Sample Preparation Using TMAH and Nitric Acid for Multielement Determination in Crustacean Samples by MIP OES

Michelle Lemos,Allan Cruz,Kelly Dantas

doi:10.21577/0103-5053.20200200

Abstract

This study proposes a simple sample preparation procedure using tetramethylammonium hydroxide (TMAH) and nitric acid (HNO3) to determine Cr, Cu, Fe, K, Mg, Mn, and Zn concentrations in shrimp (Macrobrachium amazonicum) and crab (Ucides cordatus) samples from the Amazon region by microwave-induced plasma optical emission spectrometry (MIP OES). The sample solubilization was carried out employing TMAH and HNO3 using an ultrasound bath and a thermostatic water bath. The accuracy of the proposed procedure was performed using microwave-assisted digestion as comparative method. Certified fish protein reference material (DORM-4) and also addition recovery experiments were used to assess the accuracy of the proposed procedure and recoveries obtained were adequate, ranging from 91 to 106%. In this study, the use of TMAH and HNO3 simplified sample preparation, maintaining the identity of analytes and ensuring efficiency in determinations.

Highlights

Crustaceans are highly appreciated animals worldwide due to their distinctive taste and nutritional characteristics, with high levels of protein, vitamins and minerals.[1,2] balanced consumption of crustaceans is considered beneficial to human health, aiding in disease prevention and cholesterol control,[3,4] high consumption of these animals may represent a health risk, since they have the capacity to accumulate contaminants and transfer them to the food chain.[5]Some elements are considered essential, such as copper, iron and zinc, as they contribute to the maintenance of essential biological properties for living beings
The purpose of this study was to apply a simple procedure for the preparation of shrimp (Macrobrachium amazonicum) and crab (Ucides cordatus) samples using tetramethylammonium hydroxide (TMAH) and HNO3 to determine inorganic element concentrations by microwave induced plasma optical emission spectrometry (MIP OES) aiming at reducing the volume of reagents and generating less residue when compared to acid digestion procedures
The proposed procedure using TMAH and HNO3 in the preparation of crustacean samples provided quicker and less manipulated samples, reducing the consumption of reagents when compared to most acid digestion procedures, generating smaller amounts of residue and ensuring accurate results

Summary

Introduction

Crustaceans are highly appreciated animals worldwide due to their distinctive taste and nutritional characteristics, with high levels of protein, vitamins and minerals.[1,2] balanced consumption of crustaceans is considered beneficial to human health, aiding in disease prevention and cholesterol control,[3,4] high consumption of these animals may represent a health risk, since they have the capacity to accumulate contaminants and transfer them to the food chain.[5]Some elements are considered essential, such as copper, iron and zinc, as they contribute to the maintenance of essential biological properties for living beings. When in excess, they can cause adverse effects, ranging from intestinal disorders to death.[6,7] studying the levels of inorganic constituents in crustaceans is important to evaluate the food safety of the consuming population. It is known that sample preparation is a very critical step of chemical analysis and in recent years have been the subject of studies aiming, among other aspects, to reduce costs and time of analysis and the amount of waste generated. Given that most sample preparation procedures use acid digestion, studies involving alkaline solubilization

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