The Use of Isotopically Labeled Standards in a Multipoint Internal Calibration (MPIC) for the Quantification of Amphetamine and Methamphetamine in Biological Specimens by LC-MS

Advisor(s)

Dr. Harold Schueler, Ohio Northern University, Ada, OH

Szabolcs Sofavi, Cuyahoga County Medical Examiner’s Office, Cleveland, OH

Jocelyn V. Abonamah, Cleveland Clinic Foundation, Cleveland, OH

Confirmation

1

Document Type

Poster

Location

ONU McIntosh Center; McIntosh Activities Room

Start Date

21-4-2023 12:00 PM

End Date

21-4-2023 12:50 PM

Abstract

Heavier isotopes contain atoms with greater numbers of neutrons such as deuterium (²H or D) or carbon 13 (¹³C), both of which are naturally occurring. Currently, drugs labeled with such isotopes, known as isotopologues, are used as internal standards in toxicological quantification methods, but there is potential to use them as internal calibrators. In a traditional procedure, the area ratio of amphetamine or methamphetamine - at increasing concentrations - to its internal standard - a deuterated isotopologue at constant concentration - is used to construct a calibration curve that is in turn utilized in the quantification of the respective drug in unknown specimens. Using an LC-MS, quantification of a drug is made possible through the comparison of the areas associated with the undeuterated [M+H]⁺ peak, X , in comparison to that of its isotopologues whose [M+H]⁺ peaks are greater corresponding to their number of deuterium atoms, X+D where D is the number of deuterium atoms. All isotopologues would be able to be differentiated through their mass dependent [M+H]⁺ peaks. Thus, spiking different isotopically labeled standards in the same sample at different concentrations (i.e., D₈ at 10 ng/mL, D₆ at 100 ng/mL, D₁₁ at 500 ng/mL, and D₅ at 1000 ng/mL) will provide internal calibrators in a method called Multipoint Internal Calibration (MPIC). The Cuyahoga County Medical Examiner’s Office’s validated extraction procedure for the quantification of amines was used to investigate and verify the quantification potential of the new method.

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Apr 21st, 12:00 PM Apr 21st, 12:50 PM

The Use of Isotopically Labeled Standards in a Multipoint Internal Calibration (MPIC) for the Quantification of Amphetamine and Methamphetamine in Biological Specimens by LC-MS

ONU McIntosh Center; McIntosh Activities Room

Heavier isotopes contain atoms with greater numbers of neutrons such as deuterium (²H or D) or carbon 13 (¹³C), both of which are naturally occurring. Currently, drugs labeled with such isotopes, known as isotopologues, are used as internal standards in toxicological quantification methods, but there is potential to use them as internal calibrators. In a traditional procedure, the area ratio of amphetamine or methamphetamine - at increasing concentrations - to its internal standard - a deuterated isotopologue at constant concentration - is used to construct a calibration curve that is in turn utilized in the quantification of the respective drug in unknown specimens. Using an LC-MS, quantification of a drug is made possible through the comparison of the areas associated with the undeuterated [M+H]⁺ peak, X , in comparison to that of its isotopologues whose [M+H]⁺ peaks are greater corresponding to their number of deuterium atoms, X+D where D is the number of deuterium atoms. All isotopologues would be able to be differentiated through their mass dependent [M+H]⁺ peaks. Thus, spiking different isotopically labeled standards in the same sample at different concentrations (i.e., D₈ at 10 ng/mL, D₆ at 100 ng/mL, D₁₁ at 500 ng/mL, and D₅ at 1000 ng/mL) will provide internal calibrators in a method called Multipoint Internal Calibration (MPIC). The Cuyahoga County Medical Examiner’s Office’s validated extraction procedure for the quantification of amines was used to investigate and verify the quantification potential of the new method.