Tag Archives: chemical analysis

Quantifying Human Enamel Erosion Caused By Freshly Squeezed Juices

Aims: The present in vitro study intended to investigate minimal erosive effects of different freshly squeezed fruit juices on human enamel during short time incubation by determination of calcium and phosphate dissolution.
Material and methods: Healthy adult human molars and premolars were cut in 160 blocks (5 mm x 6 mm x 2 mm) and divided randomly in sixteen groups of 10 samples each (n = 10). Each group was assigned for immersion at 37 oC in 5 ml juice, for different spot times 3, 6, 9 and 12 minutes, respectively. The freshly squeezed juices analyzed were orange juice, apple juice, orange mixed with carrot juice (1:1) and apple mixed with carrot juice (1:1). Amount of titratable acid and pH was measured for the tested solutions. Calcium and phosphate release were determined photometrically using VIS-UV/VIS spectrophotometer. ANOVA test compared the data generated (p < 0.05).
Results: The apple juice showing the lowest pH and a high value for buffering capacity had the most pronounced erosive effect. The orange juice was less erosive (p < 0.001). The least erosive was the orange mixed with carrots (1:1) (p < 0.001), which has the highest pH. The enamel demineralization increased when prolonging the immersion time (p < 0.0001).
Conclusions: All freshly squeezed juices caused the dissolution of calcium and phosphate in human enamel. Erosive capacity is mainly determined by pH and to a lesser extent by the buffering capacity. The amount of demineralization is directly correlated with the exposure time. Absorption spectroscopy allows detection of very small mineral loss using standardised human enamel samples.

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Indirect Determination of Gentamicin by Derivative Spectrophotometry

Introduction: Gentamicin sulfate is an aminoglycosidic antibiotic, used in severe infections caused by Gram-negative bacteria. UV-Vis spectrophotometry, a simple, high speed and accessible analytical method, is generally suitable for the quantitative determination of pharmaceutical active ingredients in raw materials. In the case of gentamicin, a drug that presents low absorbances on the UV-Vis domain, direct determination by UV-Vis spectrophotometry would not assure adequate detection and quantitation limits.
The aim of this study was to develop a new indirect spectrophotometric method, based on the capacity of gentamicin to form in the presence of Cu2+ ions complex combinations with increased UV-Vis light absorbing capacity.
Material and method: Optimised experimental conditions which assure formation of a stable complex was found to take place in the pre-sence of CuCl2.6H2O 0.1 mg/mL, while 1 mM NaOH was used as solvent. All readings were performed at 291 nm on the first derivative of the absorbance spectrum.
Results: The developed method was validated, and proved to be linear on the 0.051–0.261 mg/mL concentration range (r = 0.99935).
Conclusions: The developed method is fast, accessible and can be used for the determination of gentamicin in raw materials.

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