Differential Mobility Spectrometry (DMS)

An orthogonal separation mechanism based upon charge-to-mass and

molecular shape

Lecture 2, Page 84

Hardware Overview

SelexIon – Planar DMS

Lecture 2, Page 85

Mass Spec Vacuum draws ions and gas through planar DMS electrodes

(5 millisecond flight time)

2.3 torr

2.8 L/min

1 mm

3 cm

760 torr

Lecture 2, Page 86

The physics and chemistry of the separation

principle.

Specificity from nuclear properties. •Radioactivity •High Mass Resolution.

• Specificity from molecular properties. • NMR • Collision-Induced Dissociation - MSn

• Specificity from chemical properties. • Chemical interactions of analyte with environment

• HPLC, CZE, immunochemsity

• Ion Molecule Chemistry (ICP-MS Dynamic Reaction Cell)

• Ion Molecule Chemistry Mobility

Sources of Selectivity

Lecture 2, Page 87

Chemical Enhanced Separations Driven by Mobility Changes Due to Clustering / Declustering.

Low field

clustering-

mobility decreases

+

HV=3kV

Schneider BB, Covey TR, Coy SL, Krylov EV, and Nazarov EG, “Chemical Effects in the Separation Process of a Differential Mobility/Mass

Spectrometer System”, Anal. Chem., 2010, 82, 1867-1880.

High field

declustering;

mobility increases

L V=0.3 kV

F ~ 1 MHz, T= 10-6 s

Lecture 2, Page 88

Ionograms of 3 compounds with/without clustering modifiers

Dianabol

Benoxinate

Clenbuterol

Nitrogen

transport gas

Nitrogen with

44% helium

transport gas

Nitrogen with

1.5% isopropanol

transport gas

Increased mobility with helium

favors hard sphere behavior

….peaks shift to higher CV

and narrow slightly.

Lecture 2, Page 89

Different effects with different modifiers

Ketamine (blue) and sulfadiazine (red)

Ethylacetate

Acetone

Acetonitrile

Methanol

Isopropanol

m/z 238.1 m/z 251.1

Lecture 2, Page 90

Lecture 2, Page 8

Effects of Different Modifiers-Gas phase LC?

1.0

0.8

0.6

0.4

0.2

0.0

Norm

aliz

ed S

ignal

-50 -40 -30 -20 -10 0

CV (V)

Isopropanol Separation

1.0

0.8

0.6

0.4

0.2

0.0

Norm

aliz

ed S

ignal

-50 -40 -30 -20 -10 0

CV (V)

Acetone Separation

1.0

0.8

0.6

0.4

0.2

0.0

Norm

aliz

ed S

ignal

-50 -40 -30 -20 -10 0

CV (V)

Acetonitrile Separation

Red: Ephedrine Black: Acyclovir Green: Norfentanyl Blue: Clenbuterol Purple: Imipramine Brown: Diazepam Pink: Quinoxifen

Lecture 2, Page 91

Applications where Chromatography is

employed and integrated with DMS.

Lecture 2, Page 92

Testosterone Female #3 Plasma Sample: LLE

DMS OFF/

289/109

DMS OFF/

289/97

DMS ON/

289/109 DMS ON/

289/97

Interference

Ion ratio is Peak of interest Interference

Peak of interest

Lecture 2, Page 93

Testosterone Female #3 Plasma Sample: PPT

DMS OFF/

289/109

DMS OFF/

289/97

DMS ON/

289/109

DMS ON/

289/97

Peak of interest

Peak of interest @

RT 3.37 min

Lecture 2, Page 94

Separation Science References

• Basics of HPLC – http://www.waters.com/waters/nav.htm?cid=100490

64&locale=en_US

• Basics of nano LC – http://www.nanoseparations.com/

• Basics of CE – http://matematicas.udea.edu.co/~carlopez/cnq533/C

E_Basics.pdf

• Basics of IC – http://www.melvynbecerra.cl/images/ICPractica.pdf

Lecture 2, Page 95