Application of membrane filters for spectrophotometric determination of cationic surfactants in river water and sediment.

Cationic surfactant (CS+) in urban river water and sediment was extracted and determined spectrophotometrically with 2 membrane filters. The CS+ in the water samples, mostly in the form of an ion associate with the coexisting anionic surfactant (AS), was collected on a polytetrafluoroethylene (PTFE) membrane filter and eluted with methanol. Bromphenol blue (BPB), hydrochloric acid, and water were added to the methanol solution successively, and the mixed solution was filtered through a mixed cellulose ester membrane filter. The CS+-BPB- ion associate, formed by a counter ion exchange, was collected on the filter and dissolved into N,N-dimethylformamide (DMF) together with the mixed cellulose ester membrane filter. After addition of 2 drops of triethanolamine, the absorbance of the DMF solution was measured. The CS+ in sediment samples was extracted with methanol by ultrasonic irradiation; the methanol solution was then passed through a PTFE membrane filter and evaporated to dryness. The CS+ was redissolved in a small amount of methanol. For water samples, recoveries and relative standard deviations for 0.30 microM benzyldimethyl-tetradecylammonium ion, a standard material, were > or =93 and < or =5%, with a detection limit of 0.02 microM. Concentrations of CS+ in sediments were much higher than those in water samples, indicating that CS+ is adsorbed on the surface of the sediment.     

Extraction and separation of cationic surfactants from river sediments: application to a spectrophotometric determination of cationic surfactant in an aquatic environment using membrane filters.

The quantitative extraction of cationic surfactant (CS+) in river sediments was studied. Further, the developed method was applied to the spectrophotometric determination of CS+ in urban river sediment samples by solid-phase extraction with membranes. A mixture of methanol and hydrochloric acid was proposed as an eluent. Dried sediment was digested in the eluent under ultrasonic irradiation. After elution, the eluent was evaporated to almost dryness. The residue was dissolved in a small volume of methanol and diluted to a certain volume with water. The pH of the solution was adjusted to 4-5 to separate iron and some other metals as precipitates of hydroxides. The solution was passed through two-piled membranes: first glass-fiber and then polytetrafluoroethylene (PTFE) membranes. A small volume of methanol was passed through the membranes to elute any CS+ retaining on the membranes. After passing the methanol solution through a cationic exchange resin column, the retained CS+ was eluted with methanol containing a high concentration of sodium chloride. Water, Bromophenol Blue (BPB) and hydrochloric acid were added to the solution. The solution was passed through a mixed cellulose ester membrane filter to retain an ion associate of CS+.BPB-. The retained ion associate was dissolved in a small volume of N,N-dimethylformamide together with the membrane filter, followed by the addition of triethanolamine to make the solution alkaline. The absorbance due to BPB2- was measured at 603 nm against a reagent blank. This method was applied to the determination of CS+ in river water and sediment. A cationic surfactant in sediments at 10(-5) mol kg-1 levels was detected with satisfactory precision. It was found that CS+ was about 500-fold enriched in the sediment from water at the place where domestic wastewater was discharged.     

Resonance Rayleigh scattering for the determination of cationic surfactants with Eosin Y

Resonance Rayleigh scattering (RRS) of cationic surfactants–Eosin Y systems and their analytical application have been studied. In aqueous solution at pH 2～3, Eosin Y reacts with a monomer of cationic surfactants (CS), such as Zephiramine (Zeph), tetradecylpyridinium bromide (TPB), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CTMAB), to form an ion associate and a new RRS spectrum appears. The spectral characteristics of the five ion associates are similar and their maximum scattering wavelengths (λ_max) are all at 313 nm. The intensity of RRS at λ_max of the ion associate is directly proportional to the concentration of CS in the range of 0～3.0 μg/25 mL. The technique has high sensitivity for the determination of CS; their detection limit is between 5.57 ng/mL and 7.60 ng/mL depending on the CS. In this case, most metal and non-metal ions, NH₄ ⁺ and some anionic surfactants do not interfere, so that the method has a good selectivity. It can be applied to the determination of trace amounts of cationic surfactants in water samples.     

