorption spectrometer can automatically complete safe ignition, extinguishing, and switching, with a reliable structure and low failure rate, thus ensuring the sensitivity and reproducibility of the flame method.
2. The measurement data can be dynamically displayed.
3. Printout: Provide reports for single-element and multi-element analysis; printout of measurement results and instrument conditions.

Fluorescence spectrophotometer

Standard configuration wavelength365nm LED excitation light source
Emission monochromatorC - T diffraction grating monochromator (Em360 ~ 650nm, bandwidth 12nm)
Emission wavelength accuracy ±2nm
Emission wavelength repeatability ≤1nm
Quinine sulfate detection limit of 1×10 (g / ml)
Linear correlation coefficient≥ 0.995
Zero line drift±0.3% (within 10min)
Peak intensity repeatability≤ 1.5%
Supply voltage220V±22V, 50Hz±1Hz
Power 100W
1. Fluorescence spectrophotometer with emission monochromator with 1200-line grating and large aperture aspherical reflector for exceptionally high sensitivity.
2. High brightness and long life LED light source ensure high stability of the test.
3. Real-time fluorescence value, concentration printing.
4. Ultra-wide dynamic range of fluorescence values, accurate determination of small changes in the sample.

Handheld spectrometer

TypeFluorescence spectrophotometer
Degree of resolution Mobile WINDOWSCE system
Operation timeAbout 200 hours
Power supply 8 hous/2 lithium batteries and AC power supply
Weight 1.23kg
1. Handheld spectrometer can be measured and calibrated to improve efficiency, saving time and efficiency.
2. Small power, low power consumption, power-saving and efficient work.
3. All-in-one body, compact size, easy to carry.

How to use spectrophotometer?

1. Before using the instrument, the user should first understand the structure and working principle of the instrument. And the function of each operation knob. Before the power is turned on, the safety of the instrument should be checked, and the power cord should be wired firmly. The starting position of each adjustment knob should be correct, and then turn on the power switch. Before using the instrument, check the silica gel drying cylinder of the amplifier dark box (on the left side of the instrument), if it is damp and discolored, it should be replaced with dry blue silica gel or pour out the original silica gel and dry it before use.

2. Set the sensitivity knob to "1" gear (minimum magnification).

3. Turn on the power, the indicator light is on, the selection switch is set to "T", the wavelength is adjusted to the test wavelength. Instrument preheat 20 minutes.

4. Open the cover of the sample chamber (the light door is closed automatically), adjust the "0" knob, so that the digital display is "00.0", cover the cover of the sample chamber, set the cuvette in the correct position with distilled water, so that the photocell is exposed to light, adjust the transmittance "100%" knob, so that the digital display is "100.0".

5. If the display is less than "100.0", the microcurrent amplifier can be increased appropriately, but as far as possible, set the low multiplier file to use, so that the instrument will have higher stability. But after changing the multiplier, you must recalibrate "0" and "100%" according to (4).

6. After warming up, press (4) to adjust "0" and "100%" several times in succession, then the instrument can be used for measurement.

7. Absorbance A measurement according to (4) adjust the instrument "00.0" and "100%", put the selection switch in "A", adjust the absorbance zeroing knob, so that the digital display is ".000", then the measured sample will be moved into the optical path, the displayed value is the absorbance value of the measured sample.

8. Concentration C measurement: select the switch from "A" to "C", put the sample with calibrated concentration into the optical path, adjust the concentration knob so that the digital display is the calibrated value, put the sample under test into the optical path, and read out the concentration value of the sample under test.

9. If the wavelength of the test is drastically changed, wait a moment after adjusting "0" and "100%", (because of the rapid change of light energy, the photoelectric tube response to light is slow, need a period of light response balance time), when stable, re-adjust "0" and "100%" can work.

Precautions for using spectrophotometer

Spectrophotometer this kind of precision instruments and equipment to the surrounding environment has relatively high requirements, if the environment is not appropriate, when using the measurement results will not be accurate. So whether in the spectrophotometer use or storage more to pay attention to the surrounding environment, in addition to the daily maintenance is also essential. The following introduces the spectrophotometer when using a few precautions.

1. when the equipment is stored, the storage place should be put some desiccant to avoid moisture affect the use effect.

2. pay attention to the cleanliness of the stored cuvette, some parts are not allowed to be wiped directly by hand when cleaning, pay attention to the use of special cleaning tools. When taking the cuvette, fingers can only pinch the gross glass surface of the cuvette, but not touch the optical surface of the cuvette.

3. try to take care not to have any liquid dripping on the instrument, once this phenomenon happens, use special cleaning tools to wipe it within the first time. The cuvette cannot be washed with alkaline solution or strong oxidizing washing solution, nor can it be cleaned with a brush. The water or solution attached to the outer wall of the cuvette should be wiped dry with wiping paper or fine and soft absorbent paper, do not wipe, so as not to damage its optical surface.

4. After use, clean up one part by one part, especially the cuvette, wipe it clean with special cleaning solution, and then dry it after drying treatment before putting it into the storage equipment. To prevent the phototube fatigue, the sample chamber cover must be opened when not measured, so that the optical path is cut off to extend the service life of the phototube.

How to buy spectrophotometer?

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If you are interested in our spectrophotometer or have any question, please write an e-mail to [email protected], we will reply to you as soon as possible.

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