A simple and safe approach for simultaneous spectrophotometric determination of nitroglycerin and nitrocellulose in double base solid propellants.

An accurate, simple and safe method was developed for simultaneous determination of nitroglycerine (NG) and nitrocellulose (NC) in double base solid propellants (DB propellants). The proposed method is based on alkaline hydrolysis of NG and NC, and followed by colored reaction of released nitrite ion with p-nitroaniline in the presence of diphenylamine in acidic media and produce azo dye. The absorbance of the azo dye was measured at 534 nm. Two sets of reaction conditions were developed. In the first set, at room temperature, only NG was hydrolyzed and calibration curve obtained. In the second set, at 60 â„ƒ, NG and NC were hydrolyzed simultaneously. Based on obtained amount for the NG at room temperature, and total amount of NG and NC at 60 â„ƒ, the amount of NC was determined by using stoichiometric equations. The calibration curve was linear over the concentration ranges of 0.2-5.0, 0.5-10 µg mL-1 for NG and NC, respectively. The proposed method was successfully applied for the determination of NG and NC in DB propellants with good recoveries ranged from 99 to 101%, and RSD less than 2.0%. The method statistically compared based on t- and F-tests with those obtained in according to military standard method (MIL-STD-286). The results showed that the proposed method offers an accuracy and reliable approach for the determination of these compounds in DB propellants, and can be suggested as a routine method in military quality control laboratories.

Miniaturized matrix solid-phase dispersion based on deep eutectic solvent and carbon nitride associated with high-performance liquid chromatography: A new feasibility for extraction and determination of trace nitrotoluene pollutants in soil samples.

In this research, a miniaturized version of matrix solid phase dispersion (MSPD) method was developed for successful extraction of five nitrotoluenes from soil samples. The terpene based deep eutectic solvent (DES) composed of borneol and DL-menthol was used simultaneously as extraction solvent and dispersing liquid. Graphitic-carbon nitride (g-C3N4) as sorbent was prepared by pyrolysis of melamine at a muffle furnace. The MSPD mixture was obtained by grinding soil, DES, and g-C3N4. Minimum amount of acetonitrile was used in the elution step. Some experimental variables including type and volume of DES, type of dispersant, mass ratio of dispersant to sample, volume of elution solvent, grinding time, and ultrasonication time were evaluated. Analysis of extracted samples was performed by high performance liquid chromatography-ultra violet detection. Under the optimized conditions; the limits of detection were achieved in the range of 0.12-0.33 µg g-1, and the relative standard deviations were equal to or lower than 9.3%. The extraction recoveries were ranged from 78 to 96%. This straightforward and fast method is effective for environmentally friendly extraction of nitrotoluenes from soil samples.

A new approach for separation and recovery of betaine from beet molasses based on cloud point extraction technique.

The aim of this work was to explore the possibility of the application of cloud point extraction (CPE) method in micelle media to recovery betaine from beet molasses. Response surface method was employed to assess the effects of surfactant concentration, molasses concentration, incubation time, pH, electrolyte concentration, mixing time, and surfactant type on efficiency of betaine recovery from beet molasses. Also, a mathematical model was developed to predict the effect of each variable and their interactions on the efficiency of betaine recovery. The model showed that best surfactant was Triton X-114 and under the optimum conditions, betaine recovery from beet molasses was achieved up to 80% when three CPE steps with total of 1.5% (w/v) of surfactant were used. Subsequently, betaine was recovered nearly 100% from surfactant rich phase after adjusting pH at 2.5 and re-incubation at 40 °C. The results showed that the proposed method is suitable for extraction of betaine from beet molasses.

Ferrofluid of magnetic clay and menthol based deep eutectic solvent: Application in directly suspended droplet microextraction for enrichment of some emerging contaminant explosives in water and soil samples.

In this work, for the first time, ferrofluid of magnetic montmorillonite nanoclay and deep eutectic solvent was prepared and coupled with directly suspended droplet microextraction. Incorporation of ferrofluid in a miniaturized sample preparation technique resulted in achieving high extraction efficiency while developing a green analytical method. The prepared ferrofluid has strong sorbing properties and hydrophobic characteristics. In this method, a micro-droplet of ferrofluid was suspended into the vortex of a stirring aqueous solution and after completing the extraction process, was easily separated from the solution by a magnetic rod without any operational problems. The predominant experimental variables affecting the extraction efficiency of explosives were evaluated. Under optimal conditions, the limits of detection were in the range 0.22-0.91 µg L-1. The enrichment factors were between 23 and 93 and the relative standard deviations were <10%. The relative recoveries were ranged from 88 to 104%. This method was successfully applied for the extraction and preconcentration of explosives in water and soil samples, followed their determination by high performance liquid chromatography with ultraviolet detection (HPLC-UV).