Spectrophotometric determination of trace ionic and non-ionic surfactants based on a collection on a membrane filter as the ion associate of the surfactant with Erythrosine B

The spectrophotometric method for the determination of trace surfactants with Erythrosine B (EB) based on the aqueous reaction and the collection on a membrane filter by filtration was studied. Cationic surfactants (CS⁺), such as a quaternary ammonium ion, and polyoxyethylene non-ionic surfactants (NS) in the presence of potassium ion, containing a long-chain alkyl group associate with EB buffered at pH 5.5. CS⁺ associates with anionic surfactants (AS⁻). For the determination of CS⁺, four methods were employed: the collection of the ion associate of CS⁺ with EB on a mixed cellulose ester (MCE) or PTFE membrane filter, the collection of the ion associate of CS⁺ with AS⁻ on a PTFE membrane filter followed by the ion exchange of AS⁻ with EB, and the first collection of CS⁺ followed by the second collection of EB on a PTFE membrane filter. For the determination of AS⁻, the collection of the ion associate of AS⁻ with CS⁺ on a PTFE membrane filter followed by the ion exchange of AS⁻ with EB was done. For the determination of NS, the ion associate of NS with EB was collected on a MCE membrane filter. The MCE membrane filter with the analyte was dissolved in methyl cellosolve. The analyte on the PTFE membrane filter was eluted with ethanol. The CS⁺ up to 5×10⁻⁷ M can be determined by the absorbance at 542 nm of the methyl cellosolve solution or the absorbance at 535 nm of the ethanol solution. The AS⁻ up to 5×10⁻⁷ M can be determined by the absorbance at 536 nm of the ethanol solution. The NS up to 2.53×10⁻⁶ M can be determined by the absorbance at 537 nm of the methyl cellosolve solution. This is the sensitive method for the determination of 10⁻⁸ to 10⁻⁷ M order of ionic surfactants and 10⁻⁷ to 10⁻⁶ M order of NS without toxic organic solvents.     

Resonance Rayleigh scattering for the determination of cationic surfactants with Eosin Y

Resonance Rayleigh scattering (RRS) of cationic surfactants–Eosin Y systems and their analytical application have been studied. In aqueous solution at pH 2∼3, Eosin Y reacts with a monomer of cationic surfactants (CS), such as Zephiramine (Zeph), tetradecylpyridinium bromide (TPB), cetylpyridinium bromide (CPB), cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CTMAB), to form an ion associate and a new RRS spectrum appears. The spectral characteristics of the five ion associates are similar and their maximum scattering wavelengths (λ_max) are all at 313 nm. The intensity of RRS at λ_max of the ion associate is directly proportional to the concentration of CS in the range of 0∼3.0 μg/25 mL. The technique has high sensitivity for the determination of CS; their detection limit is between 5.57 ng/mL and 7.60 ng/mL depending on the CS. In this case, most metal and non-metal ions, NH₄ ⁺ and some anionic surfactants do not interfere, so that the method has a good selectivity. It can be applied to the determination of trace amounts of cationic surfactants in water samples. Received: 9 September 1998 / Revised: 17 November 1998 / Accepted: 18 November 1998     

Formation of ternary ion associates using diprotic acid dyes and its application to determination of cationic surfactants

A sensitive and selective method is described for the determination of cationic surfactants, such as benzethonium, benzalkonium, cetylpyridinium and trimethylstearylammonium, based on the formation and extraction of ternary ion associates with an acid dye (bromophenol blue or bromochlorophenol blue) and quinidine. Quinidine reacts with divalent anionic dyestuffs to form a bulky 11 complex anion, which is extractable into 1,2-dichloroethane as ternary ion associates with cationic surfactants in nearly neutral media. The ternary ion associate gives a blue product. Linearity of the calibration curve is improved and the extractability of the cationic surfactants is enhanced in the presence of quinidine. In addition, many other amines do not interfere with the determination. The blue ion associates can be used for the selective and sensitive spectrophotometric determination of cationic surfactants.     

Influence of Ionic Surfactants on Tetrabromophenylfluorone Ionic Associates

Stability constants of ionic associates of a hydroxyxanthene dye, tetrabromophenylfluorone, with a series of organic cations were determined spectrophotometrically. The possibility of quantitative determination of anionic surfactants (alkyl sulfates) in an aqueous solution in the form of a dye anion associate with tetrabutylammonium cation was considered.     

