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A novel, facile, and low-cost method was developed for determination of cetyltrimethylammonium (CTA+) cationic surfactant in water samples using diffuse reflectance Fourier transform IR (FTIR) spectroscopy and colorimetry. Cetyltrimethylammonium bromide was chosen as a model compound to demonstrate the optimization of the method for determination of CTA+ in water samples. The absorption peak at 3015.96 cm-1 (for CTA+) was enhanced when gold nanoparticles were used as a chemical sensor in diffuse reflectance FTIR spectroscopy, and this absorption peak was used for determination of CTA+. Alternatively, the color change from wine red (525 nm) to blue (740 nm) and the redshift of the localized surface plasmon resonance band in the visible region were used as a sensing probe for determination of CTA+. A linear calibration curve for determination in water samples was obtained in the range from 10 to 100 ng mL-1 with a limit of detection of 3 ng mL-1 by diffuse reflectance FTIR spectroscopy and in the range from 20 to 400 ng mL-1 with a limit of detection of 7 ng mL-1 by colorimetry. The advantageous features of the methods are their simplicity, rapidity, and sensitivity for the determination of CTA+ in water samples. [ABSTRACT FROM AUTHOR]

A novel surface enhanced infra-red spectroscopy (SEIRS) method with silver nanoparticles (AgNPs) assisted by single drop microextraction (SDME) was developed for detection of total mixed quaternary ammonium cationic surfactants (QACS) in water samples. SDME was used to separate and preconcentrate QACS from water samples into an organic solvent containing citrate-capped AgNPs through the electrostatic and hydrophobic interactions, and we abbreviated this as the “AgNP-SDME/SEIRS” method. Here, the AgNPs served to enhance the signal intensity of QACS through the aggregation of NPs, which resulted in an increase in the hot-spot density for effective absorption of IR radiation. The linearity range obtained for determination of total mixed QACS in water samples was 1–20 μg L−1 with a limit of detection (LOD) and limit of quantification (LOQ) of 0.03 μg L−1 and 2.0 μg L−1, respectively. The excellent recovery percentage (95.4–109.7%) in domestic wastewater samples showed that the method is found to be selective for the determination of total mixed QACS in complex sample matrices. The advantages of using AgNP-SDME/SEIRS are its simplicity, selectivity and sensitivity towards the analysis of total mixed QACS in various domestic effluent samples. [ABSTRACT FROM AUTHOR]

Abstract: We report a novel methyl orange paired microextraction (MOP‐ME) and diffuse reflectance‐Fourier transform infrared (DRS‐FTIR) spectral monitoring for improved signal strength of total mixed cationic surfactants (CS+) for its quantification in real water samples. To the best of our knowledge, this is the first report that describes the rapid quantitative determination of total mixed CS+ using MOP‐ME/DRS‐FTIR. The method is based on separation and preconcentration of CS+ using chloroform as the extracting solvent by the formation of ion‐pair complex with anionic methyl orange (MO−) followed by DRS‐FTIR analysis. The intense vibration peak obtained at 2919 cm−1 in the FTIR spectra was used for the optimization of all analytical parameters and for the determination of mixed CS+. The best extraction efficiency of CS+ from the aqueous solution was obtained at pH 4.0 when extracted for 3 min in chloroform at a stirring rate of 250 rpm. The linearity range obtained for the determination of total mixed CS+ in water sample was 0.150–300 μg L−1 with the limit of detection and limit of quantification as 0.05 and 0.150 μg L−1, respectively. The good recovery percentage (97.1–109.5%) from wastewater showed that the method is very selective for the determination of total CS+ in complex sample matrices. The advantages of the MOP‐ME/DRS‐FTIR method are its simplicity, selectivity, and sensitivity toward the analysis of total mixed CS+ in wastewater samples. [ABSTRACT FROM AUTHOR]

A new cloud point extraction (CPE) method for the determination of hexavalent chromium i.e. Cr(VI) in food samples is established with subsequent diffuse reflectance-Fourier transform infrared (DRS-FTIR) analysis. The method demonstrates enrichment of Cr(VI) after its complexation with 1,5-diphenylcarbazide. The reddish-violet complex formed showed λ max at 540 nm. Micellar phase separation at cloud point temperature of non-ionic surfactant, Triton X-100 occurred and complex was entrapped in surfactant and analyzed using DRS-FTIR. Under optimized conditions, the limit of detection (LOD) and quantification (LOQ) were 1.22 and 4.02 μg mL −1 , respectively. Excellent linearity with correlation coefficient value of 0.94 was found for the concentration range of 1–100 μg mL −1 . At 10 μg mL −1 the standard deviation for 7 replicate measurements was found to be 0.11 μg mL −1 . The method was successfully applied to commercially marketed food stuffs, and good recoveries (81–112%) were obtained by spiking the real samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • AuNPs /DRS-FTIR method for detection of L-cysteine was established. • Method is based on electrostatics interaction of L-cysteine and NPs. • Peak at 3415.90 cm−1 was used for optimization and quantitative analysis. • Advantages of present method are simple, sensitive and cost effective. This paper describes the sensing application of citrate functionalized gold nanoparticles (AuNPs) employing for the determination of L-cysteine in food and water samples. It is established with diffuse reflectance Fourier transform infrared (DRS-FTIR) spectroscopic analysis. The disappearance of the thiol (-SH) band in the FTIR spectra and the shift in the peaks of the amino group (NH 3 +) and carboxylate group (–COO-) indicated the Au-S interaction and the aggregation of the NPs. The signal intensity of L-cysteine was enhanced due to hot-spots formed by the aggregation of AuNPs producing the effective absorption of electromagnetic radiation in the IR region for molecular vibration. The relationship between AuNPs and L-cysteine was theoretically investigated by the Density Function Theory (DFT) based on LANL2DZ with the aid of the Gaussian 09 (C.01) software. Interaction between AuNPs and L-cysteine molecules resulted to a shift to higher wavelengths in the plasmon bands, further verified by transmission electron microscopes (TEM), which have indicated random aggregated particles. Further dynamic light scattering (DLS) measurements showed a relatively high degree of polydispersity confirming the aggregation of the particles. Under optimized conditions, the calibration curve showed a good linearity range from 20 to 150 μg mL−1 with a correlation coefficient (R2) 0.990. The limit of detection and quantification were 1.04 and 3.44 μg mL−1, respectively by DRS-FTIR. This modified AuNPs sample was used successfully in milk and water samples with adequate results to determine L-cysteine. [ABSTRACT FROM AUTHOR]

