Pre-concentrated silver: FAAS analysis

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  • Published: Apr 15, 2017
  • Author: David Bradley
  • Channels: Atomic
thumbnail image: Pre-concentrated silver: FAAS analysis

Tracing silver

Researchers in China have used a cloud point extraction (CPE) method to pre-concentrate trace levels of silver present in water samples for subsequent flame atomic absorption spectrometry (FAAS) analysis. Silver tray photo by David Bradley

Researchers in China have used a cloud point extraction (CPE) method to pre-concentrate trace levels of silver present in water samples for subsequent flame atomic absorption spectrometry (FAAS) analysis.

Silver is a non-essential metallic element that is present in the human body. Following ingestion or chronic topical application, it may accumulate in the skin and mucosa causing permanent blue-gray discolouration of tissues and in extreme cases lead to lethal toxicity. The accurate determination of silver in environmental and medical samples is therefore important for ecological wellbeing and human and animal health. Xiupei Yang, Zhihui Jia, Xiaocui Yang, and Gu Li of the China West Normal University, in Nanchong, China and Xiangjun Liao of Health Canada in Ottawa, point out that despite the putative health problems silver is widely used in industry and medicine for its excellent thermal and electrical conductivity as well as its bactericidal characteristics and other properties.

Ubiquitous silver

The widespread use of silver in various applications means that it is almost ubiquitous in the environment and in biological samples albeit most commonly at trace level concentrations. As such, highly sensitive analytical techniques are needed in order to study the metal in such samples and their impact on ecosystems and health. Numerous techniques are amenable to silver analysis including FAAS and electrothermal atomic absorption spectrometry (ETAAS), inductively coupled plasma atomic emission spectrometry (ICP-AES), and ICP-mass spectrometry. Pre-concentration is usually required in order to detect very low concentrations of the metal. This requires solvent extraction, solid phase extraction, precipitation or adsorption on tungsten wire. Of course, all such methods have their limitations and associated risk of cross contamination.

Liao and colleagues have now turned to cloud point extraction (CPE) as a novel and increasingly popular method of liquid–liquid extraction that is being used more and more separation science. The technique is considered environment friendly and can be fine-tuned for particular samples by adjusting surfactant used, solution pH, temperature, concentration, and time. The team points out that it can be used to separate hydrophobic and hydrophilic materials, is economical, safe, efficient, and convenient.

Soft soap approach

The team has now demonstrated proof of principle in pre-concentrating silver ions in known samples, stock solutions, using Triton X-114 as a non-ionic surfactant and sodium diethyl dithiocarbamate (DDTC) as a chelating agent. Subsequent successful determination by FAAS corroborated the benefits of CPE, the team reports. The researchers add that under optimised experimental conditions they saw no interference in their determination of solutions containing 100 nanograms per millilitre of silver ions in water even in the presence of cadmium, copper, lead, manganese, nickel, and zinc ions within known concentration limits. Their limit of detection (LOD) was 0.3 nanograms per millilitre of silver." The developed method was successfully applied for the determination of trace levels of silver in water samples such as river water and tap water," the team concludes.

Related Links

Saudi J Biol Sci 2017, 24, 589-594: "Cloud point extraction-flame atomic absorption spectrometry for pre-concentration and determination of trace amounts of silver ions in water samples"

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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