A new approach to highly sensitive determination of retinoic acid isomers by preconcentration with CdSe quantum dots

Unusual amounts of retinoic acid (RA) isomers play an important role in abnormal morphological development of mammals; such as rat embryos. Each isomer of RA has a unique function in first steps of embryonic life. In the current study, a new method for preconcentration and simultaneous determination of all-trans retinoic acid, 13-cis retinoic acid, 9-cis retinoic acid and 9,13-di-cis retinoic acid in rat whole rudimentary embryo culture (RWEC) has been developed. RA isomers were extracted from samples by conjugation to appropriate amount of surface modified CdSe quantum dots (QDs) prior to HPLC/UV determination. In order to quickly release of the analytes with unchanged form, separated RA–QD conjugation were irradiated by intensive near infrared wavelength (NIR). Low energy NIR irradiation results in maintaining the primary forms of RA isomers during the release. The conjugation and release mechanisms were described and experimental parameters were investigated in detail. Under optimized conditions, the method was linear in the range of 0.040–34.600 pmol g−1 for all-trans RA (R2=0.9996), 0.070–34.200 pmol g−1 for 13-cis RA (R2=0.9992), 0.050–35.300 pmol g−1 for 9,13-di-cis RA (R2=0.9998) and 0.050–32.900 pmol g−1 for 9-cis RA (R2=0.9990). The present method can be useful for retinoic acid monitoring in clinical studies.