Isopropanol Concentration Research Articles

Pervaporation dehydration of isopropanol with chitosan membranes

Homogeneous and composite chitosan based membranes were prepared by the solution casting technique. The membranes were investigated for the pervaporation dehydration of isopropanol-water systems. The effects of feed concentration and temperature on the separation performance of the membranes were studied. In terms of the pervaporation separation index (PSI), the composite membrane was more productive than the homogeneous membrane for pervaporation of feed with high isopropanol content. It was observed that permeation increased and the separation factor decreased with the temperature. Modification of the homogeneous chitosan membrane by chemical crosslinking with hexamethylene diisocyanate improved the permselectivity but reduced the permeation rate of the membrane.

Interfering substances identified in the breath of drinking drivers with Intoxilyzer 5000S.

The selectivity of analytical methods used to determine ethanol in body fluids has always been an important concern in connection with chemical testing for intoxication. Allegations of false high breath-alcohol readings obtained because of the presence of volatile organic compounds (VOCs) other than ethanol is a well-known defense argument in trials concerning driving under the influence of alcohol (DUI). However, not much information exists to substantiate this claim, especially when modern analytical technology such as multiple wavelength infrared breath-alcohol instruments is used for forensic purposes. Whenever breath tests were aborted because interfering substances were ostensibly detected during routine evidential breath-alcohol analysis in Sweden with the Intoxilyzer 5000S, a sample of venous blood was taken for analysis by headspace gas chromatography. Most of the aborted breath tests could be explained by abnormally high concentrations of acetone, isopropanol, or methyl ethyl ketone in the samples analyzed. These VOCs originate in blood and breath after DUI suspects consume denatured alcohol preparations containing these solvents. However, the intoxilyzer 5000S sometimes aborted the evidential breath test even though VOCs other than ethanol were not identified in the blood samples. The reason for these latter tests being aborted is hard to understand because the blood-breath ratios of ethanol were within the range expected (1900:1 to 2800:1) for a large number of other DUI suspects tested with Intoxilyzer 5000S under the same conditions when interfering substances were not detected.

Determination of the concentration of higher alcohols with enzyme coupled flow-injection analysis in model systems

The activities of native and immobilized alcohol oxidases (AOD) originating from Pichia pastoris, Hansenula sp., Candida boidinii and Peniophora gigantea were compared with regard to the oxidation of various higher alcohols. Except Candida boidinii, the immobilized enzymes were applied in a flow-injection analysis system and investigated as a function of the various operation variables. During the oxidation O 2 is consumed which concentration was measured with an amperometric detector. At the same time H 2O 2 is produced, the concentration of which is used for the oxidation of a redox indicator (ABTS) catalysed by peroxidase and measured with a photometer. The amperometric method is simpler and more economical, but less sensitive. The photometric method consumes the dissolved redox indicator and peroxidase, but is highly sensitive especially for higher alcohols. The concentrations of n-propanol, n-butanol and n-pentanol can be measured with satisfactory sensitivity with immobilized alcohol oxidases originating from Pichia pastoris and Peniophera gigantea in a one molar potassium phosphate buffer (pH 7.5). The concentrations of isopropanol, octanol, dodecanol and benzylalcohol can be measured only when larger than 1 g l −1.

Quantitative Evaluation of Aqueous Isopropyl Alcohol Enhancement on Skin Flux of Terbutaline (Sulfate). 2. Permeability Contributions of Equilibrated Drug Species across Human Skin in Vitro

This paper demonstrates the usefulness of an equilibria-cotransport model for understanding the isopropyl alcohol-enhanced transport of an ionizable model compound, terbutaline in its sulfate salt form, through human skin in vitro. With the same isopropyl alcohol concentrations (0-80% v/v) present at both sides of skin, the permeation experiments were conducted using split-thickness skin and dermis membranes. The equilibria-cotransport model was consistent with total terbutaline flux and a terbutaline-to-sulfate flux ratio, both increased with increasing isopropyl alcohol and/or terbutaline sulfate concentrations. From the saturated drug solutions, aqueous isopropyl alcohol enhanced terbutaline skin flux about 10-100-fold with the maximum at 60-80% isopropyl alcohol. This overall flux enhancement was quantitatively separated into the contributions of isopropyl alcohol effects on both equilibrated donor concentrations and skin permeabilities of protonated terbutaline, terbutaline-sulfate ion pair anion, and neutral terbutaline-sulfate (2:1) ion triplet. In addition to altering the species equilibria, isopropyl alcohol was found to enhance the transport of both neutral and ionic species of terbutaline sulfate across stratum corneum.

