Presence Of Cetylpyridinium Bromide Research Articles

Comparison between the interfacial and bulk rheology of sodium carboxymethylcellulose in the presence of cationic and non-ionic surfactants

The bulk and interfacial rheological behavior of concentrated solutions of Sodium carboxymethyl cellulose (NaCMC) has been investigated in presence of cationic surfactant Cetylpyridinium bromide (CPB) and nonionic surfactant Sorbitan monopalmitate (Span 40) having same hydrocarbon chain length with different head groups. At NaCMC concentrations between 1.5 wt% to 2.5 wt% the polymer solutions exhibit two regions, a dilatant (shear thickening) region at lower shear rates followed by a pseudoplastic (shear thinning) region at higher shear rates. Steady state bulk rheological experiments indicate that 1 wt% NaCMC as well as 1 wt% NaCMC with varying concentrations of Span 40 and CPB show non-Newtonian pseudoplastic behavior. Interfacial steady shear tests of 2D Langmuir monolayer of 1 wt% NaCMC at air-water interface show non-Newtonian pseudoplastic behavior, however the mixed films of the polymer in presence of CPB and Span 40 at the same interface exhibit two distinct shear thinning regions.

Water Vapor Adsorption-Desorption Behavior of Surfactant-Coated Starch Particles for Commercial Energy Wheels.

This study reports on the adsorption (dehumidification)–desorption (humidification) behavior of cetylpyridinium bromide (CPB) coated starch particles (SPs), denoted as SP-CPB, as a potential desiccant material for air-to-air energy exchangers. CPB is a cationic surfactant with antibacterial activity that can be used to modify the surface properties of SPs, especially at variable CPB loading levels (SP-CPB0.5, SP-CPB2.5, and SP-CPB5.0, where the numeric suffix represents the synthetic loading level of CPB in mM). The SP-CPB0.5 sample displayed optimal surface area and pore structure properties that was selected for water sorption isotherm studies at 25 °C. The CPB-coated SPs sample (SP-CPB0.5) showed an improved water vapor uptake capacity compared to unmodified starch (SPs) and other desiccant systems such as high amylose starch (HAS15) and silica gel (SG13). Single-step and cyclic water vapor sorption tests were conducted using a small-scale exchanger coated with SP-CPB0.5. The calculated latent effectiveness values obtained from direct measurements using cyclic tests (65.4 ± 2%) agree closely with the estimated latent effectiveness from single-step tests (64.6 ± 2%) at controlled operating conditions. Compared to HAS15- and SG13-coated exchangers, the SP-CPB0.5-coated exchanger performed much better at controlled operating conditions, along with improved longevity due to the CPB surface coating. The presence of CPB did not attenuate the uptake properties of native SPs. Latent effectiveness of SP-CPB0.5-coated exchanger was enhanced (5–30% higher) over that of the SG13- or HAS15-coated exchangers, according to the wheel angular speed. This study reports on a novel and sustainable SP-CPB0.5 material as a promising desiccant coating with tunable uptake and surface properties with potential utility in air-to-air energy exchangers for ventilation systems.

Determination of Allura Red in the Presence of Cetylpyridinium Bromide by Square-wave Adsorptive Stripping Voltammetry on a Glassy Carbon Electrode.

A simple method to determine Allura Red (AR) in cherry gelatin, chili sauce and strawberry juice by square-wave adsorptive stripping voltammetry (SWAdV) in the presence of cetylpyridinium bromide (CPB) is reported. Using a glassy carbon electrode (GCE), Amaranth (AM), Ponceau 4R (P-4R) and AR were oxidized to very close potential values in medium acid pH 3.0 with phosphate buffer solution (PBS), making selective AR detection impossible. Under these conditions AM, P-4R and AR were oxidized at 0.80, 0.77 and 0.81 V, respectively. When small amounts of CPB were added, an AR-CPB aggregate was formed. This change displaced the oxidation almost 0.14 V in the direction of the most positive potential and increased the current almost 50%, while AM and P-4R were oxidized at almost the same potential. Under these conditions, the selective determination of AR in food was possible. Detection limit was 0.032 μmol L-1. Finally, the method was successfully applied to the determination of AR in these foods.

