Propyl Orange Research Articles

Spectrophotometric assay of a wood preservative, N,N-didecyl-N-methylpoly(oxyethyl) ammonium propionate (DMPAP), in aqueous solution

A spectrophotometric assay based on the color reaction between N,N-didecyl-N-methyl-poly(oxyethyl) ammonium propionate (DMPAP) and 4-[4-(dipropylamino) phenylazo]-benzenesulfonic acid (propyl orange) was used to determine DMPAP concentrations as a wood preservative. The assay was carried out using a propyl orange solution at pH 2.9. The visible absorption spectrum of propyl orange showed an absorption maximum at 510 nm, which decreased linearly with increasing DMPAP concentration from 0 to 10 ppm. To apply this assay method to determine DMPAP retention in treated wood, the influence of wood extractives on the assay was investigated. Extractives from Japanese cedar, hinoki cypress, and Japanese larch were found to increase apparent DMPAP concentration. However, it was also found that measuring visible absorption at 477 nm prevented overestimation and gave precise values. This assay can be a viable alternative to the current methods for the determination of DMPAP concentrations.

Spectrophotometric assay of a wood preservative, didecyldimethylammonium chloride (DDAC), in aqueous solution

A spectrophotometric assay based on the color reaction between didecyldimethylammonium chloride (DDAC) and 4-[4-(dipropylamino)phenylazo]-benzenesulfonic acid (propyl orange) was used for the determination of DDAC as a wood preservative. The assay was carried out using a propyl orange solution at pH 2.9. The visible absorbance spectrum of propyl orange showed an absorbance maximum at 510 nm, which decreased continuously with increasing DDAC concentration from 0 to 20 ppm. A linear correlation was observed at a DDAC concentration lower than 8 ppm. To apply this assay method to determine DDAC retention in treated wood, the influence of wood extractives on the assay was investigated. Wood extractives from sapwood and heartwood of Japanese cedar, Hinoki cypress, Japanese larch, and Western hemlock showed no influence on DDAC determination except in the case of heartwood from Japanese cedar and Hinoki cypress, which gave apparent DDAC concentrations higher than the actual values. However, it was also found that absorbance measurement at 477 nm solved this overestimation and gave precise values. It was concluded that this assay is a viable alternative to the current methods for DDAC determination.

Spectrophotometric determination of cationic and anionic surfactants with anionic dyes in the presence of nonionic surfactants, part II: Development of batch and flow injection methods

On the basis of the changes in absorption spectra of azo dyes on the addition of an organic onium ion, spectrophotometric methods for the determination of organic onium salts and anionic surfactants were developed, and applied to flow injection method. Propyl orange (PO−) was used for the determination of organic onium ions. Pairs of PO− and Zeph+ (tetradecyldimethyl-benzylammonium ion) or PO− and nC18TMA+ (n-octadecyltrimethylammonium ion) were used for the determination of anionic surfactants. The determination range of organic onium ions were (0–3) × 10−5 M by a batch method and were (0–2) × 10−5 M by a flow injection method. The determination ranges of anionic surfactants were (0–2) × 10−5 M by the batch method, and were (0–5) × 10−5 M by the flow injection method, and the detection limit corresponding toS/N = 3 was 3 × 10−7 M by the flow injection method. By the proposed flow injection method, anionic surfactants in water samples were determined.

Spectrophotometry Determination of Calcium with Dicyclohexano-24-crown-8 and Propyl Orange by Solvent Extraction/Flow Injection Method

Calcium in water was determined by a spectrophotometric method involving flow injection coupled with solvent extraction. An ion association complex which formed between a calcium-crown complex ion and a dye anion was extracted into an organic solvent and the absorbance of the organic phase was measured after phase separation. Six derivatives of alkylaminophenylazobenzene sulfonic acid and tetrabromophenolphthalein ethylester were examined as counter anions with dicyclohexano-24-crown-8, and a mixture of benzene and chlorobenzene was examined as an extraction solvent. A suitable method for calcium determination in water was one with Propyl Orange and a (1+1 v/v) mixture of benzene and chlorobenzene. The carrier stream was distilled water, while the reagent stream was comprised of a dye anion and lithium hydroxide. The sampling rate was 20–30 per hour. The calibration graph was linear at concentrations up to 10~4 M using samples of 100 μl. The detection limit corresponding to a signal-to-noise ratio of 3 was 2×10-7 M; the relative standard deviation was 0.99% for 10 injections of 5×10-5 M calcium solution. Calcium in river water was determined satisfactorily by the proposed method.

