Evaluation of resin and fatty acid concentration levels by online sample enrichment followed by atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) |
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Authors: | Piia Valto Juha Knuutinen Raimo Alén |
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Institution: | 1.Laboratory of Applied Chemistry, Department of Chemistry,University of Jyv?skyl?,Jyv?skyl?,Finland |
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Abstract: | Background, aim, and scope In papermaking, there is a continuous interest both to minimize fresh water consumption and to reduce discharges into the
environment. These general trends mean an increase in the amounts of detrimental substances, such as resin and fatty acids,
in papermaking process waters. Resin acids, in particular, are responsible for much of the toxicity typically present in paper
mill effluents and, for this reason, the routine and rapid monitoring of these compounds in various process streams is necessary.
This also means that there is a continuous need to develop straightforward offline and online techniques to clarify problems
occurring, for example, as a result of the introduction of more intensively closed systems of water circulation. In the present
study, we describe the use of a novel, online, sample enrichment technique followed by atmospheric pressure chemical ionization–mass
spectrometry (APCI-MS) suitable for monitoring the concentration levels of common resin and fatty acids in papermaking process
waters.
Materials and methods The representative process water samples were taken from the grinding zone of a thermomechanical pulping mill. The samples
were first preconcentrated in a precolumn C18, and the analytes were transferred online to MS. The high intensive M–H]− ion was used for the identification of each analyte since, according to the present ionization method, no other fragmentation
was observed. Laboratory-scale, online measurements with an online sample feed were carried out by connecting a centrifugal
pump and a ceramic filter to the APCI-MS.
Results Quality parameters, such as repeatability, linearity, and limit of detection (LOD), were determined by using dehydroabietic
acid (DHAA) in order to evaluate the suitability of the method for the rapid screening of concentration levels. This method
provided satisfactory linearity and a good correlation between analyte concentration and peak area. The suitability of the
system for the continuous analysis of the same acids was evaluated in laboratory-scale, online experiments. In all cases,
the response to changes in the analyte concentration was linear, and the repeatability of the system was also satisfactory.
Discussion Only a few studies have been published on the analysis of resin and fatty acids with MS techniques. The present method was
applied to the monitoring of dehydroabietic, oleic, and stearic acids. The quality parameters were highly comparable with
those reported earlier, and the LOD values of the DHAA were below the levels usually encountered in process waters. The quality
parameters were only slightly higher than those obtained by the traditional methods of analysis, probably due to the absence
of an effective sample clean-up before analysis.
Conclusions The results of the laboratory-scale, online experiments indicated that the online enrichment APCI-MS system is a suitable
alternative for monitoring the concentration levels of selected resin and fatty acids in papermaking process waters. The method
can be used, for example, to provide useful information about the concentration levels of these acids in different stages
of the process, thus signaling possibly impending problems. In general, faster and simpler measurements are needed to meet
the requirements for a reduction in fresh water usage in papermaking.
Recommendations and perspectives Compared to the conventional methods used for this purpose, the main benefits of the method are rapidity of measurement, simplicity
of use, and absence of the need for multistage sample treatments (short analysis time). For this reason, this online method
is more suitable for the control of papermaking by analyzing the concentration levels of interfering substances (i.e., selected
resin and fatty acids) than an offline analysis detailing all the individual extractives-based compounds in process streams.
It is also obvious that the technique can easily be modified for other environmental pollutants as well. |
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Keywords: | Fatty acids Mass spectrometry Online Papermaking process water Resin acids Sample enrichment |
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