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.

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).

Feasibility of Rare Earth Element Determination in Low Concentration in Crude Oil: Direct Sampling Electrothermal Vaporization-Inductively Coupled Plasma Mass Spectrometry.

A comprehensive study was developed showing the feasibility of determination of rare earth elements (REE) in low concentration in crude oil by using direct sampling electrothermal vaporization system coupled to inductively coupled plasma mass spectrometry (ETV-ICP-MS). The effect of organic modifier on the REE signal was evaluated and the use of 6 mg of citric acid allowed calibration using aqueous reference solutions (selected pyrolysis and vaporization temperatures were 700 and 2200 °C, respectively). Because of the facility of REE in forming refractory compounds inside the graphite furnace during the heating step, the use of a modifier gas (Freon R-12, 3.0 mL min-1) was necessary to allow quantitative vaporization of these elements. A flow rate of 0.40 L min-1 was selected for both bypass and carrier gases. Under optimized conditions, the influence of sample mass was evaluated, and even using a relatively high mass of crude oil (up to 18 mg), accurate results were obtained. The accuracy was evaluated by the comparison of results by ETV-ICP-MS with those obtained by ICP-MS with ultrasonic nebulizer (USN) after high-pressure microwave-assisted wet digestion (MAWD) and microwave-induced combustion (MIC) and no statistical difference was observed between the results. The limits of quantification for REE by ETV-ICP-MS were lower (0.02-0.8 ng g-1) than those obtained by USN-ICP-MS after MAWD and MIC (0.6-5.1 ng g-1). Negligible blank values and relative standard deviations lower than 12% show the feasibility of the proposed ETV-ICP-MS method for routine analysis of crude oil.