Analytical Chemistry

For rapid on-column chiral separation of Amphetamine and Methamphetamine

MTPA-Pyrazol Reagent

Wako Catalog No. 134-15221 (100 mg); 130-15223 (1 g)

Usage

Assay (HPLC):   98.0+ %

Solubility: Soluble in ethanol and ethyl acetate

Usage

Draw 1.0 μL of the MTPA-pyrazole solution into the microsyringe for GC injection, then draw 2.0 μL to 4.0 μL of air, and finally 0.1 μL to 1.0 μL of the stimulant extract (*1).

By injecting this into the GC, the stimulant is derivatized with MTPA within the injection port or column, allowing for the enantiomers to be separated and detected.

*1: Free base form of a stimulant dissolved in hexane

Reagent: Dissolve this product in ethyl acetate (special grade) to obtain a concentration of about 10 % (w/v).

Outline

A new derivatization reagent, which facilitated on-column chiral separation for GC-MS detection of amphetamine (AP) and methamphetamine (MA), was developed.  In general, there are two methods to detect enantiomers using GC: one method uses a chiral stationary phase column; the other is pretreatment consisting of a reaction with a chiral derivatization reagent to form a diastereomer.  Handling both of them is rather complicated.  The reagent, (+)-α-Methyoxy-α-(trifluoromethyl)phenylacetyl pyrazole (MTPA-pyrazole), was synthesized from (+)-α-methoxy-α-(trifluoromethyl)phenylacetyl chloride and pyrazole.  AP and MA were injected with the reagent in the GC/MS system, and were separated as alpha-methoxy-α-(trifluoromethyl)phenylacetyl derivatives.  Ethyl acetate solution [10(w/v)%] of the reagent was reasonably stable, and could be used for the routine analysis of AP and MA from urine samples.  The calibration curves of AP and MA in 1 μL AP and MA hexane extract showed linearity in the range of 50~2500 μM.  This method gave good reproducibility from urine, and could be adapted to detect 25 μM of AP extract in the scan mode.

Reference:  Matsushita, T., Takatsu, M., Yoshida, Y. and Moriyasu, M.: "Development of New on-Column Chiral Derivatization Reagent for Gas Chromatographic Separation of Optical Isomeric Amphetamine and Methamphetamine", BUNSEKI KAGAKU, 56 (12), 1089-1095 (2007) (written in Japanese).