Publication: Scientists deploy optical technique for high precision measuring of lead

Richard Gomez thesis, guided by our researcher Dr. Renato Saavedra, originated the article “Determination of lead (II) by thermal lens spectroscopy (TLS) using 2 – (2′-thiazolylazo)-p-cresol (TAC) as chromophore reagent” that was recently published in Microchemical Journal. This work also has the support of CEFOP master student Ariana Munoz and Dr. Cesar Soto, professor of the Chemistry faculty at Universidad de Concepcion.

How much is the minimum water sample that can be measured to detect trace metals? The difficulty is in small concentrations in small volumes. In this experiment held in the Thermo-optic laboratory, from the Nondestructive Characterization of Materials division, researchers worked with the thermal lens an analytical method to characterize and quantify small traces of lead in water samples. “When a laser is focused on a medium, locally produces a change in the refractive index, which acts as a virtual lens”, said Dr. Saavedra.

The aim was to implement the technique here in CEFOP. “With Richard’s work, now a CEFOP former student, we started from scratch, and thanks to the support of the Center we were able to buy implementation and set up the experiment. We did different experiments to validate this technique, because is an alternative way to the chemical techniques. Then, we worked with a real situation by quantifying the presence of metal”, said Dr. Renato.

To carry out the study, Dr. Cesar Soto, professor at Department of Inorganic and Analytical Chemistry, Faculty of Cs. Chemical, prepared samples of drinking water and Los Patos lagoon’s water. Dr. Saavedra said: “We wanted to know whether the samples contained lead, according to reference standards. All was developed in a year and a half, and this is the first work published in this area”.

The cost of the difficulty

Since 10 or 15 years the thermal lens is a well known technique. It offers the ability to reduce at least two orders of magnitude compared to the techniques commonly used in Chemistry. “I mean, we can measure very small concentrations,” said Professor Saavedra. Also has a low cost, but starting from scratch is very complex because it requires a laser, a lens and is necessary learn how it works. “This doesn’t come with a manual, so you must learn by doing. It is a highly sensitive technique”, he said.

Quantification of lead in water by thermal lens effect is highly sensitive, reliable and with detection limit of 30.4 ng L-1. Thus, the study shows that the thermal lens spectroscopy is effective for determining trace levels of lead in water samples, so can be very useful in environmental studies.

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