Spectrophotometric determination of trace sulphate in rain and snow after preconcentration with 2-aminoperimidine on a membrane filter

A simple and precise preconcentration technique, based on collecting a precipitate on a membrane filter and dissolving the filter and precipitate in an organic solvent, has been applied to the spectrophotometric determination of trace sulphate in rain and snow. The sulphate is precipitated with 2-aminoperimidine and the resulting compound is dissolved in nitric acid, made alkaline with sodium hydroxide and then adsorbed on tetradecyldimethylbenzylammonium nitrate. The precipitate is then collected on a membrane filter and both precipitate and filter are dissolved in dimethylsulphoxide (DMSO). The absorbance of the DMSO solution is measured at 550 nm against a reagent blank. The molar absorptivity is 2.1 x 10(4) 1 . mole(-1) . cm(-1) and the coefficient of variation for six measurements is < 1.5%. The detection limit (S/N = 3) is 0.06 mug of sulphate in 5 ml of sample solution.     

壳聚糖·聚丙烯酸配合物半互穿聚合物网络膜及其对pH和离子的刺激响应

壳聚糖·聚丙烯酸配合物半互穿聚合物网络膜及其对ｐＨ和离子的刺激响应李文俊王汉夫卢玉华汪志亮钟伟（复旦大学高分子科学系聚合物分子工程开放实验室上海２００４３３）关键词高分子间配合物，互穿聚合物网络（ＩＰＮ），水凝胶，壳聚糖，刺激响应敏感性水凝胶是一种...     

Spectrophotometric study of the complexation and extraction of chromium(VI) with cyanine dyes

Solvent extraction of chromium(VI) ion associates with symmetric cyanine dyes including the heterocyclic radicals of 1,3,3-trimethyl-3N-indoline, benzooxazol, benzothiazol and quinoline has been studied by means of spectrophotometric method. In the acidic medium in the presence of chloride ions, extractable by aromatic hydrocarbons and esters of acetic acids, chromium(VI) ion associates are formed. The molar absorptivities of ion associates are 2.5-3.6x10(5) l mol(-1) cm(-1) in dependence on extractant and dye. The absorbance of the coloured extracts obeys the Beer's law in the range 0.01-2.1 mg l(-1). The extraction of chromium is the highest during extraction from the sulphuric acid medium in the range 0.05-03 M H(2)SO(4). It was found that the Cr(VI):Cl:R molar ratio is 1:1:1. A novel procedure of chromium(VI) extraction and spectrophotometric determination in various types of soils and sewage doped with chromium(VI) was examined.     

The association of cyanine dye cations with phenol red anions in aqueous solutions

The interaction of pinacyanol (PNC) and quinaldine red (QR) cyanine dye cations with single-and doubly charged phenol red (PR) anions in aqueous solution was investigated in detail. In spite of fundamentally different geometries, noticeable interaction between the counterions leads to the formation of ion associates. The energies of PNC, QR, PR, and their associates were calculated. The addition of cationic or anionic surfactants destroyed the associates. The nontrivial character of for the destruction of the PNC⁺-PR^? associate offers promise for the development of quantitative and test methods for the determination of cationic surfactants in solution.     

Effect of organic and inorganic acids on chitosan/glycerophosphate thermosensitive hydrogel

The influence of organic and inorganic acids on chitosan/glycerophosphate (CS/GP) hydrogel has been investigated by dissolving chitosan in different acids. The results of gelation showed that all of the chitosan dissolved in monovalent acid solutions (i.e., formic, acetic, propionic, butyric, isobutyric, lactic, nitric, hydrochloric, and chloroacetic acid), when neutralized by GP solution, could transform into hydrogel after 2–5 min at 37 °C, while those dissolved in multivalent acids failed in gel formation. The inner structures of CS/GP hydrogels prepared with monovalent acids depended on the ionic strength and chain length of acids. Morphological examination by scanning electron microphotography demonstrated that large pores occurred during the gel-forming process, and the aperture size was also related to different acids. The cytotoxicity studies indicated that CS/GP systems prepared by dissolving chitosan in tested acids except chloroacetic acid were nontoxic to mouse embryonic fibroblasts and Hela cells.     

