CONCENTRATION GRADIENT PERTURBATIONS IN MICELLAR LIQUID-CHROMATOGRAPHY WITH THERMAL LENS SPECTROPHOTOMETRIC DETECTION

In HPLC with a sodium dodecyl sulphate micellar mobile phase, a pertur bation of the sodium ion equilibrium gives rise to a refractive index gradient associated to a concentration gradient. This produces a loss of sensitivity and an increase of noise at a reproducible value of the retention time when thermal lens spectrometric detection is used. Bas eline perturbations as this one produced by retained components of the mobile phase can overlap with the peaks of the analytes.