Comparison of the non-solvents ethanol and isopropanol for the fractionation of dextran

For a proper fractionation of dextran, using the liquid-liquid two phase system water - non-solvent - dextran, the selection of the non-solvent is very important. Therefore, in this work the non-solvent isopropanol has been compared to ethanol with respect to the selectivity for a fractionation and to the required amount of non-solvent. It is shown that the influence of the concentration of ethanol and isopropanol in the total system on the molecular mass distribution of the dextran in both liquid phases is quite similar, but for getting the same result of a fractionation more ethanol than isopropanol is required.

Dose-dependent suppression of toluene metabolism by isopropyl alcohol and methyl ethyl ketone after experimental exposure of rats

In order to examine possible suppression of toluene metabolism due to coexposure to other solvents, female Wistar rats were exposed for 8 h to toluene alone (at 50 or 100 ppm), or in combination with either methyl ethyl ketone (at 50, 100, 200 or 400 ppm) or isopropyl alcohol (at 50, 100, 200, 400, 800 or 1600 ppm). Urine samples were collected for 24 h after initiation of each exposure, and subjected to analysis for two toluene metabolites, hippuric acid and o-cresol, both by HPLC. The excretion of hippuric acid, a major metabolite, was not modified when the concentrations of methyl ethyl ketone or isopropyl alcohol were low, i.e. 100 ppm or below, whereas it was reduced when methyl ethyl ketone or isopropyl alcohol concentrations were twice or more times higher than that of toluene. There were no changes in any cases in excretion of o-cresol, a minor metabolite. The observation after coexposure to methyl ethyl ketone or isopropyl alcohol at low concentration is in line with the negative interaction between toluene and methyl ethyl ketone as well as between toluene and isopropyl alcohol after occupational exposures at low concentrations. Metabolic interaction may take place when the exposure intensity is high, as observed in the present study and also after experimental exposure of volunteers to toluene and m-xylene, or occupational exposure to benzene and toluene.

Ion mobility spectrometry for continuous on-site monitoring of nicotine vapors in air during the manufacture of transdermal systems

Ion mobility spectrometry (IMS) can provide continuous on-site monitoring of nicotine in air exceeding in real-time the current OSHA eight hour exposure standard of 0.5 mg/m 3. A handheld IMS with water reagent gas, exhibited near instantaneous response, detection limits of 0.006 mg/m 3 and median relative standard deviations of 3.1% for vapor levels between 0.01 to 0.25 mg/m 3. Ion mobility spectra for nicotine showed characteristic product ions which were mass-identified as monomer (M · H +) and dimer (M 2 · H +) ions. Continuous monitoring of ambient air during the manufacture of nicotine-based transdermal systems demonstrated that short-lived, elevated concentrations of iso-propanol occurred when surfaces on the production equipment were cleaned. However, the concentration profile for nicotine in ambient air showed a gradual rise to a plateau with only minor ripple. High variability in personal samplers was attributed to localized concentrations of nicotine in the production equipment as identified using the hand-held IMS analyzer.

Direct and indirect chiral separation of amino acids by capillary electrophoresis

Two approaches to the chiral separation of racemic mixtures of amino acids by means of capillary electrophoresis have been evaluated. These were indirect separation of diastereomers formed by derivatization with (+)- or (−)-1-(9-fluorenyl)ethyl chloroformate and direct chiral separation after derivatization with 9-fluorenylmethyl chloroformate. Separation conditions were optimized by the application of a full factorial design. For indirect separation, concentration of sodium dodecyl sulphate (SDS) and pH were the most important separation variables, and for direct separation, concentration of isopropanol (IPA), β-cyclodextrin and SDS were the most prominent factors affecting separation. The presence of IPA was a prerequisite for chiral recognition. With regard to selectivity, efficiency, analysis time and ease of method development the best results were provided by the indirect method. It should be noted, however, that the success of this approach is based on the availability of a derivatization reagent in high optical purity.

Optimization of in Vitro Flux Through Hairless Mouse Skin of Cidofovir, a Potent Nucleotide Analog

Thein vitroflux (4–8 h) of cidofovir (1‐[(S)‐3‐hydroxy‐2–(phosphonomethoxy)propyl]cytosine) was measured across full–thickness hairless mouse skin to evaluate potential formulations for local treatment of herpes virus infections. The effects of propylene glycol, isopropyl alcohol, oleic acid, pH, and cidofovir concentration were examined. In addition, several prototype aqueous gel formulations were studied. Flux values (4–8 h) increased linearly with cidofovir concentration in both solution and gel formulations. Removal of the stratum corneum by tape stripping increased the flux by ∼400‐fold, whereas pH (4.5 versus 7) had little effect on flux. The presence of propylene glycol, isopropyl alcohol, or their combination did not significantly increase mean flux (p> 0.05). Pretreatment of the skin with oleic acid resulted in a significant enhancement of cidofovir flux (p<0.01). From the measured flux values, the calculated concentration of cidofovir achievable in the viable epidermis from a 1% cidofovir gel formulation was ∼14 μg/mL, which is comparable to thein vitro50% inhibitory dose (ID50) values for herpes simplex viruses HSV‐1 and HSV‐2.

