Ultrasound-assisted extraction of heavy metals from estuarine sediment samples.

CLAUDIA E. DOMINI ; LORENA VIDAL; MONTSERRAT HIDALGO; ANTONIO CANALS HERNÁNDEZ

Salamanca

Congreso; Euroanalysis XIII (European Conference on Analytical Chemistry); 2004

During the past years new methods for sample pre-treatment were developed in order to eliminate, or at least to alleviate, these drawbacks. The use of microwave radiation as a heating source has become common in almost any laboratory [1]. Despite its growing popularity, the mechanism of microwave radiation interaction with mater is somewhat difficult to understand and quite often microwave methods are hardly reproducible in other laboratories. In addition, the analytical microwave digestion systems are still expensive. Ultrasound radiation has recently been used for sample digestion [2]. The lower prices of the ultrasound instrumentation with the addition of the ability to work at relatively low temperatures are some of the reasons for the growing interest in this research area. Another advantage of this sample digestion method is its ability to extract the element of interest without completely destroying the matrix, the effect in the following analyses. However, the most common instruments used are the ultrasonic bath or probe systems with metal sonotrodes [3]. While the former is less efficient in the energy transmission the later could contaminate the samples during the treatment. Hence, sonotrodes that could be directly introduced into the sample without contamination problems are needed for analytical purposes. Hence, the goal of this work was to study the applicability of an ultrasonic processor for industrial applications of a 500 W effective power output and operating frequency of 20kHz equipped with a BS 22 glass sonotrode for extraction of heavy metals from sewage sludge samples. Microwave-assisted digestion was also used for comparative purposes. Both sample pre-treatment methods were optimized by means of multivariative approach (i.e. experimental design). In this way many variables can be studied with relatively small number of experiments [4]. The experiments bring the following conclusions: 1. The ultrasound-assisted extraction with probe system, equipped with glass sonotrode, is applicable for the determination of heavy metals in estuarine sediment samples (recoveries in the range 75-97 %) 2. The use of experimental design technique reduces the number of required experiments and gives more information that the one-at-a-time approach