How does hplc detector work

Contents 1. Refractive-Index Detector 3. Evaporative Light Scattering Detector 4. Multi-Angle Light Scattering Detector 5. Mass Spectrometer 6. Conductivity Detector 7. Fluorescence Detector 8. Chemiluminescence Detector 9. Optical Rotation Detector Electro Chemical Detector. As the sample passes through the column it interacts between the two phases at different rate, primarily due to different polarities in the analytes.

Analytes that have the least amount of interaction with the stationary phase or the most amount of interaction with the mobile phase will exit the column faster. Exceeding the pressure limits can irreversibly damage the cell, so take care that this does not happen. As with other aspects of liquid chromatography, cleanliness is essential for best operation-the detector is no different. It is easier to cause problems than prevent them, so I depend on flushing the column and system at the end of each sample batch to keep the cell clean.

Detector lamps will eventually fail. Most manufacturers today quote a h lamp lifetime. However, if you depend on the detector for trace analysis, expect shorter lifetimes. Most systems keep track of the number of hours a lamp has been in use, so you can check this once a month or so, or set an alarm to alert you when the clock gets near h. I usually wait until symptoms of lamp failure occur, such as increased noise or decreased lamp energy, before I replace this expensive part.

The UV detector should stay in calibration unless it undergoes a physical shock, such as dropping the unit. Calibration procedures vary with the individual detector model, so you should consult the operation or service manual for specific details on your detector. This may be done automatically when the detector is powered on, or it may require manually activating a calibration program.

Calibration frequency usually is a laboratory policy, but if not done more frequently, calibration should be performed at least annually. UV detectors are the most popular LC detectors in use today. They are simple to operate, robust in their performance, and give adequate response to a wide variety of analytes. With a little care, you should be able to get consistent, high-quality results from either the variable-wavelength or diode-array detector.

Direct correspondence about this column via e-mail to LCGCedit ubm. How Does It Work? Part IV: Ultraviolet Detectors. August 1, John W. Variable-Wavelength Detectors A schematic of a variable-wavelength detector is shown in Figure 1. Figure 1: Schematic diagram for a variable-wavelength UV detector. Diode-Array Detectors The diode-array detector Figure 2 has components in common with the variable-wavelength detector, but they are configured differently. Figure 2: Schematic diagram for a diode-array UV detector.

The Detector Cell The most common detector cell design is shown in Figure 3a. Comparisons At first glance, it might seem that the diode-array detector would be a much better choice than the variable wavelength detector in most applications. Conclusions UV detectors are the most popular LC detectors in use today.

References J. Download RIS. Mobile phase enters the column from the left, passes through the particle bed, and exits at the right. Flow direction is represented by green arrows. First, consider the top image; it represents the column at time zero [the moment of injection], when the sample enters the column and begins to form a band.

The sample shown here, a mixture of yellow, red, and blue dyes, appears at the inlet of the column as a single black band. After a few minutes [lower image], during which mobile phase flows continuously and steadily past the packing material particles, we can see that the individual dyes have moved in separate bands at different speeds.

This is because there is a competition between the mobile phase and the stationary phase for attracting each of the dyes or analytes. Notice that the yellow dye band moves the fastest and is about to exit the column. The yellow dye likes [is attracted to] the mobile phase more than the other dyes.

Therefore, it moves at a faster speed, closer to that of the mobile phase. The blue dye band likes the packing material more than the mobile phase. Its stronger attraction to the particles causes it to move significantly slower. In other words, it is the most retained compound in this sample mixture. The red dye band has an intermediate attraction for the mobile phase and therefore moves at an intermediate speed through the column.

Since each dye band moves at different speed, we are able to separate it chromatographically. What Is a Detector? As the separated dye bands leave the column, they pass immediately into the detector.

The detector contains a flow cell that sees [detects] each separated compound band against a background of mobile phase [see Figure H]. A choice is made among many different types of detectors, depending upon the characteristics and concentrations of the compounds that need to be separated and analyzed, as discussed earlier.