Determination of calcium in citrus juice using atomic absorption spectroscopy method

Abstract

Introduction: Atomic Absorption Spectroscopy is a modern instrumental method that gives us the possibility to determine the chemical elements, in special, in a polycomponent sample. This technique involves aspirating an aqueous sample into a flame where the analyte is atomized. An isolated atom absorbs light at very specific wavelengths that are unique for each element. The amount of light absorbed by the analyte depends upon the concentration of analyte (Beer’s law). By measuring the amount of light absorbed by the flame, it is possible to determine the concentration of analyte in the sample. Also, a series of standard solutions must be prepared in order to calibrate the response of the instrument. This method it was used for the determination of the calcium in some fresh citrus juices, as it is difficult to determine it using other methods, because of the presence of other elements and organic compounds. Materials and methods: Orange, lemon, mandarin and grapefruit fresh juice, balance, juice extractor, atomic absorption spectrometer Thermo Scientific ICE 3000, centrifugal, vacuum filtration set, pH meter, laboratory glassware, chemical reagents prepared in accordance with requirements of RF X. Results: Calcium absorbs strongly at 239.9 nm and 422.7 nm. This property allows us to determine the concentration of the calcium atom in a such complex mixture like the citrus juice. The method of Atomic Absorption Spectroscopy uses the light of the desired wavelength which passed through the flame containing the atomized analyte. For the determination of samples were diluted and for avoiding the partial ionization in the acetylene flame the lanthanum chloride was added to samples. The calibration curve was established and then the elemental calcium was determined. The analysis was made in series of three replicates for each fruit juice and showed us these results: in orange juice - 30 mg/100 ml, tangerines - 35 mg/100 ml, grapefruit - 84 mg/100 ml and lemon - 34 mg/100 ml. Conclusions: It was determined the total calcium from fresh citrus juices. The obtained results would be used for the benchmarking of ionic calcium with the total one. The applied method was efficient, sensible and precise, relative error having an acceptable value.