The Development of Atomic Absorption Spectroscopy (AAS)

It all began in the 1950s with a pioneering article by Alan Walsh. Today, it is an established standard technology in the field of analytical chemistry: atomic absorption spectrometry (AAS). AAS has experienced amazing development through the decades. In addition to newer ICP technologies, modern AAS systems such as Analytik Jena’s contrAA 800 exist thanks to ongoing technological developments.

The Beginnings of AAS

The basic principle of light absorption through atoms in their fundamental state was discovered and documented in 1860 by Kirchhoff and Bunsen. The discovery is considered to be the theoretical basis of?AAS . However, the actual year of birth of AAS is seen as 1955. That year, British-Australian physicist and chemist Alan Walsh published the groundbreaking idea of also using the spectra for chemical analyses.

According to modern legend, the idea for AAS came to Alan Walsh while gardening. Whether that is actually true can’t really be proven today. However, the fact is that his article “The application of atomic absorption spectra to chemical analysis,” published in 1955 in Spectrochimica Acta, constituted the cornerstone of modern AAS. The method made it possible for the first time to measure the concentration of numerous elements in a cost-effective and quick manner without wet-chemical analysis methods.

Around ten years passed between the initial publication of the idea and the first flame AAS devices being available on the market. Five years later, they were followed by the first electro-thermal AAS systems with graphite furnaces.

Easy and Effective – The Basic Principle of AAS

In order to determine elements in a base material, samples are atomized in front of a source of light. Sources of light are usually line sources (hollow cathode lamps) that radiate light in various defined wave lengths. Conventional AAS devices require that the corresponding light source be used for the element to be defined. In contrast, modern high-resolution continuum source AAS devices (HR-CS AAS) are equipped with one xenon short arc lamp, which can radiate light across the entire relevant wavelength spectrum and therefore do not need to be exchanged.

The atomization of the analyte in the sample into individual atoms is carried out with the help of a gas flame (flame AAS) or an electrically heated graphite furnace (GF AAS). For flame AAS, the sample solution is nebulized and carried into?the flame, while for GF AAS the solution is put in the graphite furnace first and atomized there through high temperatures.

The atomization of the sample generates an atom cloud that absorbs and debilitates the radiated light, causing it to lose intensity (absorption). Then, the intensity of the light in relation to the element-specific wavelength before and after the atomization is measured and compared. An increased concentration of an element in a sample leads to increased absorption. This absorption signal – meaning the decrease in intensity of the light compared to the radiated intensity – can be measured, thus determining the content of the analyte in the sample. For the analysis, standard solutions with known element concentrations are measured and used to generate calibration curves in order to determine the concentration of the element in the sample to be analyzed.

50 Years of AAS in Jena – Tradition and Innovation

Almost no other place is as deeply connected to atomic absorption spectrometry as the optics stronghold Jena. The university city at the heart of Germany now looks back at 50 years of AAS history. Here, the first device – named AAS 1 – was produced in 1971 by the then nationally owned Carl Zeiss Jena plant. The AAS 1 and its successor quickly gained an international reputation thanks to their particularly high longevity and reliability. In 1995, a few years after the reunification of Germany, Analytik Jena, still a young company at the time, took over the lab analysis division of Carl Zeiss, including research, development, production, and service. Thanks to numerous groundbreaking innovations, it took Analytik Jena only a few years to develop into a supplier of high-performance AAS devices and enjoy great international success. For example, the company brought the first graphite furnace system with direct solid sample analysis to the market in 1996. This was followed by the market launch of the novAA series – a compact and flexible system for routine analysis – as well as the introduction of the first third-generation Zeeman AAS in 2000. Analytik Jena catapulted into technological leadership in the AAS segment in 2004. Analytik Jena was the first company in the world to present an innovative AAS with a continuum light source, a high-resolution double monochromator and a CCD detector: The contrAA 300 was the first high-resolution continuum source AAS (HR-CS AAS).?

contrAA 800 – An AAS Success Story

The devices of?the?contrAA series ?made the previously common changing of lightbulbs of conventional AAS obsolete. Now, only one light source is needed to measure all elements and analysis lines – a single xenon short arc lamp covers the entire relevant wavelength spectrum. Users can therefore switch between elements very quickly, which enables a sequential definition of multiple elements and saves a great amount of time in the analysis process. The 2D or 3D visualization of the spectrum offered by?HR-CS AAS ?produces much more information than conventional AAS. Thanks to the high-resolution spectrometer, interferences can be immediately identified and corrected. The current devices in the contrAA 800 series combine flame and graphite furnace technologies in one flexibly expandable platform and can be easily and quickly optimized with accessories for specific applications – for example with autosamplers or systems for direct solid sample analysis.

The contrAA series has won over numerous clients thanks to these exceptional qualities. In recent years, over 1,500 devices have been installed in laboratories around the world and are used for applications in environmental analysis, food inspection, or the process and quality control in numerous industrial areas. For example, the contrAA device with flame atomization is used for the analysis of wine and fruit juice not only in Germany but also in other European countries such as Italy, Spain, and Portugal. “We have been working with the contrAA in the areas of research and routine analysis for many years,” says Dr. Claus Patz, scientist at the Department of Beverage Research of Geisenheim University, who has used the device with his team since 2009 for the mineral analysis of wines, fruit juices, and other beverages. “We particularly appreciate the flexible application, since every wavelength is available and even molecule bands can be measured.”

Customer Voice from Germany

About the use of the contrAA for mineral analysis of wines, fruit juices, and other beverages

“We particularly appreciate the flexible application of the contrAA."

We have been working with the contrAA in the areas of research and routine analysis for many years.?We particularly appreciate the flexible application, since every wavelength is available and even molecule bands can be measured.”

Dr. Claus-Dieter Patz, Geisenheim University, Germany

?(Image of?Sir Alan Walsh (1916-1998) ?by?CSIRO)