6. Flow
Flow
Sample
Channel
Second
Solution
A membrane separates the microchannel main channel from a
second solution to deliver, extract or provide electrical contact.
Membrane-Assisted Sample Preparation
Membrane
Cation or anion ion-selective Membranes
10. Distance Heavy water Glucose Hemoglobin
25 um 0.14 s 0.6 s 4.5 s
50 um 0.56 s 2.5 s 18 s
100 um 2.2 s 10 s 72 s
1 mm 3.8 min 16 min 120 min
Diffusion in Microfluidic Systems
12. - Change the composition right before the ionization
-Add reagents (no necessity of mixing or volumetric
addition)
Single Membrane Configuration
Basic application
13. e e e e e e
e
e
e
e
e
e
D O2
D O2
D O2
D O2 D O2
e e e e
O
D
+
D
+
D
+
D
+
D
+
D
+
O
D
+
H
+ H
+
H
+
M
MM M
D
D
DM
D
D
D MD
D
D
H2
O
Cation
selective
membrane
Main channel
Second channel
SINGLE MEMBRANE
Membrane Probe
24. small cation (e.g., tris-H+)
small anion (e.g., Cl-)
negatively charged molecules
neutral compounds or those with low µ
Anodic chamberCathodic chamber
Two Membrane Section
Crude sample
flows in
Uncaptured compound
flow out
current
26. Electrocapture
Charge particle
Electrocapture conditions will be fulfilled when
Ve ≥ Vf
Electrophoretic velocity is given by,
Ve = ue x E
Ve = Electrophoretic velocity
ue = Electrophoresis mobility
E = Electric field
Positive
Electrod
e
Negativ
e
Electrod
e
29. small cation (e.g., tris-H+)
small anion (e.g., Cl-)
negatively charged molecules
neutral compounds or those with low µ
Anodic chamberCathodic chamber
A. Capture
Crude sample
flows in.
Uncaptured compound
flow out.
current
30. small cation (e.g., tris-H+)
small anion (e.g., Cl-)
negatively charged
moleculesneutral compounds or those with low µ
Conditioning solution
flows in
Impurities are
washed out
Anodic chamberCathodic chamber
B. Injection of a new solution
current
31. small cation (e.g., tris-H+)
small anion (e.g., Cl-)
negatively charged molecules
neutral compounds or those with low µ
Conditioning solution
flows in Protein band is swept
Anodic chamberCathodic chamber
C. Release of the capture molecules
32. Protein band
Anodic chamber Cathodic chamber
Flow
Capillary
electrophoresis
MALDI-MS Sample Prep
Microreactions
Analytical Applications
Separations
38. 20
0
Vf = Ve = ue x E
E (V/cm)
Time
Vf > Ve = ue x E
Flow
C. Release of the capture molecules
39. Separation
Crude Sample
Separation of Tryptic Peptides for Improved MALDI-MS analysis
Arrows indicate peptides not seen on the unprocessed sample
High voltage
Low voltage
42. Image from Kisoo Yoo, Jaesool Shim, and Prashanta Dutta Biomicrofluidics 8, 064125 (2014)
Isoelectric focusing
Ampholytes:
Amphoteric molecules that contain both acid
and basic groups, and will exist as zwitterions
in a certain range of pH.
Separation is based on the migration of amphoteric compounds in a electric field, until its net
change of the analyte is cero.
In solution isoelectric focusing, the pH gradient is created by the presence of ampholytes in the
sample matrix.
49. Box plot of significantly changed focusing positions of
proteins in healthy (green) and patient with Progressive
Mild Cognitive Impairment (red) samples.
Possible Clinical Applications
59. Box plot of significantly changed focusing positions of
proteins in healthy (green) and patient with Progressive
Mild Cognitive Impairment (red) samples.
Clinical Applications