The present work deals with a new micro-extraction mode for the selective separation and determination of vanadium in the form of a metaloxy anionic species viz. vanadate ( ) using N 1-hydroxy-N 1,N 2-diphenylbenzamidine (HDPBA) reagent in to a single drop of dichloromethane and its subsequent and rapid diffuse reflectance Fourier transform infrared spectroscopic (DRS-FTIR) determination on potassium bromide matrix. The vibrational infrared peak at 500 cm−1 is selected for the quantitative analysis for the determination. The vanadate combines with the nitrogen and oxygen atoms of N 1-hydroxy-N 1,N 2-diphenylbenzamidine (HDPBA) and forms a selective 1 : 2, V(V) : HDPBA binary complex in acetic acid medium. The chemistry of pure vanadate and that of its HDPBA complex is discussed. The limit of detection (LOD) and the limit of quantification (LOQ) of the method are found to be 40 µg L−1 and 130 µg L−1 V(V), respectively. The precision of the method, in terms of standard deviation and relative standard deviation value, at a level of 10 µg V(V)/5 mL aqueous phase for n = 10 is found to be 0.26 µg V(V) and 2.6%, respectively. The relative standard deviation (n = 6) for the determination of vanadate ( ) in some environmental and real human biological fluid samples is observed to be in the range 4.6–7.8%. [ABSTRACT FROM PUBLISHER]

Experimental parameters were optimized for rapid and precise determination of ammonium ion by FTIR spectroscopy in presence of nitrate ion in water and in samples collected from humans. Nitrates, whose FTIR spectra strongly overlap with those of ammonium ion, were removed from the sample matrix by treating it with zero-valent iron nanoparticles in acidic medium. The infrared peak at 1,400 cm−1 was selected for determination of ammonium ion. Diffuse reflectance FTIR gives both qualitative and quantitative information on ammonium in a KBr matrix. The limit of detection and the limit of quantification of the method are 0.15 ng per 20 µL−1, and 0.5 ng per 20 µL−1, respectively. The relative standard deviation is 6% ( n = 8). The results were compared to those of ion chromatography and show a high degree of acceptability. The method can be applied over a wide concentration range using small sample volumes. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the development of a simple and precise analytical method for the determination of nitrogen dioxide in ambient air. In this method nitrogen dioxide is determined in the form of nitrite. The determination of nitrogen dioxide needs no reagents except for a solution of sodium hydroxide mixed with sodium arsenite (NaOH–Na2As2O3) which is used as an absorbing reagent for trapping the nitrogen dioxide from the atmosphere in the form of nitrite, i.e., a prior analysis step. The determination of submicrogram levels of nitrogen dioxide is based on the selection of a strong and sharp quantitative analytical peak at 1380 cm−1 using diffuse reflectance infrared spectroscopy (DRS-FTIR). The limit of detection (LOD) and the limit of quantification of the method are found to be 0.008 μg g−1 NO2 − and 0.05 μg g−1 NO2 −, respectively. The precision in terms of standard deviation and relative standard deviation value at a level of 2 μg NO2 − / 0.1 g KBr for n =10 is found to be 0.036 μg NO2 − and 1.8%, respectively. The relative standard deviation (n =10) for the determination of nitrogen dioxide in ambient air was observed to be in the range 2.6–3.8%. The method proposed is time-saving and eliminates the slow and cumbersome steps of pH maintenance of the reaction mixture and color formation of the EPA recommended spectrophotometric and other methods for quantitative determination of nitrogen dioxide. [Copyright &y& Elsevier]

The article discusses the development of a simple, rapid and precise diffuse reflectance Fourier transform infrared spectroscopy for the analysis of sulphur dioxide in ambient air by a gas to solid-phase conversion method. Potassium tetrachloromercurate was used as the absorbing reagent. Information regarding the limits of detection and quantification and the precision in terms of standard deviation and relative standard deviation is also mentioned.

