Synergistic effects of sodium lauroyl sarcosinate and glutamic acid in inhibition assembly against copper corrosion in acidic solution

© 2015 Elsevier B.V. All rights reserved. A self-assembled multilayer (SAM) from sodium lauroyl sarcosinate (SLS) and glutamic acid (GLU) is formed on copper surface. Its inhibition ability against copper corrosion is examined by electrochemical analysis and weight loss test. In comparison to SAM formed by just SLS or GLU, a synergistic effect is observed when the coexistence of SLS and GLU in SAM. The SLS/GLU SAM has an acicular multilayer structure, and SAM prepared under the condition of 5 mM SLS and 1 mM GLU shows the best protection efficiency. PM6 calculation reveals that the synergistic effect stems from interactions between SLS, GLU and cupric ions.

Fluid loss as a quick method to evaluate the hydraulic conductivity of geosynthetic clay liners under acidic conditions

This study investigates the performance of bentonite components of geosynthetic clay liners (GCLs) when exposed to aggressive leachates using the fluid loss test and provides a possible quick method for estimating the effect of acidic conditions on hydraulic conductivity. Fluid loss generally increases with increasing acid concentrations. Hydraulic conductivity values back-calculated from the fluid loss tests (kFL) are compared with the values measured using a flexible-wall permeameter (kTri).Generally, the predicted hydraulic conductivity values are conservative (kFL/kTri > 1) under water and low acid concentrations(≤0.015 mol/L). However, the back-calculated hydraulic conductivity is shown to be nonconservative (kFL/kTri < 1) at high acid concentrations (≥0.125 mol/L).

Acidic potassium permanganate chemiluminescence for the determination of antioxidant potential in three cultivars of Ocimum basilicum

Ocimum basilicum, a member of the family Lamiaceae, is a rich source of polyphenolics that have antioxidant properties. The present study describes the development and application of an online HPLC-coupled acidic potassium permanganate chemiluminescence assay for the qualitative and quantitative assessment of antioxidants in three cultivars of O. basilicum grown under greenhouse conditions. The chemiluminescence based assay was found to be a sensitive and efficient method for assessment of total and individual compound antioxidant potential. Leaves, flowers and roots were found to be rich reserves of the antioxidant compounds which showed intense chemiluminescence signals. The polyphenolics such as rosmarinic, chicoric, caffeic, p-coumaric, m-coumaric and ferulic acids showed antioxidant activity. Further, rosmarinic acid was found to be the major antioxidant component in water-ethanol extracts. The highest levels of rosmarinic acid was found in the leaves and roots of cultivars "holy green" (14.37; 11.52 mM/100 g DW respectively) followed by "red rubin" (10.02; 10.75 mM/100 g DW respectively) and "subja" (6.59; 4.97 mM/100 g DW respectively). The sensitivity, efficiency and ease of use of the chemiluminescence based assay should now be considered for its use as a primary method for the identification and quantification of antioxidants in plant extracts.

Design of LabVIEW® - based software for the control of sequential injection analysis instrumentation for the determination of morphine.

LabVIEW^®-based software for the automation of a sequential injection analysis instrument for the determination of morphine is presented. Detection was based on its chemiluminescence reaction with acidic potassium permanganate in the presence of sodium polyphosphate. The calibration function approximated linearity (range 5 × 10 ^-10 to 5 × 10 ^-6M) with a line of best fit of y = 1.05 x + 8.9164 (R² = 0.9959), where y is the log₁₀ signal (mV) and x is the log₁₀ morphine concentration (M). Precision, as measured by relative standard deviation, was 0.7% for five replicate analyses of morphine standard (5 × 10^-8_M). The limit of detection (3 σ) was determined as 5 × 10^-11 M morphine.

Selective determination of amino acids using flow injection analysis coupled with chemiluminescence detection

The determination of the amino acids proline, histidine, tyrosine, arginine, phenylalanine and tryptophan using flow injection analysis (FIA) with chemiluminescence detection is described. Proline was the only amino acid to exhibit chemiluminescence with the tris(2,2-bipyridyl)ruthenium(III) reaction at pH 10. While, histidine was found to selectively enhance the reaction of luminol with Mn(II) salts in a basic medium. Acidic potassium permanganate chemiluminescence was able to selectively determine tyrosine at pH 6.75. Low pressure separations using a C18 guard column allowed the simultaneous determination of tyrosine and tryptophan or phenylalanine and tryptophan with acidic potassium permanganate and copper(II)–amino acid–hydrogen peroxide chemiluminescence, respectively. Precision for each method was less than 3.9% (R.S.D.) for five replicates of a standard (1×10−5 M) and the detection limits ranged between 4×10−9 and 7×10−6 M. Preliminary investigations revealed that the methodology developed was able to selectively determine the individual amino acids in an equimolar mixture of the 20 naturally occurring amino acids.

