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High concentrations of 5-hydroxymethylfurfural (HMF) in honey provide an indication of overheating under inappropriate storage conditions or aging. Conventional methods for determining HMF are cumbersome and require expensive equipment or hazardous reagents. Hence the aim of this study was to propose a new analytical tool for HMF determination in honey, using a low cost acoustic wave sensor. Volatile organic compounds (VOCs) of honey samples were extracted, using the solid phase microextraction (SPME) technique, and HMF was quantified, using a piezoelectric quartz crystal with gold electrodes coated with a layer of decamolybdodivanado phosphoric acid, sensitive to HMF. The reliability of the proposed method was confirmed after comparing the results of HMF quantification with those obtained by the conventional spectrophotometric White method, and no statistical differences were found (α=0.05)., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Background: Iron migration from tinplate cans to pineapple drink was studied over time using flame atomic absorption spectroscopy, taking into consideration storage temperature, sell-by date and can condition (dented/undamaged). An organoleptic test, at the sell-by date, was also performed., Result: Analysis of iron in drinks from tinplate cans, glass and polyethylene terephthalate (PET) bottles was performed up until the sell-by date. For undamaged canned drinks stored at room temperature, iron was found to remain constant at 0.23 ± 0.01 mg L(-1) , from the 24th day until 1 year after production. Iron found in glass and PET bottles also remained constant until the sell-by date, at 0.15 ± 0.04 and 0.12 ± 0.04 mg L(-1) , respectively. However, migration of iron from dented cans was found to be significant. Twelve months after production, iron content in dented cans, stored at room temperature (22 °C) and in a refrigerator chamber (4 °C) was 14.4 ± 1.0 and 5.5 ± 0.4 mg L(-1) , respectively., Conclusion: Results showed that for a 35 kg child the intake of three damaged canned drinks may contribute to more than 50% of the iron provisional maximum tolerance daily intake. © 2015 Society of Chemical Industry., (© 2015 Society of Chemical Industry.)

Aluminium (Al) migration from cans to beer and tea was studied along time. Analyses of Al in the canned drinks were performed till the sell-by date, and, in seven months, aluminium migration was found to increase 0.14 mg L(-1) in beer, and 0.6 mg L(-1) in tea. This study included dented cans from which aluminium migration into tea was found to be particularly severe. Al concentration in dented canned tea increased 9.6 mg L(-1) in seven months.

A new methodology based on an inexpensive aluminium acoustic wave sensor is presented. Although the aluminium sensor has already been reported, and the composition of the selective membrane is known, the low detection limits required for the analysis of drinking water, demanded the inclusion of a preconcentration stage, as well as an optimization of the sensor. The necessary coating amount was established, as well as the best preconcentration protocol, in terms of oxidation of organic matter and aluminium elution from the Chelex-100. The methodology developed with the acoustic wave sensor allowed aluminium quantitation above 0.07 mg L(-1). Several water samples from Portugal were analysed using the acoustic wave sensor, as well as by UV-vis spectrophotometry. Results obtained with both methodologies were not statistically different (alpha=0.05), both in terms of accuracy and precision. This new methodology proved to be adequate for aluminium quantitation in drinking water and showed to be faster and less reagent consuming than the UV spectrophotometric methodology.

An acoustic wave methodology was developed to quantify alcohols in aqueous solutions. The frequency at minimum impedance of a bare quartz crystal in contact with ethanol solutions was found to be a suitable parameter to quantify ethanol. Ethanol in several Portuguese white wines was analyzed both by the proposed methodology and by the usual areometric method with no statistically significant differences (alpha = 0.05) in precision or accuracy of the results.

A quartz crystal microbalance has been used to check the purity of glycerol. The experimental procedure involves no derivatization or other preliminary step except determination of water content. The protocol consists of the direct reading of the frequency of a quartz crystal with one face in contact with an aqueous solution of the glycerol to be tested. The method is inexpensive, simple, rapid, and highly sensitive; diethylene glycol contamination at the 3.61% level could be detected.