High-resolution determination of H+ by ion chromatography. Application to the simultaneous determination of H+, Na+, NH4+ and K+ in acid rain.

An ion chromatographic (IC) method was developed for the high-resolution determination of a sample's free hydrogen ion concentration (H+). Highly purified lithium dodecyl sulfate was used as the stationary phase, a slightly acidified aqueous LiCl solution was used as the mobile phase and conductivity was used for analyte detection. An electrical double layer (EDL) containing H+ was established on the stationary phase by using a slightly acidified electrolyte solution as the eluent. H+ in the EDL protonated any weak acid groups (i.e., silanols) on the stationary phase so that H+ from the sample could be retained/separated purely by dodecyl sulfate. The optimum molar ratio of H+:Li+ in the EDL for this IC system was obtained by using an aqueous solution containing 40.0 mM LiCl and 0.07 mM H2SO4 as the eluent. After separation, H+ was detected by direct conductimetric measurement. An H+ detection limit of better than 8.2 x 10(-6) M was obtained from the analysis of standard aqueous H2SO4 solutions. Other monovalent cations could also be separated with this method, giving detection limits of 7.4 x 10(-5), 4.3 x 10(-5) and 4.2 x 10(-5) M for Na+, NH4+ and K+, respectively. The method was applied to the simultaneous determination of H+, Na+, NH4+ and K+ in acid rain. The results obtained showed a significant improvement in reproducibility when compared with those from a conventional pH-meter. Acid rain samples with a pH < 5 could be analyzed with this IC system.     

Effect of surfactants on homo- and heteroassociation of pinacyanol cation in aqueous solution

The aggregative properties of pinacyanol in aqueous solution and the capability of its ionic associates to interact with surfactants were studied. The possibility of using pinacyanol associates for quantitative determination of cationic surfactants in aqueous solution and for estimation of the critical micelle concentration of anionic surfactants was examined.     

Use of Biopolymers for the Removal of Metal Ion Contaminants from Water

Summary: Naturally abundant biosorbants such as chitin and chitosan are recognized as excellent metal ligands, forming stable complexes with many metal ions, and serving as effective protein coagulating agents. Chitosan is a heteropolymer made of D-glucosamine and a small fraction of N-acetyl-D-glucosamine residues. Therefore, the adsorption ability of chitosan is found to be much higher than that of chitin, which has relatively fewer amino groups. Zeolites are crystalline microporous aluminosilicates with ion exchange properties suitable for a wide range of applications in catalysis and separation of liquid and gaseous mixtures. Incorporation in chitosan membranes is an effective method to control the diffusion outside the zeolite crystals and appropriately designed composite systems can find numerous opportunities for applications in wastewater treatment. In this paper we present the synthesis of zeolite-chitosan and zeolite-ethyl cellulose composites by encapsulation of clinoptilolite using a gelling solution of chitosan or an ethyl cellulose solution in ethyl acetate. The adsorption process of Cu²⁺ and Cd²⁺ on some adsorbents was investigated: clinoptillolite tuff (0.05 mm), chitosan flakes, ethyl cellulose, zeolite-chitosan and zeolite- ethyl cellulose composites. Zeolite-chitosan composites have been prepared by encapsulation of zeolites by a gelling solution of chitosan. Micrometric crystals of clinoptillolite were dispersed in a 3% chitosan solution in 1% aqueous acetic acid. The chitosan gel was formed and the zeolite crystals were encapsulated during the gelling process. The same procedure was used to obtain zeolite – ethyl cellulose composites. Study of the metal ion retention properties of different adsorbent materials was carried out using a steady state regime. The concentration of heavy metal ions in supernatant was determined by the atomic absorption spectrophotometric method. Adsorption isotherms of metal ions on adsorbents were determined and correlated with common isotherm equations such as Langmuir and Freundlich models.     

