Methods for retinoid analysis in tissue include direct spectrophotometry or fluorometry and retinoid responsive reporter constructs in the form of cell reporter assays or transgenic reporter animals, but chromatographic methods dominate and posses several superior features in quantitative analysis. The multitude of extraction protocols used can coarsely be divided into manual liquid-liquid extraction protocols and semi- or fully automated solid phase extraction-based protocols. Liquid chromatographic separation in reversed phase dominates although normal phase is also used. Detection is mainly performed with UV detectors although electrochemical and fluorescence detection is also used. Mass spectrometry in combination with LC is more often used in retinoid analysis and is likely to dominate in the future.
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