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1450 K oshy et al .: J ournal of AOAC I nternational V ol . 99, N o . 6, 2016

Table 6. Retention times of analytes in standards and samples

UV detector PDA detector Retention time, min Relative retention time Retention time, min Relative retention time

Substance

Compound

Mixed standard

W-IV

15.516

0.698

16.373

0.705

W-V

19.692

0.885

20.565

0.886

WF-A

20.366

0.916

21.376

0.921

12-D

21.379

0.961

22.368

0.964

W-A

22.242

1.0

23.211

1.0

W-B

25.539

1.148

26.475

1.141

Methanolic extract WS/06Lot10

W-IV

15.376

0.695

16.576

0.713

W-V

19.537

0.883

20.672

0.889

WF-A

20.226

0.914

21.440

0.922

12-D

21.263

0.961

22.400

0.964

W-A

22.128

1.0

23.243

1.0

W-B

25.447

1.149

26.496

1.140

Raw material ERH-046

W-IV

15.547

0.699

16.576

0.713

W-V

19.698

0.886

20.661

0.889

WF-A

20.372

0.916

21.440

0.922

12-D

21.377

0.961

22.389

0.963

W-A

22.239

1.0

23.243

1.0

W-B

25.523

1.148

26.496

1.140

A

B

C

D

Figure 4. Linearity of response for withanoside IV over the full concentration range by (A) linear regression and (B) residual analysis and over a truncated concentration range by (C) linear regression and (D) residual analysis.