Safinamide Impurity Profiling by HPLC Assay Methods

Neil J. Williams¹, Jenna Milliken¹

Merck

INTRODUCTION

A simple and accurate method was developed for purity analysis of safinamide using high-performance liquid chromatography with a diode array detector (HPLC-DAD). The method was developed for a family of safinamide compounds consisting of the active pharmaceutical ingredient safinamide and multiple corresponding impurities. This is to our knowledge the first reported method for safinamide and related impurities. Safinamide free acid, safinamide mesylate, safinamide defluor-derivative, and safinamide imidazolidinone can be resolved in a 20-minute method using an Ascentis^® Express C8 column (150 x 4.6 mm, 5 μm). A gradient that utilized 0.1% trifluoroacetic acid in water and acetonitrile was employed. Under the applied conditions the system suitability criteria are met. The method demonstrates good resolution and selectivity, reproducibility, and sensitivity.

Section Overview

• Experimental Conditions
• Results
  • Chromatographic Data - Specificity (Resolution Solution)
  • Linearity - Calibration
• Conclusion
• Related Products

Safinamide Free Acid
PHR2380

Safinamide Mesylate
PHR2379

Safinamide Deflour-Derivative
PHR2381

Safinamide Imidazolidinone
PHR2382

EXPERIMENTAL CONDITIONS

Column:	Ascentis® Express C8, 150 x 4.6 mm I.D., 5µm (50392-U)
Mobile phase:	[A] Water with 0.1 % trifluoroacetic acid; [B] Acetonitrile
Gradient:	Time (min)       %A           %B     0-5                         90            10          5-8                   90-80      10-20       8-10                80-70      20-30   10-15             70-60      30-40 15-17             60-85      40-15 17-18             85-90      15-10 18-20                   90           10
Flow rate:	1.50 mL/min
Pressure:	184-197 bar (2669-2858 psi)
Temperatures:	Column: 45°C Autosampler: 4°C
Detection:	UV @ 226 nm (analytical flow cell; 10 µL)
Injection:	10 µL
Samples
Diluent:	Methanol
System suitability solution:	10.0 mg of safinamide mesylate in 25 mL diluent (0.400 mg/mL)
Resolution solution:	12.0 mg of each respective compound (safinamide mesylate, safinamide free acid, safinamide defluor-derivate and safinamide imidazolidinone) individually in 25 mL diluent. Then 0.25 mL of each solution were combined in a 1.5 mL vial via syringe (0.120 mg/mL)

Results

Figure 1. Blank chromatogram.

Figure 2. Chromatogram for safinamide mesylate system suitability solution.

Figure 3. Chromatogram for resolution solution.

Chromatographic Data - Specificity (Resolution Solution)

Peaks	Compound	Retention Time (min)	RRT	Resolution	Theoretical plates	Tailing factor
1	Safinamide imidazolidinone	10.7	0.94	-	87122	0.93
2	Safinamide defluor-derivative	11.0	0.97	2.1	100843	0.93
3	Safinamide mesylate	11.4	1.00	2.9	114974	0.96
4	Safinamide free acid	11.7	1.03	2.7	93783	1.06

Linearity - Calibration

Figure 4. Calibration curve of safinamide mesylate.

Figure 5. Calibration curve of safinamide free acid.

Figure 6. Calibration curve of safinamide defluro-derivative.

Figure 7. Calibration curve of safinamide imidazolidinone.

CONCLUSION

A new method was developed for analyzing the purity of safinamide and its related compounds using high-performance liquid chromatography with a diode array detector. The method uses an Ascentis^® Express C8 HPLC column and a gradient of 0.1% trifluoroacetic acid in water and acetonitrile and takes 20 minutes to resolve the compounds. The method is reproducible and sensitive and shows good resolution and selectivity.

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