“…The studies reviewed revealed a constant change, which affect retention time and peak focusing in a HPLC method: flow rate, gradient and oven temperature. Apart from an isocratic [43] and three-solvent eluents [10], [32], using aqueous -organic solvent gradients by increasing organic solvent percentage appeared in stepped (two [21], [40], [48] to three [25], [29], [38], [39] plateau steps or two [6], [69] to three [51] inclined steps), curved (exponential, [8], [37], [45], [67] logarithmic, [2], [19], [24], [41], [42], [50], [71] or s-curve [20], [27], [39], [49], [59], [63], [66]) and most popularly in linear [3], [9], [12], [13], [16], [17], [18], [22], [26], [28], [33], [34], [47], [52][53][54], [56],…”