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Ultra-pure water purification method suitable for organic analysis (HPLC, LC / MS)
HPLC is often used for the analysis of various organic substances. When combined with a mass spectrometer, it is LC / MS, which can perform extremely small amounts of analysis.
Ultrapure water is used for mobile phase preparation, standard solution preparation, and as a blank experiment. Organic matter in the ultrapure water used in the experiment will cause the occurrence of background values ​​and noise, which will interfere with the analysis results. When HPLC (detected by UV) was used to detect the organic content of different ultrapure water, the results showed that the organic content had a positive correlation with the absorption background value (Figure 1).
At this time, the ultraviolet lamp (wavelength 185 nm) can be used to reduce the content of organic matter, and the oxidized and decomposed organic matter exists in the form of ions in the water, which can be removed using ion exchange resin in the subsequent purification process (Figure 2) . Therefore, ultraviolet light can be used to significantly reduce the concentration of TOC in the purification process (Table 1).
LC / MS is a high-sensitivity system that uses liquid chromatography to separate the sample to be tested, and then uses ionization analysis to determine the quality of the substance. Therefore, the requirements for the content of organic matter in the pure water used are very strict. The ultra-pure water irradiated with ultraviolet rays was compared and analyzed with four synthetic fungicides.
The results show that the standard solution prepared with ultrapure water irradiated with ultraviolet light can obtain stable and low background values ​​with symmetrical and non-overlapping peaks. When using ultrapure water that has not been treated with ultraviolet radiation, the analysis results show that the background value is too high, resulting in overlapping with the target components, so that the analysis results cannot be correctly analyzed. Therefore, the above results confirm that the ultrapure water purified using the ultrapure water system with an ultraviolet lamp is suitable for the analysis of trace organic substances in LC / MS.
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