The present manuscript describes a radical departure from the traditional HILIC elution approach, where separations are achieved via increasing salt (sodium perchlorate) gradients in the presence of high isocratic concentrations (>80%) of acetonitrile, denoted HILIC/SALT.
Elution was performed at 40 °C, either isocratic at different methanol concentrations or using a binary gradient.
The diazinon concentration was measured using isocratic reverse-phase HPLC (model of KNAUER, Germany) and the EZ-chrome software with a UV Vis absorbance detector at the wavelength of 269 nm in column C-18.
The optimal condition was predicted at a gradient slope of 3.8% min−1 to linearly modify the modifier proportion between 5 and 40%, an isocratic time of 3 min, a concentration of TFA of 25 mM, and a temperature of 60.5 °C.
The isocratic elution result showed that the concentration of liriodendrin reached maximum values when eluting with 2 BV of 40% v/v ethanol aqueous solutions.
Phenylacetic acid and penicillinG concentrations were determined by isocratic HPLC using a Platinum EPS C18 column (Alltech, Deerfield, USA) at 30°C.
In addition, arginine (n = 1,678) and tryptophan (n = 742) concentrations were determined by isocratic and reverse-phase high-performance liquid chromatography, respectively, as previously described (23, 24).
Serum carotenoids (α-carotene, β-carotene, β-cryptoxanthin, lutein/zeaxanthin, and lycopene) and vitamin E concentrations were measured by isocratic HPLC with detection at 300, 325, and 450 nm using a Waters HPLC system (Waters Chromatography Division of Millipore Corporation, Marlboro, MA, USA) at the NHANES Laboratory.
The gradient slope, the isocratic plateau before the gradient, the temperature, and the concentration of trifluoroacetic acid (TFA) in the mobile phase were the potentially influential factors.
Etoposide concentration in micelles was measured using an isocratic HPLC method developed and validated in our laboratory according to a previously published method with a minor modification [ 17].
