Direct detection of gradient-eluted non-labeled amino acids using micro-HPLC with ultraviolet thermal lensing

Thermal lensing (TL) permits ultrasensitive measurements of optical absorption of analytes in very small volumes. Separation-detection conditions of non-labeled amino acids with micro-HPLC/UV absorption detector are optimized, and direct determination of non-labeled amino acids by micro-HPLC/UV-excitation TL detection in a gradient elution is successfully demonstrated. Non-labeled amol-level amino acids is detectable with the TL detection system, which has thousand times better sensitivity than a conventional UV detector.