Binding of methyl orange and its homologs by powdered nylon 612: Peculiar temperature dependence on the binding

AbstractThe ability of powdered Nylon 612 to bind methyl orange, ethyl orange, propyl orange, and butyl orange was investigated at 5, 15, 25 and 35°C in an aqueous solution. The amount of binding of the dye is much higher with this polyamide than with powdered Nylon 66 reported previously,1 although the former polymer has fewer amide end groups. The Van't Hoff plots of the first binding constant for the binding of butyl orange and propyl orange by powdered Nylon 612 exhibit a bell‐shaped curve, whereas the plots for methyl orange and ethyl orange do not. Maximal binding occurs at approximately 15°C for propyl orange and at about 25°C for butyl orange. This is the first instance where the peculiar temperature dependence of the binding constant has been found in the binding of propyl orange, whose hydrophobicity is less than that of butyl orange. These tendencies can be accounted for in terms of increased hydrophobic of butyl orange. These tendencies can be accounted for in terms of increased hydrophobic domains in powdered Nylon 612 and enhanced hydrophobic contributions in the binding process.

Peculiar temperature dependence of the binding of methyl orange and its homologs by 2‐diethylaminoethyl methacrylate‐N‐vinyl‐2‐pyrrolidone copolymers

Abstract2‐Diethylaminoethyl methacrylate (DEAEMA)–N‐vinyl‐2‐pyrrolidone (VPy) copolymers of various compositions have been synthesized. The resultant copolymers were examined for their ability to bind methyl orange and its homologs, in particular butyl orange, at 5, 15, 25, and 35°C in aqueous solutions. The amount of binding of butyl orange is much higher with the copolymers than with polyvinylpyrrolidone or with 2‐hydroxyethyl methacrylate–N‐vinyl‐2‐pyrrolidone copolymers. Introduction of only 3% of the hydrophobic DEAEMA residue increases markedly the binding affinity toward the cosolute. Maximal binding is obtained at 15°C in the temperature range measured. This peculiar temperature dependence of the extent of binding is explicable on the basis of hydrophobic effects involved in this binding. The peculiar temperature dependence disappeared in aqueous solution of NaSCN which acts as a water‐structure breaker: the extent of binding changes regularly with temperature. This is interpretable only in terms of reduction of hydrophobic contribution to the binding. With propyl orange, which is a less hydrophobic cosolute than butyl orange, the peculiarity of the binding was not detected.

Peculiar temperature dependence on the binding of methyl orange and its homologs by 2‐hydroxyethyl methacrylate‐N‐vinyl‐2‐pyrrolidone copolymers

Abstract2‐Hydroxyethyl methacrylate (HEMA)‐N‐vinyl‐2‐pyrrolidone (VPy) copolymers of various compositions have been prepared. The copolymers obtained were examined for their ability to bind a homologous series of methyl orange derivatives, methyl orange, ethyl orange, propyl orange, and butyl orange, at 5, 15, 25, and 35°C, respectively, in an aqueous solution. The first binding constants and the thermodynamic parameters that accompanied the binding were evaluated. The binding ability of the copolymer for the small cosolute was enhanced with an increase of the HEMA content in the copolymer. Moreover, a bell‐shaped curve appeared in the binding of butyl orange by the copolymers having higher HEMA residues when the first binding constant was plotted as a function of temperature, whereas no such phenomenon was detected for the copolymers with less HEMA content or for the less hydrophobic dye, methyl orange, ethyl orange, or propyl orange. This peculiar temperature dependence of the first binding constant shows that the enthalpy of the binding varies from a positive (unfavorable) value below ca. 15°C to a negative (favorable) one above this temperature. This behavior can be accounted for in terms of more hydrophobic effects involved in the binding process.

