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Development of analytical methodologies to quantify metals in mineral waters using a quartz crystal microbalance
Coordinator - Maria Teresa Seabra dos Reis Gomes
Programme - POCTI/QUI/48832/2002
Execution dates - 2012-02-19 - 2012-02-20 (0 Months)
Funding Entity - FCT
Funding for CESAM - 36 €
Total Funding - 36 €
Proponent Institution - Universidade de Aveiro


Mineral waters contain metal ions important to the proper functioning of the body. The concentration of sodium, potassium, calcium and magnesium are ordinarily displayed in the label. Sodium and potassium play an important role in the nerve function and muscle contractions and blood pressure regulation. Sodium is an essential element that is present in excess in the western countries diets. Therefore, sodium amount must be controlled in every dietary source, with a particular attention to the diet of hypertense patients. For newborn babies sodium content in water should be less than 20 mg L-1. Potassium is essential to maintain proper pH balance and whenever the levels in the body drop, due to high fever, prolonged vomiting, diarrhea, use of diuretic drugs or physical intense exercise of the athletes, supplements must be administered. Calcium plays an important role in building strong bones and teeth and magnesium contributes to muscle relaxation and also works with enzymes in braking down sugars.
Minerals also affect organolectic water characteristics and for instance potassium makes it sweeter and calcium and magnesium give it fullness and turns it harder.
The quartz crystal microbalance is an affordable method that can be used to analyse metals [1]. The research group has experience in developing those kind of sensors, and has already reported a sensor for potassium and another one for calcium [2,3]. Selectivity of the sensors arises only from coating but no careful choice can produce a sensor capable of responding just to a single metal. Therefore, it is the purpose of this project to develop an electronic tongue, composed of an array of sensors, who is less demanding with respect to selectivity of each sensor, at the expenses of a more complex mathematical treatment. The integration of several sensors on a single substrate would be an interesting and elegant solution although it demands the preparation of ferroelectric ceramic films [4,5].
Aluminium is part of EPA secondary drinking water regulations and although its analysis is recommended it does not require systems to comply. Its importance is such that it was the cause of dead of dialysed patients in Portugal and it is a fact that all Alzheimer patients who have been autopsied had high levels of aluminium in their brains This project is not concerned with the analysis of heavy metals, very important for the health of consumers, as it is supposed that location and facilities of mineral plants have already assured water is not contaminated. However, water later uses can introduce problems, and a sensor for aluminium will also be developed thinking on contamination of soft drinks, that can be extremely acidic and take out aluminium through the liner of the can, specially if they sit on the shelf for too long. As admissible limits for aluminium are low, pre-concentration methods need to be implemented and studied.




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