Chromoionophoric probe-anchored mesoporous silica nanospheres for rapid and reliable naked-eye detection of Ni(II) ions in petroleum products and removal from electroplating wastewater.

This paper presents the expansion of an optical, chemical sensor that can rapidly and reliably detect, quantify, and remove Ni(II) ions in oil products and electroplating wastewater sources. The sensor is based on mesoporous silica nanospheres (MSNs) that have an extraordinary surface area, uniform surface morphology, and capacious porosity, making them an excellent substrate for the anchoring of the chromoionophoic probe,3'-{(1E,1' E)-[(4-chloro-1,2 phenylene)bis (azaneylylidene)]-bis(methaneylylidene)}bis(2-hydroxybenzoic acid) (CPAMHP). The CPAMHP probe is highly selective and sensitive to Ni(II), enabling it to be used in naked-eye colorimetric recognition of Ni(II) ions. The MSNs provide several accessible exhibited sites for uniform anchoring of CPAMHP probe molecules, making it a viable chemical sensor even with the use of naked-eye sensing. The surface characters and structural analysis of the MSNs and CPAMHP sensor samples were examined using various techniques. The CPAMHP probe-anchored MSNs exhibit a clear and vivid color shift from pale yellow to green upon exposure to various concentrations of Ni(II) ions, with a reaction time down to approximately 1 minute. Furthermore, the MSNs can serve as a base to retrieve extremely trace amounts of Ni(II) ions, making the CPAMHP sensor a dual-functional device. The calculated limit of recognition for Ni(II) ions using the fabricated CPAMHP sensor samples is 0.318 ppb (5.43 × 10-9 M). The results suggest that the proposed sensor is a promising tool for the sensitive and reliable detection of Ni(II) ions in petroleum products and for removing Ni(II) ions in electroplating wastewater; the data indicate an excellent removal of Ni (II) up to 96.8%, highlighting the high accuracy and precision of our CPAMHP sensor.

Modified lanthanide-doped carbon dots as a novel nanochemosensor for efficient detection of water in toluene and its potential application in lubricant base oils.

A fast and efficient method was developed for obtaining europium(III)-doped surface-modified carbon dots with a hydrophobic coating. This surface functionalization improved the dispersibility of the nanoparticles in non-polar media, as well as modified the accessibility of water molecules to the europium ions. These two features allowed studying the application of doped carbon dots as moisture nanochemosensor, demonstrating high stability over time of both the photoluminescent signal intensity and the stability of the dispersions. The developed nanochemosensor was used to determine water in toluene with a detection limit of 8.5 × 10-4 M and a quantification limit of 2.4 × 10-3 M. The proposed system matches and even improves other methodologies for water determination in organic solvents; it has a low detection limit and a fast response time (almost instantaneous) and requires neither expensive material nor trained personnel. The results suggest a promising future for the development of a new sensing phase for moisture determination in lubricant base oil.

N, Cl-doped carbon dots for fluorescence and colorimetric dual-mode detection of water in tetrahydrofuran and development of a paper-based sensor.

N, Cl-doped carbon dots (N, Cl-CDs) were prepared by hydrothermal method from rhodamine B (RhB) and ethylenediamine (EDA). The resulting N, Cl-CDs exhibited fascinating solvent dependence and strict excitation independence. As the polarity of the solvent increased (from tetrahydrofuran (THF) to water), the emission spectrum of N, Cl-CDs was redshifted and the fluorescence efficiency decreased, which were attributed to hydrogen bond-induced aggregation. Taking advantage of these attributes, the N, Cl-CDs were used as suitable probes for fluorescence and colorimetric dual-mode detection of water in THF. The linear relationship was 0.5-100% water with the detection limit down to 0.093%. Moreover, the sensing platform was converted into a paper-based sensor for handy, real-time, and visible humidity sensing. N, Cl-CDs/PVA films were fabricated and realized continuously tunable solid-state fluorescence, further expanding their practical application.

Synthesis of a highly fluorescent N,N-dimethyl benzylamine-palladium(II) curcuminate complex and its application for determination of trace amounts of water in organic solvents.

