Simultaneous Analysis of Active Pharmaceutical Ingredients and Their Counter-Ions Using a Mixed-Mode Column

Transcription

1 P-CN54E Simultaneous Analysis of Active Pharmaceutical Ingredients and Their Counter-Ions Using a Mixed-Mode Column Pittcon 5 9-6P Kenichiro Tanaka, William Hedgepeth, Yuki Sato Shimadzu Scientific Instruments, Inc., Columbia, Maryland, Shimadzu GLC Ltd., Tokyo, Japan

2 Introduction Approximately 5 % of all drug molecules used in pharmaceutical products are reported to be ionic compounds. Ion chromatography is generally appropriate to analyze inorganic or organic ions, but not suitable for active pharmaceutical ingredients (APIs) analysis due to their hydrophobicity. n the other hand, reversed phase liquid chromatography (RPLC) is mainly applied for analysis of APIs, but cannot retain commonly-used ions for drugs. Consequently, it is difficult to analyze APIs and their counter-ions simultaneously. In this study, we evaluated the ReDual column, our newly-developed mixed-mode column, for simultaneous analysis of APIs and their counter-ions. Mixed-mode column usage has increased because of the ability to analyze a wide range of compounds in a single run by multimode retention mechanisms. First, we investigated how retention behavior changes with parameters such as concentration of organic solvents, ion strength, and ph of the mobile phase using the ReDual CX-C8 mixed-mode column. Secondly, we analyzed naproxen sodium and potassium clavulanate. They were successfully analyzed on the column just by changing mixing ratio of the mobile phase. Materials and Method Reagents and standards Reagents: Diclofenac sodium, naproxen sodium, potassium clavulanate, formic acid, and ammonium formate were purchased from Sigma-Aldrich. Water was made in house using a Millipore Milli-Q Advantage A Ultrapure Water Purification System. was purchased from Honeywell. Methods Samples were injected to a Shimadzu Nexera X UHPLC system consisting of two LC-3AD pumps (one of the pumps was equipped with low pressure gradient unit), DGU-A5R degassing unit, SIL-3AC autosampler, CT-3A column oven, ELSD-LT II evaporative light scattering detector, and CBM-A system controller. Samples: Diclofenac sodium, naproxen sodium, and potassium clavulanate were separately dissolved in water to mg/l. Active pharmaceutical ingredients and their counter-ions were separated on the ReDual CX-C8 mixed-mode column and detected by the ELSD-LT II. Fig. and Table shows flow diagram and analytical conditions, respectively. The Nexera X allows a solvent blending function that can mix solvents according to desired ratios. A B Low pressure gradient unit Pump X Autosampler Analytical column Detector C D Pump Y Fig. Flow diagram

3 Table Analytical conditions System : Shimadzu Nexera X UHPLC System Column : ReDual CX-C8 (5 mm L. x 4.6 mm I.D., 3 μm) : A: Water B: mmol/l Formic acid in water C: mmol/l Ammonium formate in water (Solvent blending function was used to prepare mobile phase X) : Flow Rate :.8 ml/min Column Temperature : 4 C Injection Volume : 5 μl Detection : ELSD-LT II (Temp.: 4 C, Gain: 6, Nebulizer gas: N, Gas pressure: 35kPa) Results Retention behavior First, we investigated how retention behavior changes with parameters such as concentration of organic solvents, ion strength, and ph of the mobile phase using a mg/l diclofenac sodium solution (diclofenac: 98 mg/l, sodium: 7 mg/l) as a sample. The ReDual CX-C8 mixed-mode column has octadecyl and weak cation exchange groups that can retain hydrophobic compounds and cations simultaneously. When analyzing diclofenac sodium, diclofenac and sodium ion are retained by hydrophobic and ionic interaction, respectively as shown in Fig.. Therefore, their retentions can be controlled by concentration of organic solvents, ion strength, and ph of the mobile phase. Fig. 3 shows how each parameter affected retention behavior. With the decrease of organic solvent: Hydrophobic interaction becomes strong (factor of retention increase of diclofenac). Concentration of ammonium ion in the mobile phase increases (factor of retention decrease of sodium ion). With the increase of ion strength: Concentration of ammonium ion in the mobile phase increases (factor of retention decrease of sodium ion). With the decrease of ph (concentration of ammonium formate is kept constant): Diclofenac becomes undissociated and hydrophobic (factor of retention increase of diclofenac). The weak cation exchange group becomes undissociated (factor of retention decrease of sodium ion). Si Hydrophobic interaction Cl - NH Ionic interaction Cl - Na + Fig. Retention mechanism of diclofenac and sodium ion on ReDual CX-C8 3

4 . Changing concentration of organic solvent A/B/C=5/5/5 X/Y: See below X/Y=/8 X/Y=5/75 X/Y=3/7 X/Y=35/65 X/Y=4/6 X/Y=45/55 X/Y=5/5 X/Y=55/45 X/Y=6/ min. Diclofenac. Na Retention factor rganic solvent ratio in mobile phase (v/v %) Diclofenac Sodium. Changing ion strength A/B/C: See below X/Y=5/5. Diclofenac. Na A/B/C=8// ( mmol/l) A/B/C=7/5/5 (3 mmol/l) A/B/C=6// (4 mmol/l) A/B/C=5/5/5 (5 mmol/l) A/B/C=4/3/3 (6 mmol/l) A/B/C=3/35/35 (7 mmol/l) A/B/C=/4/4 (8 mmol/l) A/B/C=/45/45 (9 mmol/l) A/B/C=/5/5 ( mmol/l) min Retention factor Concentration of buffer (mmol/l) Diclofenac Sodium 3. Changing ph 75 5 A/B/C: See below X/Y=5/5. Diclofenac. Na A/B/C=84.9/./5 (ph 5.8) A/B/C=84.8/./5 (ph 5.36) A/B/C=84./.8/5 (ph 4.83) A/B/C=8.5/.5/5 (ph 4.34) A/B/C=77.5/7.5/5 (ph 3.9) A/B/C=6/5/5 (ph 3.4) A/B/C=/75/5 (ph 3.3) min Retention factor ph Diclofenac Sodium Fig.3 Retention behavior by changing parameters 4

5 Application This method was applied to analyses of naproxen sodium and potassium clavulanate. They were successfully analyzed just by changing mixing ratio of the mobile phases as shown in Fig. 4.. Analysis of naproxen sodium A/B/C=/5/5 X/Y=4/6. Naproxen. Na Na min. Analysis of potassium clavulanate 75 A/B/C=/5/5 X/Y=95/5. Clavulanic acid. K 5 5 N - K + 75 H H min Fig.4 Chromatograms of naproxen sodium and potassium clavulanate 5

6 Conclusions Retention behavior of an API and counter-ion on ReDual CX-C8 was investigated by changing concentration of organic solvents, ion strength, and ph of the mobile phase. Naproxen sodium and potassium clavulanate were successfully analyzed just by changing mixing ratio of the mobile phase. The Nexera X equipped with the solvent blending function was useful as a platform for method development by a mixed-mode column. First Edition: March, 5 For Research Use nly. Not for use in diagnostic procedures. The content of this publication shall not be reproduced, altered or sold for any commercial purpose without the written approval of Shimadzu. The information contained herein is provided to you "as is" without warranty of any kind including without limitation warranties as to its accuracy or completeness. Shimadzu does not assume any responsibility or liability for any damage, whether direct or indirect, relating to the use of this publication. This publication is based upon the information available to Shimadzu on or before the date of publication, and subject to change without notice. Shimadzu Corporation, 5