Abstract
Knowledge of the behaviour of cellulose, hemicelluloses,
and lignin during wood and pulp processing is essential
for understanding and controlling the processes.
Determination of monosaccharide composition gives
information about the structural polysaccharide
composition of wood material and helps when determining
the quality of fibrous products. In addition, monitoring
of the acidic degradation products gives information of
the extent of degradation of lignin and polysaccharides.
This work describes two capillary electrophoretic methods
developed for the analysis of monosaccharides and for the
determination of aliphatic carboxylic acids from alkaline
oxidation solutions of lignin and wood.
Capillary electrophoresis (CE), in its many variants is
an alternative separation technique to chromatographic
methods. In capillary zone electrophoresis (CZE) the
fused silica capillary is filled with an electrolyte
solution. An applied voltage generates a field across the
capillary. The movement of the ions under electric field
is based on the charge and hydrodynamic radius of ions.
Carbohydrates contain hydroxyl groups that are ionised
only in strongly alkaline conditions. After ionisation,
the structures are suitable for electrophoretic analysis
and identification through either indirect UV detection
or electrochemical detection.
The current work presents a new capillary zone
electrophoretic method, relying on in-capillary reaction
and direct UV detection at the wavelength of 270 nm. The
method has been used for the simultaneous separation of
neutral carbohydrates, including mono- and disaccharides
and sugar alcohols. The in-capillary reaction produces
negatively charged and UV-absorbing compounds. The
optimised method was applied to real samples. The
methodology is fast since no other sample preparation,
except dilution, is required.
A new method for aliphatic carboxylic acids in highly
alkaline process liquids was developed. The goal was to
develop a method for the simultaneous analysis of the
dicarboxylic acids, hydroxy acids and volatile acids that
are oxidation and degradation products of lignin and wood
polysaccharides. The CZE method was applied to three
process cases. First, the fate of lignin under alkaline
oxidation conditions was monitored by determining the
level of carboxylic acids from process solutions. In the
second application, the degradation of spruce wood using
alkaline and catalysed alkaline oxidation were compared
by determining carboxylic acids from the process
solutions. In addition, the effectiveness of membrane
filtration and preparative liquid chromatography in the
enrichment of hydroxy acids from black liquor was
evaluated, by analysing the effluents with capillary
electrophoresis.
Original language | English |
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Qualification | Doctor Degree |
Awarding Institution |
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Supervisors/Advisors |
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Award date | 14 Dec 2012 |
Place of Publication | Espoo |
Publisher | |
Print ISBNs | 978-951-38-7944-0 |
Electronic ISBNs | 978-951-38-7945-7 |
Publication status | Published - 2012 |
MoE publication type | G5 Doctoral dissertation (article) |
Keywords
- wood
- capillary electrophoresis
- carbohydrates
- carboxylic acids
- oxygen delignification
- alkaline oxidation