Kinetics and thermodynamics of bromophenol blue adsorption by a mesoporous hybrid gel derived from tetraethoxysilane and bis(trimethoxysilyl)hexane

A mesoporous hybrid gel is prepared with tetraethoxysilane (TEOS) and bis(trimethoxysilyl)hexane (TSH) as precursors without using any templating agent. Nitrogen sorption, TG-DTA, FTIR, and point of zero charge (PZC) measurement are used to characterize the gel. The gel has a specific surface area of 695 m(2) g(-1) with a pore size of 3.5 nm, a pore volume of 0.564 cm(3) g(-1), and a point of zero charge (PZC) of 6.2. The kinetics and thermodynamics of bromophenol blue (BPB) adsorption by the gel in aqueous solution are investigated comprehensively. The effects of initial BPB concentration, pH, ionic strength, and temperature on the adsorption are investigated. Kinetic studies show that the kinetic data are well described by the pseudo-second-order kinetic model. Initial adsorption rate increases with the increase in initial BPB concentration and temperature. Adsorption activation energy is found to be 62.5-67.5 kJ mol(-1) depending on the initial BPB concentration. Internal diffusion appears to be the rate-limiting step for the adsorption process. The equilibrium adsorption amount increases with the increase in the initial BPB concentration, solution acidity, and ionic strength, but decreases with the increase in temperature. The thermodynamic analysis indicates that the adsorption is spontaneous and exothermic. The adsorption isotherms can be well described with Freundlich equation indicating the heterogeneity of the hybrid gel surface. Electrostatic and hydrophobic interactions are suggested to be the dominant mechanism for adsorption.     

同时测定无机离子的改良离子色谱法在河水和废水质量监控中的应用（英文）

In this study,our recent work on advanced ion chromatographic methods for the simultaneous determination of inorganic ionic species such as common anions(SO2-4,Cl-and NO-3) and cations(Na+,NH+4,K+,Mg2+,and Ca2+),nutrients(phosphate and silicate) and hydrogen ion/alkalinity are summarized first.Then,the applications using these methods for monitoring environmental water quality are also presented.For the determination of common anions and cations with nutrients,the separation was successfully performed by a polymethacrylate-based weakly acidic cation-exchange column of TSKgel Super IC-A/C(Tosoh,150 mm×6.0 mm i.d.) and a mixture solution of 100 mmol/L ascorbic acid and 4 mmol/L 18-crown-6 as acidic eluent with dual detection of conductivity and spectrophotometry.For the determination of hydrogen ion/alkalinity,the separation was conducted by TSKgel ODS-100Z column(Tosoh,150 mm×4.5 mm i.d.) modified with lithium dodecylsulfate and an eluent of 40 mmol/L LiCl/0.1 mmol/L lithium dodecylsulfate/0.05 mmol/L H2SO4 with conductivity detector.The differences of ion concentration between untreated and treated wastewater showed the variation of ionic species during biological treatment process in a sewage treatment plant.Occurrence and distribution of water-quality conditions were related to the bioavailability and human activity in watershed.From these results,our advanced ion chromatographic methods have contributed significantly for water quality monitoring of environmental waters.     

Monitoring propofol serum levels by rapid and sensitive reversed-phase high-performance liquid chromatography during prolonged sedation in ICU patients.

A quick and sensitive reversed-phase high-performance liquid chromatography (HPLC) method has been developed in order to determine the concentration of Propofol (2,6 diisopropylphenol) in human serum. Propofol can be isolated from serum by adding 0.5 mL precipitating solution. This consists of an acetonitrile and perchloric acid (67:33, v/v) mixture, which also contains dibutylphthalate (2 mg/100 mL) as internal standard. The sample is then mixed for 1 min on a vortex-mixer. The endogenous serum substances precipitated by acetonitrile and perchloric acid are further separated by centrifugation. The supernatant is directly injected into the HPLC system. A 250- x 4.6-mm column, packed with 10-microns Spherisorb reversed-phase octadecylsilane particles (C18), is used for chromatographic separation. The mobile phase consists of an acetonitrile-water mixture (67:33 ratio) with 0.4 mL acetic acid (pH 4). Propofol is monitored by a UV-visible detector at 270 nm and 0.1-0.002 absorbance units full scale (AUFS). The detection limit of Propofol (in human serum) is 0.1 mg/L for a 20-microL injection volume. The time of the assay is less than 20 min, including sample preparation.     