In this work a new highly fluorescent N,N-dimethyl benzylamine-palladium(II) yu complex was synthesized by the reaction of [Pd2 {(C,N-C6 H4 CH2 N(CH3 )2 }2 (µ-OAc)]2 ] with curcumin. The structure of the synthesized complex was characterized using Fourier transform infra-red (FT-IR) spectroscopy, 1 H nuclear magnetic resonance spectroscopy, and elemental analysis. Fluorescence quantum yield (ΦF ) values of the synthesized complex in dimethyl sulfoxide (DMSO), acetonitrile, ethanol, and methanol were 0.160, 0.104, 0.068, and 0.061, respectively. The fluorescence signal of the complex in the organic solvents was very sensitive to the water content of the organic solvent. The quenching effect of water was used to determine trace amounts of water in the heteroatom-containing organic solvents (ethanol, methanol, acetonitrile) and redox-active solvents (DMSO). The linear ranges for determination of water (v/v %) in ethanol, DMSO and acetonitrile were found to be 0.03-14.5, 0.08-13.8, and 0.07-18.8, respectively. Two linear ranges were found for determination of water (v/v %) in methanol (0.1-1.2 and 4.7-25.0). Detection limit (DL) values were calculated to be 0.001, 0.05, 0.004, and 0.01 (v/v %) in ethanol, methanol, acetonitrile, and DMSO, respectively. The proposed method overcomes the problems of the standard Karl Fischer method for determination of water in DMSO. In addition, it gave the best DL value for determination of water in ethanol compared with all published papers to date.

The application of 7H-indolo[1,2-a]quinolinium merocyanine as a new water sensor in organic solvents.

ABSTRACT: The 7H-indolo[1,2-a]quinolinium merocyanine was applied as a new water sensor in organic solvents such as ethanol, propane-1-ol, propane-2-ol, DMSO, and DMF. The spectral changes of the dye caused by the addition of increasing amount of water into an organic solvent were investigated. Based on the results, the calibration curves were found as a relation between the position of the absorption band of the dye and the water concentration ranging from about 0.05 to 11% (w/w). In case of ethanol, propane-1-ol and propane-2-ol the plots were linear, whereas in DMSO and DMF, better results were obtained with the use of a polynomial function. The method allowed to determine the water content in a fast and precise manner.

Two Sensitive Fluorescent BOPIM Probes with Tunable TICT Character for Low-Level Water Detection in Organic Solvents.

Two novel Boron-fluorine derivatives bearing dimethylamino moieties, BOPIM-1 and BOPIM-2, were proposed as sensitive fluorescent sensors for low-level water quantification in organic solvents. Two BOPIMs exhibit typical phenomenon for an emission from a twisted intra-molecular charge transfer (TICT) state, the emission red shift and intensity weakening with solvent polarity. Introduction of trace amount of water to solvent resulted in fluorescent quenching, accompanied by the red shift of the emission, which was attributed to the formation of TICT excitation of BOPIMs by hydrolysis. A quantification method to detect water content was developed, described by a linear equation lg(I/I(0)) vs. lg φ(w) in the range of φ(w) (volume fraction of water) 0.001~0.01, 0.01~0.1, respectively. The experiment results of determination of water in real 1, 4-dioxane (Diox) samples proved that this method can be used in practical application.

Full evaporation headspace gas chromatography with thermal conductivity detection for the direct determination of water in solid pharmaceutical bulk products.

Headspace gas chromatography (HS-GC) has the potential to be used for water determination in pharmaceutical products. In this article, its use for the determination of water in solid samples is explored without the need of dissolution by means of the full evaporation technique (FET). This way, water is thermally removed from a small amount of sample which is directly weighed in the vial. This simplifies considerably the method since no diluent has to be searched and HS saturation is avoided. Blank corrections were performed to compensate for atmospheric moisture variation. Moreover, the performance of mass spectrometry (MS) and thermal conductivity detection (TCD) was compared. The method showed excellent figures of merit when working with TCD, such as R2> 0.99 and RSD< 5% for each level of the calibration curve. Eight samples were carefully studied at different equilibration temperatures to find the optimal working conditions for each case and the results were compared to the ones obtained by Karl Fischer titration (KFT). Both methods showed restrictions and proper case by case optimization/validation turned out to be mandatory. Hyphenation with a flame ionization detector (FID) in series with the TCD showed the benefit to be useful for testing residual solvents (RS) simultaneously.

Determination of trace water contents of organic solvents by gas chromatography-mass spectrometry-selected ion monitoring.

