For analyzing non-UV absorbing substances, such as carbohydrates, lipids and polymers. This is also the detector of choice for gel permeation chromatography. The refractive index detector is one of the least sensitive LC detectors. It is very sensitive to changes in ambient temperature, pressure changes, flow-rate changes and can not be used for gradient elution. Despite these many disadvantages, this detector is extremely useful for detecting those compounds that are nonionic, do not adsorb in the UV, and do not fluoresce. There are many optical systems used in refractive index detectors but one of the most common is the differential refractive index detector.