Abstract: The feasibility of employing diffuse reflectance Fourier transform infrared spectroscopy (DRS-FTIR) as a sensitive tool in the submicrogram level determination of sulphate (SO4 2−) was checked in this work. This paper presents the development of a new, rapid and precise analytical method for ppb levels of sulphate (SO4 2−) in environmental samples like coarse and fine aerosol particles, dry deposits and soil. The determination of submicrogram levels of sulphate is based on the selection of a quantitative analytical peak at 617cm−1 among the three observed vibrational peaks and preparing calibration curve using different known concentrations of sulphate by diffuse reflectance-Fourier transform infra red spectrometric (DRS-FTIR) technique. Pre-weighed and ground IR grade KBr was used as substrate over which remarkably wide range of known concentration of sulphate was sprayed and dried. The dried sample was analysed by DRS-FTIR. Three calibration curves for three different concentration ranges of sulphate were prepared for samples containing low and relatively higher sulphate contents. The relative standard deviation (n =8) for the sulphate concentration ranges, 2.5–35.5, 25.5–165, 55–1000μg/0.5g KBr, as used to prepare calibration curves, were 2.4%, 2.1% and 1.5%, respectively. The relative standard deviation for the sulphate concentration in real samples were found to be in the range, 3.11–5.76% (n =16), 4.05–7.75% (n =16) and 1.48–3.52% (n =10) for aerosol, dry deposits and soil, respectively. The LOD of the method is 0.20μg/g SO4 2−. The F- and t-tests were performed to check the analytical quality assurance test. The noteworthy feature of the reported method is the non-interference of any of the associated anions and cations. The results were compared with that of ion-chromatographic method with high degree of acceptability. The method can be applied in wide concentration ranges. A method for sulphate determination was introduced that did not require pretreatment of samples. This method employed the direct determination of the sulphate. The method is reagent less, nondestructive, very fast, repeatable, and accurate and has high sample throughput value. [Copyright &y& Elsevier]

Abstract: This paper presents the development of a new, rapid and precise analytical method for submicrogram levels of nitrate (NO3 −) in environmental samples like soil, dry deposit samples, and coarse and fine aerosol particles. The determination of submicrogram levels of nitrate is based on the selection of a quantitative analytical peak at 1385cm−1 among the three observed vibrational peaks and preparing calibration curves using different known concentrations of nitrate by diffuse reflectance Fourier transform infra red spectrometric (DRIFTS) technique. Pre-weighed and ground infrared (IR) grade KBr was used as substrate over which remarkably wide range of known concentration of nitrate was sprayed and dried. The dried sample was analyzed by DRIFTS and absorbance was measured. Eight calibration curves for four different concentration ranges of nitrate for absorbance as well as peak area were prepared for samples containing lower and relatively higher values of nitrate. The relative standard deviation (n =8) for the nitrate concentration ranges, 0.05–40, 0.05–1.5, 1.5–25, 5–40μg/0.1gKBr were in the range 1.6–2.3% for the above calibration curves. The limit of detection (LOD) of the method is 0.07μgg−1 NO3 −. The F- and t-tests were performed to check the analytical quality assurance test. The noteworthy feature of the reported method is the noninterference of any of the associated cations. The results were compared with that of ion-chromatographic method with high degree of acceptability. The method can be applied in wide concentration ranges. The method is reagent less, nondestructive, very fast, repeatable, and accurate and has high sample throughput value. [Copyright &y& Elsevier]

Samples of ambient aerosols were collected at an urban site of eastern central India from monsoon to summer 2016–17 for the characterization of biogenic secondary organic aerosols (BSOA). The BSOA tracers derived from isoprene, α / β -pinene and β -caryophyllene in size-distributed aerosols were studied. Concentrations of total SOAI (Isoprene secondary organic aerosols) were found more abundant than α / β -pinene in summer, while contradictory trends were found in the winter season, where SOAM (monoterpene derived SOA) and SOAS (sesquiterpenes derived SOA) were dominated. Size-distribution study revealed that most of the BSOA were formed in the aerosol phase and dominated in fine mode, except cis-pinonic acid. They were formed in the gaseous phase and partitioned onto the aerosol phase. The alkaline nature of mineral dust particles that triggered the adsorption of gaseous species onto pre-existing particles could be the reason for bimodal size distribution with major coarse mode peak and miner fine mode peak. Temporal variations suggest that the BSOA must be derived from terrestrial vegetation and biomass burning. The isoprene SOC (secondary organic carbon) contributed 0.91%, 1.38%, 0.88% and 1.04% to OC during winter, summer, post-monsoon and monsoon season, respectively. The isoprene SOC in fine mode was found to be higher than the coarse mode. • Size distribution and seasonal variation of biogenic SOA was studied. • Sources of biogenic SOA were identified. • Enhanced BSOA effect due to NO 2 and SO 2 were found. • The bimodal size distribution is obtained for most of the BSOA tracers. • The cis-pinonic acid was found to be enriched in the coarse mode, due to its volatile nature. [ABSTRACT FROM AUTHOR]

The review initiates with current state of information on the atmospheric reaction mechanism of biogenic volatile organic compounds (BVOCs) and its fate in the atmosphere. The plants release BVOCs, i.e., isoprene, monoterpenes, and sesquiterpenes, which form secondary organic aerosols (SOA) upon oxidation. These oxidation reactions are primarily influenced by solar radiations along with other meteorological parameters viz.; temperature and relative humidity, therefore, the chemistry behind SOA formation is different during day than the night time. The review throws light upon the day and nighttime formation mechanism of SOA, recent advancements in the analytical techniques available for the measurements, and its impact on the environment. Studies have revealed that day time SOA formation is dominated by OH and O 3 , however, NOx initiated SOA production is dominated during night. The formation mechanism addresses that the gaseous products of VOCs are firstly formed and then partitioned over the pre-existing particles. New particle formation and biomass-derived aerosols are found to be responsible for enhanced SOA formation. 2-Dimensional gas chromatography-mass spectrometer (2D-GC/MS) is observed to be best for the analysis of organic aerosols. Radiative forcing (RF) SOA is observed to be a useful parameter to evaluate the environmental impacts of SOA and reviewed studies have shown mean RF in the ranges of −0.27 to +0.20 W m−2. Image 1 • The BSOA exhibit distinct day and nighttime formation mechanism. • Analytical advancements and their ability to examine SOA are compiled and compared. • SOA can cause significantly enhanced radiating forcing. • Anthropogenic gaseous pollutants have strong influence over BSOA formation. • Meteorological variables can effectively control BSOA formation. [ABSTRACT FROM AUTHOR]

