Successive digestions for pre-concentration and ultra-trace determination of Br and I by plasma-based atomic spectrometry and ion chromatography

Pyrohydrolysis as a sample preparation method for the subsequent halogen determination: A review

The use of pyrohydrolysis as a sample preparation method for further halogen determination is extensively discussed in this review, covering studies published in the last 30 years. This method is compatible with both organic (such as cellulose, fossil fuels, carbon nanotubes, and graphite) and inorganic (such as rocks, silicates, alumina, and nuclear fuels) matrices. It has also been used for samples with different organic matter content, such as coal, mineral supplements, and soil. Sample masses vary greatly and are dependent on organic matter content in the samples, ranging from 50 mg to up to 500 mg for organic samples, and up to 4 g to inorganic samples. Different additives, such as V2O5 and cellulose, or flame retardants, such as silica, could also be used to improve analyte recovery using pyrohydrolysis. Dilute alkaline solutions or even water have been used as absorbing solutions, with mainly NaOH, NH4OH, and mixtures of NaHCO3 and Na2CO3 being applied. Furthermore, pyrohydrolysis is compatible with detection techniques such as ion chromatography, inductively coupled plasma mass spectrometry, ion selective electrode, inductively coupled plasma optical emission spectrometry, energy-dispersive X-ray fluorescence spectrometry, spectrophotometry, and isotope ratio mass spectrometry. Other advantages usually related to this method are the low residual carbon concentration of digests and the low residue generation. A critical comparison with alkaline extraction, alkaline fusion, Schöniger oxygen flask combustion, combustion bomb and microwave-induced combustion is also provided.

Construction and application of a novel electrochemical sensor for trace determination of uranium based on ion-imprinted polymers modified glassy carbon electrode

In the present work, a novel electrochemical sensor modified glassy carbon electrode with ion-imprinted polymers (IIP-GCE) was applied for uranyl ions (UO₂²⁺) determination. Surface modifier was synthesized through precipitation polymerization method, using acrylic acid as a monomer, benzoyl peroxide (BPO) as initiator, and trimethylolpropane triacrylate (TMPTA) as cross-linker. A new uranyl-trans-3-(3-pyridyl) acrylic acid complex was employed, serving as an active and specific site on the synthesized modifier. Next, the synthesized modifier was characterized using X-ray diffraction (XRD), Scanning Electron microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. UO₂²⁺ ions were detected using a differential pulse adsorptive anodic stripping voltammetry method. Under the optimized conditions (pH = 8.0, pre-concentration time = 10 min and pre-concentration potential = -0.30 V), the modified electrode exhibited linear behavior in the interval of 1.27-95.49 μg.L^-1 with a limit of detection (LOD) of 0.43 μg.L^-1. Also, the constructed ion-imprinted sensor showed a successful application for determining UO₂²⁺ ions with recovery range of 97.6-101% in real samples.

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.