SIMULTANEOUS DETERMINATION OF METHOCARBAMOL AND ITS RELATED SUBSTANCE (GUAIFENESIN) IN TWO TERNARY MIXTURES WITH IBUPROFEN AND DICLOFENAC POTASSIUM BY RP-HPLC METHOD

Abstract

Accurate, sensitive, and precise RP-HPLC methods were developed and validated for determination of Methocarbamol and its related substance (Guaifenesin) in two ternary mixtures with Ibuprofen and Diclofenac potassium. The first mixture containing Methocarbamol, Ibuprofen, and Guaifenesin was separated using Isocratic elution on a Phenomenex C₁₈ column using 0.05 M KH₂PO₄ (pH = 7): acetonitrile methanol (90:25:15, by volume) as a mobile phase at a flow rate of 1.2 mL.min⁻¹ and UV detection at 220 nm. The second mixture containing Methocarbamol, Diclofenac potassium, and Guaifenesin was separated using Isocratic elution on a Phenomenex C₁₈ column using 0.05 M KH₂PO₄ (pH = 7): acetonitrile (80:30, v/v) as a mobile phase at a flow rate of 1.5 mL.min⁻¹ and UV detection at 278 nm. The proposed methods were successfully applied for determination of Methocarbamol, Ibuprofen, and Diclofenac potassium in presence of Methocarbamol related substance (Guaifenesin) either in bulk powder or in its pharmaceutical formulation.

Keywords:

• diclofenac potassium
• guaifenesin
• ibuprofen
• methocarbamol
• RP-HPLC

ACKNOWLEDGMENT

The authors would like to express their appreciation and thanks to Global Napi Pharmaceuticals and October Pharma for the provision of the necessary material to carry out this study.

Notes

RSD% ^a and RSD% ^b ; the intra-day and inter-day relative standard deviation, respectively.

*Average of 3 experiments.

**Average of 6 experiments.

HETP ^a  = height equivalent to theoretical plate, (cm/plate).

Note: Figures between parenthesis represent the corresponding tabulated values of t and F at P = 0.05.

^a The method is based on RP-HPLC using isocratic elution with 0.2% orthophosphoric acid:methanol (45:55, v/v) as a mobile phase and UV detection at 215 nm.

^b The method is based on RP-HPLC using isocratic elution with 25 mM phosphate buffer:acetonitrile (65:35, v/v) as a mobile phase and UV detection at 225 nm.

The authors declare no conflict of interests.