Ratiometric Interactions of Anionic Surfactants with Calf Thymus DNA Bound Cationic Surfactants: Study II

AbstractCationic surfactant cetyltrimethylammonium bromide (CTAB) and cetylpyridinium bromide (CPB) bind to the calf thymus DNA (ct‐DNA) like anionic biopolymers electrostatically, and establish equilibrium in aqueous medium at pH 7. At low concentration, ct‐DNA does not interact with anionic surfactants, sodium dodecylsulfate (SDS) and sodium dodecylbenzylsulfonate (SDBS). However, in the ground state, anionic surfactant is found to clearly establish equilibrium with ct‐DNA‐bound cationic surfactant whereby the same surfactant–DNA isosbestic point reappears. We herein report a detail ratiometric binding of CPB with ct‐DNA, and interaction of anionic SDBS with DNA‐bound CPB in comparison with the combined ct‐DNA–CTAB–SDS system. Compaction of ct‐DNA in presence of CPB and its decompaction using anionic SDBS is also studied in comparison with CTAB–SDS combination. The techniques used are tensiometry, spectrophotometry, viscometry, cyclic voltammetry, circular dichroism, isothermal titration calorimetry, and density functional theory (DFT)‐based computational calculations. The size and surface charge density of the surfactant headgroups and the phosphate group in DNA have a contributing role in the DNA compaction–decompaction phenomenon.

Determination of arsenic in the presence of copper by adsorptive stripping voltammetry using pyrrolidine dithiocarbamate or diethyl dithiophosphate as chelating-adsorbent agents. Effect of CPB on the sensitivity of the method

A sensitive method for the determination of arsenic based on the formation of their complexes with ammonium pyrrolidine dithiocarbamate (APDTC) or ammonium diethyl dithiophosphate (ADDTP) prior to the formation of the intermetallic compound (CuxAsy) whose reduction is directly related to As(III) concentration is presented. The effects of various operational parameters such as HCl, Cu(II) and ligand concentrations (CHCl, CCu(II), CAPDTC, CADDTP); accumulation potential and time (Eads, tads) were optimized. The optimum experimental conditions chosen were CHCl: 1.25 and 2.00molL−1; CCu(II): 60 and 40mgL−1; Eads: −0.40 and −0.30V; and tads: 80 and 60s for APDTC and ADDTP, respectively. On the other hand, the optimum ligand concentrations were 0.20 and 1.50μmolL−1 for APDTC and ADDTP, respectively (CAs(III): 15.00μgL−1). It was found that in the presence of cetylpyridinium bromide (CPB) the peak current of the arsenic signal is higher than in the absence of this cationic surfactant, and these values attained a maximum at 7.8 and 2.6μmolL−1 for APDTC and ADDTP, respectively. Under these conditions, the reduction signals of CuxAsy are found at −0.82 V and −0.64 V for APDTC and ADDTP, respectively. The relationship between peak current and As(III) concentration is linear in the 0.50–3.00μgL−1 (APDTC) and 2.50–15.00μgL−1 (ADDTP) range. The detection limits (DLs) were found to be 0.08 and 0.27μgL−1 for APDTC and ADDTP, respectively (tads: 30s). The relative standard deviations for 30 replicate measurements at the lowest level of each method, 0.10μgL−1 for APDTC and 2.00μgL−1 for ADDTP, were 3.9 and 25.2%, respectively. The results showed that the presence of ligand plays an important role, improving the signal current of As(III) and preventing the oxidation of As(III) to As(V), achieving the best sensitivity and repeatability when APDTC was used. Finally, the method was validated using synthetic drinking water spiked with As(III) and was applied to the determination of total arsenic in water from the Loa River (North of Chile) with satisfactory results.

