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Abstract

The environmental significance of resin acids originating from pulp
and paper industry effluent has led to a detailed investigation of
techniques used for their analysis. The chromatographic separation
of a number of resin acids (based on those found in Pinus radiata)
and their coumarin derivatives was investigated using High Perform-
ance Liquid Chromatography (HPLC) with a view to developing a sen-
sitive quantitative technique for analysis of total resin acids in
pulp and paper industry effluent and in waterways receiving those
effluents.

Seven resin acids (sandaracopimaric, isopimaric. levopimaric, palust-
ric, dehydroabietic, abietic. and neoabietic acid) were reacted with
4-bromomethyl-7-methoxycoumarin (4BrMMC) or 4-bromomethyl-7-acetoxy-
coumarin (4BrMAC) to form (7-methoxy-coumarin-4-yl)methyl (MMC)
esters and (7-acetoxy-coumarin-4-yl)methyl (MAC) esters respectively.
The molar absorptivity of the resin acid MMC esters at 318 nm was
shown to be the same for each resin acid ester, thus making it poss-
ible to measure them quantitatively by HPLC even though they were not
all chromatographically separated. Fluorescence quantum yield meas-
urements of the MMC esters however showed a variation in fluorescence
response that depended on the resin acid. There was also a variation
in fluorescence quantum yield with solvent and water content of the
solvent. These two factors precluded the use of the fluorescent
properties of the MMC esters for quantitative analysis.

Like the MMC esters, the molar absorptivity of the resin acid MAC
esters was the same for each resin acid ester, thus enabling use of
the chromophore at 310 nm for quantitative analysis. The resin acid
MAC esters possessed no fluorescence. but reaction with alkaline
methanolic solution was shown to hydrolyse the acetoxy group of the
coumarin compound while maintaining the ester linkage to the resin
acid. Fu1the1more the fluorescence response of each of the seven
resin acids was the same in alkaline media.

In the course of these studies, both 4BrMMC and 4BrMAC were found to
decompose rapidly when exposed to light with up to half the reagent
decomposing in only 30 minutes. The consequences of this photolabil-
ity were explored to ascertain the probability of reactions with
resin acids during the derivatisation reaction. Similar decomposit-
ion products were observed for both coumarin compounds. In the
presence of oxygen. 4-methyl-. 4-formyl-. 3-bromo-4-methyl-, and
3-bromo-4-formyl- derivatives of both methoxy and acetoxy coumarin
were formed. In the absence of oxygen. and using a high intensity
mercury discharge lamp light source. 4BrMMC was shown to produce
4-methyl-, and 3-bromo-4-methyl-7-methoxycoumarin as well as a photo-
dimer. The latter two compounds eluted after the 4BrMMC peak thus
posing a potential inte1ference problem for HPLC analysis. It was
concluded that for the purposes of the analytical technique, it was
important to protect solutions containing the coumarin derivatisation
reagent from light during all stages of the derivatisation process
apart from volumetric transfer of solutions.

Derivatisation procedures rep01ted in the literature for similar
types of reactions rely on the use of heat and crown ether catalysts
to achieve rapid quantitative derivatisation. The effect of tempera-
ture, crown ether catalyst, solvent and ratio of derivatisation
reagent to resin acid were studied. Quantitative conversion to both
the methoxy- and acetoxy-coumarin esters was obtained at room temp-
erature, without catalyst. in either acetonitrile or acetone in I 0-15
mins., provided a 10-20 molar excess of derivatisation reagent was
present.

Application of the technique to extracts from water samples contain
mg a variety of other organic compounds and resin acid concentrate-
ions was pursued. Apart from the coumarin derivative of dehydroa-
bietic acid. all of the resin acid coumarin esters studied co-eluted
on a C-8 reverse phase HPLC column. A gradient elution programme
based on acetonitrile and water was optimised to obtain adequate
resolution of the resin acid coumarin esters from other components
present m the effluent extracts. The method was applied to the
analysis of resin acids in a river estuary into which pulp and paper
effluent was discharged. Based on extraction of 100 ml samples. a
detection limit of 0.005 mg C1 was calculated for the technique
using 4BrMMC as the derivatisation reagent and UV absorption for
detection. A detection limit of 0. OOO 1 mg C 1 was calculated for the
techniques using 4BrMAC with fluorescence detection of the hydrolysed
ester derivative. The lower detection limit associated with 4BrMAC
esters offers a significant improvement over current gas chromato-
graphy methods using flame ionisation detection.

Item Type:	Thesis - PhD
Authors/Creators:	Richardson, DE
Keywords:	Organic acids, Paper industry, Pulpwood industry
Copyright Holders:	The Author
Copyright Information:	Copyright 1987 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Thesis (Ph.D.)--University of Tasmania, 1989. Includes bibliography
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