The determination of urea in soil extracts and related samples - a review

Although the dominant methods for the determination of urea in clinical applications incorporate selective enzymatic hydrolysis of urea, the determination of urea in soil extracts is complicated by the presence of urease inhibitors. The spectrophotometric determination of urea with an acidic solution diacetyl monoxime and semicarbazide is a viable option but traditional manual procedures are time-consuming. New variations on these procedures, based on microplates or flow-injection analysis methodologies, allow a far greater number of samples to be analysed with high precision and sensitivity.

Determination of selected neurotransmitter metabolites using monolithic column chromatography coupled with chemiluminescence detection

The oxidation of selected clinically important neurotransmitter metabolites with acidic potassium permanganate in the presence of polyphosphates evokes chemiluminescence of sufficient intensity to enable the sensitive determination of these species. Limits of detection for 5-hydroxyindole-3-acetic acid (5-HIAA), vanilmandelic acid (VMA; α,4-dihydroxy-3-methoxybenzeneacetic acid), 4-hydroxy-3-methoxyphenylglycol (MHPG), homovanillic acid (HVA, 4-hydroxy-3-methoxyphenylacetic acid) and 3,4-dihydroxyphenylacetic acid (DOPAC) were between 5 × 10⁻⁹ and 4 × 10⁻⁸ M, using flow-injection analysis methodology. In addition, we demonstrate the rapid determination of homovanillic acid and 5-hydroxyindole-3-acetic acid in human urine – without the need for extraction procedures – using monolithic column chromatography with chemiluminescence detection.

New light from an old reagent: chemiluminescence from the reaction of potassium permanganate with sodium borohydride

When aqueous sodium borohydride (50 mM) is added to a solution of potassium permanganate (1mM, in sodium hexametaphosphate) at acidic pH, bright red-orange emission is easily visible in a darkened room. This chemiluminescence emission is due to an excited state of manganese (II) that undergoes solution phase phosphorescence and provides an excellent opportunity for students to explore the relationship between the initial oxidation state of the manganese and the likelihood of luminescence. Not surprisingly Mn(VII), Mn(IV) and Mn(III) all give rise to chemiluminescence where as Mn(II) fails to react.

The effects of dye dopants on the conductivity and optical absorption properties of polypyrrole

Ten anionic compounds, including four acidic dyes, were used to dope polypyrrole powder. The effects of the dopants on density, optical absorption and conductivity of the polypyrroles were studied. The presence of the dopant in the conducting polymer matrix was verified by ATR-FTIR spectroscopy. Density function theory (DFT) simulation was used to understand the effect of the dopants on the solid structure, optical absorption and energy band structures. Anthraquinone-2-sulfonic acid-doped polypyrrole yielded the highest conductivity. The dye-doped polypyrrole showed an enhancement in its UV–vis optical absorption.

A rapid test for heroin (3,6-Diacetylmorphine) based on two chemiluminescence reactions

A rapid method for screening drug seizure samples for 3,6-diacetylmorphine (heroin), which consists of a simple hydrolysis procedure and flow-injection analysis with two chemiluminescence reagents, is described. Before hydrolysis, 3,6-diacetylmorphine evokes an intense response with a tris(2,2'-bipyridyl)ruthenium(III) reagent (prepared by dissolving the perchlorate salt in acetonitrile), and a relatively weak chemiluminescence response with a second reagent: potassium permanganate in an aqueous acidic polyphosphate solution. However, the permanganate reagent is extremely sensitive toward the hydrolysis products of 3,6-diacetylmorphine (i.e., 6-monoacetylmorphine and morphine). Some compounds commonly found in drug laboratories may cause false positives with tris(2,2'-bipyridyl)ruthenium(III), but do not produce the markedly increased response with the permanganate reagent after the hydrolysis procedure. The combination of these two tests therefore provides an effective presumptive test for the presence of 3,6-diacetylmorphine, which we have verified with 14 samples obtained from a forensic science laboratory.