Transition of viscous fingering patterns in polymer solutions

Viscous fingering patterns of aqueous hydroxypropyl methyl cellulose (HPMC) solutions pushed by air in the Hele–Shaw cell were observed as a function of isopropyl alcohol content under a constant pressure of 15 cm H2O. A morphological transition from side branching patterns to tip splitting ones with increasing isopropyl alcohol content, accompanied with a decrease in surface tension and an increase in viscosity is found. The observed morphology transition was correlated with the dimension of the fingering pattern, as well as the average tip velocity in the fingering.

Diffuse reflectance fourier transform infrared spectroscopy of phospholipid adsorption onto silicic acid

AbstractDiffuse reflectance Fourier transform infrared spectroscopy was used to study the mode of adsorption of phosphatidylcholine (PC) in hexane onto silicic acid (SA). PC adsorption was mainly through the charged phosphate group with minimal binding through the ester carbonyl. When the SA surface with adsorbed PC is washed with hexane, containing a small concentration of isopropanol, the desorbed PC is recovered without structural change, i.e., there is no evidence of PC hydrolysis in the adsorption process. Adsorbent misture probably promotes PC adsorption due to the increased availability of surface water hydroxyl groups for interaction with the PC phosphate groups. Isopropanol promoted PC binding by destabilizing PC reverse miscelles in solution, thus promoting its adsorption.

Polymer Adsorption Effects on Structures and Rheological Properties of Silica Suspensions

By a combination of small angle neutron scattering (SANS) and rheological measurements, characterization of silica suspensions in aqueous (hydroxypropyl)methyl cellulose (HPMC) solutions and their shear stresses and dynamic moduli measurements were performed as a function of concentrations of silica, HPMC, and isopropyl alcohol, which plays a role to displace molecules of HPMC. Aerosil and Snowtex C silicas were used : the former is easily to aggregate in water and the latter is stable in water, and the respective structures were confirmed by a SANS technique. From the SANS measurements, adsorption of HPMC induced a small portion of the Snowtex C silica particles to form a cluster, whereas it did not influence the self-similar structures of Aerosil silicas suspensions. The amounts of HPMC adsorbed on the silica surfaces decreased with an increase in the displacer concentration. In the flow curves, plots of steady-state shear stress against the shear rate of the Aerosil silica suspensions, there was a bump, which is more like a plateau around 0.1 s -1 , in shear rate and this bump did not disappear with addition of isopropyl alcohol. However, the shear stress of the Snowtex C increased monotonically with an increase in the shear rate and its magnitude decreased with increasing displacer concentration. Upon addition of isopropyl alcohol the dynamic moduli of the respective silica suspensions decreased with the amounts of HPMC desorbed from the silica surfaces. For the Aerosil silica suspensions the storage modulus was more sensitive to the adsorbed amounts of HPMC than the loss modulus.

Influence of Indomethacin and Isopropanol on Hydrophobic Interaction through Long-Chain Alkyl Groups of Hydrophobically-Modified Hydroxypropyl Methylcellulose.

The hydrophobic interaction between long-chain alkyl groups of hydrophobically-modified hydroxypropyl methylcellulose (HM-HPMC) and indomethacin (IM) was studied using a fluorescence probe method in which pyrene molecules are allowed to associate with long-chain alkyl groups.In an HM-HPMC solution, the hydrophobicity of the pyrene environment markedly increased as the concentration of HM-HPMC was increased, indicating an increase of hydrophobic interaction between the long-chain alkyl groups. When IM was added to this solution, the hydrophobicity of the pyrene environment decreased as the IM concentration increased. Thus, it was suggested that the hydrophobic interaction between long-chain alkyl groups and IM caused a weakening of the hydrophobic interaction between HM-HPMC molecules themselves. When isopropanol (IPA) was added to an HM-HPMC solution, IPA weakened the hydrophobic interaction through long-chain alkyl groups. Thus, IPA caused an expansion of the intermolecular hydrophobic regions. For this reason, the amount of IM entrapped in these regions increased when the IPA concentration was increased. However, when the IPA concentration was further increased, the hydrophobic interaction finally disappeared. Thus, as IM molecules could no longer be trapped in the hydrophobic regions, the activity of HM-HPMC suppressing the growth of IM crystals disappeared.