Surface-enhanced infrared absorption spectroscopy (SEIRS) using a dry-state method was established for the ultra-sensitive detection of glutathione using citrate functionalized silver nanoparticles (AgNPs) in human biological blood and serum samples. The signal intensity of glutathione was enhanced due to the hot-spots created by the aggregation of AgNPs causing the effective absorption of electromagnetic radiation in the IR region for molecular vibrations. The study revealed that the possibility of the interaction of silver with glutathione might rule out structural orientation, energy and affinity as the reason for the detection. The selective determination of glutathione was experimentally confirmed by performing controlled testing with other amino acids. The absorption peak at 3257.84 cm−1 (NH3+) was used for the quantitative analysis of glutathione when AgNPs were used as a chemical sensor in dry state SEIRS. A pre-treatment process was employed for human biological samples such as blood and serum in order to determine glutathione using AgNPs coupled with dry-state SEIRS analysis. A linear range was obtained for the quantitative determination of glutathione in human biological samples from 10 to 100 μg mL−1 with a correlation coefficient (R2) of 0.993. The limit of detection was 1.74 μg mL−1 and the limit of quantification was 5.30 μg mL−1. The advantages of using the presented dry-state SEIRS are its simplicity, selectivity and sensitivity towards the analysis of glutathione using AgNPs in human biological blood and serum samples. [ABSTRACT FROM AUTHOR]

Herein, a rapid, precise alpha-cyclodextrin (α-CD) based gold nanoparticles (AuNPs) for selective detection of malathion pesticides has been reported. These are organophosphorus pesticides (OPPs), that can cause a neurological disease by inhibiting the activity of acetylcholinesterase (AChE). It is important to exploit a quick and sensitive approach for monitoring OPPs. Hence in the present work, a colorimetric assay for the detection of malathion has been developed as a model of OPPs from the environmental sample matrices. The physical and chemical properties of synthesized alpha-cyclodextrin stabilized gold nanoparticles (AuNPs/α-CD) were studied with various characterization techniques, including UV–visible spectroscopy, TEM, DLS and FTIR. The designed sensing system displayed linearity in the broad range of malathion concentrations, 10–600 ng mL−1 with a limit of detection and the limit of quantification values 4.03 ng mL−1 and 12.96 ng mL−1, respectively. The application of the designed chemical sensor was extended to the malathion pesticide determination in real samples such as vegetables, which resulted in almost 100% recovery rates in all the spiked samples. Thus, due to these advantages, the present study established a selective, facile and sensitive colorimetric platform for the direct detection of malathion within a very short time (5 min) with a low detection limit. The practicality of the constructed platform was further executed by the detection of the pesticide in vegetable samples. [Display omitted] • AuNPs/α-CD based colorimetric method for detection of malathion pesticides. • Mechanism is based on the non-covalent and H-bonding interaction of malathion with AuNPs/α-CD. • Applications to the determination of malathion in vegetable samples. • Advantages of present method are simple, sensitive, selective and excellent recovery %. [ABSTRACT FROM AUTHOR]

Abstract Silver nanoparticles (AgNPs) functionalized with glutamic acid (GA) was used as a biochemical sensing probe in colorimetry for detection of lysozyme protein in milk samples. The method is based on the color change of AgNPs/GA from yellow to reddish-yellow differentiated with naked eyes for qualitative determination and red shift of localized surface plasmon resonance (LSPR) absorption signal intensity of AgNPs/GA in visible region used for quantitative determination of lysozyme. The control experiments were performed to demonstrate the electrostatic force of interactions between AgNPs/GA and protein molecule. A wide linear range of 3‐150 nM with limit of detection of 1.5 nM was acquired for quantitative determination of lysozyme using AgNPs/GA as a biochemical sensing probe. The advantages of using AgNPs/GA as a biochemical sensing probe are simple, label-free and economic for determination of lysozyme from milk samples. Graphical Abstract The sensing of lysozyme is based on the color change of AgNPs/GA from yellow to reddish-yellow and red shift of localized surface plasmon resonance (LSPR) absorption peak in visible region. The mechanism for color change and red shift (∆λ) of LSPR band is due to the aggregation of particles by electrostatic force of interactions between carboxylate ions (COO-) of glutamic acid capped NPs and ammonium group (NH 3 +) of protein molecule in the pH range of 5.0–9.0. Unlabelled Image Highlights • Silver nanoparticles (AgNPs) capped with glutamic acid (GA) used as a sensing probe for detection of lysozyme protein in milk • Detection of lysozyme based on color change of AgNPs/GA from yellow to reddish-yellow and red shift of LSPR absorption band • This is because of electrostatic force of interaction between carboxylate ions of NPs and ammonium group of protein molecule • Advantages of biochemical sensing probe are simple, label-free and economic for determination of lysozyme from milk samples [ABSTRACT FROM AUTHOR]