Characterization of cetylpyridinium bromide-modified montmorillonite incorporated cellulose acetate nanocomposite films

An organoclay (MMT–CPB) based on montmorillonite (MMT) and cetylpyridinium bromide (CPB) was synthesized by a cationic interchange process. The presence of CPB into the clay structure was evidenced by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA). This organoclay was then used to prepare cellulose acetate (CA) nanocomposite films with different content of this nanofiller (2.5–7.5 wt%) through a casting technique. All nanocomposites were characterized by XRD, FTIR, differential scanning calorimetry, TGA, optical and mechanical analyses. So, nanocomposites were characterized by the intercalation of CA into the clay structure. Organoclay content did not affect the glass transition (T g) and melting temperature (T m) of CA; however, thermal stability of CA was slightly improved with the presence of the organoclay. Therefore, optical and mechanical properties were significantly affected with the increase of the organoclay content into the CA. On the other hand, electrical conductivity (EC) measurement was performed to evaluate the release of cetylpyridinium from the CA nanocomposites to an aqueous medium. An important increase of the EC over time was observed. Therefore, the EC values were dependent on the content of MMT–CPB in the CA nanocomposites. However, a likely degradation of cellulose acetate in the aqueous medium affected the surfactant quantification.

A method of high sensitivity and in situ determination of trace cobalt(II) in water samples with salicyl fluorone.

Based on the sensitive reaction of Co(II) and salicyl fluorone with the presence of cetylpyridinium bromide in basic solution, a new method of flow injection micelle-solubilized spectrophotometry was developed for the determination of cobalt. The reaction was monitored for the absorbance of Co(II) at 540 nm. The reagents, flow injection variables and effects of foreign ions were investigated and the optimum conditions were established. At the optimum test conditions, the developed method provides a linearity range of 3-40 μg L(-1) with a detection limit of 0.1 μg L(-1) at about 60 h(-1) sampling frequency. Relative standard deviation of 0.91, 0.95 and 0.89% were obtained for the determination of 3, 15 and 30 μg L(-1) Co(II) solution. The proposed method has been successfully applied for analysis of trace amounts of cobalt in water samples.

Adsorptive Stripping Voltammetric Determination of Tartrazine and Sunset Yellow in Gelatins and Soft Drink Powder in the presence of Cetylpyridinium Bromide

Adsorptive Stripping Voltammetric Determination of Tartrazine and Sunset Yellow in Gelatins and Soft Drink Powder in the presence of Cetylpyridinium Bromide

Spectrophotometric Study of Ternary Complex Forming Systems of Some Lanthanide Metal Ions with Eriochrome Cyanine R in Presence of Cetylpyridinium Bromide for Microdetermination

Study of coordination compounds of lanthanide elements has received a great attention due to growing applications in science and technology. Number of chromogenic reagents form water soluble colored complexes with lanthanides. Eriochrome cyanine R (ECR) a member of triphenylmethane type of dye has been reported to form green colored complexes with lanthanides and has been used for microdetermination of these metal ions. Addition of cationic surfactant, Cetylpyridinium bromide (CPB), a cationic surfactant sensitizes the color reactions of Gd(III), Tb(III), Dy(III), Ho(III) and Lu(III) with ECR. Formation of water soluble, highly colored ternary complexes with a considerable bathochromic shift of about 50 nm in presence of surfactant has been observed. Optimum reaction conditions and other analytical parameters were also evaluated. Stoichiometric ratio 1:3:3 of Ln: ECR: CPB are responsible for the observed rise in molar absorptivity and sensitivity. Beer’s law was obeyed between 0.50 to 13.00 ppm. Effective photometric range and molar absorptivity of these ternary complexes have been calculated. Effect of some common interfering ions on determination of these lanthanide metal ions was studied. A simple, rapid and highly sensitive spectrophotometeric method has been proposed for the determination of metal ions understudy.

ChemInform Abstract: Simultaneous Determination of Niobium and Tantalum with Bromopyrogallol Red in the Presence of Cetylpyridinium Bromide and Triton X 305.

ChemInform Abstract: Simultaneous Determination of Niobium and Tantalum with Bromopyrogallol Red in the Presence of Cetylpyridinium Bromide and Triton X 305.

Pyrogallol red and bromopyrogallol red in new optical methods for the determination of molybdenum(VI) and tungsten(VI)

The complexation of molybdenum(VI) and tungsten(VI) with pyrogallol red (PR) and bromopyrogallol red (BPR) in the presence of a cationic surfactant, cetylpyridinium bromide was studied. Conditions of the preconcentration of molybdenum(VI) and tungsten(VI) as complexes with PR and BPR on Silochrom S-120 were found. The concentration coefficients were no lower than 67 for a volume of the aqueous phase of 20 mL and a mass of the sorbent of 0.3 g. Chromaticity characteristics of the complexes in solutions and on the sorbent were determined. It was demonstrated that the complex of molybdenum(VI) with BPR in the presence of cetylpyridinium bromide should be used in the analysis of materials with low concentrations of molybdenum.

