Μg Cm-2 Research Articles

Determination of Fenpyroximate Acaricide in Vegetables, Soil and Water Samples using UV-Visible Spectroscopy

Modern agriculture makes use of chemical pesticides to increase the crop productivity so as to meet the daily needs of uncontrolled population growth. These increase the productivity neglecting the fertility of soil and food quality, hence risking the health of human beings including animals. Fenpyroximate is a kind of acaricide which attacks and kills mites and decreases the growth of larvae. A method is established for the detection of fenpyroximate and stop excessive use of pesticide. After performing several tests on various wavelengths, the λmax for the detection of fenpyroximate was 435 nm for azo dye. Limit of detection (LOD) and limit of quantification (LOQ) was found to be 0.687 μg mL-1 and 2.083 μg mL-1, respectively. Furthermore, molar absorptivity, Sandell′s sensitivity were calculated to be 2.3 × 10-7 mol-1 cm-1 and 1 × 10-5 μg cm-2, respectively. The azo dye follows Beer′s law in the range 5 μg to 14 μg in 10 mL that can be easily detected by using spectrophotometric analysis. This method is very sensitive, low cost and less time consuming. The present method is applied successfully in various vegetables (i.e. apple, cucumber, potato, spinach, etc.) soil and water samples.

Impact of MS concentration and light qualities on alpine red ginger elongation and rooting in vitro

Some factors in in vitro cultivation, such as formulation of the culture medium and the quality of the light source, may vary the responseof the plants in those conditions, favoring the photosynthetic metabolism obtaining more rustified plants capable of benefiting from the conditions of ex vitro cultivation. Thus, the objective was to evaluate in vitro elongation/rooting of Alpinia purpurata cv. Red Ginger under different light-emitting diodes (LEDs) and saline concentration of the MS medium. For this, previously established invitro plants were maintained for 55 days in 550 mL glass flasks containing Carolina® substrate and MS culture medium with different salt concentrations, under LEDs qualities. The following parameters were evaluated: number of green and senescent leaves, shoot length, length of the largest root, fresh and dry mass of leaves, stem and root, root volume, photosynthetic pigments [chlorophylla, chlorophyll b, total chlorophylls (a+b) and carotenoids (μg cm-2)], stomatal density and acclimatization percentage (after 33 daysof ex vitro cultivation). After 55 days, plants grown under red LEDs and full-strength MS culture medium is indicated and promote efficient shoot length and photosynthetic pigment content, respectively. These conditions provided plants better adapted for exvitro acclimatization.Index terms: Alpinia purpurata; light-emitting diode (LEDs); culture medium.

Complexation-association-extraction spectrophotometric determination of Pt cations based on a multi-reagent analytical system with I- anions and 2-[2-[4-[(2-cyanoethyl)methylamino]phenyl]vinyl]-1,3,3-trimethyl-3H-indolium cations.

A new multi-reagent analytical system with 2-[2-[4-[(2-cyanoethyl)methylamino]phenyl]vinyl]-1,3,3-trimethyl-3H-indolium chloride (CPVTI), which is a styryl hemicyanine cationic dye with good photostability and a high molar absorption coefficient, as its core is first established and utilized successfully to determine the content of Pt ions via a spectrophotometric method. The process involves two treatment steps: adding CPVTI and I solutions to the Pt solution to be detected, and then using butyl acetate for vortex liquid-liquid extraction. A Pt cation can be incorporated into the CPVTI cation with the help of an I- anion, initially converting the Pt cation into a [PtI6]2- complex anion. After forming a [PtI62-·2CPVTI+](aq) ion associate in the aqueous phase, the Pt cation can be extracted selectively by butyl acetate with maximum extraction efficiency, and exists as [PtI62-·2CPVTI+](org) in the extract phase. Via the formation of the iodo-complex of Pt and its ion associate with CPVTI, and the extraction with butyl acetate, Pt is selectively partitioned into the butyl acetate extractant in a step-by-step manner with good interference resistance. In the CPVTI-Pt-I analytical system, the charge state of CPVTI is retained by adjustment with H2SO4; the monovalent CPVTI+ presents a strong spectrophotometric absorbance signal at 530 nm with long-term stability, which allows determination of the Pt content. The system shows a high molar absorption coefficient of 6.52 × 104 L mol-1 cm-1 at 530 nm, a lower limit of detection of 0.07 mg L-1, and a good Sandell's sensitivity of 0.0030 μg cm-2. Mechanistic analysis of the establishment of the system, concentration optimization, standard working curve, system sensitivity and stability, resistance against interference from diverse metal ions, and practical applications are investigated and discussed.

