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Title: Detection methods of organic acid in steam/water circuits and optimisation using HPLC-UV
Authors: Ramrung, Arthi 
Issue Date: 2009
This study was mainly a response to a challenge faced by ESKOM in its coal-fired power
stations. In spite of using high purity water to drive the turbines, the latter were damaged by
‘pitting’, possibly related to acids generated at high temperatures. In the light of this a
relatively simple method for determination of short chain organic acids was identified by
comparing the efficacies of several methods. It was found that high performance liquid
chromatography (HPLC) method preceded by derivatization (with o-nitrophenyl hydrazine)
is suitable for analyzing mixtures of simple acids at ppb levels.
Calibration was effected by using methanoic acid (formic acid), ethanoic acid (acetic acid),
propanoic acid (propionic acid) and butanoic acid (butyric acid). The HPLC instrument used
was from Thermo Separations with P2000 pump, SN 4000 interface and UV1000 with a
column heater. A comparative study between the HPLC methods using ion exclusion and
partition chromatography was carried out in order to find a suitable method that can be used
with aqueous environmental samples. The two essential columns that were used were ion
exclusion Phenomenex Rezex OA column and a Nucleodur C8 column.
The method of partition chromatography using a C8 column showed the most success using a
mobile phase consisted of acidified water using HCl (pH4.5) along with a 60:40
Acetonitrile/Methanol mixture. Both isocratic and gradient programs were utilized. Limits of
detection were improved from 800ppb (formic acid), 480ppb (acetic), 350ppb (propionic) and
680ppb (butyric acid) to 25ppb (acetic), 60ppb (propionic) and 90ppb (butyric).
Samples used in analysis were collected from the main stream, economiser, condensers,
polishing plant and turbines of the Tutuka Power Station in Mpumalanga province and
analysed using with final developed method
Dissertation presented in partial compliance with the requirements for the Masters Degree in Technology: Chemistry, Durban University of Technology, Durban, South Africa, 2009.
Appears in Collections:Theses and dissertations (Applied Sciences)

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