Fluorine, chlorine, bromine, and iodine have been studied in biological samples and other related matrices owing to the need to understand the biochemical effects in living organisms. In this review, the works published in last 20 years are covered, and the main topics related to sample preparation methods and analytical techniques commonly used for fluorine, chlorine, bromine, and iodine determination in biological samples, food, drugs, and plants used as food or with medical applications are discussed. The commonest sample preparation methods, as extraction and decomposition using combustion and pyrohydrolysis, are reviewed, as well as spectrometric and electroanalytical techniques, spectrophotometry, total reflection X-ray fluorescence, neutron activation analysis, and separation systems using chromatography and electrophoresis. On this aspect, the main analytical challenges and drawbacks are highlighted. A discussion related to the availability of certified reference materials for evaluation of accuracy is also included, as well as a discussion of the official methods used as references for the determination of halogens in the samples covered in this review.

Analytical methods for the determination of halogens in bioanalytical sciences: a review

A review of recent literature focused on iodine determination/speciation in environmental, biological and clinical materials is provided. The review covers the different sample pre-treatments to extract total iodine, as well as specific iodinated forms, and the most used analytical techniques for assessing total iodine (cathodic stripping voltammetry, differential pulse voltammetry, neutron activation analysis, catalytic spectrophotometry, and atomic spectrometric techniques, mainly inductively coupled plasma-mass spectrometry) and iodine speciation (nonchromatographic methods, and mainly high performance liquid chromatography, gas chromatography and capillary electrophoresis coupled to electrochemical, UV spectrophotometric and mass spectrometric detection).

A review on iodine speciation for environmental, biological and nutrition fields

A procedure coupling acid decomposition and precipitation, using inductively coupled plasma optical emission spectrometry (ICP- OES) is proposed for the determination of Cl, Br and I in milk samples. During the mineralization process in closed and open vessels (microwave ovens), anions are precipitated as salts of low solubility products (AgCl, AgBr and AgI). After separation from digestate solution, precipitates are dissolved with ammonia resulting in a 20% v/v solution. The final solution was directly introduced into the ICP-OES without any damage to the sample introduction system and with no severe spectral interference. Three biological reference materials were used to validate the methodology: Non-Fat Milk Powder SRM 1549 from NIST, Skim Milk Powder RM-151 from BCR and Whole Egg Powder RM 8415, also from NIST. The limits of detection (3σb/s) for Cl, Br and I in the solid sample were 30, 40 and 280 µg g−1 for the closed vessel microwave oven, and 15, 20 and 40 µg g−1 for the open vessel microwave oven, respectively. Relative standard deviations, considering five replicates of sample submitted to the proposed methodology, were 1% for Cl and Br, and 2% for I, when a closed vessel microwave was used. The results for Cl were in good agreement with the certified values (90% confidence level). For Br, recoveries ranged from 87 to 104% for closed vessel microwave oven and from 90 to 102% for open vessel microwave oven. As for I, recoveries ranged from 85 to 98% with a closed vessel microwave oven. Accurate results for determinations in certified materials and good recoveries demonstrated the efficiency of the procedure.

Determination of chlorine, bromine and iodine in milk samples by ICP-OES

Water-soluble ionic liquids (IL) were used as reaction media to perform homogeneous polymerizations under microwave irradiation. The investigated reaction systems include the free radical polymerization of methyl methacrylate and the cationic ring opening polymerizations of 2-phenyl-2-oxazoline and 2-(m-difluorophenyl)- 2-oxazoline. The incorporation of ILs into the polymerizations showed a more efficient heating profile of the reaction mixtures under microwave irradiation in comparison to the cases without ILs. Moreover, a convenient approach for the polymer isolation and recovery of the ILs for further polymerizations is demonstrated taking advantage of the water solubility of the investigated ILs. This synthetic approach is an alternative, efficient, and green method for the manufacture of hydrophobic polymers which may allow depletion of the emission of volatile organic compounds into the environment and for energy

Microwave‐Assisted Homogeneous Polymerizations in Water‐Soluble Ionic Liquids: An Alternative and Green Approach for Polymer Synthesis

Hollow fiber based liquid-phase microextraction for the determination of mercury traces in water samples by electrothermal atomic absorption spectrometry

To complete these microwave distillation studies, a method for
iodide determination in milk-type samples is proposed. The iodide contained
in the sample is oxidized to iodine, which is distilled by means of microwave
energy and reduced back to iodide. This iodide is combined with Hg(II)
and 2,2′-dipyridyl to give an ion pair, which is selectively extracted
into IBMK. Mercury is determined in the extract by ETAAS in order to determine
iodide. The yield of the distillation process (100%) was
evaluated using the Sandell–Kolthoff reaction. In addition, for the
solvent extraction, no buffer was needed; 3/5 was the best phase ratio (organic/aqueous);
30 s was the shaking time and the extracts were stable for 24 h,
at least. The yield of the extraction procedure (studied also using the
Sandell–Kolthoff reaction) was 87.5 and 87.1%, for standards
and samples, respectively. Regarding the ETAAS measurements, the ashing temperature
selected for both samples and standards was 150 °C; 800 and 1000 °C
were the atomization temperatures chosen for samples and standards, respectively.
Palladium in IBMK was the chemical modifier at a concentration of 3.0 µg ml−1,
both for samples and standards. The sensitivity was 3.50 × 10−3 l µg−1
(standard additions); the LOD and LOQ were 0.2 and 0.6 µg ml−1,
referred to sample; the mean characteristic mass within the linear range of
concentrations (0–17.5 µg l−1)
was 27.3 pg; the mean analytical recovery within that range was 97.5%
for a liquid whole milk sample and 100.6% for a CRM, which also gave
results within certification. The method was applied to liquid whole milk,
milk powder and infant formulae samples.

Ma. Luisa Cervera

Papers

Microwave-assisted distillation of iodine for the indirect atomic absorption spectrometric determination of iodide in milk samples