Spectrophotometric Determination of Cerium(III) in Some Industrial and Plant Samples using New Synthesized Azo-dye Reagent: Synthesis and Characterization

New spectrophotometric method was proposed for the rapid and accurate determination of Ce(III) using a new synthesized sulfacetamide azo-dye reagent [N-(4-((2,3-dihydroy-5-(3,5,7-trihydroxy-4-oxo-4H-chromen-2-yl)phenyl)diazenyl) phenylsulfonyl)acetamide] [DTPPA]. The reagent was characterized by IR, 1HNMR and mass spectra. The developed method was based on the reaction of Ce(III) with DTPPA reagent to form brown colored complex in an alkaline medium using borate buffer at pH = 9 with absorption maximum at 560 nm. The method was enhanced by the use of cationic surfactant of cetylpyridinium bromide (CPB). Different factors affecting the formation and stability of the complex such as reagent concentration, time, temperature, solvents and order of addition were also studied. The composition of the complex was found 1:2 (metal: ligand) by both Job's and molar ratio methods. The stability constant of the complex was calculated to be 3.387×106. Beer's law was obeyed in the concentration range of 5.0-100 µg mL-1 of Ce(III) with molar absorpitivity and Sandell’s sensitivity 1.020×104 L mol-1 cm-1 and 0.01373 µg cm-2, respectively. The proposed method was applied for the determination of micro-amounts of Ce(III) in some industrial and plant samples. The Ce(III) complex was also prepared in the solid state.

Low-Iridium-Content IrNiTa Metallic Glass Films as Intrinsically Active Catalysts for Hydrogen Evolution Reaction.

Although various catalytic materials have emerged for hydrogen evolution reaction (HER), it remains crucial to develop intrinsically effective catalysts with minimum uses of expensive and scarce precious metals. Metallic glasses (MGs) or amorphous alloys show up as attractive HER catalysts, but have so far limited to material forms and compositions that result in high precious-metal loadings. Here, an Ir25 Ni33 Ta42 MG nanofilm exhibiting high intrinsic activity and superior stability at an ultralow Ir loading of 8.14 µg cm-2 for HER in 0.5 m H2 SO4 is reported. With an overpotential of 99 mV for a current density of 10 mA cm-2 , a small Tafel slope of 35 mV dec-1 , and high turnover frequencies of 1.76 and 19.3 H2 s-1 at 50 and 100 mV overpotentials, the glassy film is among the most intrinsically active HER catalysts, outcompetes any reported MG, representative sulfides, and phosphides, and compares favorably with other precious-metal-containing catalysts. The outstanding HER performance of the Ir25 Ni33 Ta42 MG film is attributed to the synergistic effect of the novel alloy system and amorphous structure, which may inspire the development of multicomponent alloys for heterogeneous catalysis.

Antifeedant, contact toxicity and oviposition deterrent effects of phyllostine acetate and phyllostine isolated from the endophytic fungus Diaporthe miriciae against Plutella xylostella larvae.

Larvae of the diamond back moth (DBM), Plutella xylostella, are destructive cabbage pests causing economic losses worldwide. Continuous application of synthetic pesticides to control this pest has resulted in environmental pollution and resistant pest strains. Thus, there is a crucial need to seek natural alternatives with minimal detrimental effects. This study was designed to investigate the antifeedant activities of endophytic fungi of Cyperus iria and to determine the antifeedant, contact toxicity and oviposition deterrent activities of phyllostine acetate and phyllostine of the endophytic Diaporthe miriciae fungus. Two cyclohexeneoxidediones, phyllostine acetate (1) and phyllostine (2), isolated from an ethyl acetate extract of D. miriciae exhibited strong antifeedant, contact toxicity, and oviposition deterrent activities against P. xylostella. Phyllostine acetate (1) and phyllostine (2) showed feeding deterrent indexes of 100% at 50 μg cm-2 in the no-choice leaf disc assay and 50% feeding deterrence (DC50 ) values of 9 and 4.7μg cm-2 respectively. The median lethal concentration (LC50 ) values of phyllostine acetate (1) and phyllostine (2) were 4.38 and 6.54 μg/larva in the contact toxicity assay. The oviposition deterrent indexes of the two compounds were 100% for phyllostine acetate (1) and 28.6% for phyllostine (2) at 50 μg cm-2 . Phyllostine acetate and phyllostine show promise as compounds for the control of P. xylostella. This study encourages further investigation of endophytic fungi of the family Cyperacea, for the development of natural pest control agents in agriculture. © 2019 Society of Chemical Industry.

