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.

A coacervative extraction based on single-chain and double-chain cationic surfactants.

A coacervative extraction (CAE) with the common cationic surfactants dodecyltrimethylammonium bromide (DTAB) and didodecyldimethylammonium bromide (DDAB) was firstly developed. Notable characteristics of the CAE was the use of low concentration of salt (0.1molL-1 NaBr) at ambient temperature and without the requirement of organic solvent. The CAE was based on phase separation due to the neutralization of the surface charge of the micelle by electrostatic interaction with the predominant common counter ion (bromide). The coacervative phase was subjected to an optimized micellar liquid chromatography with UV (MLC-UV) method without any treatments. The method was applied to the determination of penicillins including amoxicillin, ampicillin, penicillin-G, oxacillin, and cloxacillin in milk samples. Method detection limits (MDLs) from standard were 0.5-2ngmL-1, and 40-80-fold analyte enrichment were obtained. The CAE-MLC-UV has shown to be of high potential for the analysis of five penicillins in milk with recoveries >90%.

Interface-free two-dimensional heart-cutting capillary electrophoresis for the separation and stacking of anionic and neutral analytes.

Interface-free two-dimensional heart-cutting capillary electrophoresis for two different classes of analytes (anionic and neutral) in a single capillary is presented. Simultaneous sample stacking and orthogonal separation were demonstrated. The anionic species were first analyzed by capillary zone electrophoresis in the first dimension. Then, the neutral compounds were separated in the second dimension by micellar electrokinetic chromatography using the common anionic surfactant sodium dodecyl sulfate. The first and second dimensions occurred automatically without changing the electrolyte and without polarity switching. Artificial mixtures (five anions and four neutral compounds) were successfully analyzed with sensitivity enhancement factors from 7 to 28. The orthogonal separation was complete within 8 min. Some analytical features and application to a spiked real river water sample were also studied.

Cloud point sample clean-up and capillary zone electrophoresis with field enhanced sample injection and micelle to solvent stacking for the analysis of herbicides in milk.

Sample clean-up by cloud point phase separation and analysis by capillary electrophoresis with stacking was developed for quaternary ammonium herbicides (i.e., paraquat and diquat) in milk. For sample clean-up, a mixture of 845µL of milk sample, 5µL of 100mM phosphoric acid, and 150µL of Triton X-114 was heated (60°C for 2min) and centrifugated (3000rpm for 2min) in 2-mL Eppendorf tube. The upper phase was directly analysed by capillary electrophoresis via electrokinetic injection at 10kV for 150s. The separation electrolyte was 100mM phosphate buffer with 20% acetonitrile at pH 2.5. Before sample injection, a micellar solution (10mM SDS in 80mM phosphate buffer at pH 2.5) and an organic solvent rich solution (30% ACN) was hydrodynamically introduced into the capillary. These solutions provided the necessary conditions for stacking the cationic herbicides via the combination of field enhanced sample injection and micelle to solvent stacking. The LODs (S/N=3) obtained from the entire strategy for paraquat and diquat in milk was 0.004 and 0.018µg/mL, respectively. This is 1.5 to >2 orders of magnitude better than the corresponding LODs obtained from the electrophoretic analysis of herbicide standards prepared in the separation electrolyte. The strategy was also successfully applied to 5 milk samples available in the market.

Anionic microemulsion to solvent stacking for on-line sample concentration of cationic analytes in capillary electrophoresis.

The common SDS microemulsion (i.e. 3.3% SDS, 0.8% octane, and 6.6% butanol) and organic solvents were investigated for the stacking of cationic drugs in capillary zone electrophoresis using a low pH separation electrolyte. The sample was prepared in the acidic microemulsion and a high percentage of organic solvent was included in the electrolyte at anodic end of capillary. The stacking mechanism was similar to micelle to solvent stacking where the micelles were replaced by the microemulsion for the transport of analytes to the organic solvent rich boundary. This boundary is found between the microemulsion and anodic electrolyte. The effective electrophoretic mobility of the cations reversed from the direction of the anode in the microemulsion to the cathode in the boundary. Microemulsion to solvent stacking was successfully achieved with 40% ACN in the anodic electrolyte and hydrodynamic sample injection of 21 s at 1000 mbar (equivalent to 30% of the effective length). The sensitivity enhancement factors in terms of peak height and corrected peak area were 15 to 35 and 21 to 47, respectively. The linearity R(2) in terms of corrected peak area were >0.999. Interday precisions (%RSD, n = 6) were 3.3-4.0% for corrected peak area and 2.0-3.0% for migration time. Application to spiked real sample is also presented.

