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Quantification of Polyphosphonates and Scale
Inhibitors in High Ionic Strength Matrix
Effluents Using IC-MS/MS
Charles Yang
1
, Stacy Henday
2
, Leo Wang
2
, and Bill Schnute
2
1
Thermo Fisher Scientific, San Jose, CA;
2
Dionex Corporation, Sunnyvale, CA
Introduction
Scale deposits and corrosion formation in aqueous
industrial cooling systems reduce the efficiency of heat
transfer and can lead to equipment failure and increased
operating costs. The addition of scale and corrosion
inhibitors to cooling tower water streams helps to
minimize corrosion formation by allowing dissolved
minerals to remain soluble in water instead of depositing
as scale. In turn, these additives permit the repeated
cycling of water in cooling systems.
Before scale and corrosion inhibitors were commonly
used, all cooling systems were “once-through” systems.
Copious amounts of water were removed from lakes and
streams by the cooling systems, greatly stressing aquatic
life and negatively affecting the environment. By adding
polyphosphonate compounds, such as HEDP
(1-hydroxy ethylidene-1, 1-diphosphonic acid) and
PBTC (2-phosphonobutane-1,2,4-tricarboxylic acid), to
cooling water, corrosion and scale are minimized so that
the cooling water can be cycled repeatedly through the
system before it is released back into the environment.
When the cooling water is released back to the lake or
stream, it must meet the standards of the United States
Environmental Protection Agency (US EPA) Clean Water
Act (CWA). Section 316(b) requires industrial plants to
employ the best technology available to protect fish and
aquatic life.
1
With the increased use of scale and corrosion
inhibitors, polyphosphonates are now an emerging
environmental contaminant and few quantitation methods
exist. The ion chromatography – mass spectrometry
(IC-MS/MS) technique described here provides robust
quantitation in less than 20 minutes for five common scale
and corrosion inhibitors in cooling water effluents –
ATMP (amino trimethylene phosphonic acid), HEDP,
PBTC, HPMA (hydrolyzed polymaleic anhydride), and
PSO (a proprietary phosphinosuccinic oligomer)
2-4
.
Goal
To develop a robust IC-MS/MS method for the
quantitation of scale and corrosion inhibitors in a high
anionic matrix.
Experimental Conditions
Ion Chromatography
IC analysis was performed on a Dionex ICS 3000 ion
chromatography system (Dionex Corporation, Sunnyvale,
CA). The polyphosphonate and scale inhibitor samples
were directly injected and no sample pre-treatment was
required. The IC conditions were as follows:
Column set: IonPac
®
AG21 (2.1 × 50 mm) / AS21
(2.1 × 250 mm); guard and separator
columns (Dionex)
Suppressor: ASRS
®
300, 2 mm; operated at 38 mA
(Dionex)
Column temperature: 30 °C
Injection volume: 100 µL
Mobile phase: Potassium hydroxide, electrolytically
generated with an EGC-KOH cartridge
Gradient: 0–7 min: 20 mM KOH
7–12 min: 20–60 mM KOH
12–17 min: 60 mM KOH
17.1 min: 20 mM KOH
Flow rate: 300 µL/min
Eluent generation technology allows automatic in-situ
production of high-purity IC eluent (Figure 1). The pump
delivers water to an eluent generator cartridge (EGC) that
converts the water into a selected concentration of
potassium hydroxide eluent using electrolysis. After
separation on the column, the eluent enters the ASRS
suppressor, which produces hydronium ions to exchange
with potassium in the eluent and neutralizes the
hydroxide. This makes the mobile phase compatible with
an atmospheric ionization source as featured on LC-MS
and LC-MS/MS systems.
Key Words
• TSQ Quantum
Access
• SRM
• Ion
chromatography
• Water analysis
Application
Note: 479