This paper describes the development of a novel gas chromatography-mass spectrometry-selected ion monitoring (GC/MS-SIM) method for the determination of trace water contents of organic solvents, using the characteristic m/z 18, m/z 17, and m/z 16 ions of H2O as the qualitative ion and the m/z 18 ion as the quantifier ion. The accuracy and precision of this method were validated. An excellent linear correlation was obtained for trace water contents between 0 and 0.5217 wt%, with a correlation coefficient (R2) of 0.9999, in addition to spike recoveries of 82.6-112.6%, and relative standard deviations (n = 6) of 0.4-7.2%. The limit of detection (S/N = 3) and limit of quantitation (S/N = 10) for the trace water contents of organic solvents were 0.0005% wt% and 0.0016% wt%, respectively.The analytical results confirmed that this method was useful for determining the trace water contents of organic solvents, because it has a low detection limit and wide linear range. It requires only small amounts of the samples and enables sample batch analysis. It is very environmentally friendly and saves reagents.

Ultrasensitive 4-methylumbelliferone fluorimetric determination of water contents in aprotic solvents.

A novel approach to the quantification of relatively small amounts of water present in low polarity, aprotic solvents is proposed. This method takes advantage of protolitic reaction of 4-methylumbelliferone dissolved in the solvent with water, acting as a base. The low emission intensity neutral 4-methylumbelliferone is transformed in reaction with water to a highly fluorescent anionic form. Thus the increase in emission intensity is observed for increasing water contents in aprotic solvents. For low water contents and highly lipophilic solvents, this method yields (in practical conditions) higher sensitivity compared to biamperometric Karl Fischer titration method in volumetric mode. It is also shown that organic compounds of protolitic character (amines, acids) not only interfere with water contents determination but increase the sensitivity of emission vs. water contents dependence. Introduction of aqueous solution of strong acid or base (HCl or NaOH) has similar effect on the system as introduction of pure water.

Determinação do teor de umidade em grãos empregando radiação micro-ondas / Determination of grain moisture content using microwave radiation

A determinação de umidade em grãos é um parâmetro de qualidade importante, uma vez que o teor de água presente no alimento tem influência tanto no armazenamento quanto na comercialização do produto. Os métodos usados como referência na determinação de umidade em grãos empregam a perda por dessecação em estufa (LOD). Apesar de ser de fácil execução, esse método dispende cerca de 24h de aquecimento, normalmente, em 105°C, para obtenção do resultado. No presente estudo, é proposta a determinação da perda por dessecação assistida por radiação micro-ondas (MALOD) para amostras de grãos moídos de arroz branco, arroz integral, ervilha, feijão branco, feijão carioca, feijão preto, grão-de-bico, lentilha e milho, buscando reduzir o tempo de análise. Parâmetros como potência irradiada, massa de amostra, influência do recipiente e tempo de irradiação com micro-ondas foram avaliados e os resultados obtidos foram comparados com a LOD (sugerido pelo MAPA) e, também, por radiação infravermelha (IRLOD). Verificou-se que não houve diferença significativa do teor de umidade empregando massas de amostra entre 2 e 15g por LOD, porém, para MALOD, ocorreram hot spots (carbonização da amostra) com massas superiores a 2g. Resultados similares de umidade foram encontrados entre os diferentes recipientes (pesa-filtros e frascos de polipropileno), optando-se pela utilização dos frascos de polipropileno, devido à diminuição do tempo de pré-condicionamento. A MALOD apresentou concordância entre 94% e 102% com o método oficial, sendo que apenas 50min foram suficientes para determinar a umidade para todos os grãos, perfazendo uma redução do tempo de análise de até 29 vezes.

The determination of moisture in grains is an important quality parameter, since the water content in food has an influence on both storage and commercialization of product. The methods often used for determination of moisture in grains are based on the loss on drying in an oven (LOD). Although it is easy to perform, this method spent about 24h of heating, usually at 105°C, to obtain the result. In the present study is proposed the determination of the loss on drying assisted by microwave radiation (MALOD) for samples of grounded grains of white rice, brown rice, peas, beans, bean, black beans, chick-peas, lentils and corn, in order to reduce the analysis time. Parameters such as irradiated power, sample mass, container and influence of irradiation time with microwave were evaluated and the results were compared with those obtained by LOD (suggested by MAPA) and also by infrared radiation (IRLOD). It was found that there was no significant difference in moisture content in samples between 2 and 15g using LOD, but there were hot spots for MALOD (carbonization of the sample) with masses higher than 2g. Similar results for moisture content were found by the use of different containers (glass weighing bottle and polypropylene flasks) and the polypropylene cups were selected due to the reduction of conditioning time of flasks. The agreement of MALOD with the official method was between 94% and 102% and only 50min were enough to determine the moisture of all grains, making a reduction of analysis time by 29 times.