Evaluation of the Use of Diluted Formic Acid in Sample Preparation for Elemental Determination in Crustacean Samples by MIP OES.

A simple procedure for determination of Al, Cr, K, Mg, Mn, and Zn using diluted organic acid in the preparation of shrimp (Macrobrachium amazonicum) and crab samples (Ucides cordatus) was proposed in this study. Determinations were performed using microwave-induced plasma optical emission spectrometer (MIP OES). The contents of elements were evaluated after solubilization of samples in 50% formic acid (v v-1) and subsequent heating in bath with stirring and heating at 90 °C. The accuracy of the proposed procedure was assessed using certified fish protein reference material (DORM-4) and the recovery percentages ranged from 91 to 117%. Microwave-assisted acid decomposition was used for a comparison of results with the procedure proposed using diluted formic acid, and the values obtained for all analytes were statistically equal at 95% confidence level. Cr levels were below the limit of detection. Potassium (7917-19,644 mg kg-1), Mg (1319-5376 mg kg-1), and Zn (43-307 mg kg-1) were the most abundant elements in the crustacean species studied can be considered good sources of these constituents for human diet. The proposed procedure using diluted formic acid was considered simple and suitable to determine Al, Cr, K, Mg, Mn, and Zn concentrations in crustaceans using MIP OES.

Microwave-Assisted Digestion Procedures Using Diluted Oxidant Mixture for Elemental Analysis of Crustaceans by MIP OES.

The aim of this study was to evaluate three digestion procedures using a diluted oxidant mixture of nitric acid, hydrogen peroxide, and water for determination of Cu, Fe, K, Mg, Mn, and Zn in shrimp and crab samples from Northern Brazil by microwave-induced plasma optical emission spectrometry. The efficiency of the digestion procedure was evaluated by comparing the residual carbon content, residual acidity, and elemental concentrations obtained in the samples. Digestion procedure 2 (4 mL HNO3 + 4 mL H2O2 + 4 mL H2O) was chosen due the adequate residual carbon content (5.85%) and low residual acidity (2.94 mol L-1). The recoveries obtained using the certified reference material (DORM-4) varied from 90 to 105%. High contents of K and Mg were found in the studied crustaceans. Also, it can give an excellent contribution to the recommended daily intake of Cu and Zn, indicating that these foods can be considered a good source of these minerals for the human diet.