Since its introduction in 1975, ion chromatography (IC) has been used in most areas of analytical chemistry and has become
a versatile and powerful technique for the analysis of a vast number of ions present in the environment. Although conductivity
detection is still the most popular detection method, other types of detection can be applied for different analytes. These
include the following methods: electrochemical (for example, amperometric and potentiometric), photometric (UV–vis and chemiluminescence),
and spectrometric (used mainly in hyphenated techniques). The most versatile and powerful detection method is mass spectrometry
(MS). The main advantages of IC–MS are extremely low detection and quantification limits, insignificant interference influence,
and high precision and repeatability of the determinations. This article is a review of possible uses of IC in combination
with MS detection for environmental research.
Speciation, as a word borrowed from biology, is a term describing the existence of various chemical and physical forms of
a particular element, and speciation analytics denotes the determination of those forms (1). The notion of speciation is used
in chemistry to determine the occurrence of diverse forms of a given element (for example, elements at various oxidation states
or bound with different ligands) in the analyzed sample. The forms might differ in physical and chemical characteristics as
well as in the influence they exert on living organisms. In the last several decades, speciation analytics has become one
of the most central issues in analytical chemistry. Even though its cost is significant, speciation analytics has become more
important when it comes to solving problems that concern not only the determination of total element contents, but also taking
into account various forms of occurrence. It plays an exceptional role in the examination of biochemical cycles of selected
chemical compounds, determination of toxicity and ecotoxicity of selected elements, food and pharmaceutical product quality
control, and technological process control as well as health risk assessment and clinical analytics (2).
It is reasonable to differentiate between chemical and physical speciation. In chemical speciation, it is possible to distinguish
between screening speciation, which searches for and determines selected chemical forms, and distribution speciation, which searches for and determines selected chemical individuals in specific elements of the examined sample. Another division
within chemical speciation concerns group speciation, which is defined as searching for and determining specific groups or classes of chemical forms, and individual speciation, which is searching for and determining all chemical individuals present in the sample. When it comes to liquid sample analyses,
the most common technique is the one developed by Florence and Batley (3). According to this method, a water or wastewater
sample filtered through a 0.45-μm filter is divided into a solid phase and a mobile phase, in which the determinations of
total metal contents and the metal labile and bound forms are carried out. The division suggested by Tessier and colleagues
(4) is recommended in the research concerning the speciation of heavy metals in bottom sediments. They distinguished and defined
five fractions: exchangeable metals, carbonate-bound metals, iron and manganese oxides-bound metals, organic matter-bound
metals, and other mineral-bound metals. Nonetheless, this method of speciation does not differentiate between oxidation states
of elements, which may be of great importance when considering their toxicity.
Lowering the detection limits of analytes to extremely low concentration levels resulted in methods that did not always meet
the necessary requirements. For that reason, there has been a tendency to combine various methods and techniques. These combinations
are known as hyphenated techniques. A suitable hyphenated technique should be selective toward determined analytes, should
be sensitive within a wide range of concentrations, and should enable the best possible identification of the determined substances.
In speciation analytics, chromatographic methods are largely used for separation whereas spectroscopic ones are used for detection
The application of hyphenated techniques entails a perfect understanding of analytical methodologies and detailed knowledge
of instrumentation. These are expensive systems used in scientific research rather than in routine analyses. The earliest
hyphenated techniques were developed by coupling gas chromatography (GC) with various detectors. The following systems were
then developed: gas chromatography–atomic absorption spectrometry (GC–AAS), gas chromatography–atomic emission spectrometry
(GC–AES), gas chromatography–mass spectrometry (GC–MS), and gas chromatography–inductively coupled plasma–time-of-flight mass
spectrometry (GC–ICP-MS-TOF). Because of technological reasons, systems using liquid chromatography (LC) methods for the separation
of analyzed substances, such as high performance liquid chromatography (HPLC)–ICP-MS, appeared in the market slightly later.
There are couplings of various LC types among the most popular hyphenated techniques used to determine different ionic forms
of metals and metalloids. These include HPLC, ion chromatography (IC), ion-exclusion chromatography, and size-exclusion chromatography
(SEC) with ICP-MS or electrospray ionization (ESI) MS. The most popular hyphenated techniques using ion chromatography are
IC–ICP-MS and IC-MS (6).