Simple and sensitive spectrophotometric determination of ziram, zineb and ferbam in commercial samples and foodstuffs using phenylfluorone

A procedure has been developed for the determination of ziram, zineb and ferbam dithiocarbamate pesticides by converting ziram and zineb into a zinc-phenylfluorone complex and ferbam into an iron phenylfluorone complex, which are then dissolved in water in the presence of cetylpyridinium bromide and pyridine as a surfactant. The method is sensitive, highly selective and can be used for the determination of ziram, zineb and ferbam in commercial samples and in foodstuffs.

Synthesis, characterization, and catalytic testing of W-MCM-41 mesoporous molecular sieves

A novel tungsten-containing MCM-41 mesoporous molecular sieve was synthesized by the hydrolysis of tetraethylorthosilicate and ammonium tungstate in the presence of cetylpyridinium bromide as template in strongly acidic medium. Physicochemical characterizations of this composite performed by means of powder X-ray diffraction, ICP atomic emission, FT-IR, laser Raman, and diffuse reflectance UV–Vis spectroscopy verified that tungsten ion could be isolated in framework positions of the MCM-41 mesostructure by this approach. Thermo-gravimetric study on this composite suggested that above 90% of the template encapsulated in the as-synthesized mesophase was recoverable by direct ethanol extraction. A catalytic test using hydrogen peroxide hydroxylation of cyclohexene as probe reaction proved that the framework tungsten site in the W-MCM-41 could afford the mesophase with fairly high activity in promoting this reaction, wherein acetic acid was found to be useful as solvent.

Synthesis of highly active tungsten-containing MCM-41 mesoporous molecular sieve catalyst

A tungsten-containing MCM-41 mesoporous molecular sieve is synthesized by the hydrolysis of tetraethylorthosilicate and ammonium tungstate in the presence of cetylpyridinium bromide as template in acidic medium and found to be more active than the conventional WO3 catalyst in the hydroxylation of cyclohexene using H2O2 as oxidant.

Fluorescence Quenching of Polycyclic Aromatic Hydrocarbons by Cetylpyridinium Bromide: Discrimination between Alternant and Nonalternant Hydrocarbons

Molecules of polycyclic hydrocarbons (PAHs) that contain between two and five rings undergo quenching processes in the presence of cetylpyridinium bromide (CPB), which can act as quencher and as surfactant. The CPB concentration and the nature of the PAHs notably influence the inhibition mechanisms of fluorescence. Dynamic quenching is predominant for all hydrocarbons in solutions in which CPB is found in the form of monomers. When the quencher forms premicellar aggregates, fluoranthene, benzo[ a]pyrene, and benz[ a]anthracene undergo dynamic quenching, while for the remaining PAHs the dynamic and static processes coexist. In micellar CPB solutions the static quenching mechanism is predominant. The correlations existing between the quenching constant in the premicellar zone and topological and geometrical descriptors of the PAHs show the different behavior of alternant and nonalternant hydrocarbons.

Spectrophotometric and derivative spectrophotometric study of the reaction of palladium (II) and rhodium (III) with 5-(3,4-methoxyhydroxybenzylidene)rhodanine and cationic surfactants

Spectrophotometric and derivative spectrophotometric methods for the determination of Pd(II) and Rh(III) are proposed. Pd(II) forms with 5-(3,4-methoxyhydroxybenzylidene)rhodanine [3,4-MHBR], in the absence and presence of cetylpyridinium bromide [CPB], 1∶4 binary and 1∶3∶4 ternary complexes having molar absorptivities of 5.77 × 104 and 7.46 × 104M−1cm−1 at 525 and 530 nm, respectively. Rh(III) forms a 1∶4 complex with 3,4-MHBR in the presence of cetyltrimethylammonium bromide [CTAB], which gives a maximum absorbance at 445 nm with a molar absorptivity of 5.13 × 104M−1cm−1. Derivative spectrophotometric methods are employed for the determination of Pd(II) and Rh(III) at ng ml−1 levels utilizing these complexes. Under the optimum conditions the calibration lines for Pd(II) and Rh(III) determination fit the equations d4A/dλ4 = 1.10 × 106 [Pd] − 0.018 (r = 0.9967) and d4A/dλ4 = 2.25 × 106 [Rh] + 0.03 (r = 1.0426) and have detection limits of 5.6 and 1.2 ng ml−1, respectively. The influences of experimental variables and foreign ions are studied. The methods are free of interference from most common metal ions and anions. The results of the analysis of some synthetic mixtures of Pd(II) and Rh(III) are reported.