Binding of methyl orange and its homologs by polyion complex in ethylene glycol

AbstractThe extent of binding of methyl orange, ethyl orange, propyl orange, and butyl orange by a polyion complex, which consists of equimolar sodium polymethacrylate and a piperidinium cationic polymer, was measured in ethylene glycol at 25, 30, and 35°C. The effects of aqueous and nonaqueous media on the binding of the dye by the polymer matrix were compared. In ethylene glycol only noncooperative binding (Langmuir type) was observed, whereas two modes of binding, noncooperative and cooperative, were involved in the aqueous environment. The first binding constants and the thermodynamic parameters associated with the binding in ethylene glycol were evaluated. The polymer matrix exhibited a higher affinity toward the dye in ethylene glycol than in water at low concentrations of free dye and bound these anionic cosolutes with different hydrophobicities but the same affinity as in ethylene glycol. These interactions are highly exothermic and characterized by relatively large negative entropy changes. Electrostatic forces are the principal contributors to the dye–polymer complex formation. The binding behavior observed in the nonaqueous solvent is reasonably accounted for in terms of disappearance of hydrophobic interactions between the dye and the polymer and an increase in electrostatic attraction between the anionic small molecule and the positively charged sites on the polyion complex.

Cross‐linked polyvinylpyrrolidones with increased affinity and specificity for methyl orange and its homologs

AbstractPolyvinylpyrrolidones of various degrees of cross‐linkage have been prepared by radical polymerization of N‐vinylpyrrolidone with methylenebisacrylamide to regulate the fraction of cross‐linkage. The insoluble polymers obtained were examined for their ability to bind methyl orange and its homologs, methyl orange, ethyl orange, propyl orange, and butyl orange at 5, 15, 25, and 35°C, respectively, in an aqueous solution. The first binding constants and the thermodynamic parameters that accompanied the binding were calculated. For any particular dye the extent of binding, the absolute magnitude of ΔF°, and the value of ΔS° increased as the degree of cross‐linkage increased, starting with water‐soluble polyvinylpyrrolidone (zero cross‐linkage) and proceeding to the polymer with high cross‐linking density. This behavior can be accounted for in terms of more extensive hydrophobic domains in the cross‐linked polymeric matrix that enhances hydrophobic interactions in the binding process. Moreover, the cross‐linked macromolecule polymerized in the presence of methyl orange and then stripped of the bound methyl orange shows substantially stronger binding for this small molecule than the polymer cross‐linked in the absence of methyl orange. In contrast, the cross‐linked polymer prepared similarly in the presence of the larger molecule, butyl orange, exhibits decreased affinity toward the smaller consolute, methyl orange, than either of the other polymers described. It seems, therefore, that the polymeric matrix provides favorable binding sites or pockets that can accommodate a specific small molecule. The preparative procedure, which uses a small‐molecule template, molds into the polymer some structural specificity in the binding of small molecules.

Binding of methyl orange and its homologs by polyion complexes in aqueous solution

AbstractPolyion complexes of sodium poly(methacrylate) and piperidinium cationic polymers [I], which are insoluble in water and have an equal number of positive and negative charges, bind organic anions (methyl orange, ethyl orange, propyl orange, butyl orange, and pentyl orange) in aqueous solution. The strength of the binding is enhanced by an increase in the hydrophobicity of the polyion complex and the small cosolute. Moreover, strong cooperative interactions appear with increased uptake of the small molecule. Urea and an inorganic electrolyte (KCl) were examined for their effect on the binding, the amount of which is strongly suppressed by these additives. The significance of hydrophobic and electrostatic interactions which accompany the binding is described.

Interaction of crosslinked polyvinylpyrrolidone with a homologous series of methyl orange derivatives in aqueous and nonaqueous solutions: Thermodynamics of the binding equilibria

AbstractThe extent of binding of methvI orange, ethyl orange, propyl orange, and butyl orange by crosslinked polyvinylpyrrolidone was measured in all aqueous Solution. The first binding constants and the thermodynamic parameters accompanying the binding were evaluated. These values were compared with those of water‐soluble polyvinylpyrrolidone. The first binding constant, the absolute magnitude of ΔF°, and the value of ΔS° of the crosslinked polyvinylpyrrolidone are substantially larger than those of the water‐soluble product for any particular dye. These behaviors can be accounted for in terms of increased hydrophobic domains in the former and enhanced hydrophobic contribution in the binding process. Also the binding of the dye by the crosslinked polymer in a nonaqueous solvent, ethylene glycol, was measured to assess the contribution of hydrophobic interaction to the dye‐polymer complex formation in aqueous medium. It was found that the binding of butyl orange by the crosslinked polymer is suppressed in ethylene glycol and the contribution of entropy term to the free energy change in the aqueous environment is large compared with that in ethylene glycol. The significance of the hydrophobic of the hydrophobic interaction in the dye‐polymer association process is described.

