HETEROGENEOUS NANOSTRUCTURES FOR BIOMEDICAL DIAGNOSTICS - Bio-Inspired and Nanoscale Integrated Computing - page 446

Column

Sensor

Parylene Oxide Bead

Pt/Ti

Silicon

Figure 16.17. MEMS LC system. The top diagram illustrates the key components,
including the column packed with beads and on-chip conductivity sensor. The
photograph shows column. The column inner diameter is at 50 mm and the length
at 1 cm.

chromatography beads, LDL subfractions were separated by anion exchange
chromatography into native LDL (nLDL) and oxLDL in terms of LDL LDL 2 ,
with LDL 2 being more electronegative [40]. An LDL chromatogram was
obtained using the MEMS LC with isocratic elution and on-chip conductivity
sensing (Fig. 16.18). The result was compared with the chromatogram obtained
from HPLC with salt gradient elution and UV detection (Fig. 16.19).

40.0k

Buffer A: 20 mM TRIS, pH 7.2
Buffer B: 20 mM TRIS; 1 M NaC1, pH 7.2
Elution: Salt gradient,
100%A, 0%B to 62%A, 38%B
Sample: 198

nLDL

g (LDL − + LDL 2 − )
Separation column: Hamilton PRP-X500
4.6

μ g (nLDL), 2 μ

20.0k

m beads
Flow rate: 1 mL/min

× 50 mm, 7 μ

LDL −

LDL 2 −

0.0

0 5 10 15 20 25

Elution Time (min)

Figure 16.18. Chromatogram obtained from HPLC with the identical LDL sample and
buffer solution A and B. The elution contains salt gradient from 100% A and 0% B to
62% A and 38% B. The flow rate was 1ml/min. The identical beads used for the
MEMS LC were packed the Hamilton PRP-X500 (4.650mm) separation column.