The present work reported a novel strategy to construct supported cationic-polystyrene-resin-bound silver nanocomposites for enhanced catalytic reduction of 4-nitrophenol in an aqueous medium. The Fourier transform infrared spectroscopy (FTIR) was used as a model instrument for the study of catalytic reduction of 4-nitrophenol using cationic-polystyrene-resin-bound silver nanocomposite materials. The mechanism is based on the reduction of 4-nitrophenol to 4-aminophenol due to the electron transfer process that occurred between donor borohydride (BH4−) and acceptor 4-nitrophenol. The polystyrene resin provides support and surface area to increase the catalytic activity of silver nanoparticles. The diffused reflectance-Fourier transform infrared spectroscopy revealed the binding of silver particles onto the surface of cationic polystyrene resin beads. Furthermore, the catalyst was easily separated by the filtration and drying process and was able to reuse. A quantitative analysis of this work has also been performed. The linearity range, the limit of detection, and the limit of quantification obtained for the present method were 0.1 × 10−4 to 1.0 M, 0.6 M, and 2.1 M, respectively. Moreover, a good catalytic efficiency was found to be 96.8%. The advantages of the current method are its simplicity, sensitivity, rapidity, low cost, ease of preparation, and excellent catalytic efficiency to reduce 4-nitrophenol from an aqueous solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile and eco-friendly method is reported for synthesis of R-AuNCs adsorbents. • The adsorption isotherm models were performed in SEIRA spectroscopy. • Mechanism is based on electrostatic attraction with CDs and anionic R-AuNCs. • Characterization and application of R-AuNCs for removal of MB dye from water. • The method is simplicity, sensitivity and excellent adsorption efficiency. In the present work, we report the adsorption of the methylene blue (MB) dye from an aqueous solution employing resin immobilized gold nanocomposites (R-AuNCs) assisted surface-enhanced infrared absorption (SEIRA) spectroscopy. The appropriate adsorption isotherm models, including the Langmuir, Freundlich, and Temkin are tested to reveal the interactive behavior between the adsorbent (R-AuNCs) and adsorbed (MB). Interestingly, Fourier transform infrared spectroscopy (FTIR) in combination with R-AuNC materials could be another approach through which the analysis of adsorption-desorption of MB on the surface of nanocomposite adsorbents is possible in a more precise way with high sensitivity and adsorptivity. In addition, a 10-fold enhancement of the signal intensity of MB dye was obtained due to the electrostatic interaction and H-bonding interaction between COO− groups of adsorbent and the positively charged active sites of the dye molecules. The value of % removal efficiency and % adsorption obtained in the present method was 77.64% and 186.61%, respectively. Desorption of MB from adsorbent surface was also carried out using 0.1 M cetylpyridinium chloride as cationic surfactant; resulting process shows for 'n' number of cyclic process. The maximum desorption capacity for MB found in the present investigation was 44.38 mg/g, The advantages of current method are its simplicity, sensitivity, rapidity, ease to fabrication and excellent adsorption efficiencies to remove MB dye from aqueous solution. [ABSTRACT FROM AUTHOR]

Abstract: The present paper deals with a new micro-extraction procedure for selective separation of Cr(VI) in the form of a metaloxy anionic species namely dichromate (Cr2O7 2−) with N 1-hydroxy-N 1,N 2-diphenylbenzamidine (HOA) in to dichloromethane and its subsequent and rapid diffuse reflectance Fourier transform infrared spectroscopic (DRS-FTIR) determination employing potassium bromide matrix. The diffuse reflectance Fourier transform infrared spectroscopy gives both qualitative and quantitative information about the dichromate. The determination of chromium is based on the analytical peak selection, among the various vibrational peaks, at 902cm−1. The micro-extraction was based on the liquid–liquid solvent extraction (LLSE) principle. The dichromate binds with the nitrogen and oxygen atoms of N 1-hydroxy-N 1,N 2-diphenylbenzamidine (HOA) and forms 1:2, Cr(VI):HOA complex in 0.1molL−1 HCl medium. The formation of above complex, in the acidic medium, is confirmed by the appearance of chocolate-brown color in the micro-extract. The speciation studies of Cr(III) and Cr(VI) is done by conversion of Cr(III) into Cr(VI) utilizing H2O2 as an oxidizing agent. The chemistry of pure dichromate and that of its HOA complex is discussed. The limit of detection (LoD) and the limit of quantification (LoQ) of the method are found to be 0.01μgg−1 Cr2O7 2− and 0.05μgg−1 Cr2O7 2−, respectively. The standard deviation value and the relative standard value at a level of 10μg Cr2O7 2−/0.1g KBr for n =10 is found to be 0.26μg Cr2O7 2− and 2.6%, respectively. The relative standard deviation (n =8 and 6) for the determination of dichromate (Cr2O7 2−) in real human biological fluid samples is observed to be in the range 3.1–7.8%. [Copyright &y& Elsevier]

Herein, an inkjet-printed paper electrode (PPE) with gold nanoparticle (AuNP)-ink as a non-enzymatic electrochemical sensor for detection of glucose in blood serum is reported. In this work, a green method is used for the synthesis of the aqueous AuNP-ink and the electrode is fabricated on a paper substrate using an office desktop inkjet-printer. The developed AuNP-ink is stable and has a surface tension and viscosity of 70.2 mN m−1 and 2.1 mPa s (2% aqueous AuNP ink). The PPE with AuNPs is sintered at 100 °C for 30 min to obtain a conductive film for electrochemical sensing. The prepared AuNP-PPE is employed as a working electrode in cyclic voltammetry (CV) for the sensitive measurement of glucose in blood serum. The fabricated AuNP-PPE demonstrated excellent electrochemical activity and rapid electron transfer kinetics towards the oxidation of glucose. A wide linear range, 0.05–35 mM, with a limit of detection of 10 μM is observed for the determination of glucose. The advantages of using the AuNP-PPE in electrochemical measurements are that it is flexible, user-friendly, biodegradable, economic and enzyme-free with respect to the commercially available electrochemical sensors. [ABSTRACT FROM AUTHOR]