Thermodynamics of binding methyl orange and its homologs by polyvinylpyrrolidone: The effect of hexamethylenetetramine

AbstractHexamethylenetetramine (HMT) has been examined for its effect on the binding of methyl orange homologs, methyl orange, ethyl orange, propyl orange, and butyl orange by polyvinylpyrrolidone (PVP). In the presence of HMT the entropy changes associated with the binding tend to become more positive and the absolute magnitude in the enthalpy changes becomes smaller compared with those in the absence of HMT. These tendencies are accounted for in terms of the water‐structure‐promoting effect of HMT, hence the enhancement of hydrophobic interactions in the binding. PVP undergoes changes in conformation on the addition of HMT and its conformation becomes more compact. This also increases the contribution of the hydrophobic interactions to the macromolecule‐small molecule interaction. Some other effects exerted by the added HMT on the binding system are also described.

DIFFUSION OF METHYL ORANGE AND ITS HOMOLOGS IN WATER AND IN MICELLAR SOLUTION OF DODECYLTRIMETHYLAMMONIUM BROMIDE

Diffusion coefficients of Methyl Orange, Ethyl Orange, Propyl Orange, and Butyl Orange in 0.03M NaCl, and 0.025M dodecyltrimethylammonium bromide have been obtained by means of diaphragm diffusion procedures with a Stokes'type cell. In NaCl solution, the radii of diffusion particles of MO, EO, PO, and BO are 4.01, 4.33, 5.05, and 6.02×10-8cm, respectively. Diffusion coefficients of MO and PO in the surfactant solution are 2.15 and 2.24×10-6cm2 sec-1, respectively. MO and PO diffuse with the surfactant micell having about 12×10-8cm radius.

The Activities of Methyl Orange and Homologs in Aqueous Solutions

Abstract The mean activity coefficients of Methyl Orange (MO), Ethyl Orange (EO), Propyl Orange (PO), and Butyl Orange (BO) in aqueous solutions ranging in concentration from 10−3 to 10−2 mol kg−1 have been determined by means of isopiestic measurements at 50 and 60 °C respectively. It has been found that the mean activity coefficients of MO being the largest, and those of BO, the smallest. The coefficients have been found to decrease with an increase in the dye concentration. The examination of the results by Milicéivic treatment suggests that MO, EO, and PO are present as a monomer or a dimer, while BO exists as a trimer at 60 °C.

Thermodynamics of binding of methyl orange and its homologs by poly(vinylpyrrolidone): The effect of inorganic electrolytes

AbstractThe extent of binding of methyl orange, ethyl orange, propyl orange, and butyl orange by poly(vinylpyrrolidone) has been measured in aqueous solutions of inorganic electrolytes such as NaCl, LiCl, NaSCN, and NaClO4 by an equilibrium dialysis method. The effect of the salts on the first binding constants and the thermodynamic functions which are accompanied by the dye—polymer association process was investigated relative to the corresponding values in the absence of such salts. It was found that in aqueous solutions of NaCl and LiCl the enthalpy change accompanying the binding is small and the largest contribution to the free energy of binding is from the positive entropy gain. For NaSCN and NaClO4, the values of ΔF° and ΔH° were both large and negative and the value of ΔS° was small and negative. Thus, the favorable free energy for the complex formation was due entirely to the negative enthalpy term. These characteristics of the thermodynamic quantities are discussed in terms of changes in structural properties of water in the vicinity of the binding entities and conformational changes of the polymer to which the dye is bound due to the added foreign electrolytes.

Interaction of poly(vinylpyrrolidone) with methyl orange and its homologs in aqueous solution over the temperature range 60–90°c

AbstractThe binding of methyl orange, ethyl orange, propyl orange, and butyl orange by poly(vinylpyrrolidone) has been examined by a technique of equilibrium dialysis over a high temperature range (60–90°C). The first binding constants and the thermodynamic parameters in the course of the binding were evaluated. The results obtained at these temperatures were compared to those at lower ones (5–35°C) described previously in order to estimate the contribution of hydrophobic bonds to the binding. It was found that at the 60–90°C range complex formation between the dye and the macromolecule is associated with an exothermic enthalpy change and a positive entropy change. The enthalpy and entropy changes of the binding are of the order of −4.5 kcal/mole and 6 eu, respectively, for each dye measured. Thus the binding is mainly enthalpy‐controlled. Furthermore the effect of the alkyl chain length of the dye on both the ΔH° and ΔS° values is not pronounced. Also temperature dependences of the ΔH° and ΔS° terms were not observed. All these observations in the higher temperature range can be explained as a result of the disruption of water structure in the binding environment and hence a decrease in hydrophobic bond formation between the dye and the polymer.