Stacking and separation of neutral and cationic analytes in interface-free two-dimensional heart-cutting capillary electrophoresis.

Interface-free two-dimensional heart-cutting capillary electrophoresis is typically used to purify/concentrate and separate a single target fraction. Here, we demonstrate the simultaneous stacking and orthogonal separation of target fractions that belong to two different classes of compounds. The cationic species were first analyzed by capillary zone electrophoresis using an electrolyte of low pH in a fused-silica capillary. The neutrals that remained inside the capillary after the first dimension analysis were then separated by micellar electrokinetic chromatography using sodium dodecyl sulfate micelles that were electrophoretically introduced into the capillary. The suppression of electro-osmotic flow using low pH was essential in shifting the separation selectivity from electrophoresis to electrokinetic chromatography. Two approaches to stacking based on the solubility of the species present were developed. Stacking was achieved during the first dimension analysis via sweeping and/or analyte focusing by micelle collapse. Two artificial mixtures (eight cationic drugs/five neutral steroids, and three quaternary ammonium/three neutral organophosphate pesticides) were successfully analyzed with sensitivity enhancement factors from 15 to 100. Some analytical parameters and application to a spiked real water sample were also studied.

High performance liquid chromatography for the simultaneous analysis of penicillin residues in beef and milk using ion-paired extraction and binary water-acetonitrile mixture.

An ion-paired extraction (IPE) has been developed for the analysis of penicillin antibiotics (penicillin G, oxacillin and cloxacillin) in beef and milk samples using tetrabutylammonium bromide (TBABr) as ion-pairing agent and binary water-acetonitrile as extractant. The factors affecting the IPE efficiency were optimized including solution pH, volume of acetonitrile (ACN), concentration of TBABr and electrolyte salt (NH(4))(2)SO(4). The optimum IPE conditions were 10 mmol L(-1) phosphate buffer pH 8, 2 mL of ACN, 6 mmol L(-1) of TBABr and 2.5 mL of saturated ammonium sulfate. Under the HPLC condition: an Xbridge™ C18 reversed-phase column, isocratic elution of 5 mmol L(-1) phosphate buffer (pH 6.6) and acetonitrile (75:25, v/v) and a flow rate of 1 mL min(-1), with UV detection at 215 nm, the separation of three penicillins was achieved within 10 min. Under the selected optimum conditions, the enhancement of 21-53 folds compared to that without preconcentration and limits of detection (LODs) of 1-2 ng mL(-1) were obtained. Good reproducibility was achieved with RSD<2% for retention time and <5% for slope of calibration curves. The average recoveries higher than 85% were obtained. The proposed IPE-HPLC method has shown to be high efficient preconcentration and analysis method for penicillin residues in beef and milk with LOD lower than the maximum residue limits.

Mixed micelle-cloud point extraction for the analysis of penicillin residues in bovine milk by high performance liquid chromatography.

A mixed micelle-cloud point extraction (MM-CPE) has been developed for the analysis of penicillin antibiotics (ampicillin, penicillin G, oxacillin, and cloxacillin) in milk samples using Triton X-114 (TX-114) and cethyl trimethylammonium bromide (CTAB) as the mixed micellar extractant. The parameters affecting the MM-CPE that were investigated including solution pH, CTAB concentration, TX-114 concentration, electrolyte salt, equilibration temperature and incubation time. The optimum MM-CPE conditions were: 10 mmol L(-1) phosphate buffer pH 8, 0.06% (w/v) CTAB, 1.5% (w/v) TX-114, and 7% (w/v) Na(2)SO(4), and 5 min equilibration at 40 degrees C. The separation of penicillins was achieved within 8 min under the HPLC conditions: a Vydac C(18) column, isocratic elution of 5 mmol L(-1) phosphate buffer (pH 6.6) and methanol (55:45, v/v), and a flow rate of 1 mL min(-1), with photodiode array detection at 215 and 244 nm. Under the selected condition, the proposed method gave linear calibrations in the range 0.002-10 microg mL(-1) with correlation coefficients greater than 0.999. Limits of detection (LOD) were 2-3 ng mL(-1), and 15-40-fold enhancement compared to that without preconcentration. Good reproducibility was achieved with relative standard deviation <5% for peak area and <3% for retention time. High accuracy, with recoveries higher than 80%, was obtained. The proposed mixed micelle-CPE-HPLC method has shown to be of high potential for the analysis of penicillin residues in milk with LOD comparable to the established maximum residue limits (4-30 ng mL(-1)).