The determination of morphine in the larvae of calliphora stygia using flow injection analysis and HPLC with chemiluminescence detection

Selective determination of morphine in the larvae of Calliphora stygia (Fabricius) (Diptera: Calliphoridae) using acidic potassium permanganate chemiluminescence detection coupled with flow injection analysis and high-performance liquid chromatography (HPLC) is described. Larvae of C. stygia were reared on minced meat substrates that had been spiked with varying concentrations of morphine. Morphine concentrations were chosen to reflect typical levels in human tissues from opiate overdose victims. After maturing on substrates, larvae were analyzed for the presence of morphine using chemiluminescence detection coupled to flow injection analysis and a rapid HPLC method. Analysis of the larval matrix by flow injection analysis with chemiluminescence detection indicated the presence of interferants capable of generating chemiluminescence. A rapid chromatographic separation with a monolithic column allowed selective determination of morphine in larvae using postcolumn chemiluminescence detection. Larvae of C. stygia reared on substrates containing morphine at concentrations of 500 and 1000 ng/g did not sequester morphine at detectable concentrations. Larvae reared on substrates containing morphine concentrations of 2500, 5000, and 10,000 ng/g tested positive for the drug at concentrations of 765, 2720, and 3010 ng/g, respectively.

Rapid determination of papaver somniferum alkaloids in process streams using monolithic column high-performance liquid chromatography with chemiluminescence detection

We have combined high-performance liquid chromatography (HPLC) separations using a monolithic column with acidic potassium permanganate and tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection in a rapid and highly sensitive method to monitor the process of extracting opiate alkaloids from Papaver somniferum. Due to the high flow rates allowed with the monolithic column and the inherent selectivity of the chemiluminescence reactions, the four predominant alkaloids – morphine, codeine, oripavine and thebaine – were determined in less than 2 min. The results obtained with numerous process samples compared favourable with those of the standard HPLC methodology. Limits of detection were 1 × 10⁻¹⁰ M, 5 × 10⁻¹⁰ M, 5 × 10⁻¹⁰ M and 1 × 10⁻⁹ M, for morphine, codeine, oripavine and thebaine, respectively.

Soluble manganese(IV) as a chemiluminescence reagent for the determination of opiate alkaloids, indoles and analytes of forensic Interest

We present the results of our investigations into the use of soluble manganese(IV) as a chemiluminescence reagent, which include a significantly faster method of preparation and a study on the effect of formaldehyde and orthophosphoric acid concentration on signal intensity. Chemiluminescence detection was applied to the determination of 16 analytes, including opiate alkaloids, indoles and analytes of forensic interest, using flow injection analysis methodology. The soluble manganese(IV) reagent was less selective than either acidic potassium permanganate or tris(2,2′-bipyridyl)ruthenium(III) and therefore provided a more universal chemiluminescence detection system for HPLC. A broad spectral distribution with a maximum at 730 ± 5 nm was observed for the reaction between the soluble manganese(IV) and a range of analytes, as well as the background emission from the reaction with the formaldehyde enhancer. This spectral distribution matches that reported for chemiluminescence reactions with acidic potassium permanganate, where a manganese(II) emitting species was elucidated. This provides further evidence that the emission evoked in reactions with soluble manganese(IV) also emanates from a manganese(II) species, and not bimolecular singlet oxygen as suggested by previous authors.

A hybrid FIA/HPLC system incorporating monolithic column chromatography

We have combined the generation of solvent gradients using milliGAT pumps, chromatographic separations with monolithic columns and chemiluminescence detection in an instrument manifold that approaches the automation and separation efficiency of HPLC, whilst maintaining the positive attributes of flow injection analysis (FIA), such as manifold versatility, speed of analysis and portability. As preliminary demonstrations of this hybrid FIA/HPLC system, we have determined six opiate alkaloids (morphine, pseudomorphine, codeine, oripavine, ethylmorphine and thebaine) and four biogenic amines (vanilmandelic acid, serotonin, 5-hydroxyindole-3-acetic acid and homovanillic acid) in human urine, using tris(2,2′-bipyridyl)ruthenium(III) and acidic potassium permanganate chemiluminescence detection.

Synthesis and fractionated crystallization of organic-inorganic hybrid composite materials from an amphiphilic polyethylene-block-poly (ethylene oxide) diblock copolymer

Mesostructurally ordered inorganic–organic hybrid composite materials were successfully synthesized by utilizing a low-molecular-weight amphiphilic polyethylene-block-poly(ethylene oxide) (PE–PEO) diblock copolymer as the directing agent. The hybrid composites were formed via the sol–gel reaction of inorganic precursor tetraethoxysilane (TEOS) in an acidic ethanol/water solution with various amounts of PE–PEO. In these composite materials, the hydrophobic PE block of the PE–PEO copolymer forms separate microphase on the nanoscales within the rigid matrix of silica network. The crystallization of the PE block is strictly restricted within the microphase by the rigid silica matrix and takes place through homogeneous nucleation under the nanoscale confinement environment.