Identification of Stingless Bee Honey Adulteration Using Visible-Near Infrared Spectroscopy Combined with Aquaphotomics

Honey is a natural product that is considered globally one of the most widely important foods. Various studies on authenticity detection of honey have been fulfilled using visible and near-infrared (Vis-NIR) spectroscopy techniques. However, there are limited studies on stingless bee honey (SBH) despite the increase of market demand for this food product. The objective of this work was to present the potential of Vis-NIR absorbance spectroscopy for profiling, classifying, and quantifying the adulterated SBH. The SBH sample was mixed with various percentages (10–90%) of adulterants, including distilled water, apple cider vinegar, and high fructose syrup. The results showed that the region at 400–1100 nm that is related to the color and water properties of the samples was effective to discriminate and quantify the adulterated SBH. By applying the principal component analysis (PCA) on adulterants and honey samples, the PCA score plot revealed the classification of the adulterants and adulterated SBHs. A partial least squares regression (PLSR) model was developed to quantify the contamination level in the SBH samples. The general PLSR model with the highest coefficient of determination and lowest root means square error of cross-validation (RCV2=0.96 and RMSECV=5.88 %) was acquired. The aquaphotomics analysis of adulteration in SBH with the three adulterants utilizing the short-wavelength NIR region (800–1100 nm) was presented. The structural changes of SBH due to adulteration were described in terms of the changes in the water molecular matrix, and the aquagrams were used to visualize the results. It was revealed that the integration of NIR spectroscopy with aquaphotomics could be used to detect the water molecular structures in the adulterated SBH.     

Enhanced Optical Properties of FeS2 Using Ni@Cu Doping and Characterization of the Structural and Chemical Compositions for Solar Cell Applications

Crystallography Reports - Transition metals doped FeS2 thin films are promising materials for optoelectronics, energy saving and storage applications. This is a first time report on the...     

Perovskite-sensitized solar cell utilizing TiO2 nanograss: Effect of dipping time of CH3NH3PbI3 perovskite

Organic perovskite has potential to replace organic dye as light absorber in solar cell since it possesses better optical absorption in visible region than organic dye. This work is concerned with the investigation of the influence of CH₃NH₃PbI₃ perovskite dipping time on the performance of perovskite-sensitized solar cell (PSSC). The effect of the dipping time on the morphology and photoluminescence of the sample has also been investigated. It was found that the device achieved a power conversion efficiency (PCE) as high as 5.57 ± 0.4% at the optimum dipping time of 4 h. The highest PCE is due to the highest IPCE, lowest R_ct and the longest carrier lifetime (τ).     

Chemometric approach to the optimisation of LC-FL and GC-MS methods for the determination of nitrite and nitrate in some biological,food and environmental samples

Gas chromatography–mass spectrometry (GC-MS) method and a liquid chromatography–fluorescence (LC-FL) detection method using experimental design and optimisation approach were improved for the quantitative determination of nitrite and nitrate in biological, food and environmental samples. The obtained recoveries of nitrite and nitrate ions from samples based on both GC-MS and LC-FL results ranged from 98.5% to 98.9% for nitrite and 97.9% to 98.4% for nitrate. The precision of these methods, as indicated by the relative standard deviations (RSDs), was within the range from 2.4% to 3.6% for nitrite and 2.5% to 3.8% for nitrate, respectively. The limits of detection of nitrite and nitrate ions from samples based on GC-MS and LC-FL results ranged from 0.01 to 0.14 ng L^?1 for nitrite and 0.02 to 0.71 ng L^?1 for nitrate, respectively. The optimised isolation procedure by central composite design was successfully applied to real samples. The results revealed that the proposed procedure combined with GC-MS and LC-FL techniques is more sensitive, reliable and selective compared to the other methods available for the precise determination of trace levels of nitrite and nitrate in biological, food and environmental samples.     

Quenchofluorimetric Determination of Mercury Trace with Murexide

 A sensitive and fairly selective quenchofluorimetric method for the determination of mercury ultra-trace with murexide (ammonium purpurate) has been developed. The method is based on the instantaneous quenching action of the metal-ion upon the native fluorescence of murexide [λ_ex(max) = 360 nm; λ_em(max) = 445 nm] in the optimum pH range of 5.8 to 6.6 at room temperature (25±0.5) °C. The fluorescence quenching is collinear in the range of 5 μg/L to 100 μg/L mercury. The developed method is very precise and accurate (RSD = 2.2% for 11 determination of 50 μg/L Hg(II). Large excesses of more than 50 cations, anions and complexing agents were found to have no interference. The developed method was successfully tested over synthetic mixtures of various compositions, certified reference materials and factory effluents. Received November 16, 1999. Revision March 30, 2001.     

Determination of low level nitrite and nitrate in biological, food and environmental samples by gas chromatography-mass spectrometry and liquid chromatography with fluorescence detection

Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography with fluorescence detection (LC-FL) methods have been proposed for the determination of low level nitrite and nitrate in biological, food and environmental samples. The methods include derivatization of aqueous nitrite with 2,3-diaminonaphthalene (DAN), enzymatic reduction of nitrate to nitrite, extraction with toluene and chromatographic analyses of highly fluorescent 2,3-naphthotriazole (NAT) derivative of nitrite by using GC-MS in selected-ion-monitoring (SIM) mode and LC-FL. Nitrite and nitrate ions in solid samples were extracted with 0.5 M aqueous NaOH by sonication. The recoveries of nitrite and nitrate ions based on GC-MS and LC-FL results were 98.40% and 98.10% and the precision of these methods, as indicated by the relative standard deviations (RSDs) were 1.00% for nitrite and 1.20% for nitrate, respectively. The limits of detection of the GC-MS in SIM mode and LC-FL methods based on S/N = 3 were 0.02 and 0.29 pg/ml for nitrite and 0.03 and 0.30 pg/ml for nitrate, respectively.