Ultra-trace determination of bromine and iodine in rice by ICP-MS after microwave-induced combustion

New Analytical Strategy for Bioaccessibility Evaluation of Bromine and Iodine from Edible Seaweeds

A strategy for determining the bioaccessibility of bromine and iodine from edible seaweeds was proposed for the first time using microwave-induced combustion (MIC) and ion chromatography coupled to mass spectrometry (IC-MS) after in vitro digestion. The concentrations of bromine and iodine in edible seaweeds using the proposed methods (MIC and IC-MS) were not statistically different from those using MIC and inductively coupled plasma mass spectrometry (p > 0.05). Trueness was assessed by recovery experiments (101-110%, relative standard deviation <10%). Following an in vitro digestion protocol, MIC was proposed as sample preparation for bioaccessible and residual fractions. Using this strategy, the mass balance totaled from 97 to 111%. No statistical difference (p > 0.05) was observed between the total concentration of bromine or iodine and their concentration in bioaccessible and residual fractions for three edible seaweed species, indicating full analyte quantification in the fractions.

Determination of Halogens by Ion Chromatography in Edible Mushrooms after Microwave-Induced Combustion for Sample Preparation

In this study, the microwave-induced combustion (MIC) method was evaluated for the sample preparation of the most consumed mushroom species in Brazil (Champignon, Shiitake, and Shimeji) and further halogen determination by ion chromatography (IC). For this, sample mass, combustion aid mass, and absorbing solution (H₂O and 50 mmol·L^-1, 100 mmol·L^-1, or 150 mmol·L^-1 NH₄OH) were evaluated. Bromine and iodine concentrations, determined by IC, were lower than the limits of detection (LODs, Br: 6 mg·kg^-1 and I: 24 mg·kg^-1). Inductively coupled plasma mass spectrometry (ICP-MS) was also used for Br and I determination, and the LODs were lower (Br: 0.066 mg·kg^-1 and I: 0.014 mg·kg^-1) than those obtained by IC. Concentrations of Cl, obtained by IC, ranged from 523 mg·kg^-1 to 13053 mg·kg^-1 with LOD of 40 mg·kg^-1. In turn, Br and I concentrations, obtained by ICP-MS, ranged from 2.49 mg·kg^-1 to 5.50 mg·kg^-1 and from <0.014 mg·kg^-1 to 0.047 mg·kg^-1, respectively. Fluorine concentrations, determined by IC, were always lower than LOD (23 mg·kg^-1). The trueness of the proposed methods was evaluated by recovery tests using standard solutions and a reference material (RM NIST 8435). When using the standard solution, recoveries ranged from 95% to 103% for halogen determination by IC and from 105% to 109% for Br and I determination by ICP-MS. When using the RM, recoveries of 102% for Cl by IC and of 87% and 86% for Br and I by ICP-MS, respectively, were obtained.

Challenges and trends for halogen determination by inductively coupled plasma mass spectrometry: A review

RATIONALE

In this review, works published in the past 25 years for fluorine, chlorine, bromine, and iodine determination in several matrices by inductively coupled plasma mass spectrometry (ICP-MS) were covered. Usually, the determination of halogens has been performed by ICP-MS using a previous sample preparation step or, more recently, by direct analysis of solid or liquid samples.

METHODS

Methods based on combustion, extraction, pyrohydrolysis, sample dilution in organic or aqueous medium, and wet digestion, among others, are discussed. Moreover, the recent applications of methods based on laser ablation (LA) and electrothermal vaporization (ETV) coupled to ICP-MS are discussed.

RESULTS

The main challenge for methods using sample preparation has been to obtain a final solution compatible with ICP-MS, as well as to overcome problems related to analyte losses and contamination. Interferences due to the presence of dissolved organic compounds in solution, enhancement or suppression of ionization of analytes, and related matrix effects have been of concern when using ICP-MS. For the determination of halogens by ICP-MS using LA and ETV systems, some limitations related to the difficulty of calibration are pointed out, impairing the widespread use of this approach.

CONCLUSIONS

A critical view is presented for further halogen determination by ICP-MS, mainly for matrices considered difficult to digest using conventional protocols.

