Two novel UPLC methods utilizing two different analytical columns and different detection approaches for the simultaneous analysis of velpatasvir and sofosbuvir: application to their co-formulated tablet

BMC Chemistry

Table 1 Optimization of the chromatographic conditions for determination of VPS by Method 1

Parameter	No. of theoretical plates (N)		Capacity factor (k′)		Tailing factor (T_f)
Parameter	Column (A)	Column (B)	Column (A)	Column (B)	Column (A)	Column (B)
Column temperature °C
Room temperature	2900.3	406.2	1.839	2.675	0.532	0.831
30 °C	2941.6	–	1.987	–	0.660	–
40 °C	4547.4	1009.7	2.183	2.038	0.536	0.900
50 °C	5030.4	644.4	2.348	3.179	0.517	0.877
60 °C	–	799.3	–	3.454	–	0.908
pH of mobile phase
2.5	2900.3	406.2	1.839	2.675	0.532	0.831
3.3	3921.4	408.2	2.744	4.150	0.528	0.947
4.0	3305.7	410.6	3.976	6.425	0.491	0.924
Type of organic modifier of Conc 40% (v/v)
Acetonitrile	2720.4	378.8	1.831	2.583	0.556	0.867
Methanol	1140.1	365.4	1.843	2.621	0.514	0.907
Ethanol	2304.3	352.9	1.870	2.592	0.413	0.871
Ratio organic modifier: mobile phase (acetonitrile) (v/v)
40:60	3145.5	372.7	1.824	2.554	0.525	0.825
60:40	2720.4	378.8	1.831	2.583	0.556	0.867
80:20	2386.9	314.5	1.844	2.642	0.552	0.906
90:10	2210.2	316.7	1.848	2.654	0.575	0.866
Effect of flow rate (mL/min)
0.3	–	452.8	–	4.613	–	0.768
0.5		205.0		1.433		0.750
1.0	3551.6		2.376		0.571
1.2	2900.3	–	1.839	–	0.532	–

\( {\text{Number of theoretical plates }}\left( {\text{N}} \right)\, = \,5.54\left( {\frac{{{t}_{{R}} }}{{{Wh}/2}} } \right)^{2} \)
\( {\text{Tailing factor }}\left( {\text{T}} \right)\, = \,\frac{{{W}_{0.5} }}{{2{f}}} {\text{k}^{\prime}} \, = \,{{({\text{tR}} {-}{\text{ t}}0)} \mathord{\left/ {\vphantom {{({\text{tR}} {-}{\text{ t}}0)} {{\text{t}}0}}} \right. \kern-0pt} {{\text{t}}0}} \),