EFFECT OF BASIC ADDITIVES ON PEAK SHAPES OF STRONG BASES SEPARATED BY PACKED-COLUMN SUPERCRITICAL FLUID CHROMATOGRAPHY

Strong bases added to the mobile phase dramatically improve the peak shapes of phenylenediamines and benzylamines. Acidic ion-pairing additives do not improve peak shapes, suggesting peak improvement involves ion suppression. The solutes produce very poor peak shapes or do not elute using pure or methanol-modified supercritical fluids from either standard or deactivated columns. Decreasing the stationary phase polarity and improving deactivation are ineffective alone in improving peak shapes.