Table 2.

Retention Projection Error When Using the Three Types of Gradients

	tR, experimenta	tideal -tRb	tdelayed -tRc	tback-calculated -tRd
indazole	101.952	0.708	0.558	−0.108
thymidine	144.072	8.19	0.768	2.184
puromycin	307.344	106.458	19.656	0.42
patulin	101.496	0.516	0.426	−0.462
barbital	100.776	0.45	0.33	−0.396
phe-phe	419.502	157.488	14.448	0.582
imidazole	174.6	18.138	1.152	2.976
nicotinamide	145.938	7.062	0.954	1.524
ribitol	236.292	44.916	3.024	1.272
caffeine	120.084	1.53	0.312	−0.132
naphthalene acetic acid	254.1	70.704	0.324	−5.532
MOPSO	241.272	57.216	2.91	1.248
L-proline	530.232	140.028	−7.17	5.598
Overall prediction error e (s)		±71.51	±7.17	±2.51
Overall prediction error f (%)		±28.98	±2.26	±1.04

3.5% mobile phase B/min (started at 5%) at flow rate 0.2 mL/min, mobile phase B: water with 20 mM ammonium acetate (pH 4.7)

^athe experimental retention time (s) in the gradient

^bthe retention time differences (s) between the experimental retention time and the projected retention time, calculated using the ideal gradient profile (dotted line in Fig. 5), t_{ideal gradient} -t_{R, Experiment}

^cthe retention time differences (s) between the experimental retention time and the projected retention time, calculating using the delayed gradient profile (green line in Fig. 5), t_{ielayed gradient} -t_{R, Experiment}

^dthe retention time differences (s) between the experimental retention time and the projected retention time, calculating using the back-calculated gradient profile (red line in Fig. 5), t_{back-calculated gradient} -t_{R, Experiment}

^eOverall prediction error is defined as the RMS (root-mean-square) error of the test compounds. $\text{RMS}(\sqrt{\frac{1}{n}(x_1^2+x_2^2+x_3^2\dots +x_n^2)})$, x means the prediction error of each test compound

^f $\text{Prediction}\text{error}(\%)=(\sqrt{\frac{1}{n}(y_1^2+y_2^2+y_3^2\dots +y_n^2)})$, y means the prediction error (%) of each test compound