Determination of Thorium Using Phenylfluorone and Quercetin in the Presence of Surfactants and Protective Colloids

Abstract Two sensitive spectrophotometric methods have been proposed for the determination of thorium with phenylfluorone (PF) and quercetin (Quer) in the presence of cetylpyridinium bromide (CPB) and polyvinylpyrrolidone (PVP), respectively. The optimum conditions for complexation reactions have been thoroughly investigated. The 1:3:4 (Th-PF-CPB) ternary complex and the 1:3 (Th-Quer) binary complex in the presence of PVP, are formed in the pH range 8.0-8.6 and 9.8-10.6, with molar absorptivities of 1.55 × 105 and 6.25 × 104 1.mol−1.cm−1, at 568 and 445 nm, respectively. The methods are rectilinear for 0.10-1.66 and 0.21-4.3 mg Th.l−1 and their detection limits (signal-to-noise ratio = 3) are 0.082 and 0.139 mg.l−1, respectively. Results of analysis of thorium in monazite samples using these methods were in good agreement with those obtained by x-ray fluorescence spectrometry.

The activity of lipase from Rhizopus sp. in native form and after immobilization on hollow-fiber membranes

The activity of immobilized and native lipase and the stability of immobilized enzyme at various temperatures were determined. The highest activity of native enzyme occurred at 30°C and the maximal initial activity of immobilized enzyme was observed at 45° C. The best stability of immobilized enzyme was at 30° C. The activity decreased with 0.8% per 24 h. The hydrolysis of sunflower oil by immobilized and native Rhizopus sp. lipase in the presence of surfactants, proteins and metals was studied. The native enzyme lost activity in the presence of cetylpyridinium bromide, Triton X-100, and sodium dodecyl sulphate (SDS) at concentrations of 0.1, 0.75, and 4 mM, respectively. The immobilized lipase was more resistant to inhibition than the native one. Bovine serum albumin, soybean trypsin inhibitor and ovalbumin had a small influence on the activity of the native lipase. However, BSA inhibited the immobilized enzyme. Cd 2+, Zn 2+, Hg 2+ and Cu 2+ inhibited the native enzyme while Cd 2+ and Cu 2+ strongly inhibited the immobilized one.

Spectrophotometric determination of rare earth elements by flow injection analysis based on their reaction with xylenol orange and cetylpyridinium bromide

Individual rare earth elements (REE) and their mixtures were determined by a FIA method based on the reaction with Xylenol Orange (XO) in the presence of cetylpyridinium bromide (CPB). Volumes of 30 μl of 2.5–25 μ M REE solutions were injected into a carrier stream of 0.1 M acetate butter of pH 4.5 or 5.5 that was 0.06 m M in XO and 0.6 m M in CPB. At 1.8 ml/min flow rate, a sampling frequency of up to 100 samples per hour was achieved. The detection limits were in the range of 0.1–0.4 μg/ml REE and relative standard deviation of the measurement was 0.88% rel.

Reentrant conformational transition of polyelectrolyte network in water alcohol mixtures in the presence of oppositely charged surfactant

Reentrant conformational transitions are observed in polyelectrolyte networks of sodium methacrylate-acrylamide copolymers in water-alcohol mixtures in the presence of cetylpyridinium bromide. At low alcohol content, gel shrinking is induced by complex formation between charged network and oppositely charged surfactant. In media with high alcohol content the complex dissociates and the collapse comes as a result of volume interactions between charged network and the solvent. At intermediate alcohol concentration, hydrophobic interactions between hydrocarbon groups of surfactant ions are suppressed and the gel swelling is observed.