The global distribution of leaf chlorophyll content

Leaf chlorophyll is central to the exchange of carbon, water and energy between the biosphere and the atmosphere, and to the functioning of terrestrial ecosystems. This paper presents the first spatially-continuous view of terrestrial leaf chlorophyll content (ChlLeaf) at the global scale. Weekly maps of ChlLeaf were produced from ENVISAT MERIS full resolution (300 m) satellite data using a two-stage physically-based radiative transfer modelling approach. Firstly, leaf-level reflectance was derived from top-of-canopy satellite reflectance observations using 4-Scale and SAIL canopy radiative transfer models for woody and non-woody vegetation, respectively. Secondly, the modelled leaf-level reflectance was input into the PROSPECT leaf-level radiative transfer model to derive ChlLeaf. The ChlLeaf retrieval algorithm was validated using measured ChlLeaf data from 248 sample measurements at 28 field locations, and covering six plant functional types (PFTs). Modelled results show strong relationships with field measurements, particularly for deciduous broadleaf forests (R2 = 0.67; RMSE = 9.25 μg cm-2; p < 0.001), croplands (R2 = 0.41; RMSE = 13.18 μg cm-2; p < 0.001) and evergreen needleleaf forests (R2 = 0.47; RMSE = 10.63 μg cm-2; p < 0.001). When the modelled results from all PFTs were considered together, the overall relationship with measured ChlLeaf remained good (R2 = 0.47, RMSE = 10.79 μg cm-2; p < 0.001). This result is an improvement on the relationship between measured ChlLeaf and a commonly used chlorophyll-sensitive spectral vegetation index; the MERIS Terrestrial Chlorophyll Index (MTCI; R2 = 0.27, p < 0.001). The global maps show large temporal and spatial variability in ChlLeaf, with evergreen broadleaf forests presenting the highest leaf chlorophyll values, with global annual median values of 54.4 μg cm-2. Distinct seasonal ChlLeaf phenologies are also visible, particularly in deciduous plant forms, associated with budburst and crop growth, and leaf senescence. It is anticipated that this global ChlLeaf product will make an important step towards the explicit consideration of leaf-level biochemistry in terrestrial water, energy and carbon cycle modelling.

Is the skin an important exposure route for workers during cyanogen fumigation?

Cyanogen is a toxic flammable gas used as a fumigant in numerous industries. Occupational exposure to cyanogen can occur during its production and use. The most serious human health risk from exposure to cyanogen is via the respiratory system. However, there is also potential for skin exposure in many workplace situations. The extent of skin absorption under occupational exposure scenarios has not been directly assessed. Understanding skin uptake potential may inform risk assessment and exposure control measures. We describe an in vitro experimental system using human epidermis and dynamic atmosphere exposure to cyanogen to mimic potential workplace exposures. The influence of clothing and ventilation on skin permeation outcomes were also assessed. No evidence of transdermal permeation was found at 100 or 1000 ppm exposures, while permeation of 0.99 ± 0.38 μg cm-2 was observed after 60 min exposure to 10 000 ppm. Fabric on skin and skin ventilation had no additional influence on transdermal permeation compared with naked skin, but fabric provided a reservoir for potential secondary exposures. Results show dermal uptake following cyanogen exposure is possible, but only at very high atmospheric concentrations (10 000 ppm after >15 min exposure). Importantly, this could have implications for fumigant applicators who may only be wearing personal respiratory protection. These empirical data may be used in conjunction with other relevant toxicological information in determining whether a Skin Notation is warranted for Workplace Exposure Standard setting. © 2019 Society of Chemical Industry.