Deep eutectic solvent based magnetic nanofluid in the development of stir bar sorptive dispersive microextraction: An efficient hyphenated sample preparation for ultra-trace nitroaromatic explosives extraction in wastewater.

A deep eutectic solvent based magnetic nanofluid was coupled with stir bar sorptive dispersive microextraction as a hyphenated sample preparation technique. The neodymium core magnetic stir bar was coated physically with nanofluid of magnetic carbon nanotube nanocomposites and deep eutectic solvents. The prepared nanofluid has magnetic and strong sorbing properties and is compatible with gas chromatography. In this nanofluid, the deep eutectic solvent acts simultaneously as both carrier and stabilizer for magnetic nanotubes. The predominant experimental variables affecting the extraction efficiency of nitroaromatic compounds were evaluated. Under the optimized conditions, the limit of detection and enrichment factor were in the range of 0.2-4.9 ng/L and 852-1480, respectively. The relative standard deviations were between 5.6 and 10.2% (n = 6). Method validation was performed by both spiking-recovery method and comparison of results with other methods. Finally, the proposed method was successfully applied for the extraction and pre-concentration of nitroaromatic explosives in water samples, followed by determination by gas chromatography with micro-electron capture detection.

Degradation of nitro-aromatic explosives using recyclable magnetic photocatalyst: Catalyst synthesis and process optimization.

In this research, degradation of P-Nitrophenol (PNP) as a model nitro-aromatic compound was carried out by photocatalytic process using magnetic Titania nano particles (MTNPs). The recyclable MTNPs were synthesized with average diameter of 22nm and a narrow size distribution. The process was modeled and optimized by a second order reduced polynomial model. Based on the model prediction, the process can be degraded PNP up to 90% under the optimum conditions of the initial pH=4, [PNP]=15mgL-1, [MTNPs]=85mgL-1, and T=25°C. PNP mineralization was obtained 69%, at the optimum condition after 120min of the process. The process kinetic was well fitted by pseudo first order kinetic model and electrical energy consumption of the process was obtained about 177.8kWh/m3. Furthermore, the effect of sodium sulfite, sodium sulfate and sodium nitrite on the photocatalytic degradation process was assessed. The results showed that sulfite or sulfate ions decrease and nitrite ions increase the process efficiency. Also, a sample of redwater as a nitro-aromatic effluent was treated.

Design and fabrication of optical chemical sensor for detection of nitroaromatic explosives based on fluorescence quenching of phenol red immobilized poly(vinyl alcohol) membrane.

The present study developed a new optical chemical sensor for detection of nitroaromatic explosives in liquid phase. The method is based on the fluorescence quenching of phenol red as fluorophore in a poly(vinyl alcohol) (PVA) membrane in the presence of nitroaromatic explosives as quenchers, e.g., 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), 4-nitrotoluene (4-NT), 2,4,6-trinitrobenzene (TNB), and nitrobenzene (NB). For chemical immobilization of phenol red in PVA, phenol red reacted with formaldehyde to produce hydroxymethyl groups and then attached to PVA membrane through the hydroxymethyl groups. The optical sensor showed strong quenching of nitroaromatic explosives. A Stern-Volmer graph for each explosive was constructed and showed that the range of concentration from 5.0 × 10(-6) to 2.5 × 10(-4) mol L(-1) was linear for each explosive and sensitivity varied as TNB >TNT>2,4-DNT>NB>4-NT. The response time of the sensor was within 1 min. The proposed sensor showed good reversibility and reproducibility.

Selective cloud point extraction for the spectrophotometric determination of cetylpyridinium chloride in pharmaceutical formulations.

In this work, we developed a simple and selective method for separation and spectrophotometric determination of trace amounts of cetylpyridinium chloride (CPC) in pharmaceutical products using cloud point extraction (CPE) technique. The method is based on cloud point extraction of the CPC in alkali conditions using of nonionic surfactant Triton X-114. Under optimal conditions, the calibration graph was linear in the range of 0.50-30 µg/ mL of CPC with r=0.9993 (n=10). Average recoveries for spiked samples were determined to be between 95-104%. The relative standard deviation (RSD) for 5.0 µg/mL of CPC was 1.86 % (n=10). Also, the use of micellar extraction for extracting CPC was enhanced the molar absorptivity (ε) from 1.83×10(3) L/mol.cm in aqueous solution to 1.539×10(4) L/mol.cm in surfactant-rich phase. The proposed method was applied for the determination of CPC in a commercial mouth washer product.

