Ultraviolet radiation combined with microwave-assisted wet digestion of Antarctic seaweeds for further determination of toxic elements by ICP-MS

Abstract

In this work, the use of ultraviolet radiation combined with microwave-assisted wet digestion (MW-UV) was applied for digestion of seaweed samples and further determination of As, Cd and Pb by inductively coupled plasma mass spectrometry (ICP-MS). In the proposed method, UV radiation was generated in situ by electrodeless Cd discharge lamps inserted into digestion quartz vessels. This approach increased the digestion efficiency allowing lower consumption of acids. The feasibility of using diluted acid solution (0.5 to 7 mol L À1 HNO 3 ) was evaluated for relatively higher sample masses (up to 800 mg). The efficiency of digestion was evaluated taking into account the residual carbon content and residual acidity in digests. Under the selected conditions, it was possible to digest up to 700 mg of sample using a nitric acid solution as diluted as 2 mol L À1 HNO 3 allowing an efficiency of digestion higher than 77% (considering the total C content in the sample) and acidity as low as 0.19 mol L À1 that is convenient for ICP-MS measurements. The accuracy of the proposed MW-UV method was evaluated by the digestion of two certified reference materials of aquatic plant (BCR 060 and BCR 670) and by comparison with the results obtained after digestion by microwave-assisted wet digestion in a high pressure system using concentrated HNO 3 (MW-AD). The results obtained by the proposed method did not present difference (t-test, 95% confidence level) with the certified values and with results obtained after seaweed sample digestion using the MW-AD method. Using 700 mg of sample, the limit of detection was 0.005, 0.001, and 0.012 mg g À1 for As, Cd, and Pb, respectively. A clear advantage of the proposed method over classical approaches is that only diluted solution was necessary and it is possible to digest a relatively high sample mass, that is important to minimize the generation of laboratory residues and to improve the limits of detection, respectively.

Development of microwave assisted-UV digestion using diluted reagents for the determination of total nitrogen in cereals by ion chromatography

“…However, one drawback of UV-photolysis is the long irradiation time of 1–24 ​h ( De Borba et al., 2014 ). But UV-photolysis in combination with MW reduces the digestion time to half an hour for many matrices ( Pereira, Wiltsche, Knapp, Flores ; Hartwig et al., 2017 ; Hartwig et al., 2016 ; Cerveira et al., 2020 ; Dash et al., 2012 , 2016 ; Iop et al., 2017 ; Mesko et al., 2015 ). This formed the basis of using microwave assisted UV digestion of cereal flours in our experiments.…”

An integrated approach based on oxidative pyrolysis and microwave-assisted digestion for the multi-elemental analysis of coal samples by ICP-based techniques

“…Due to the growing interests toward the implementation of ''Green Chemistry'' principles, recent studies indicated that the use of dilute mineral acids along with auxiliary reagents such as H 2 O 2 for the quantitative extraction of a wide range of elements in various solid matrices can be achieved [47][48][49]. The two major components with a high influence on the MWD procedure are the concentration of nitric acid and auxiliary reagent H 2 O 2 [47,48].…”

Microwave-assisted ultraviolet digestion of petroleum coke for the simultaneous determination of nickel, vanadium and sulfur by ICP-OES

“…The use of diluted solutions is an important feature because high acid concentration of digests can cause interferences in ICP-based analytical techniques [18]. In this way, microwave-assisted ultraviolet digestion (MW-UV) has been applied to reduce the organic carbon from natural water [19] and for digestion of skimmed milk [20], Antarctic seaweeds [21] and crude oil samples [17] using diluted acids. This method is based on the use of an electrodeless discharge lamp, which is activated by microwave radiation in a closed system that enables an efficient digestion at high temperature and pressure [17,[19][20][21].…”

“…In this way, microwave-assisted ultraviolet digestion (MW-UV) has been applied to reduce the organic carbon from natural water [19] and for digestion of skimmed milk [20], Antarctic seaweeds [21] and crude oil samples [17] using diluted acids. This method is based on the use of an electrodeless discharge lamp, which is activated by microwave radiation in a closed system that enables an efficient digestion at high temperature and pressure [17,[19][20][21]. Despite the advantages of the combination of microwaves with ultraviolet radiation (e.g., use of diluted reagents, high efficiency of organic matter digestion, compatibility of digests with atomic spectrometric techniques, etc.)…”