The development of analytical methods to determine metoclopramide-hydrochloric acid in the standard raw and it compared with pharmaceuticals

The three novel easy, to the prepare and sensitive spectral methods, were used to estimate metoclopramide in both standard and pharmaceuticals. The effective double–electron, was present in the metoclopramide compound helps to interact in an acidic medium with a reagent such as diazetide resorcinol and 8-hydroxyquinoline reagents. The present article was extended to find out three analytical methods with UV-V is the detector. In both A and B methods, two azo-dyes are formed, they are orange-red and red stable and have high water solubility, giving highest absorption values at 415 nm and 485 nm but the C method will depend on a complex colour configuration with the p-benzoquinone reagent, which has a maximum absorption at a wavelength of 285 nm. Beer's law was applied in a range of concentrations between 1 and 10 μg / ml, 2-20 μg / ml and 1-30 μg / ml. The values ​​of the molar absorption factors were (4.1224 × 104, 3.0229 × 104 and 1.7373 × 104) L mol-1cm-1 with a sensitivity of Sandell’s equal to 0.2606 × 10-4, 0.9834 × 10-4 and 0.2568 × 10 - 4 μg cm-2 to methods A, B respectively and LLOD values ​​were 0.255, 0.553 and 0.158 μg / ml to methods A, B and C. LLOQ 0.512, 0.898 and 0.455 μg / ml to methods A, B, C respectively. The constant fixed Kf configuration was also calculated for the colored outputs of the reaction where it was found to be equal to 43.6435 × 108, 54.6261 × 10-8 and 17.29099 × 106 L2 mol-2 to all methods A, B, C respectively. The values ​​of G were calculated based on -43.9293 KJ / mol, -44.3735 and -51.2019. G values, molar absorption factor, Sandell sensitivity, detection limit.

Tuning the Electron Localization of Gold Enables the Control of Nitrogen-to-Ammonia Fixation.

The (photo)electrochemical N2 reduction reaction (NRR) provides a favorable avenue for the production of NH3 using renewable energy in mild operating conditions. Understanding and building an efficient catalyst with high NH3 selectivity represents an area of intense interest for the early stages of development for NRR. Herein, we introduce a CoOx layer to tune the local electronic structure of Au nanoparticles with positive valence sites for boosting conversion of N2 to NH3 . The catalysts, possessing high average oxidation states (ca. 40 %), achieve a high NH3 yield rate of 15.1 μg cm-2 h-1 and a good faradic efficiency of 19 % at -0.5 V versus reversible hydrogen electrode. Experimental results and simulations reveal that the ability to tune the oxidation state of Au enables the control of N2 adsorption and the concomitant energy barrier of NRR. Altering the Au oxidation state provides a unique strategy for control of NRR in the production of valuable NH3 .

Fabrication of Curcumin-Modified TiO2 Nanoarrays via Cyclodextrin Based Polymer Functional Coatings for Osteosarcoma Therapy.

The incomplete removal of bone tumors leads to increased local recurrence and poor prognosis. To prevent ostoperative tumor recurrence and simultaneously repair surgery-caused bone defects, there is a need of great significance to develop implantable biomaterials possessing both cancer cell-killing ability and excellent bioactivity. In this work, a functionalized titanium-based implant is successfully fabricated by loading curcumin (CUR) onto cyclodextrin based polymer (pCD) modified titanium dioxide (TiO2 ) nanorod arrays. Herein, a polydopamine (pDA) assisted film is implemented as a first coating layer onto the surface of the TiO2 nanoarrays to guarantee the robust anchorage of the pCD. The pCD coating acts as a reservoir for CUR, allowing for efficient drug loading and sustained release of anticancer drugs. Studies show that the CUR-modified surfaces (TiO2 /pDA/pCD/CUR) can significantly promote apoptosis of osteosarcoma cells in vitro by inducing mitochondrial dysfunction caused by the ROS overproduction, and meanwhile, effectively inhibit the tumor growth in vivo. Moreover, such functionalized implants with surface density of loaded CUR at 22.48 µg cm-2 or lower support the attachment and proliferation of osteoblasts in vitro. These results successfully demonstrate that as-prepared TiO2 /pDA/pCD/CUR constructs have combined anticancer performance and good biocompatibility, which has great promise for the surgical therapy of bone tumors.