Development of a dispersive liquid-liquid microextraction method for spectrophotometric determination of barbituric acid in pharmaceutical formulation and biological samples.

In this paper, a novel and simple method for the determination of trace amounts of barbituric acid in water and biological samples was developed by using dispersive liquid-liquid microextraction (DLLME) techniques combined with spectrophotometric analysis. The procedure is based on color reaction of barbituric acid with p-dimethylaminobenzaldehyde and extraction of the color product using the DLLME technique. Some important parameters such as reaction conditions and the type and volume of extraction and dispersive solvents as well as the extraction time were investigated and optimized in detail. Under the optimum conditions, the calibration graphs were linear over the range of 5.0 to 200 ng ml(-1) with limit of detection of 2.0 ng ml(-1). Relative standard deviation for five replicate determinations of barbituric acid at 50 ng ml(-1) concentration level was calculated to be 1.64%. Average recoveries for spiked samples were determined to be between 94% and 105%. The proposed method was applied for the determination of barbituric acid in pharmaceutical formulation and biological samples.

Cloud point formation based on mixed micelle in the presence of electrolyte for extraction, preconcentration, and spectrophotometric determination of trace amounts of hydrazine in water and biological samples.

A cloud point extraction process using mixed micelle of the anionic surfactant sodium dodecyl sulfate and the nonionic surfactant Triton X-114 to extract hydrazine from aqueous solutions was investigated. The method is based on the condensation reaction of hydrazine with p-(dimethylamino)benzaldehyde, azine formation, and mixed micelle-mediated extraction of azine in the presence of NaCl electrolyte as an inducing phase separation. An azine product was concentrated in surfactant-rich phase after separation. The optimal extraction and reaction conditions (e.g., surfactant, reagent and electrolyte concentrations, and centrifuge time) were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 0.50-110ngml(-1) of hydrazine and the detection limit of the method is 0.08ngml(-1). The interference effect of some cations, anions, and organic compounds was also tested. The method was successfully applied to the determination of hydrazine in water and biological samples.

Cloud-point formation based on mixed micelles for the extraction, preconcentration and spectrophotometric determination of trace amounts of beryllium in water samples.

A cloud-point extraction process using a mixed micelle of the cationic surfactant cetyl pyridinium chloride (CPC) and non-ionic surfactant Triton X-114 to extract beryllium from aqueous solutions was investigated. The method is based on the color reaction of beryllium with Chrome Azurol S (CAS) in acetate buffer and the mixed micelle-mediated extraction of the complex. This complex was concentrated in a surfactant-rich phase after separation. The optimal extraction and reaction conditions (e.g. pH, reagent and surfactant concentrations, temperature, incubation and centrifuge times) were evaluated and optimized. Under the optimized conditions, the analytical characteristics of the method (e.g. limit of detection, linear range and preconcentration factor) were obtained. Linearity was obeyed in the range of 0.30 - 18 ng mL(-1) of beryllium and the detection limit of the method was 0.05 ng mL(-1). The interference effect of some cations and anions was also studied. The proposed method was successfully applied to the determination of beryllium in real water samples.

Simultaneous kinetic spectrophotometric determination of cyanide and thiocyanate using the partial least squares (PLS) regression.

The partial least squares (PLS-1) calibration model based on spectrophotometric measurement, for the simultaneous determination of CN(-) and SCN(-) ions is described. The method is based on the difference in the rate of the reaction between CN(-) and SCN(-) ions with chloramine-T in a pH 4.0 buffer solution and at 30 degrees C. The produced cyanogen chloride (CNCl) reacts with pyridine and the product condenses with barbituric acid and forms a final colored product. The absorption kinetic profiles of the solutions were monitored by measuring absorbance at 578nm in the time range 20-180s after initiation of the reaction with 2s intervals. The experimental calibration matrix for partial least squares (PLS-1) calibration was designed with 31 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 10.0-900.0 and 50.0-1200.0ng mL(-1) for CN(-) and SCN(-) ions, respectively. The proposed method was successfully applied to the simultaneous determination of cyanide and thiocyanate in water samples.

Simultaneous spectrophotometric determination of paracetamol and salicylamide in human serum and pharmaceutical formulations by a differential kinetic method.