• The severe acute respiratory syndrome coronavirus-2 pandemic has led to an urgent need to assess its epidemiology • The global spread of virus is due to human-to-human transmission • Existing treatment is essentially supportive; the role of antiviral agents is yet to be established • Biomarker detection could be useful in early screening for infection Image, graphical abstract The emergence and rapid spread of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), a potentially fatal disease, is swiftly leading to public health crises worldwide. The origin of SARS-CoV-2 infection was first reported in people exposed to a seafood market in Wuhan City, China in December 2019. It has been suggested that the infection is likely to be of zoonotic origin and transmitted to humans through a not-yet-known intermediary. As of 22 May 2020, the World Health Organization reported that there were approximately 4,995,996 confirmed cases and 327,821 deaths. SARS-CoV-2 is transmitted via inhalation or direct contact with droplets from infected people. It has an incubation period ranging from 2 to ≥14 days. The rate of spread of SARS-CoV-2 is greater than that for severe acute respiratory syndrome coronavirus and Middle East respiratory coronavirus. The symptoms are similar to influenza (i.e. breathlessness, sore throat and fatigue) and infected cases are isolated and treated. Infection is mild in most cases, but in elderly (>50 years) patients and those with cardiac and respiratory disorders, it may progress to pneumonia, acute respiratory distress syndrome and multi-organ failure. People with strong immunity or those who have developed herd immunity are asymptomatic. The fatality rate ranges from 3% to 4%. Recommended methods for diagnosis of COVID-19 are molecular tests (e.g. polymerase chain reaction) on respiratory secretions, chest scan and common laboratory diagnosis. Currently, treatment is essentially supportive, and the role of antiviral agents is yet to be established as a vaccine is not yet available. This review will focus on epidemiology, symptoms, transmission, pathogenesis, ongoing available treatments and future perspectives of SARS-CoV-2. [ABSTRACT FROM AUTHOR]

We report a plasmonic colorimetric sensing strategy using polyvinyl alcohol (PVA) modified silver nanoparticles (AgNPs) and paper-based analytical devices (PADs) for selective detection of lead (Pb). Method is based on the measurement of red shift of localized surface plasmon resonance (LSPR) absorption band of AgNPs/PVA in visible region after the addition of Pb(II) using UV–Vis spectrophotometry and color intensity of PADs was recorded with Smartphone followed by the processing in ImageJ software. The mechanism of color change and red shift (∆λ) of LSPR band from 410 nm to 550 nm is due to the interaction of Pb(II) ions towards the PVA through strong ion-dipole interaction perturbing the stability AgNPs which further directed the aggregation of particles. The density functional theory (DFT) using Gaussian (C.01) program assisted by experimental data was used to elucidate the plausible mechanism for selective detection of analyte. The calibration curve gave a good linearity in the range of 20–1000 μgL−1 with limit of detection (LOD) of 8 μgL−1 by colorimetry and 50–1000 μgL−1 with LOD value of 20 μgL−1 using PADs. In addition, the results obtained with UV–Vis and PADs were compared with ICP-AES for quantitative determination of Pb(II) in different water samples. The advantages of using AgNPs/PVA as plasmonic colorimetric probe and PADs found to be simple, low cost and selective for determination of lead from surface water and industrial waste water samples. • Plasmonic colorimetric sensing using silver nanoparticles and paper-based analytical devices for selective detection of Pb • Method is based on the measurement of red shift of LSPR band of AgNPs/PVA in visible region after the addition of Pb • Paper is based on color developement paper after addition of analyte followed by processing in ImageJ software • Density functional theory assisted by experimental data is used to elucidate the plausible mechanism for detection of Pb [ABSTRACT FROM AUTHOR]

We report a smartphone–paper-based sensor impregnated with cetyltrimethylammonium bromide modified silver nanoparticles (AgNPs/CTAB) for determination of Fe3+ in water and blood plasma samples. The methodology for determination of Fe3+ is based on the change in signal intensity of AgNPs/CTAB fabricated on a paper substrate after the deposition of analyte, using a smartphone followed by processing with ImageJ software. The mechanism of sensing for detection and determination of Fe3+ is based on the discoloration of AgNPs which impregnated the paper substrate. The discoloration is attributed to the electron transfer reaction taking place on the surface of NPs in the presence of CTAB. Fe3+ was determined when the paper was impregnated with 1 mM AgNPs for 5 min of reaction time and the substrate was kept under acidic conditions. The linear range for determination of total iron in terms of Fe3+ was 50–900 μg L−1 with a limit of determination (LOD) of 20 μg L−1 and coefficient of variation (CV) of 3.2%. The good relative recovery of 91.3–95.0% and interference studies showed the selectivity of the method for determination of total iron in water and blood plasma samples. Smartphone–paper-based sensors have advantages of simplicity, rapidity, user-friendliness, low cost, and miniaturization of the method for on-site determination of total iron compared to methods that require sophisticated analytical instruments. [ABSTRACT FROM AUTHOR]