UV-Visible Spectrophotometric Determination of Lambda-Cyhalothrin Insecticide in Vegetables, Soil and Water Samples

In modern age pesticide is used widely in agriculture. Lambda-cyhalothrin (LCT) is one of the most used pesticides which are used as a insecticide to kill pest, tricks, flies etc in agricultural field and it is also used for crop production. We have developed new method to detect LCT insecticide in agriculture field and reduce its uses. In this method we found the maximum absorbance at 460 nm for yellow colour dye. We also calculated limit of detection and limit of quantification 0.001 mg kg-1 and 0.056 mg kg-1 respectively. Molar absorptivity and Sandell’s sensitivity was also calculated and obtained 1.782 ×107 mol-1 cm-1 and 9.996 ×10-6 µg cm-2 respectively. The obtained yellow colour dye obeyed Beer’s law limit range of 0.5 µg ml -1 to 16 µg ml-1 in 25 ml. This method is less time consuming, selective, simple, sensitive and low cost. Present method is successfully applied in various soil, water and vegetable samples.

A Spectrophotometric Determination of Myclobutanil and it’s Applications

A new spectrophotometric method has been developed for determination of fungicide myclobutanil is based on the bromination of myclobutanil to form dibromo myclobutanil which react with Potassium iodide-Potassium iodate mixture in the presence of leucocrystal voilet (LCV) to form a violet colored complex. The complex shows maximum absorbance at 590 nm. Beer’s law obeyed over the concentration range of 0.5-4.0 µg in final solution volume of 10 mL. The reproducibility assessed by carrying out seven days replicate analysis of a solution containing 10 µg of myclobutanil in a final solution of 10 mL. The molar absorptivity of the coloured system is 1.29×105 L mol-1cm-1 and Sandell’s sensitivity is 1.03×10-3 µg cm-2. The standard deviation and relative standard deviation for the absorbance value were found to be ±0.00652 and 1.14% respectively. The proposed method is free from the interference of other toxicants. The analytical parameters were optimized and the method was applied to the determination of myclobutanil in water, soil and food samples.

(Amazon Catalyst at ECS Grant Winner) Enhancing the Rate of Electrocatalytic Conversion of N2 to NH3 Using Bimetallic Au-Pd Nanoparticles

Ammonia is one of the widely produced chemicals in the world, with broad applications in producing nitrogen-based fertilizer, energy, and in the pharmaceutical industry. The current industrial method for ammonia production is energy intensive and heavily relies on fossil fuels, which are responsible for environmental pollution. To meet ammonia demands, it is necessary to develop sustainable and environmentally friendly production methods that consume significantly less energy than the current methods. Here, the use of hollow gold nanocages (AuHNCs) as an effective electrocatalyst is evaluated for electrochemical nitrogen reduction reaction (NRR) under ambient conditions. The electrochemical experiments are carried out at various potentials in 0.5M LiClO4 aqueous solution using AuHNCs, and their catalytic efficiency is determined for the conversion of nitrogen to ammonia [1, 2]. The highest ammonia Faradaic efficiency (30.2%) is achieved at−0.4 V vs. RHE while the highest ammonia yield (3.9 μg cm-2 h-1) is obtained at −0.5 V vs. RHE. The electrocatalytic activity of NRR using AuHNCs is further compared with that of solid Au nanoparticles of various shapes (i.e., rods, spheres or cubes) to elucidate the enhanced rate of the reaction resulting from the increase in surface area and confinement effects. The three-fold enhancement in ammonia Faradaic efficiency is achieved by using the AuHNCs (30.2%) compared to the solid Au nanocubes (11.4%) [1]. It has been demonstrated that electrochemical N2 reduction for NH3 production using Pd nanoparticles requires lower overpotential and results in higher electrocatalytic efficiency for NH3 compared with Au nanoparticles. The use of Pd and hybrid Au-Pd nanoparticles is evaluated for electrochemical nitrogen reduction reaction (NRR) under ambient conditions. The results are further complemented by in-situ surface-enhanced Raman spectroscopy (SERS) and ex-situ 1H NMR to monitor the trace amount of NH3 over the course of the experiment and elucidate the possible differences in the reaction mechanism for electrosynthesis of NH3 on Pd and Au surfaces.