A rapid, simple, and sensitive differential kinetic method is presented for the determinations of acetaminophen (also known as paracetamol) and salicylamide. The method is based on their oxidation reaction by Fe3+ ion in the presence of 1, 10-phenanthroline as indicator. The reactions can be monitored spectrophotometrically by measuring the increase in the absorbance of the solution at 510 nm. Two times were selected one in which only paracetamol is oxidized by Fe3+ ion and the other in which both drugs are oxidized by Fe3+ ion. The data were evaluated by the proportional equations method. The method allowed the simultaneous determination of paracetamol and salicylamide at concentrations between 0.5-20 and 1-40 microg/mL with relative standard deviations of 3.47 and 2.58%, respectively. The method was applied to the simultaneous determination of paracetamol and salicylamide in human serum and pharmaceutical formulations.

Simultaneous kinetic-spectrophotometric determination of hydrazine and acetylhydrazine in micellar media using the H-point standard addition method.

The H-point standard addition method (HPSAM), based on a spectrophotometric measurement for the simultaneous determination of hydrazine and acetylhydrazine, is described. This method is based on the difference between the rates of their reactions with N,N-dimethylaminobenzaldehyde (DAB) in the presence of sodium dodecyl sulfate (SDS) in acidic media. The results showed that hydrazine and acetylhydrazine could be determined simultaneously in the range of 0.020 - 0.70 and 0.20 - 5.0 mg L(-1), respectively. Under the working conditions, the proposed method was successfully applied to the simultaneous determination of hydrazine and acetylhydrazine in several synthetic mixtures and plasma and water samples.

Simultaneous spectrophotometric determination of hydrazine and phenylhydrazine based on their condensation reactions with different aromatic aldehydes in micellar media using H-point standard addition method.

H-point standard addition method (HPSAM) was applied to the simultaneous determination of hydrazine and phenylhydrazine. The method is based on the hydrazone formation reactions of hydrazine and phenylhydrazine in the presence of micellar sodium dodecyl sulfate (SDS). Mixed reagents of p-(dimethylamino)benzaldehyde (DAB) and p-nitrobenzaldehyde (NB) was used as selective chromogenic reagents for hydrazine and phenylhydrazine. Hydrazine and phenylhydrazine can be determined simultaneously in the range 0.020-0.50 and 0.20-10.0mugml(-1), respectively. The results allowed that simultaneous determination could be performed with the ratio 1:500 to 1:10 hydrazine-phenylhydrazine. Under working conditions, the proposed method was successfully applied to the simultaneous determination of hydrazine and phenylhydrazine in several synthetic mixtures and plasma and water samples.

Simultaneous kinetic determination of beryllium and aluminium by spectrophotometric H-point standard addition method.

The H-point standard addition method (HPSAM), based on spectrophotometric measurements for simultaneous determination of beryllium and aluminium, is described. This method is based on the difference between their rates of reactions with Chrome Azurol S (CAS) in cetyltrimethylammonium bromide (CTAB) micellar media. The results showed that beryllium and aluminium could be determined simultaneously in the ranges of 10-200 and 10-300 ng mL(-1), respectively. Under working conditions, the proposed method was successfully applied to the simultaneous determination of beryllium and aluminium in environmental, geochemical and alloy samples.

Simultaneous spectrophotometric determination of Bi(III) and Sb(III) based on their complexes with iodide in acidic media using the H-point standard addition method and first-derivative spectrophotometry.

The H-point standard addition method (HPSAM) was applied to the simultaneous determination of Bi(III) and Sb(III). This method is based on the difference in the absorbance of complexes of Bi(III) and Sb(III) with iodide in acidic media in different wavelength pairs. The results showed that Bi(III) and Sb(III) can be determined simultaneously with concentration ratios of 15:1 to 1:20. First-derivative spectrophotometry was also used for the simultaneous determination of Bi(III) and Sb(III) based on their complexes with iodide. The proposed methods were successfully applied to the simultaneous determination of Bi(III) and Sb(III) in synthetic samples.

Simultaneous kinetic-spectrophotometric determination of periodate-bromate and iodate-bromate mixtures using the H-point standard addition method.

The H-point standard addition method (HPSAM), based on spectrophotometric measurement, for simultaneous determination of periodate-bromate and iodate-bromate mixtures is described. This method is based on the difference between the rates of their reactions with iodide in acidic media. The results showed that simultaneous determinations could be performed with the ratio 1:15-12:1 for periodate-bromate and 15:1-1:15 for iodate-bromate. The proposed method was successfully applied to the simultaneous determination of periodate-bromate and iodate-bromate in water and synthetic samples.