Measurement of Serum Isopropanol and the Acetone Metabolite by Proton Nuclear Magnetic Resonance: Application to Pharmacokinetic Evaluation in a Simulated Overdose Model

The purpose of this investigation was to 1) compare the performance of proton nuclear magnetic resonance spectroscopy to gas chromatography head-space analysis in the measurement of serum isopropanol and its metabolite, acetone, obtained during a simulated overdose, and 2) compare pharmacokinetic parameters obtained using the two analytical techniques. Three healthy volunteers ingested 0.6 mL/kg of 70% isopropanol and blood samples were obtained at baseline, 0.16, 0.33, 0.66, 1.0, 1.5, 2.0, 3.0, 4.0, 6.0, 8.0, 12.0, and 24.0 hours post-ingestion. Resulting sera were analyzed by gas chromatography head-space analysis and proton nuclear magnetic resonance spectroscopy for determination of isopropanol and acetone concentrations. A correlation between concentrations quantitated by gas chromatography head-space analysis versus proton nuclear magnetic resonance spectroscopy was determined using linear regression. Pharmacokinetic disposition parameters were determined from serum concentration-time data and compared using analysis of variance. For isopropanol, the linear regression equation which describes the relationship between gas chromatography head-space analysis and proton nuclear magnetic resonance spectroscopy was y = 1.041x - 2.180 (r2 = 0.995, p < 0.0001); for acetone, y = 1.022x - 0.946 (r2 = 0.984, p < 0.0001). Pharmacokinetic disposition parameters derived from the two analytical methods were comparable. Proton nuclear magnetic resonance spectroscopy can be used to rapidly quantitate serum isopropanol and acetone concentrations in the same sample when gas chromatography head-space analysis is unavailable. Also, proton nuclear magnetic resonance spectroscopy can be used to follow serial serum concentrations during an ingestion for the purpose of pharmacokinetic analysis.

Solvent effects in competition between guest molecules for?-cyclodextrin

The effect was investigated of increasing concentrations of co-solvents ethanol, isopropanol, tetrahydrofuran (THF), dimethylformamide (DMF), formamide and ethylene glycol on the selectivity of inclusion for binary mixtures of the following guest molecules: pinene, eugenol, cineole, limonene and camphor, and of isopropanol for the ternary mixtures eugenol/cineole/pinene; and limonene/cineole/pinene. In contrast to the strong solvent dependent effects onβ-cyclodextrin solubility, the changes in selectivity are similar for each system, show little variation from solvent to solvent and are guest dependent. Similar guest induced effects are observed for ternary mixtures. They appear to be additive.

Effects of polymer adsorption and desorption on rheological properties of silica suspensions

Shear stresses and dynamic moduli of silica suspensions in aqueous hydroxypropyl methyl cellulose (HPMC) solutions were measured by using a cone-plate geometry as functions of the concentrations of silica, HPMC, isopropyl alcohol, acetic acid and pyridine. Isopropyl alcohol and pyridine behaved as displacers and they cause desorption of HPMC from the silica surfaces. The amounts of HPMC adsorbed on the silica surfaces decrease with an increase in the displacer concentration. In plots of steady state shear stress against shear rate, there was a shear rate of about 0.1 s −1 due to aggregation of the silica particles and this did not disappear on addition of isopropyl alcohol or acetic acid. However, the silica suspensions with pyridine must show some stress responses, although these may be outside the measurement range for the instrument. Pyridine increases the pH in the dispersion, leading to stable and unaggregated silica particles. By adding isopropyl alcohol to the silica suspensions, the storage modulus decreases with the amount of HPMC desorbed from the silica surfaces. The larger amounts of HPMC desorbed resulted in no second plateau in the dynamic moduli, showing the weaker aggregated structures in the silica suspensions. In contrast, pyridine had no detectable effect on the dynamic moduli of the silica suspensions.