Vibrating Powders: Electrochemical Quartz Crystal Microbalance Measurement of Potential Dependent IrO2 and Pt/C Mass Changes for Reversal Tolerant PEMFC Anodes

Oxygen evolution reaction (OER) catalysts are used to protect carbon components of polymer electrolyte membrane fuel cell (PEMFC) anodes during transient fuel starvation conditions such as start-up/shut-down [1]. OER catalysts such as IrO2 or RuO2 promote the oxidation of water instead of the corrosion of carbon components [1, 2]. However, the conditions in a PEMFC during normal operation (ca. 0 V and low pH) can induce instability in these metal oxides. IrO2 in particular can form soluble Ir3+ species [3] that migrate across the membrane electrode assembly and deposit on the cathode causing poisoning of the oxygen reduction reaction (ORR) catalyst (typically Pt/C). Currently, OER catalysts for reversal tolerant anodes (RTAs) are investigated using prototype MEA single unit cell testing which is time consuming and expensive to perform [4]. Previously, our group investigated the dissolution of different IrO2 based powder catalysts using a potential stepping stress test. The dissolution of Ir3+ from this test was compared with reversal tolerance of a membrane electrode assembly fabricated using the same IrO2 catalyst [5]. To further investigate the potential dependent mass changes of IrO2 powder layers, we have devised a series of experiments (with potential cycling between 0.05 to 1.2, 1.4 and 1.6 V vs. RHE, 30 times each at 100 mV s-1 and 298 K) using the electrochemical quartz crystal microbalance (EQCM) technique. The EQCM uses a vibrating quartz crystal and measures its frequency (inversely proportional to crystal mass) as a function of potential. Our method was used to investigate a commercially available IrO2 powder (Alfa Aesar) heat treated in air at 350, 450 and 550 °C. This heat treatment improves durability while reducing OER activity [6]. The powders were deposited (24 μg cm-2) onto a gold EQCM crystal to investigate the dissolution behavior as a function of particle size, crystallinity and electrode potential. We observed that the frequency of the untreated IrO2 increased by ca. 80 Hz (-570 ng cm-2) during the initial polarization from 1.15 V to 0.05 V vs. RHE (Figure a). The electrolyte was tested for dissolved Ir by inductively coupled plasma mass spectrometry (ICP-MS) but it was below the detection limit. This suggests that the first cycle frequency increase is caused by decreased rigidity of the IrO2 particle aggregates. During subsequent cycles, the untreated IrO2 frequency profile was consistent with previous reports. Birss et al. reported the formation of an iridium oxo-hydroxide at low potentials which causes a mass decrease (frequency increase) when polarizing to from 0 to 1.0 V vs. RHE [7]. Conversely, the frequency of heat treated layers first decreases by ca. 70 Hz (500 ng cm-2) before increasing again when polarizing to from 0.05 to 1.6 V vs. RHE (Figure b). Over the course of 90 CV cycles, there was an increase in film mass from the formation of iridium oxo-hydroxide species; confirmed by XPS. A platinum on carbon catalyst (Pt/C) was added to the IrO2 powders and the same experiment was performed (Figure c and d). This produced a dramatic increase in frequency which corresponded to a mass increase larger than the total deposited mass. Therefore, this mass decrease cannot be caused by dissolution of Pt or carbon corrosion alone and is instead attributed to loss of adhesion and changes in the viscoelasticity of the Pt/C aggregates. [8] The main challenge to using EQCM for powder catalyst investigation is producing layers with consistent and repeatable frequency behavior. In this work, the IrO2 and Pt/C deposition conditions were tightly controlled and each experiment was repeated to ensure the consistency of the results. It can also be difficult to interpret results and various analytical techniques should be used to supplement the EQCM technique. Despite these drawbacks, EQCM is a rapid and powerful tool to learn about potential dependent reactions using a myriad of powder catalysts. Ralph TR, Hudson S, Wilkinson DP (2006) ECS Trans 1:67–84.Patterson TW, Darling RM (2006) Electrochem Solid-State Lett 9:A183–A185.Danilovic N, Subbaraman R, Chang K-C, et al (2014) J Phys Chem Lett 5:2474–2478.Makharia R, Kocha S, Yu P, et al (2006) ECS Trans 1:3–18.Moore CE, Eastcott J, Cimenti M, Kremliakova N, Gyenge EL (2019) J Power Sources 417:53-60da Silva GC, Perini N, Ticianelli EA (2017) App Cat B: Env 218 287–297.Birss VI, Elzanowska H, Gottesfeld S (1991) Journal of Electroanalytical Chemistry and Interfacial Electrochemistry 318:327–333.Lu S, Chung DDL (2013) Carbon 60:346–355. Figure 1

