Chiral Separation of Methamphetamine and Amphetamine on an Agilent Infinitylab Poroshell 120 Chiral-V Column with Detection by LC/MS

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Chiral separation of methamphetamine and amphetamine on an Agilent InfinityLab Poroshell 120 Chiral-V column with detection by LC/MS

Authors Abstract

Carl Griffin and William Long An Agilent InfinityLab Poroshell 120 Chiral-V 2.1 × 150 mm, 2.7 μm column Agilent Technologies, Inc. (p/n 683775‑604) was used to analyze methamphetamine and amphetamine Wilmington, DE, USA by LC/MS, using a mobile phase of methanol with 0.1 % acetic acid and 0.02 % ammonium hydroxide. The analysis was accomplished in 5 minutes, with a resolution Rs of 1.9 or better for racemic amphetamine and methamphetamine. Introduction H NH Experimental N 2 Superficially porous particle columns are An Agilent 1290 Infinity LC system CH3 a popular tool in liquid chromatography. with an Agilent 6460 triple quadrupole Superficially porous particle columns (S)-(+)-Methamphetamine (S)-(+)-Amphetamine LC/MS was used in this experiment. The generate high efficiency at lower Dextromethamphetamine Dextroamphetamine system was modified from its standard pressure relative to their totally porous configuration to have low system volume 1 particle column counterparts . This is H NH and dispersion. Table 1 shows the primarily due to a shorter mass transfer N 2 instrument configuration details. Table 1 distance and substantially narrower CH lists the Agilent InfinityLab Poroshell 120 particle size distribution of the particles 3 Chiral-V 2.1 × 150 mm, 2.7 μm column in the column2. The current trend with (R)-(–)-Methamphetamine (R)-(–)-Amphetamine used in this work. Table 2 shows the LC superficially porous particles is reducing Levomethamphetamine Levoamphetamine and MS parameters. particle size for further efficiency Figure 1. Chemical structures of amphetamine and The methamphetamine and methamphetamine enantiomers. improvements. The higher efficiency can amphetamine samples were bought be used to speed up analyses, or improve as a racemic mixture from Cerriliant, results by increasing resolution and This study demonstrates the Round Rock, Texas, USA, at 1 mg/mL in sensitivity. UHPLC performance of a 2.7 µm methanol. The samples were diluted in Using LC/MS in the analysis of Agilent InfinityLab Poroshell 120 Chiral-V mobile phase prior to injection. Acetic therapeutics and metabolites has column using LC/MS, including the acid was bought from Sigma-Aldrich. become increasingly popular due to its baseline resolution of two racemic pairs. Ammonium hydroxide was bought selectivity, sensitivity, and speed. For from GFS Chemicals as Veritas Grade the analysis of amphetamines, LC/MS double‑distilled, Columbus, Ohio USA. eliminates the need to derivatize, and Methanol was bought from Honeywell facilitates direct, 100 % detection. (Burdick and Jackson). Water was However, mass spectrometry alone 0.2 µm filtered 18 MW from a Milli-Q is unable to distinguish between system (Millipore). stereoisomers, since it characterizes Table 1. Instrument configuration details. compounds solely in terms of mass. Consequently, separations are required Parameter Value before the mass spectrometer. LC Methamphetamine and amphetamine Column Agilent InfinityLab Poroshell 120 Chiral-V 2.1 × 150 mm, 2.7 µm (p/n 683775-604) Methanol:acetic acid:ammonium hydroxide 1,000:1:0.2 (isocratic) are chiral molecules (Figure 1). For Mobile phase Flow rate 0.25 mL/min both compounds, the D-enantiomer Column temperature 20 °C has greater biological activity Injection volume 0.2 µL than the L-enantiomer. Both the MS individual enantiomers and the Ionization mode ESI positive (Agilent Jet Stream) racemate of methamphetamine are Gas temperature 300 °C controlled substances (Class A in Gas flow 5.0 L/min Europe and Schedule II in the US). Sheath gas temperature 250 °C Levomethamphetamine is the chemical Capillary voltage 3,500 V precursor of the anti-Parkinson’s Nozzle voltage 500 V drug Selegiline3. Selegiline is also metabolized into levomethamphetamine Table 2. Standards and MRM values. and levoamphetamine4,5. This has caused users to test positive for Precursor ion Product ion Fragmentor Collision Cell accelerator Dwell amphetamines6,7. The traditionally used Analyte (m/z) (m/z) voltage energy voltage time method for analysis, immunoassay, Methamphetamine 150.1 91.1 75 20 4 200 is unable to distinguish between the Methamphetamine 150.1 65.1 75 44 4 200 136.1 119 90 4 3 200 enantiomers, and can give incomplete, Amphetamine 136.1 91 90 16 3 200 inconclusive results. Amphetamine