EFFECT OF AN INORGANIC ELECTROLYTE ON INTERACTION OF METHYL ORANGE AND ITS HOMOLOGS WITH POLYCATIONS CONTAINING VARIOUS APOLAR GROUPS: CONTRIBUTION OF ELECTROSTATIC AND HYDROPHOBIC INTERACTIONS

The binding of methyl orange, ethyl orange, and propyl orange by polycations involving various apolar pendant groups has been investigated in thee presence of sodium chloride by the equilibrium dialysis method. The polycations used in this experiment were copolymer of dimethyldiallylammonium chloride and sulfur dioxide (PAS-1), copolymer of diethyldliallylammonium chloride and sulfur dioxide (PAS-2), and copolymer of dimethyldiallylammonium chloride and sulfur dioxide (80%)-methyldodecylbenzyldiallylammonium chloride and sulfur dioxide (20%) (PAS-4). The first binding constants and the thermodynamic parameters for the binding were calculated in various concentrations of NaCl in order to clarify the effects of the salt on the binding behaviors and to gain some insight into the nature of binding energy.It was found that the first binding constants decrease with an increase in the salt concentration and tend to approach a constant value above 1.0 mole NaCl. This might be due to the shielding of the electric field around the binding system on addition of the salt and the competition between the dye anion and Cl- ion for loci of cationic attachment on the polymer molecules. Therefore, it is likely that the electrostatic force in the binding decreases with increasing salt concentration and then disappears around 1.0 mole NaCl or above. Thus, the electrostatic force for the binding of methyl orange by PAS-2 was estimated to be -3210 cal and the other binding forces -4980 cal. The hydrophobic interaction in addition to the electrostatic one seems to play an important role in the binding. The change in conformation of the polymer induced by the addition of the salt and the effect of the conformational change on the binding forces are discussed. Also the intrinsic binding constant of the polycation for Cl- ion was evaluated from a binding isotherm introduced for two competitive binding species, dye anion and Cl- ion.

Binding of methyl orange and its homologs by polycations containing apolar pendant groups

AbstractThe binding of methyl orange, ethyl orange, and propyl orange by polycations involving various apolar pendant groups such as methyl, ethyl, benzyl, or dodecylbenzyl groups has been examined quantitatively by an equilibrium dialysis method at 5, 15, 25, and 35°C. The first binding constants and the thermodynamic parameters in the course of the binding have been calculated. The favorable free energy of the binding is accompanied by an entropy gain and an exothermic enthalpy change. The shorter the alkyl chain of the dyes or the polymers, the more negative is the enthalpy change and hence the smaller is the entropy change. Furthermore, an increase in binding affinity can be created in the polycation upon introduction of hydrophobic groups. In particular, the binding ability of the polycation containing a dodecylbenzyl group for methyl orange is almost 300‐fold that of bovine serum albumin. Therefore it is clear that hydrophobic interactions, as well as electrostatic ones, are involved in the binding.

Interaction of polyvinylpyrrolidone with methyl orange and its homologs in aqueous solution: Thermodynamics of the binding equilibria and their temperature dependences

AbstractThe interaction of polyvinylpyrrolidone with methyl orange, ethyl orange, propyl orange, and butyl orange has been studied by an equilibrium dialysis method at 5, 15, 25, and 35°C. The first binding constants and the thermodynamic parameters in the course of the binding have been calculated. It was found that the free energy and the enthalpy changes are all negative and the entropy change is largely positive. The longer the alkyl chain of the dyes, the more positive is the enthalpy change (though it is always in the negative direction) and hence the larger is the entropy change. The favorable free energy of the binding of butyl orange observed for the formation of the dye–polymer complex seems to be a result of a favorable entropy change rather than any favorable enthalpy change. Temperature dependences of the thermodynamic functions were apparently observed. That is, ΔF and ΔH become larger in absolute magnitude as the temperature increases. The positive quantity of ΔS tends to decrease with increasing temperture. All these facts obtained can be interpreted satisfactorily by the hydrophobic interaction between hydrocarbon portions of the dyes and nonpolar parts of the macromolecule.