Sounding out heavy metals: Ultrasonic AAS booster

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  • Published: May 15, 2012
  • Author: David Bradley
  • Channels: Atomic
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A Green Analytical Method Using Ultrasound in Sample Preparation for the Flow Injection Determination of Iron, Manganese, and Zinc in Soluble Solid Samples by Flame Atomic Absorption Spectrometry
Ultrasound offers and attractive approach
to trace metal determination in food
and drink samples

Ultrasonic water dissolution at room temperature facilitates a rapid and simple analytical approach to the determination of iron, manganese and zinc with flow injection flame atomic absorption spectrometry.

Chemist Carmen Yebra of the Department of Analytical Chemistry, Nutrition and Bromatology, at the University of Santiago de Compostela, in Spain, explains how it is well known that trace metals can have important biological functions. Iron, manganese and zinc have, she says, a wide spectrum of activities. In order to understand their roles and to carry out diagnostics in connection with imbalances in these trace metals it is essential to have simple and precise techniques for their analysis in aqueous samples derived from biological specimens. The same techniques should be equally applicable to the food and pharmaceutical industries that require determinations of trace metals in their starting materials, feedstocks, formulations and final products.

Unfortunately, analysis of trace metals is usually fraught with preparative obstacles, time-consuming and error prone steps. Yebra suggests that a way to circumvent such issues would allow much timelier analyses to be carried out and she has turned to ultrasonics to assist in this endeavour.

"In spite of major advances in the instrumentation used in determinative steps, many laboratories use sample preparation techniques that are time consuming and labour intensive," Yebra says. Dissolving samples is often the mission critical step but commonly requires hazardous inorganic acids. Ultrasonic dissolution offers a much simpler and safer alternative.

As such, Yebra has tested sonication as a "chemical-free" approach to dissolving trace metals. Ultrasound energy precludes the need for acids or chemical modifiers, such as chelating agents. She points out that others researchers have demonstrated its efficacy for analytical procedures where it speeds up the analytical process as well as cutting costs without compromising accuracy. Moreover, it is amenable to continuous-mode processing and analysis.

Yebra explains that successful tests of a continuous ultrasound dissolution system have now been carried out and coupled to a flow-injection (FI) manifold to enable continuous determination of the three important trace metals mentioned above to be analysed using flame atomic absorption spectrometry (FAAS). "The proposed method is based on the use of non-toxic reagents that makes it friendly both for the operator and the environment," says Yebra, writing in a recent issue of the Journal of Analytical Methods in Chemistry.

One additional benefit of such a "chemical-free" approach to sample dissolution is that there are no losses of the analytes of interest that might occur with the use of acids or other chemical reagents. "This methodology provides accurate results with high precision," says Yebra. It also precludes random errors that are introduced during the process of glassware calibration. "The proposed method can be considered as environmentally friendly at every step of the analytical procedure," she adds. "All these characteristics make the method easy to apply to quality control in industry."

Related Links

J Anal Methods Chem, 2012, online: "A Green Analytical Method Using Ultrasound in Sample Preparation for the Flow Injection Determination of Iron, Manganese, and Zinc in Soluble Solid Samples by Flame Atomic Absorption Spectrometry"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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