Biodegradation of pesticides in nonionic water‐in‐oil microemulsions of tween 85: Relationship between micelle structure and activity

Water-in-oil microemulsion systems have been studied in recent years for a number of applications in protein separation and enzymology. Although it is well established that reversed micelle systems provide an excellent medium for nonaqueous biocatalytic studies, there is still much speculation as to the interaction of the enzyme with the surfactant interface. Polyoxyethylene sorbitan trioleate (Tween 85) is a nonionic surfactant which has some interesting properties for microemulsion formation and protein solubilization. In conjunction with a separate article describing the structural features of Tween 85 reversed micelles in hexane with isopropanol as a cosurfactant, this work describes the activity of an enzyme, organophosphorus hydrolase, for degrading organophosphorus pesticides in this microemulsion system. Ternary phase diagrams were constructed to outline the phase boundaries at different temperatures and isopropanol concentrations, which elucidate the role of the cosurfactant alcohol, as well as some features of micelle structure. Kinetic and stability studies with organophosphorus hydrolase show the effect of enzyme partitioning between the micelle surfactant layer and aqueous core. (c) 1994 John Wiley & Sons, Inc.

Phase equilibria of ternary and quaternary systems containing carbon dioxide, water, isopropanol, and glucose

Vapor-liquid equilibrium data have been measured for the ternary carbon dioxide-isopropanol-water system and for the quaternary carbon dioxide-isopropanol-water-glucose system at 313 and 333 K and at pressures between 13.8 and 30.0 MPa. For the quaternary system, densities were also obtained. A special high-pressure apparatus with vapor-phase recirculation and'a sample bomb placed in the recirculation loop was used for the measurements. The results show a phase behavior in the ternary system similar to that described in the literature at lower pressures. In the quaternary system, glucose concentrations in the vapor phase vary between 4.4 × 10 -4 and 0.11 mol %. While the glucose concentration is strongly dependent on the vapor-phase concentration of isopropanol and water, pressure and vapor-phase density do not influence the solubility of glucose in the vapor phase significantly. Comparing the effect of isopropanol and ethanol on the entrainment of glucose in the vapor phase, it is evident that while the measured maximum glucose solubilities in the vapor phase are of the same order of magnitude (0.11 mol % at 13.79 MPa, 313.15 K for the isopropanol system and 0.17 mol % at 25.0 MPa, 313.15 K for the ethanol system), higher pressures are needed with ethanol as a cosolvent to achieve the same glucose solubilities possible with isopropanol.

Diffuse reflectance Fourier transform infrared spectroscopy of oleic acid adsorption on silicic acid

AbstractDiffuse reflectance Fourier transform infrared spectroscopy was used to observe adsorption complexes of oleic acid and isopropanol (IPA) on silicic acid in hexane. The spectra provide definite evidence of the molecular nature of the surface interaction. In addition, the effect on oleic acid adsorption of modifying the solvent with IPA, which competes for adsorption sites and modifies the solvent polarity, was studied. Oleic acid adsorption was reduced in the presence of an equimolar IPA concentration in hexane, relative to that from hexane alone. This could be explained by a combination of competitive adsorption of IPA and IPA interacting with oleic acid in solution. IPA, in solution, and silica are probably competing for the lipid. This is additional evidence that suggests that lipid adsorption onto silicic acid is influenced by competitive adsorption. The adsorption of oleic acid and IPA, from a mixture of the two in hexane, was controlled by (i) the equilibrium between surface‐bound species and molecules in solution and (ii) the polar interaction between oleic acid and IPA in solution. Thus, washing pre‐bound oleic acid with hexane removed only a small amount of oleic acid, while washing with a solution of IPA in hexane removed most of the pre‐bound oleic acid.

Peptidyl methyl ketones as ligands in affinity chromatography of serine and cysteine proteinases

Peptidyl methyl ketones are reversible inhibitors of serine and cysteine proteinases and can be employed as ligands in affinity chromatography. Serine proteinases of the subtilisin family may be purified using the tripeptidyl methyl ketone -Ala 2PheCH 3 as ligand, whereas for papain, the best-known cysteine proteinase, both the -Ala 2PheCH 3 and the -PheAlaCH 3 ligands are efficient. Complete elution of affinity-bound proteinases with isopropanol was demonstrated by investigations with thermitase, a subtilisin-type serine proteinase, which was 14C labelled. Bound proteinases with different affinity for a defined ligand may be consecutively eluted using increasing concentrations of isopropanol in the elution buffer, as was shown, for example, with a mixture of thermitase and subtilisin DY. The quality of the lyophilized affinity-purified thermitase is similar to that of thermitase preparations purified by isoelectric focusing and adsorption on porous glass bodies. The affinity of thermitase for the immobilized -Ala 2PheCH 3 ligand linked to Divicell via an ε-aminocaproic acid (Aca) spacer is about two orders of magnitude lower than its affinity for the soluble inhibitor benzyloxycarbonyl—Ala 2PheCH 3 and one order of magnitude lower than its affinity for AcAcaAla 2PheCH 3. In comparison with affinity gels made with commercial CH-Sepharose 4B, the Divicell gels possess higher concentrations of ligands and have a higher stability.