Carbohydrate system with 871 Bioscan and dialysis
Automated sample preparation is becoming more and
more an integral part of a high-performance IC System.
With the introduction of the
patented dialysis method Metrohm has placed a new milestone on the way towards
this goal.
In food chemistry the determination of sugars in dairy
products is of the utmost importance. When carrying out
direct ion chromatographic determinations the precipitation
of protein constituents on the column is a recurring
problem. Instead of demanding precipitation procedures
the dialysis technique can be used to separate the interfering
protein matrix. The use of dialysis as an inline sample
preparation step results in a rapid automated analysis
system. The sugar constituents are determined by means
of pulsed amperometric detection.
Dialysis is neither filtration, nor extraction, nor
digestion. In dialysis the analytes pass from the sample
solution into the acceptor solution by diffusion through
a dialysis membrane. After only a short time a concentration
equilibrium is established between the sample solution
and the acceptor solution. The number of analytes in
the sample solution is not reduced as these are constantly
being resupplied. Whereas the mono-, di- and oligosaccharides
can pass through the membrane almost without any hindrance,
polysaccharides or larger particles - the matrix - are
simply transported past the dialysis membrane. Matrix
effects are therefore reduced to an absolute minimum.
The Metrohm dialysis method works according to the stopped-flow
principle: About 10 mL of sample is passed along the
dialysis membrane by the peristaltic pump built into
the 838
Advanced IC Injection Sample Processor (2.838.0020),
while the acceptor solution remains at rest. The acceptor
solution is then
transferred to the sample loop of the 812
Valve Unit and the sample is analyzed in the normal
manner.
High reproducibility, long membrane life, dialysis rates >98%
and very low detection limits for sugars make the Metrohm
IC dialysis system into a powerful tool for overcoming
difficult application problems.
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