Feasibility of Matrix-Matched Material for Determining Elements in Rice Flour by SN-ICP-MS and LA-ICP-MS.

The preparation of matrix-matched material for elemental quantitative analysis in rice flour matrix is proposed here for the first time as part of a feasibility study using the SN-ICP-MS and LA-ICP-MS methods. It was prepared via the spiking process in colloidal solution of rice flour with different levels of arsenic (As), cadmium (Cd) and lead (Pb), followed by drying in a climatic chamber. Comparative studies of the results on external calibration and gravimetric standard addition ICP-MS approaches through the use of calibration standard solutions were discussed. Method bias from the external calibration method was investigated, demonstrating the systematic effect arising from the sample matrix. Characterizing the concentration of measurands was then reasonably proposed using the gravimetric standard addition ICP-MS. Using powdered rice matrix reference material for ICP-MS calibration following acid digestion, the study showed a good agreement of recovery studies. A feasibility study of the LA-ICP-MS method as a direct solid analysis performed on the matrix-matched standard was then discussed. In the study, large fluctuation of signals was found for constructing calibration curve, generating poor linearity, especially for As and Pb, although yttrium (Y) as internal standard was applied. This might be ascribed to a limited microscale of homogeneity, and particularly laser-induced preferential evaporation of volatile elements. Using a number of measured data points, the mean and median were statistically recommended to improve precision. An attempt to use of similar matrix in both standard and sample is a critical point to consider to minimize the elemental fractionation effect. The proposed approach to prepare matrix-matched material could be a potential means for achieving elemental quantitation.

Combination of light stable isotopic and elemental signatures in Thai Hom Mali rice with chemometric analysis.

This study aims to discriminate the geographical origin of Thai Hom Mali rice in order to protect consumers from mislabeling. Stable isotopic and elemental compositions (δ13C, δ15N, δ18O, As, Br, K, Mn, Rb, and Zn) of Thai Hom Mali rice cultivated inside and outside the Thung Kula Rong-Hai Plain were combined with chemometric analysis, linear discriminant analysis (LDA) and partial least squares-discriminant analysis (PLS-DA). The 9 variables combined with LDA can distinguish Thai Hom Mali rice cultivated inside and outside the Thung Kula Rong-Hai Plain with 98.2 % correct classification and 94.6 % cross-validation. The efficiency in using stable isotopic and elemental compositions combined with soft PLS-DA was achieved 100 % in discrimination of Thai Hom Mali rice cultivated inside and outside the Thung Kula Rong-Hai Plain. The variables δ15N, Br, K, and Rb were key parameters to discriminate the geographical origin of Thai Hom Mali rice.

Tracing the Geographical Origin of Thai Hom Mali Rice in Three Contiguous Provinces of Thailand Using Stable Isotopic and Elemental Markers Combined with Multivariate Analysis.

Rice is a staple food for more than half of the world's population. The discrimination of geographical origin of rice has emerged as an important issue to prevent mislabeling and adulteration problems and ensure food quality. Here, the discrimination of Thai Hom Mali rice (THMR), registered as a European Protected Geographical Indication (PGI), was demonstrated. Elemental compositions (Mn, Rb, Co, and Mo) and stable isotope (δ18O) in the rice were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) and elemental analyzer isotope ratio mass spectrometry (EA-IRMS), respectively. The recoveries and precisions of all elements were greater than 98% and lower than 9%, respectively. The analytical precision (±standard deviation) was below ±0.2‰ for δ18O measurement. Mean of Mn, Rb, Co, Mo, and δ18O levels was 14.0 mg kg-1, 5.39 mg kg-1, 0.049 mg kg-1, 0.47 mg kg-1, and 25.22‰, respectively. Only five valuable markers combined with radar plots and multivariate analysis, linear discriminant analysis (LDA) could distinguish THMR cultivated from three contiguous provinces with correct classification and cross-validation of 96.4% and 92.9%, respectively. These results offer valuable insight for the sustainable management and regulation of improper labeling regarding geographical origin of rice in Thailand and other countries.

Ultrasound-irradiated synthesis of 3-mercaptopropyl trimethoxysilane-modified hydroxyapatite derived from fish-scale residues followed by ultrasound-assisted organic dyes removal.

We report a novel method for the synthesis of 3-mercaptopropyl trimethoxysilane-modified hydroxyapatite (FHAP-SH) derived from fish-scale residues by using ultrasound irradiation. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used for the FHAP-SH characterization. Then, the organic dye adsorption on the FHAP-SH was monitored through an ultrasound process. After the dye removal optimization, significant improvements were observed in the maximum adsorption capacities for Congo Red (CR, 500 mg g-1), Coomassie Brilliant Blue G 250 (CB, 235 mg g-1), and Malachite Green (MG, 625 mg g-1). The adsorption behaviors of these dyes were fitted by using the Langmuir isotherm model with a high coefficient of determination values ranging from 0.9985 to 0.9969. The adsorption of the three dyes onto FHAP-SH was an endothermic process based on the adsorption thermodynamics model, while the adsorption kinetics analysis of the dyes presented a good alignment with the pseudo-second-order kinetics. The FHAP-SH exhibits a remarkably high adsorption capacity, is inexpensive, and fulfills the ecofriendly requirements of dye wastewater treatment, especially in the textile industry.

Heavy metals and probabilistic risk assessment via rice consumption in Thailand.

In this study, heavy metals including Cr, Mn, Co, Ni, Cu, Zn, As, and Cd in 55 Thai local rice (4 varieties) were measured using ICP-MS. Health risks were estimated from various Thai population groups, classified according to ages and genders. The potential impact on Thai population who consumed Thai local rice contained heavy metals was assessed by means of probabilistic approach. The hazard quotient (HQ) for non-carcinogenic risks from heavy metal exposure was below the threshold limit of 1 for all rice varieties except Mn in Pka Am Pun rice and As in Pka Am Pun rice, Jek Chuey Sao Hai rice, and Leb Nok rice. Only the hazard index (HI) for consumption of Khaowong Kalasin sticky rice was below 1. The maximum cancer probabilities over the lifetime consumption of Thai local rice were in the range of 5 in 10,000 to 3 in 1000 chances in developing cancer.

Green and facile synthesis of water-soluble carbon dots from ethanolic shallot extract for chromium ion sensing in milk, fruit juices, and wastewater samples.

Self-functionalized carbon dots (CDs) were prepared from ethanolic shallot extract to obtain a total phenolic precursor. The total phenolic extract was then heated at 180 °C for four hours in an autoclave. Only 1 mg L-1 of CDs had high fluorescence emission at 430 nm after excitation at 340 nm and manifested a high selectivity for Cr(vi) ions. The inter- and intra-day emission stability, pH, ionic strength, solvent effect, Stern-Volmer constant, incubation time, speciation of Cr(iii) and Cr(vi) ions, and ion selectivity of the as-prepared CDs were investigated in detail. The proposed method was validated in 20-100 µM linearity with y = 2.2346x as the set-zero intercept linear equation, 0.9981 as the correlation coefficient, 3.5 µM as the limit of detection (LOD), 11.7 µM as the limit of quantification (LOQ), and 2.78% and 5.29% as the intra-day and inter-day relative standard deviations (RSD), respectively. The recovery of drinking water, milk, soymilk, fruit juices (apple and coconut), tap water, and chromium-coated industrial waste water by the investigated Cr sensor was found to be 78.58-119.69%. Therefore, the proposed Cr(vi) sensor had superior advantages of sensitivity, selectivity, rapidity, and reproducibility.