Inorganic Species Savior

At the beginning of the twenty-first century, analytical chemistry had to face new challenges.  First and foremost, new information about the toxicological properties and forms of elements was appearing and there was a necessity for the detection and determination of gradually lowering analyte concentrations – often in complex matrix samples.

When it comes to living organisms, biological activity and toxicity of elements is governed primarily by the existence of ionic forms. Among the many analytical methods applied for ion analysis, ion chromatography (IC) is perhaps the best suited. It is a well-established regulatory method for analyzing anions and cations in environmental, food and many other samples. IC offers: 

• high capacity and selective stationary phases and sensitive detectors
• simple sample preparation
• avoidance of hazardous chemicals
• decreased sample volumes 
• flexible reaction options when changing sample matrix to be analyzed
• the option to operate a fully-automated system.

However, at present, there are several areas that must be addressed for ion chromatography to advance, including the need to:

• introduce new ion-exchange stationary phases
• improve the suppressor operation efficiency 
• lower the limits of detection and quantification
• introduce new sample preparation methods
• extend the analysis range with new organic and inorganic substances
• increase use in molecular biology and genetics research (genomics, proteomics, metabolomics, transcriptomics)
• further develop new standards and detection methods
• miniaturize apparatus. 

As noted above, toxicological tests show that what often decides the element’s influence on living organisms is not the total concentration but the participation of the element’s individual forms. Consequently, detection and quantitation of the various analytes forms/species (as they pertain to toxicity, bioavailability and reactivity) is the primary goal in environmental and biomedical fields. Because of the inherent challenges, there is an increasing tendency to combine diverse separation methods (for example, chromatography) and detection (for example, mass spectrometry), to which the term ‘hyphenated techniques’ is often given. A specific hyphenated technique should be selective towards the determined analytes, sensitive in a wide range of concentrations, and should enable the best possible identification of the determined species. The most popular hyphenated techniques employing ion chromatography are  IC-inductively coupled plasma-mass spectrometry (IC-ICP-MS) and IC-MS; both are powerful tools when it comes to the unambiguous determination of different organic and inorganic compounds in a single run. The extremely low limits of detection and quantification as well as high accuracy and repeatability of determinations are particularly desirable in species analysis and open up several new analytical avenues.

Unfortunately, like other advanced methods, hyphenated techniques have certain limitations, such as high price and complexity, which means that they do not enjoy common usage in routine laboratories. However, in my opinion, the role and potential of hyphenated techniques in speciation analytics should not be underestimated – indeed, they are invaluable, if we wish to move forward.

I suspect that the next steps for ion chromatography (hyphenated with MS or otherwise) will include the development of new stationary phases with improved separation selectivity and new detection modes, as well as the development of capillary and two-dimensional systems. I would also add that increasing usage of IC with advanced automated in-line sample preparation techniques in species analysis will help extend its application to other complex samples. As to whether it will be a “remedy” for inorganic and organic species analysis... Why not? It simply depends on our scientific courage, curiosity and imagination.