A new fluorescence derivatization technique for the determination of the thyroid hormones, 3,3',5triiodo-L-thyronine (T-3, triiodothyronine) and 3,3',5,5'-tetraiodo-L-thyronine (T-4, L-thyroxine), in human serum was developed based on the Sonogashira coupling reaction. This derivatization reaction was recently utilized by our research group as a promising solution for the derivatization of ortho-substituted aryl halides that suffer from steric hindrance. T-3 and T-4 possess amino groups that could be derivatized by many reagents; however, these reagents are not useful in the case of biological analysis as they could non-selectively react with many biogenic amines and amino acids. Thus, herein we aimed at labeling the iodo-phenyl group of T-3 and T-4 as a selective fluorescence labeling approach suitable for biological analysis. The fluorescent alkyne, 2-(4-ethynylphenyl)-4,5-diphenyl-1H-imidazole (DIB-ET), can label the ortho-substituted aryl halides T-3 and T-4 in the presence of palladium and copper as catalysts, overcoming the steric hindrance of ortho-substitution. Furthermore, the application of the proposed method for the selective analysis of T-3 and T-4 in biological samples was successfully performed even in the presence of numerous biological components. The formed fluorescent derivatives produced from the reaction of DIBET and T-3 and T-4 could be determined by an HPLC system with fluorescence detection. The proposed method was successfully applied for the selective and sensitive determination of T-3 and T-4 in human serum with detection limits (S/N = 3) of 4.0 and 6.1 ng/mL and the recovery rate in the ranges of 84.392.1% and 81.3-84.9%, respectively. Therefore, the proposed method could be used as a new simple tool for the simultaneous determination of T-3 and T-4 in biological samples. (C) 2022 Elsevier B.V. All rights reserved.
Cyanide is highly toxic but used in many industrial processes, such as acrylic fibers, processing metals, and plating [1]. Many suicides and homicides due to cyanide exposure have been reported [2, 3]. In addition to carbon monoxide, cyanide gas can be produced during a fire [4]. Moreover, cyanide is reportedly produced by bacteria and postmortem blood [5]. Therefore, analyzing blood cyanide is one of the most important analytical targets used to determine the cause of death in forensic science. In forensic toxicology, gas chromatography–mass spectrometry (GC–MS) and liquid chromatography–mass spectrometry (LC–MS) are frequently used to get evidences. They exhibit high sensitivity and selectivity, and analytical headspace GC–MS methods have been reported [6–8]. Although these methods have the advantages of few inspection steps, simplicity, and speed of measurement, N2 (m/z = 28), which closely resembles the molecular weight of HCN (m/z = 27), is detected and generally difficult to identify HCN. Therefore, methods have been developed to derivatize cyanide compounds for analysis by GC–MS [9–17] and LC–MS [18, 19]. Among them, pentafluorobenzyl (PFB) derivatization is an excellent method for analyzing many anions, such as cyanide, sulfide, thiocyanate, and azide [10–14]. However, the PFB derivatization accelerates the degradation of capillary columns. Kudo et al. [14] reported column degradation caused by the phase-transfer catalyst, tetradecyldimethylbenzylammonium chloride, which was removed using an ethyl benzoic sulfonic silica gel column [14]. Moreover, the PFB derivatization is difficult to identify by full scan at the poisoning level (19 μM) [20] because of the low sensitivity of the electron ionization (EI). This derivatization exhibited high sensitivity during negative ion chemical ionization; however, the identification was difficult because of the small number of fragments obtained. A GC–MS derivatization method with low instrument contamination and high sensitivity by EI is required to overcome these problems. We focused on indolium compounds as new derivatization reagents. Several indolium derivatives have been reported as fluorescent sensors for cyanide ions of the donor–π-acceptor type, using the indolium moiety as an electron acceptor with a unit that serves as an electron donor [21–26]. The detection mechanism of these sensor molecules is based on the nucleophilic addition to the carbon of C = N+ of the indolium ring. Therefore, simple indolium is a relatively small molecule that can be analyzed by GC–MS, even when adding cyanide. Several sensors based on nucleophilic addition reactions are limited to reports using organic solvents [27–30]; however, indolium is water-soluble and usable without organic solvents. Thus, the derivatization reagent using indolium compounds should exhibit high selectivity for cyanide and prevent the degradation of capillary columns, because it does not use phase-transfer catalysts. Here, we investigated the derivatization of cyanide using a commercially available reagent, water-soluble 1,2,3,3-tetramethyl-3H-indolium iodide (TMI) (Fig. 1). Considering that the relationship between toxic effects and blood concentrations of cyanide has been established [20], the cyanide concentrations of blood are the most feasible proof of cyanide poisoning. However, blood contains * Yasuhiro Morikawa morikawa.fsl.kyoto@gmail.com
Age estimation by use of DNA methylation rate have recently been one of the hottest topics in forensic genetics, thus many age prediction models have been developed. The age prediction model developed by Bekaert et al was evaluated as the best method comparing six blood-based models in 2019. In this study, Bekaert's age estimation model was validated with 143 Japanese blood samples (98 living and 45 dead blood samples). The difference between duplicate measurement of DNA methylation rate with pyrosequencer was less than one-year per one-gene in age prediction result. Overall mean absolute error (MAE) was 3.24, and root mean square error (RMSE) was 4.13. MAE of the elder group was larger than that of the young group. No statistically significant difference in absolute prediction error was observed between living and deceased or male and female blood samples. Furthermore, a novel model was developed with support vector regression. The MAE and RMSE were 3.49 and 4.51 for test set, respectively. In total, 200 ng of pre-bisulfite-treated DNA was essential to perform these predictions. To reduce the required amount of DNA, new models based on only ELOVL2 methylation rate requiring only 40 ng of DNA were also developed. The MAE and RMSE were 3.15 and 4.20 for test set, respectively. These results suggest that both Bekaert's age estimation model and our novel model have great potential in estimating one's age on forensic practices with some points to note.
Cyanide is highly toxic to humans and the environment. It is very important to develop an on-site system for the quantitative analysis of cyanide with high sensitivity and reliability. In this study, we developed a cyanide detection system based on the reaction of vaporized cyanide on a glass-fiber filter soaked in a mixture of naphthalene-2,3-dicarboxaldehyde (NDA)-taurine-borate solution. Although the reaction product was stable for at least 3 days at room temperature, the reaction product on the strip was quickly quenched within a few minutes by direct irradiation with 405 nm light. To overcome this problem, we fabricated a simple device designed to detect the fluorescence intensity immediately after inserting a reaction strip into the device. The linearity of the calibration was obtained over a range of 1–100 µM of cyanide with good repeatability. The device is cost-effective (~ $300) and powered by batteries; therefore, it is suitable for the on-site determination of cyanide in crude samples.
A new cyanide ion sensor with a large Stokes shift and a good fluorescence quantum yield was prepared.
