If the condition of Eq. ( ) is not met, a series of if statements are evaluated to change the gradients to be more well-suited to the actual retention behavior of the solute on the column, as outlined in the bottom of Fig. . This includes the option of four more gradients: Gradient 5: 5-25 %; Gradient 6, 15-45 %; Gradient 7, 10-30 %; Gradient 8, 55-85 %. Each of these if statements suggests an additional gradient to evaluate. Once the end of the if statements is reached for any given gradient and the condition of Eq. ( ) is met, the gradient is then repeated at tG = 15tM and 35tM, except for the last if statement for Case 3, Gradient 3 (see Fig. ), where the gradient is run at tG = 20tM and 25tM.