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Matec Applied Sciences
56 Hudson St., Northborough, MA 01532 Ph: (508) 393-0155 Fax: (508) 393-5476
www.matec.com
e-mail: [email protected]
replacement. For the CHDF-2000, this filter is optional. You may operate your CHDF-2000 without
this filter if you so prefer.
8.
Noise and drift are present in the Raw Data baseline.
This is probably due to a defective Whatman filter. Replace this filter and observe the baseline. This filter
must be filled with eluant when in operation. Use the purge knob on the filter is order to draw any air
from the filter. Another possibility is that the UV lamp may need replacement if it has been used for
more than 1000 hours (see the troubleshooting section of the hardware manual).
9.
How should samples be prepared for CHDF analysis?
Only aqueous samples can be analyzed on the current CHDF setup. Dry powders must be dispersed in
GR500. Sonication should be applied in order to help suspend the particles in the liquid. Concentrated
samples should be diluted in GR500 eluant. The solids contents are typically in the range 0.1% to 5%
by volume. UV-absorbing samples can be analyzed at lower concentrations while non-UV absorbing
samples (such as colloidal silica) must be run at higher concentrations. Sonication may be used in
order to break-up particle aggregates. Reasonable sample concentrations should produce peak heights
of 20 to 50 mAU’s for the CHDF-2000, and 5,000 to 15,000 counts for the CHDF-1100. A syringe
filter may be used on the sample syringe in order to remove aggregates from samples prior to
injection. Syringe filters may only be used once per sample. Marker, as well as, Rinse filters may be
reused until leaks are observed on the filters.
10.
No peaks are detected in the Raw Data graph upon sample, and marker injection.
The fractionation cartridge is likely plugged. Refer to the troubleshooting section of the hardware manual
for cartridge cleaning instructions.
11.
The pump pressure is higher than normal.
The filter element in the cartridge in-line filter must be either cleaned or replaced. Refer to the
troubleshooting section of the hardware manual. The CHDF-1100 is affected by ambient temperature.
Low ambient temperatures result in high CHDF-1100 pressures.
12.
What Noise Level should be used under Configure System in the CHDF software?
30-40 for the CHDF-2000; 400 for the CHDF-1100.
13.
Can any wavelength be used on the CHDF UV-detector?
The CHDF UV-detector wavelength can be varied from 190 to 380 nm. However, the CHDF PC software
only contains particle extinction cross section curves for 200 nm, and 220 nm. One of these values
must be selected in the active Method file. Inaccurate results are obtained if the UV-detector, and the
software wavelengths differ.
14.
What is the sharp peak in the Raw Data between the sample peak and the marker peak?
This peak corresponds to UV-absorbing molecular species present in the sample. Molecular species
include surfactants, electrolytes, acids, or bases. These molecules have a smaller size than the particles
themselves, and therefore exit the capillary after the particles.
15.
A broad peak after the marker peak is displayed in the Raw Data.
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