2 Results and discussion detector resolves the analytes by their resolution and retention time at three specific mass fragments. However, when temperatures, and Table 3 presents Figure 2 shows the separation of enantiomeric compounds are present, a summarization of them. Increasing (R)‑(–)‑ and (S)-(+)-methamphetamine baseline chromatographic resolution is temperature has the effect of decreasing and (R)-(–)- and (S)-(+)-amphetamine necessary. In this case, chromatographic retention time and increasing selectivity, on an InfinityLab Poroshell 120 resolution for methamphetamine and while lowering column pressure Chiral‑V 2.1 × 150 mm, 2.7 µm column. amphetamine enantiomers were found decreases mobile phase viscosity. With LC/MS detection, baseline to be two or better at 20 °C, providing chromatographic resolution is not good integration and quantitation of necessary for all compounds, as the these two isomers. Figure 3 shows

×103 3 2.0 3.63

1.8 4 1. (S)-(+)-Amphetamine 3.97 2. (R)-(–)-Amphetamine 1.6 3. (S)-(+)-Methamphetamine 1.4 4. (R)-(–)-Methamphetamine 1.2

Counts 1.0 1 2 0.8 2.90 3.24 0.6

0.4 181 bar at 20 °C 0.2

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Acquisition time (min)

Figure 2. Analysis of methamphetamine and amphetamine using an Agilent InfinityLab Poroshell 120 Chiral-V 2.1 × 150 mm, 2.7 µm column. Injection volume 0.2 µL with 5 µg/mL each of methamphetamine and amphetamine. The column was connected to the MS using 320 mm, 0.075 mm id tubing to reduce extra-column broadening.

×103 2.0 3.63 3.97 1.5 1.0 2.90

Counts 3.24 0.5 181 bar at 20 °C 0 2 ×10 3.51 3.80 6 4 2.86 3.14 Counts 164 bar at 30 °C 2

×102 7 3.43 6 3.68 5 4 2.83 3.07

Counts 3 149 bar at 40 °C 2 1

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Acquisition time (min)

Figure 3. Analysis of methamphetamine and amphetamine using an Agilent InfinityLab Poroshell 120 Chiral-V 2.1 × 150 mm, 2.7 µm column at different temperatures. Flow rate 0.25 mL/min, 1 L MeOH, 1 mL acetic acid, 200 µL NH4OH.

3 Conclusions Table 3. Retention and resolution at varied temperatures.

The Agilent InfinityLab Poroshell 120 Temperature Retention time (min) Resolution Chiral-V 2.7 μm column was used (°C) Peak 1 Peak 2 Peak 3 Peak 4 Peaks 1–2 Peaks 2–3 Peaks 3–4 to accomplish a separation of chiral 20 2.39 3.24 3.63 3.94 2.1 2.1 1.8 methamphetamine and amphetamine by 30 2.86 3.14 3.51 3.80 1.8 2.2 1.6 LC/MS. The high efficiency of this small 40 2.83 3.07 3.43 3.68 1.5 2.2 1.4 superficially porous particle column Peak 1: (S)-(+)-Amphetamine provided sufficient resolution to resolve Peak 2: (R)-(–)-Amphetamine Peak 3: (S)-(+)-Methamphetamine the racemic pairs at baseline. Peak 4: (R)-(–)-Methamphetamine Sample: 5 µg/mL each of (±)methamphetamine and (±)amphetamine diluted in mobile phase. Flow rate: 0.25 mL/min, 1 L MeOH, 1 mL acetic acid, 200 µL NH OH. References 4

1. Gratzfeld-Huesgen, A.; Naegele, E. 5. Magyar, Kálmán, M. Maximizing efficiency using The pharmacology of Agilent Poroshell 120 Columns, selegiline, International Review of Agilent Technologies Application Neurobiology 2011, 100, 65–84. Note, publication number 5990‑5602EN, 2016. 6. Cody, J. D. Metabolic Precursors to Amphetamine and 2. Meyer, V. R. Practical Methamphetamine, Forensic Science High Performance Liquid Review 1993, 5(2), 109–127. Chromatography, Fourth Edition, Wiley, 2004, p. 34. 7. Cody, J. T. Precursor medications as a source of methamphetamine 3. Method for the production of and/or amphetamine positive selegiline hydrochloride, European drug testing results, Journal of Patent, retrieved 2015-10-04. Occupational and Environmental 4. Kalász, H.; et al. Metabolism of Medicine/American College of selegiline [(-)-deprenyl)], Current Occupational and Environmental Medicinal Chemistry 2014, 21(13), Medicine 2002, 44(5), 435–450. 1522–1530.

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