Atmospheric PM2.5 pollution, has shown potential impact on the human health in general, thus it requires to look into the chemical characteristics of PM2.5 masses for designing effective policies to reduce health risks amongst public under exposure. The study carried out, here, has presented the ambient PM2.5 concentrations, concentrations of chemical components and associated health risks over rural and urban environments in the area of mineral based coal-fired industrial areas of central India for a period of one year (2015-16). Overall 260 PM2.5 samples, collected from rural, urban and industrial sites, were analyzed for various elements Al, As, Ca, Hg, Cr, Co, Cu, Fe, Mn, K, Cd, Mo, Ni, Pb, Se, Sb, Na, Mg, K, V and Zn, ions such as Na+, Mg2+, K+, Ca2+, F-, Cl-, NH4 +, NO3 -, SO4 2- and carbonaceous matter. The annual average PM2.5 mass concentrations were found to be ~2 to ~6 folds higher than the annual National Ambient Air Quality standard (40 µg m-3). Further this study also evaluates, carcinogenic and non-carcinogenic health risks associated with ambient PM2.5 exposures (via ingestion, inhalation and dermal). The elemental species that have shown non-carcinogenic risks for both children and adults of all three sites are: Co, Mn, Ni (rural), As, Cd, Cr, Mn, Ni, V (urban and industrial sites). Similarly, the excess carcinogenic risks, in total, from Cd, Co, Cr, Ni, Pb was found to be higher than acceptable limits (10-6 to 10-4). [ABSTRACT FROM AUTHOR]

Abstract Emission factors (EFs) of PM 2.5, carbon fractions, major ionic (K+, Ca2+, NH 4 +, SO 4 2−, NO 3 − and Cl−) and elemental (Al, Cr, Cu and Fe) species from combustion of commonly used household solid fuel were determined in 10 different states in India during cooking practices. The study involved sampling during actual household cooking involving use of a variety of fuels including coal balls (CB), fuel wood (FW), dung cakes (DC), crop residues (CR), mixed fuels (MF: dung cakes + fuel woods). Species-wise highest EFs (g·kg−1) were: 34.16 ± 10.1 for PM 2.5 (CB), 14.18 ± 5.8 for OC (CB), 2.33 ± 1.4 for EC (DC), 1.03 ± 0.2 for K+ (CR), 2.21 ± 0.6 NH 4 + (DC), 0.61 ± 0.2 for NO 3 − (CB), 0.59 ± 0.1 for SO 4 2− (CB), 0.69 ± 0.1 for Cl− (CR) among the fuels. Higher OC EFs for CB could be attributed to higher moisture content (>13%) in coal-powder that is used to handmade coal balls. It is observed that, in general, OC3 and EC1 were the dominant thermally evolved carbon mass fractions. The study averaged MCE values were in the range 0.93–0.98, which could be attributed to higher variability in flaming and smoldering episodes during the combustion of selected fuels. Sum of ionic EFs for emissions from DC, CR and MF were found to be higher than those observed for FW and CB. The K+/EC and Cl−/EC (~1) ratios could be better indicators of CR fuels to differentiate it from FW, whereas NH 4 +/EC (~1) is suitable to indicate DC. Average annual emission estimates of PM 2.5 (2.00 ± 0.53 Tg·yr−1), OC (0.86 ± 0.23 Tg·yr−1) and EC (0.11 ± 0.02 Tg·yr−1) for tested fuels are evaluated to be contributing 27, 15 and 4% of total PM 2.5 , OC and EC, respectively, toward annual emission budget from different anthropogenic activities in India. Graphical abstract Unlabelled Image Highlights • 63–74% of carbon (OM + EC) is found in PM 2.5 emissions from household solid fuel combustions. • Highest PM 2.5 , OC EFs were found for coal balls and highest EC EFs was found for dung cake. • SO 4 2−/NO 3 − (>1 for coal balls), a ratio to differentiate emissions of coal and bio-fuels [ABSTRACT FROM AUTHOR]

To develop coarse particle (PM 10–2.5 , 2.5 to 10 μm) chemical source profiles, real-world source sampling from four domestic cooking and seven industrial processing facilities were carried out in “Raipur-Bhilai” of Central India. Collected samples were analysed for 32 chemical species including 21 elements (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, Pb, S, Sb, Se, V, and Zn) by atomic absorption spectrophotometry (AAS), 8 water-soluble ions (Na + , K + , Mg 2+ , Ca 2+ , Cl − , F − , NO 3 − , and SO 4 2− ) by ion chromatography, ammonium (NH 4 + ) by spectrophotometry, and carbonaceous fractions (OC and EC) by thermal/optical transmittance. The carbonaceous fractions were most abundant fraction in household fuel and municipal solid waste combustion emissions while elemental species were more abundant in industrial emissions. Most of the elemental species were enriched in PM 2.5 (<2.5 μm) size fraction as compared to the PM 10–2.5 fraction. Abundant Ca (13–28%) was found in steel-rolling mill (SRM) and cement production industry (CPI) emissions, with abundant Fe (14–32%) in ferro-manganese (FEMNI), steel production industry (SPI), and electric-arc welding emissions. High coefficients of divergence (COD) values (0.46 to 0.88) among the profiles indicate their differences. These region-specific source profiles are more relevant to source apportionment studies in India than profiles measured elsewhere. [ABSTRACT FROM AUTHOR]

We report simple and selective method for detection of vitamins B 1 and B 6 in brown and white rice samples using localized surface plasmon resonance (LSPR) of sucrose capped gold nanoparticles (AuNPs) as a chemical sensor colorimetrically. Here, detection is based on the color change of AuNPs from pink to blue followed by a red shift of LSPR absorption band in UV–vis region with the addition of vitamins B 1 and B 6 into the NPs solution . A good linear range was observed in the range of 25–1000 ngmL −1 with detection limit of 8 ngmL −1 for B 1 and 50–1000 ngmL −1 with detection limit of 15 ngmL −1 for vitamins B 6 . The employment of AuNPs for detection of B 1 and B 6 vitamins in rice food samples showed remarkable abilities in terms of the simplicity, low cost, stability, reproducibility and sensitivity. [ABSTRACT FROM AUTHOR]