Formation of the Self-assembled Multilayers Containing the Temperature/ pH Dual-responsive Microgels

&lt;P&gt;Background: Stimuli-responsive microgels have attracted extensive investigations due to their potential applications in drug delivery, catalysis, and sensor technology. The self-assembled mcirogel films can contain different functional groups (e.g., -COOH, -NH2, -C=ONH2) to interact with specific molecules and ions in water, and their study is becoming increasingly important for developing both absorbent materials and sensor coatings. This paper is aimed to obtain a better understanding of the LbL multilayer formation of microgels and the branched PEI using the mass sensitive QCM. Additionally the influence of the temperature and pH on the formation of the microgel films can be achieved. &lt;/P&gt;&lt;P&gt; Methods: The temperature and pH sensitive P(NIPAM-co-AA-co-TMSPMA) microgels were prepared by surfactant-free emulsion polymerization and confirmed by FT-IR, laser particle size analysis, and SEM. The obtained microgel and PEI were further used to prepare multilayer thin films by the LbL self-assembly technique monitored by QCM, and their morphology and hydrophilic properties were determined by AFM and water contact angle measurements. &lt;/P&gt;&lt;P&gt; Results: The thermosensitive and pH sensitive P(NIPAM-co-AA-co-TMSPMA) microgels were prepared by surfactant-free emulsion polymerization. The size and swelling properties of the microgels prepared are highly dependent on the preparation conditions such as the AA and crosslinker content, and microgels showed good temperature and pH responsive properties. SEM images showed that microgels dispersed evenly on the substrate and had a uniform particle size distribution, which was consistent with the light particle size analysis results. Furthermore, multilayer films composed of the negatively charged microgels and the positively charged PEI have been built up by a facile LbL assembly method and the influence of the deposition conditions on their formation was monitored in real time by QCM. Compared to the temperature of 25 °C, the high temperature of 35°C above the phase transition temperature leads to the more adsorbed mass of microgels on the gold surface of QCM sensors. The absorbed mass values at the deposition pH 7 and 10 are 9.82 and 7.28 µg cm-2, respectively, which are much higher than 1.51 µg cm-2 of the layers deposited at pH 4. The water contact angle and AFM both confirmed the wettability properties and morphology of multilayers on the gold surface of QCM sensors. &lt;/P&gt;&lt;P&gt; Conclusion: The formation of the multilayer films on the gold surface by the layer-by-layer deposition technique of the negatively charged microgels and the oppositely charged PEI can be achieved. The controllable multilayer formation can be attributed to the size difference, changes in the hydrophilic property and surface charge density of microgels responsive to the external temperature and pH.&lt;/P&gt;

Titrimetric and Spectrophotometric Assay of Pantoprazole in Pharmaceuticals Using Permanganate

Titrimetric and spectrophotometric assay of pantoprazole sodium (PPS) using permanganate as the oxidimetric reagent is described. In titrimetry, PPS is treated with a measured excess of permanganate in H2SO4 medium followed by the determination of unreacted oxidant by back titrating with a standard iron(II) solution. Spectrophotometry involves addition of a known excess of permanganate to PPS in H2SO4 medium followed by the measurement of absorbance of the residual permanganate at 545 nm. In both the methods, the amount of permanganate reacted corresponds to the PPS content. Experimental conditions that provide wide linear range, maximum sensitivity and selectivity, and accuracy and precisions have been optimized. In titrimetry, the calculations are based on a 1:1 (PPS : KMnO4) reaction stoichiometry and the method is applicable over 1.0-7.0 mg range. In spectrophotometry, Beer’s law is obeyed over the concentration range 15.0-150.0 µg mL-1. The linear regression equation of the calibration graph is A = 0.78 + 0.005 C with a regression coefficient (r) of 0.9982 (n = 11). The apparent molar absorptivity is calculated to be 2.213 × 103 l mol-1cm-1 and the Sandell sensitivity is 0.1954 µg cm-2. The limits of detection (LOD) and quantification (LOQ) calculated as per the ICH guidelines are 0.73 and 2.21 µg mL-1, respectively. Accuracy and precision of the assays were determined by computing the intra-day and inter-day variations at three different levels of PPS; the intra-day and inter-day RSD was &lt; 3.09 % and the accuracy was better than 3.5 %. The methods were successfully applied to the determination of PPS in three different brands of tablets with good accuracy and precision, and without detectable interference by excipients. The accuracy was further ascertained by placebo blank and synthetic mixture analyses and also by recovery experiments via standard-addition procedure.

