Definition
The core function of the three-purpose ultraviolet analyzer is to use specific wavelengths of ultraviolet light and visible light to irradiate the sample, and realize the qualitative and semi-quantitative analysis of the sample by stimulating the fluorescence generated by the sample, or observing the absorption and reflection characteristics of the sample to ultraviolet light. The reason why this instrument is called "three-use" usually means that it integrates three light source modes: long-wave ultraviolet light (about 365 nanometers), short-wave ultraviolet light (about 254 nanometers) and visible white light, which can adapt to different detection needs.
Principle
The basic working principle of the instrument is based on the interaction of light and matter. When ultraviolet light is irradiated on a sample, two main phenomena may be caused: first, after some material molecules absorb ultraviolet light energy, electrons transition to the excited state, and release energy in the form of fluorescence with a longer wavelength when returning to the ground state, which is the basis of fluorescence analysis; second, the sample itself has characteristic absorption or reflection of specific wavelengths of ultraviolet light, which is analyzed by observing its chiaroscuro or imaging differences. The instrument separates the desired monochromatic excitation light through a filter and is usually equipped with a corresponding protective filter in the viewing window to isolate harmful UV light and clearly observe fluorescence or absorption phenomena.
Measurement method
Conventional measurement methods are non-contact visual observation or recording in combination with an imaging system. The appropriate light source mode is first selected based on the characteristics of the sample being tested, such as the expected fluorescence excitation wavelength. Place the sample on the sample stage in the camera obscura, turn on the corresponding light source, and visually view it directly through the viewing window in a dark environment, or use the matching camera system to capture the image. For fluorescence analysis, the fluorescence color, intensity and distribution of the sample are observed when excited. For absorption analysis, observe the dark spots or characteristic patterns of the sample under UV light. The analysis process usually requires comparison with a known standard sample or atlas.
Influencing factors
The accuracy and repeatability of measurement results are affected by a variety of factors. The stability and wavelength accuracy of the light source are fundamental, and the aging of the light source will cause the output light intensity to be attenuated. Ambient light interference needs to be minimized through a camera obscura design. The characteristics of the sample, such as the concentration of fluorescent substances, quenching effect, uniformity, and interference from the background matrix, directly affect the observation effect. Operating factors include viewing distance, angle, and performance and cleanliness of the instrument's filters. In addition, the subjective visual judgment of the operator is also a factor to consider in the visual method.
Applications
The instrument has a wide range of applications. In biochemistry, it can be used to observe nucleic acids (e.g., EB-stained DNA) or protein bands in electrophoresis gels. In materials science, it is used to detect uniformity or defects in certain fluorescent materials. In criminal investigations and document inspections, it can be used to identify altered or forged documents or detect specific traces. In the food industry, it can be used for the initial screening of certain mycotoxins or adulterants. In the textile and chemical sectors, it can be used for the detection of fluorescent brighteners or special dyes. As a fast and intuitive screening tool, it is often used as a precursor to further precise analysis.
Selection considerations
When choosing a tri-purpose UV analyzer, consider comprehensively. In terms of light source performance, attention should be paid to the accuracy and purity of UV wavelengths, as well as the intensity and stability of light sources in each wavelength. The design of the instrument structure should take into account the airtightness of the camera obscura, the protection and safety of the observation window, and the size and adjustment flexibility of the sample stage. Depending on the inspection needs, decide whether to integrate the imaging system and the resolution and sensitivity of the system. User-friendly design, such as the layout of the control panel and the convenience of switching light sources, also need to be noted. In addition, the safety certification of the instrument, compliance with relevant standards, and the manufacturer's after-sales service and technical support capabilities are also important aspects to ensure the long-term reliable operation of the instrument.