Weft detector is a modern detector. What are the common weft detectors?

　　1. Ultraviolet absorption detector (UVD) is widely used in HPLC. Its main characteristics are high sensitivity, wide linear range, insensitive to the change of flow rate and temperature, and can be used for gradient elution. It requires UV absorption of the detected sample components and belongs to the selective detector.

　　2. Weft detector is a kind of optical multi-channel detector which appears in modern times. After scanning the spectrum of each eluting component, a three-dimensional spectrum combined with spectrum and chromatography was obtained. Absorption spectrum is used for qualitative analysis (to confirm whether it is a single pure substance), chromatography is used for quantitative analysis, and is often used for qualitative and quantitative analysis of complex samples (such as biological samples and Chinese herbal medicines).

　　3. Fluorescence detector (FLD) is also a selective detector, its sensitivity is high in the current commonly used HPLC detector, and its application is also more than UVD. It is suitable for compounds that can excite fluorescence. Many substances related to life science, such as amino acids, amines, vitamins, steroids and some metabolic drugs, can be detected by fluorescence method. Fluorescence detector is very useful for trace analysis of biological samples, especially for the detection of very small amounts of amino acids and peptides after fluorescence derivatization.

　　Universal detector

　　1. The differential refractive detector (RID) is a universal detector, which can be used as long as the refractive index of the detected component is different from that of the eluent. In life science, we often encounter all kinds of carbohydrate compounds, which have no ultraviolet absorption, and usually use differential refractive detector. Its versatility is wider than that of UVD, but its sensitivity is lower, it is sensitive to temperature change, and it is not compatible with gradient elution, so its application is limited.

　　2. Evaporative light scattering detector (ELSD) is also a universal detector, which can detect any sample whose volatility is lower than that of the mobile phase without any chromogenic group in the sample. The response value of ELSD is directly proportional to the mass of the sample, so it can be used to determine the purity of the sample or to detect unknown substances. ELSD is more sensitive than rid, insensitive to temperature change, stable baseline, and can be used for gradient elution. Now ELSD has been widely used in the detection of carbohydrates, lipids, fatty acids and amino acids, drugs and polymers.

　　3. Mass spectrometry detector (MSD) is another universal detector, which has outstanding advantages in sensitivity, selectivity, versatility, and the provision of molecular weight and structure information of compounds. But its high operation cost and complexity limit its application