Ion chromatography coupled to mass spectrometry as a powerful technique for halogens and sulfur determination in egg powder and its fractions

RATIONALE

To increase the consumption of egg powder and its fractions a suitable quality control method is required to obtain more information on its nutritional composition. The proposed method enables the quantification of important elements for the functioning of the human organism, such as halogens and sulfur, in egg powder and its fractions.

METHODS

Up to 350 mg of egg powder or its fractions (egg white powder and egg yolk powder) were digested by microwave-induced combustion using 20 bar pressure of oxygen. The analytes were absorbed in 100 mmol L^-1 of NH₄ OH solution. The determination of halogens (chlorine, bromine, fluorine, and iodine) and sulfur was performed in a single analysis using ion chromatography with conductivity detection coupled to mass spectrometry.

RESULTS

Using the proposed method, spike recoveries between 99% and 104% for all analytes were obtained, and results agreed with certified values of reference materials (agreements were between 100% and 109%). The relative standard deviations were below 8%. The variation in elemental concentration over a wide range in different fractions (whole egg powder, egg white powder, and egg yolk powder) and different brands was also observed.

CONCLUSIONS

The proposed method provides reliable information about minerals in whole egg powder and its fractions, contributing to better quality control of these products. Because these food products are widely consumed, these results suggest the safe ingestion levels of these elements.

Feasibility of microwave-induced combustion combined with inductively coupled plasma mass spectrometry for bromine and iodine determination in human nail

RATIONALE

Bromine and iodine have important physiological functions; however, in inadequate concentration, they can also cause several physiological problems. Their mobility assessment in human organisms through biological sampling may help clarify some doubts related to metabolic routes, which are still not well elucidated. In this context, a suitable analytical method for this purpose should be developed.

METHODS

An analytical method for determining ultratrace levels of bromine and iodine in human nail samples was developed. Inductively coupled plasma mass spectrometry (ICP-MS) using a conventional nebulization system was immediately chosen as the determination tool because of its powerful sensitivity and selectivity. Sample preparation methods including microwave-induced combustion (MIC), microwave-assisted extraction, and microwave-assisted digestion were evaluated. The compatibility of the final solutions with ICP-MS analysis was considered while the method was developed.

RESULTS

MIC was chosen as the most suitable method for the sample preparation for determining the levels of bromine and iodine in human nail samples using ICP-MS. Unlike other sample preparation methods, this one fully eliminated interferences related to the carbon content and memory effects. Sample masses up to 100 mg were efficiently digested, and the analytes were quantitatively absorbed using only 50 mmol L^-1 NH₄ OH solution. Recoveries ranged from 93% to 102%, and the relative standard deviation was < 8%.

CONCLUSIONS

The proposed analytical method presents important characteristics for routine analysis. It allows ultratrace determination even when low sample masses are used because of the low blank values, reduced volume of reagents, and powerful detectability using ICP-MS.

Bromine and iodine determination in human saliva: Challenges in the development of an accurate method

In this work, an analytical method for bromine and iodine determination in human saliva was proposed. A simple protocol based on centrifugation and direct analysis of supernatant by inductively coupled plasma mass spectrometry (ICP-MS) was investigated. Although this method was feasible for bromine determination, iodine was partially present in the supernatant and an agreement about 54% with reference value was obtained. In addition, microwave-induced combustion (MIC) and microwave-assisted dissolution were also evaluated. Using MIC, 0.2 mL of saliva added on 300 mg of microcrystalline cellulose were efficiently digested. A diluted solution (50 mmol L^-1 NH₄OH) was used for analytes absorption, and a reflux step of 5 min was applied to ensure quantitative recoveries of Br and I. Accuracy was evaluated by analyte recovery experiments, and recoveries between 94% and 98% were obtained. Microwave-assisted dissolution was evaluated for 2.0 mL of saliva using also a diluted alkaline solution (25 mmol L^-1 NH₄OH) and a microwave irradiation program of 35 min (including the cooling step). Results for this method agreed with those obtained using MIC. Although MIC has also been appropriated for further determination of Br and I in saliva, microwave-assisted dissolution can be considered a simpler sample preparation method and it was effective for high amount of sample (up to 2.0 mL). Moreover, final solutions were compatible with ICP-MS analysis, allowing the quantification of Br and I in human saliva at ultra-trace concentrations (limits of quantification were 0.052 μg mL^-1 for Br and 0.022 μg mL^-1 for I).