Rapid and Sensitive Spectrophotometric Method for the Determination of the Trace Amount of Thallium (III) in Water and Urine Samples by New Oxidative Coupling Reaction

A very simple, sensitive and fairly selective direct spectrophotometric method is presented for the rapid determination of thallium(III) at trace level. The method is based on the oxidation of 2-hydrazono-3-methyl-2,3-dihydrobenzo[d]thiazole hydrochloride (MBTH) by thallium(III) in phosphoric acid medium to form a diazoniumcation, which couples immediately with 10,11-dihydro-5Hdibenzo[b,f]azepine (IDB) at room temperature giving a blue colored species having a maximum absorption at 660 nm. The reaction conditions and other important analytical parameters were optimized.The calibration curve was found to be linear over the range of 0.1-4 μg/mL with molar absorptivity of 4.5 × 104 L mol- cm-1 and Sandell’s sensitivity of 0.00454 μg cm-2. The relative standard deviation and limit of detection have been found to be 0.58% and 0.0147 μg/mL respectively. Almost all common anions and cations are found notto interfering in matrix level of the analytical process. The method has been successfully applied for the determination of thallium(III) in synthetic standard mixtures, water and human urine samples. The performance of proposed method was evaluated in terms of student’s t-test and variance ratio F-test, to find out the significance of proposed method over the reported methods.&#x0D; &#x0D;

Spectrophotometric Determination of Citalopram Hydrobromide in Pharmaceuticals

Simple, rapid and sensitive methods are described for the spectrophotometric determination of citalopram hydrobromide (CIT) in pharmaceuticals. The method A is based on the oxidation of citalopram by a known excess of bromate-bromide mixture in hydrochloric acid medium, reduction of the residual oxidant by a fixed amount of iron(II) and the formation of iron(III)-thiocyanate-complex which is measured at 480 nm. In the method B, 1,10-phenanthroline is used as a complexing agent and the formation of iron(II)-1,10-phenanthroline, which is measured at 510 nm. The system obeys Beer’s law in the concentration range of 1.0-7.0 μg mL-1 of CIT for method A and 0.6-6.2 μg mL-1 of CIT for method B. No interference observed from common pharmaceutical adjuvants. Both methods are equally precise as shown by the relative standard deviation values less than 2%. The apparent molar absorptivities and Sandell’s sensitivity for method A and B are found to be 2.10x104 L mol-1 cm-1, 0.019 μg cm-2 , 7.30x104 L mol-1 cm-1 and 5.5x10-3 μg cm-2, respectively. The methods have been successfully applied to the determination of citalopram hydrobromide in pure and dosage forms.

Sensitive and Selective Extractive Spectrophotometric Method for the Determination of Hydroxyzine Dihydrochloride in Pharmaceuticals

Hydroxyzine dihydrochloride (HDH), a piperazine H1-receptor antagonist and antihistamine, is a rapid acting anxiolytic used principally as an anti-emetic. A sensitive, selective, and precise and accurate spectrophotometric method based on the formation of an ion-pair with orange II (ORG II) as ion-pair complexing agent was developed and validated for the determination of HDH in pharmaceuticals. The chloroform-extractable ion-pair complex exhibited an absorption maximum at 480 nm. Optimization of different experimental conditions is described. Beer’s law is obeyed in the range of 1.5-15 μg mL-1 with an apparent molar absorptivity value of 2.07 x 104 L mol-1 cm-1 and Sandell’s sensitivity value of 0.0216 μg cm-2. The limit of detection (LOD) and limit of quantification (LOQ) are 0.14 and 0.41 μg mL-1, respectively. A Job’s plot of absorbance versus molar ratio of HDH to ORG II indicated (1:2) stoichiometric ratio. Within- and between-day relative standard deviations at three different concentration levels were &lt; 3%. The developed method was successfully applied to commercial tablets. The results obtained were in good agreement with those obtained using the official method.&#x0D; No interference was encountered from co-formulated substances.&#x0D; Recoveries were 96-109 %.