2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
L11 POTENTIAL APPLICAbILITy OF A
hIGh PERFORMANCE ChELATION ION
ChROMATOGRAPhIC METhOD TO ThE
DETERMINATION OF ALuMINIuM IN
ANTARCTIC SuRFACE SEAwATER
JULIETTE TRIA, PAUL R. HADDAD and PAVeL
nESTEREnKO
Australia Centre for Research on Separation Science
(ACROSS), School of Chemistry, University of Tasmania,
Private Bag 75, Hobart, Tasmania, Australia, 7001,
jtria@utas.edu.au
Introduction
In oceanography, aluminium is used as a tracer to fingerprint
the location and magnitude of atmospheric dust deposition.
Aluminium is particularly suitable as a tracer because
of its short residence time in surface seawater, its relatively
simple seawater chemistry and the fact that primary input to
the open ocean is by atmospheric deposition. The information
supplied by surface aluminium concentrations is vitally
important to understanding the role that aeolian deposition
plays in supplying trace elements to the surface ocean and
subsequent effects on biological processes. The information
is especially important for furthering knowledge of the biogeochemistry
of iron. Iron is of particular interest because
it is an essential element for the growth and metabolism of
all marine organisms despite only being available in extremely
low concentrations (0.1–0.5 nM) 1 . Iron has been shown
to limit phytoplankton growth, which in turn may have
implications on global climate through drawdown of gases
used in photosynthesis, such as carbon dioxide. An accurate
and robust method for determining aluminium is thus
vital for continuing studies into atmospheric deposition and
subsequently climate control.
Flow injection analysis (FIA), has typically been used
for the quantification of aluminium in seawater, due to its
portability for shipboard use, suitable limit of detection and
relative ease of use. However, this technique still requires
preconcentration of as much as 10 ml of seawater in order to
achieve the required sensitivity 2 . Other common techniques
for the determination of trace concentrations of aluminium,
such as ICP-MS, are unsuitable for use at sea due to the size
of the instrumentation as well as the amount of sample pretreatment
required.
Chromatographic techniques have become increasingly
popular for the quantification of aluminium in recent years.
Ion chromatography has successfully been used for the separation
of aluminium in a selection of matrices including natural
waters 3–6 and biological samples 7 . The technique is relatively
simple and can be coupled with a variety of detection
methods such as UV-VIS and mass spectrometry, allowing
for both high selectivity and sensitivity.
Chelation ion chromatography (CIC) offers an alternative
to traditional ion-exchange IC, particularly for samples
of high ionic strength. CIC functions by retaining metal ions
s319
according to the stability of the corresponding complexes and
allows for the separation and preconcentration of aluminium
in complex samples. In addition, CIC also offers the advantages
of using only one type of material for both preconcentration/matrix
elimination and separation and also the ability
to acquire a simplified chromatogram identifying only kinetically-labile
and chemically inert species 8,9 . Ion-exchange
interactions are likely to occur simultaneously; however, high
ionic strength eluents are typically used to ensure chelation is
the dominant mechanism.
The iminodiacetic acid functional group has been shown
to be a highly promising ligand for the separation of metal
ions by CIC 10 . Our previous work has shown the applicability
of iminodiacetic acid functionalised silica (IDAS) to
the determination of aluminium in paper mill process water 11 .
This work detailed the optimised separation conditions of an
IDAS packed column including eluent composition, flowrate
and column temperature. Good separation in a complex
matrix was achieved, with high column efficiency.
The most commonly used method for the detection of
aluminium at low concentrations is the highly sensitive fluorescent
detection of its lumogallion complex. This approach
has been applied successfully to the determination of aluminium
in a wide range of samples, including those with a high
salt content, e.g. saline water and body fluids. nishikawa
and co-workers were the first to describe application of the
technique to seawater and the batch method has since been
incorporated into FIA systems 12 . The limit of detection for
the technique has been improved through the addition of surfactants
and through optimisation of conditions such as pH
and temperature.
This paper is a continuation of our work with IDAS but
for the specific purpose of the direct determination of aluminium
in seawater. The determination of Al in seawater poses
a myriad of potential problems including sample matrix interferences
and extremely low concentrations. We have developed
a HPCIC method coupled with fluorescent detection of
the aluminium-lumogallion complex. The system has been
successfully applied to seawater samples obtained in the Ross
Sea, Antarctica.
Experimental
A p p a r a t u s
A Metrohm 844 UV/VIS Compact IC was used for all
analyses. The system delivered the eluent at 0.3 ml min –1 and
was set up with a post-column reactor, consisting of a 2 m
PTFE reaction coil (1/16” × 0.02”). This reactor was immersed
in a water bath for heating above room temperature. Peristaltic
pump tubing delivered the PCR reagent at a constant
flow-rate of 0.36 ml min –1 . A 20 µl sample loop was used
unless specified.
A column heater set to 71 °C housed a 200 × 4 mm i.d.
column packed with 5 µm IDAS (JPP Chromatography Ltd,
UK). Detection was carried out using a Varian Prostar 363
fluorescence detector fitted with a xenon lamp. The excitation
and emission wavelengths were set to 500 and 550 nm