Abstract
This work describes the application of potentiometric stripping analysis (PSA) at mercury film electrodes for zinc determination in coconut water. A sample ultrasound-assisted treatment was developed and optimised for the total zinc determination by PSA. One milliliter of sample was treated with 2 mL of 1:1 (v/v) concentrated HCl and H2O2 (30% m/v) mixture in closed (4 mL) vessels under sonication (in ultrasonic bath), followed by a thermal step (in a boiling bath, for 15 min). This methodology was optimised for total zinc determination and was validated by graphite furnace atomic absorption spectrometry (GFAAS) analysis utilizing the sample without any treatment. The limit of detection obtained by the proposed PSA method was 1.35 µg L-1 (applying 45 s of preconcentration). Attempts to evaluate the amount of copper in the same sample show that the content of this metal is lower than the detection limits of both techniques, GFAAS and PSA (0.030 µg L-1 after 600 s of preconcentration) at gold film electrodes.
Highlights
Coconut water is a common refreshing drink and has been used as an excellent isotonic in Brazil and other tropical countries.[1]
Copper release from the sample matrix cannot be evaluated as was done for zinc due to the very low concentration of the metal in the different analyzed samples, which was lower than the limit of detection (LOD) obtained by graphite furnace atomic absorption spectrometry (GFAAS) (0.49 μg L-1) and even lower than the obtained by the Potentiometric stripping analysis (PSA) method at gold electrode (0.030 μg L-1)
PSA was successfully applied for the total zinc determination in coconut water after sample ultrasoundassisted treatment in 1:1 (v/v) concentrated HCl and H2O2 (30% m/v) mixture, followed by heating treatment
Summary
Coconut water is a common refreshing drink and has been used as an excellent isotonic in Brazil and other tropical countries.[1]. We evaluated the use of PSA for zinc determination in the matrix of coconut water samples.
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