The liquidlike ordering of lipid A-diphosphate colloidal crystals: the influence of Ca2+, Mg2+, Na+, and K+ on the ordering of colloidal suspensions of lipid A-diphosphate in aqueous solutions

A comprehensive study was performed on electrostatically stabilized aqueous dispersion of lipid A-diphosphate in the presence of bound Ca2+, Mg2+, K+, and Na+ ions at low ionic strength (0.10-10.0-mM NaCl, 25 degrees C) over a range of volume fraction of 1.0 x 10(-4)< or =phi< or =4.95 x 10(-4). These suspensions were characterized by light scattering (LS), quasielastic light scattering, small-angle x-ray scattering, transmission electron microscopy, scanning electron microscopy, conductivity measurements, and acid-base titrations. LS and electron microscopy yielded similar values for particle sizes, particle size distributions, and polydispersity. The measured static structure factor, S(Q), of lipid A-diphosphate was seen to be heavily dependent on the nature and concentration of the counterions, e.g., Ca2+ at 5.0 nM, Mg2+ at 15.0 microM, and K+ at 100.0 microM (25 degrees C). The magnitude and position of the S(Q) peaks depend not only on the divalent ion concentration (Ca2+ and Mg2+) but also on the order of addition of the counterions to the lipid A-diphosphate suspension in the presence of 0.1-microM NaCl. Significant changes in the rms radii of gyration (R2G) 1/2 of the lipid A-diphosphate particles were observed in the presence of Ca2+ (24.8+/-0.8 nm), Mg2+ (28.5+/-0.7 nm), and K+ (25.2+/-0.6 nm), whereas the Na+ salt (29.1+/-0.8 nm) has a value similar to the one found for the de-ionized lipid A-diphosphate suspensions (29.2+/-0.8 nm). Effective particle charges were determined by fits of the integral equation calculations of the polydisperse static structure factor, S(Q), to the light-scattering data and they were found to be in the range of Z*=700-750 for the lipid A-diphosphate salts under investigation. The light-scattering data indicated that only a small fraction of the ionizable surface sites (phosphate) of the lipid A-diphosphate was partly dissociated (approximately 30%). It was also discovered that a given amount of Ca2+ (1.0-5.0 nM) or K+ (100 microM) influenced the structure much more than Na+ (0.1-10.0-mM NaCl) or Mg2+ (50 microM). By comparing the heights and positions of the structure factor peaks S(Q) for lipid A-diphosphate-Na+ and lipid A-diphosphate-Ca2+, it was concluded that the structure factor does not depend simply on ionic strength but more importantly on the internal structural arrangements of the lipid A-diphosphate assembly in the presence of the bound cations. The liquidlike interactions revealed a considerable degree of ordering in solution accounting for the primary S(Q) peak and also the secondary minimum at large particle separation. The ordering of lipid A-diphosphate-Ca2+ colloidal crystals in suspension showed six to seven discrete diffraction peaks and revealed a face-centered-cubic (fcc) lattice type (a=56.3 nm) at a volume fraction of 3.2 x 10(-4)< or =phi< or =3.9 x 10(-4). The K+ salt also exhibited a fcc lattice (a=55.92 nm) at the same volume fractions, but reveals a different peak intensity distribution, as seen for the lipid A-diphosphate-Ca2+ salt. However, the Mg2+ and the Na+ salts of lipid A-diphosphate showed body-centered-cubic (bcc) lattices with a=45.50 nm and a=41.50 nm, respectively (3.2 x 10(-4)< or =phi< or =3.9 x 10(-4)), displaying the same intensity distribution with the exception of the (220) diffraction peaks, which differ in intensity for both salts of lipid A-diphosphate.     

CS2O+ and CS2O in the gas phase: an experimental and computational study

The CS2O+ ion and CS2O molecule were prepared and structurally characterized by mass spectrometric techniques as isolated species in the gas phase. The theoretical analysis, performed by B3LYP and CCSD(T) computational methods, predicted different CS2O+ isomers, SSCO+, O(CS2)+, SCSO+, SCOS+ and S(COS)+, and structurally related singlet and triplet CS2O. Experiment and theory agree in identifying the obtained CS2O+ ions as a mixture of SCSO+ and SCOS+ isomers. CS2O neutral species, prepared by neutralization-reionization mass spectrometry, were directly characterized as intact, long-lived species with a lifetime tau > or =2 micros.