We report a novel UV-Vis spectrophotometry combined with micro Soxhlet extraction method for the detection of CPS pesticide in fruits and vegetables based on alpha-cyclodextrin capped silver nanoparticles (AgNPs/α-CD). Recently, CPS pesticide has been used as a disinfectant in post-harvesting agriculture to prevent or inhibition of recent outbreaks (COVID-19) with pathogens contamination resulting in an increased concentration of pesticides in the environment. Therefore, we developed an AgNPs/α-CD as a chemical sensor for the detection of CPS loaded on agricultural products. The sensing mechanism for the detection of CPS pesticide is based on the change in color of the AgNPs/α-CD from yellow to red followed by the redshift of the LSPR absorption band (410/570 nm) in the UV-Vis region after the addition of the analyte into the NPs solution. The changes of color and LSPR band shifting of AgNPs are observed only in CPS pesticides due to the H-bonding and non-covalent interactions of oxygen moieties with AgNPs/α-CD. Limit of detection (LOD) and limit of quantification (LOQ) in the region of 4.0 and 13.0 ngmL−1 have been achieved for CPS pesticide using AgNPs/α-CD, respectively. These data establish the potential for this sensor for the use CPS pesticide analysis at trace levels. [Display omitted] [ABSTRACT FROM AUTHOR]

• Smartphone-integrated printed-paper sensor for detection of dimethoate in foods. • Detection is based on the change of yellow color NPs to reddish-yellow. • Smartphone-color detector App and colorimetry used for analysis of dimethoate. • Advantages of the method are user-friendly, portable and low cost. Herein, a user-friendly and portable smartphone-integrated printed-paper sensor was designed with Cu@Ag nanoparticles (NPs) for on-site monitoring of dimethoate pesticide in food samples, and the results obtained are compared with those obtained by UV–vis spectrophotometry. The working principle for identification of dimethoate pesticide is the change of yellow color NPs to reddish-yellow with associated bathochromic shift of absorption peak when pesticide introduced onto the fabricated paper or glass vial containing the NPs. A smartphone-color detector App and colorimetry were used for quantitative analysis of dimethoate in food samples. Linearity range for analysis of dimethoate using paper sensor and colorimetry were 100–2000 µgL−1 and 50–2500 µgL−1 with detection limit of 30 and 16 µgL−1, respectively. The advantages of using smartphone-integrated paper devices are rapid, instrument-free detection and economic in terms of consumption of lower amounts of NPs solution compared to other NPs-based colorimetric methods. [ABSTRACT FROM AUTHOR]

We report an inkjet-printed paper based colorimetric sensor with silver nanoparticles (AgNPs) using smartphone and color detector App for on-site determination of mercuric ion (Hg2+) from environmental water samples. The AgNPs printed on Whatman filter paper (No. 1) is employed for detection of Hg2+ which is reliant on the color change of NPs from yellow to discoloration depending on the concentration of target analyte in sample solution. The quantitative determination was performed by calculating the signal intensity of AgNPs on printed paper substrate after the introduction of Hg2+ using smartphone and RGB color detector. The mechanism for detection of Hg2+ on paper substrate is verified using UV-Vis spectrophotometry (UV-Vis), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS) and basic chemical assays. The linear range acquired for paper based colorimetric detection in the range of 40–1200 µgL−1 with limit of detection of 10 µgL−1. The results obtained using an inkjet-printed paper-based chemical sensor combined with a smartphone is validated with data of inductively coupled plasma-atomic emission spectroscopy (ICP-AES) measurement. The advantages of paper based detection are simple, rapid, economic and can be applied at the sample sources for determination of Hg2+. [Display omitted] • Inkjet-printed paper-based sensor with silver nanoparticles (AgNPs) using smartphone for determination of Hg2+. • Detection of Hg2+ is based on color change of paper impregnated with AgNPs from yellow to colorless after addition of analyte. • Paper based sensor coupled with smartphone is validated with result of inductively coupled plasma-atomic emission. • The advantages of paper based detection are simple, rapid, low-cost. [ABSTRACT FROM AUTHOR]

• Development of low-cost paper based disposable printed electrodes with silver nano-ink using desktop inkjet printer. • Fabricated paper electrode exploited as a counter electrode in cyclic voltammetry (CV) analysis. • Printed paper electrode is demonstrated to used as a working electrode for analysis of nitrate in CV. Development of low-cost paper based disposable electrodes printed with silver nano-ink using desktop inkjet printer is reported in this work. A stable nano-ink was prepared by dissolving 3% silver nanoparticles (AgNPs) capped with polyvinylpyrrolidone (PVP) in ethanol as a dispersing solvent. Highly stable silver nano-ink with surface tension of 21.1 mN/M and viscosity of 2.6 mPa.S was prepared for printing on photo paper that can be used as an electrode for electrochemical analyses. The fabricated paper electrode was exploited as a counter electrode in cyclic voltammetry (CV) analysis of potassium ferricyanide with better stability and reproducibility (relative standard deviation (RSD) 1.6%) for multiple times of analyses (n = 60) and compared with the results of conventional electrodes. Further, the printed paper electrode was demonstrated to be used as a working electrode for analysis of nitrate by CV. The use of paper electrode is found to be simple, rapid, user-friendly and can be applied at the sample source for determination of nitrate from different samples. [ABSTRACT FROM AUTHOR]