Thermal Analysis & Rheology
THERMAL SOLUTIONS
Thermal Stability Determination of Bonded Silicas for use
in Packing Columns by Thermogravimetric Analysis
PROBLEM
Silica materials used as chromatography support material
gave inconsistent performance when packed in columns.
This inconsistency was believed to be associated with poor
bonding between the silica support and the active phase
such that leaching occurred. Hence, a quick test which gave
an indication of the stability of the bonding between the
silica and active phase was desired.
SOLUTION
Thermogravimetric analysis (TGA), which is a thermal analysis technique used to measure weight changes in a material
Figure 1.
with temperature, can provide information about the relative
thermal stabilities of these silica packing materials which in
turn provides an indication of the bond strength between
the silica and active phase. Figure 1, for example, shows the
comparative TGA results for a good and bad silica material.
The good material (silica A), as expected, exhibited a smaller
total weight loss over the temperature range evaluated. In
both materials, the initial weight loss (Figures 2 and 3) represented the loss of surface moisture, while the second weight
loss corresponded to loss of the active phase. Total analysis time was about an hour, but with faster heating rates or
the use of an autosampler, the productivity of this TGA
testing could easily be improved to levels acceptable for QC
analysis.
COMPARISON OF SILICA MATERIALS
102
100
Weight (%)
98
96
SILICA A
94
92
SILICA B
90
88
0
100
200
300
400
500
Temperature (oC)
600
700
800
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Figure 2.
WEIGHT LOSS - SILICA B
102
100
LOSS
(1)
96
4.825 %
(0.7996 mg)
0.10
LOSS (2) =
5.772 %
(0.9566 mg)
0.08
0.06
370.97oC
94
Residue:
89.35%
(14.81 mg)
92
90
88
0.00
N2 PURGE - 100 mL/MIN
0
200
400
Temperature (oC)
Figure 3.
-0.02
800
600
WEIGHT LOSS - SILICA A
0.05
100
Weight (%)
LOSS 0.02
(2)
10oC/MIN HEAT RATE
101
LOSS (1) =
2.159 %
(0.4223 mg)
LOSS (2) =
1.169 %
(0.9667 mg)
LOSS
(1)
99
0.04
0.03
Residue:
96.67 %
(18.91 mg)
98
0.02
0.01
97
96
0.04
LOSS
(2)
HEAT RATE = 10oC/MIN
N2 PURGE - 100 mL/MIN
0
200
400
Temperature (oC)
600
[- - - - -] Deriv. Weight (%/oC)
Weight (%)
98
LOSS (1) =
[- - - - -] Deriv. Weight (%/oC)
0.12
0.00
-0.01
800
Acknowledgment: TA Instruments would like to thank Phase Separation Ltd. for their cooperation in writing this
application note.
For more information or to place an order, contact:
TA Instruments, Inc., 109 Lukens Drive, New Castle, DE 19720, Telephone: (302) 427-4000, Fax: (302) 427-4001
TA Instruments S.A.R.L., Paris, France, Telephone: 33-01-30489460, Fax: 33-01-30489451
TA Instruments N.V./S.A., Gent, Belgium, Telephone: 32-9-220-79-89, Fax: 32-9-220-83-21
TA Instruments GmbH, Alzenau, Germany, Telephone: 49-6023-30044, Fax: 49-6023-30823
TA Instruments, Ltd., Leatherhead, England, Telephone: 44-1-372-360363, Fax: 44-1-372-360135
TA Instruments Japan K.K., Tokyo, Japan, Telephone: 813-5434-2771, Fax: 813-5434-2770
Internet: http://www.tainst.com
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Thermal Analysis & Rheology
A SUBSIDIARY OF WATERS CORPORATION