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. On this aspect, the main analytical challenges and drawbacks are highlighted. 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. 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 limit of detection (LOD, 3σ/s) for Cl in methods A and B was 18 μg g− 1 and 9 μg g− 1, respectively, 1.7 and 3.3 times lower compared to published work using inductively coupled plasma optical emission spectrometry, and absolute LODs were 2.4 and 1.2 ng, respectively.įluorine, 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. This is because the formation of silver chloride prevented analyte losses by volatilization. The experimental results obtained with method B were in good agreement with the certified values and demonstrated that the proposed method is more accurate than method A.
To evaluate the feasibility of a simple procedure for the determination of chlorine in food samples present in our daily lives, two different digestion methods were applied, namely (A) an acid digestion method using HNO3 only at room temperature, and (B) a digestion method with Ag, HNO3 and H2O2, where chlorine is precipitated as a low-solubility salt (AgCl), which is then dissolved with ammonia solution. The pyrolysis and vaporization temperatures were 500 ☌ and 2200 ☌, respectively. A spectral interference due to the use of Al–Ag–Sr as mixed modifier was easily corrected by the least-squares algorithm present in the spectrometer software. For the analysis, 10 μL of the sample followed by 10 μL of a solution containing Al–Ag–Sr modifier, (1 g L− 1 each), were directly injected onto the platform. Accurate results for determinations in certified materials and good recoveries demonstrated the efficiency of the procedure.ĭetermination of chlorine using the molecular absorption of aluminum mono-chloride (AlCl) at the 261.418 nm wavelength was accomplished by high-resolution continuum source molecular absorption spectrometry using a transversely heated graphite tube furnace with an integrated platform. As for I, recoveries ranged from 85 to 98% with a closed vessel microwave oven. For Br, recoveries ranged from 87 to 104% for closed vessel microwave oven and from 90 to 102% for open vessel microwave oven. The results for Cl were in good agreement with the certified values (90% confidence level). 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 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. 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 final solution was directly introduced into the ICP-OES without any damage to the sample introduction system and with no severe spectral interference.
After separation from digestate solution, precipitates are dissolved with ammonia resulting in a 20% v/v solution. During the mineralization process in closed and open vessels (microwave ovens), anions are precipitated as salts of low solubility products (AgCl, AgBr and AgI). 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.
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