Spectrophotometric Determination Of Anionic Surfactants Research Articles

Spectrophotometric determination of anionic surfactants: optimization by response surface methodology and application to Algiers bay wastewater.

A simple analytical method for quantitative determination of an anionic surfactant in aqueous solutions without liquid-liquid extraction is described. The method is based on the formation of a green-colored ion associate between sodium dodecylbenzenesulfonate (SDBS) and cationic dye, Brilliant Green (BG) in acidic medium. Spectral changes of the dye by addition of SDBS are studied by visible spectrophotometry at maximum wave length of 627nm. The interactions and micellar properties of SDBS and cationic dye are also investigated using surface tension method. The pH, the molar ratio ([BG]/[SDBS]), and the shaking time of the solutions are considered as the main parameters which affect the formation of the ion pair. Determination of AS in distilled water gives a significant detection limit up to 3 × 10-6 M. The response surface methodology (RSM) is applied to study the absorbance. A Box-Behnken is a model designed to the establishment of responses given by parameters with great probability. This model is set up by using the three main parameters at three levels. Analysis of variance shows that only two parameters affect the absorbance of the ion pair. The statistical results obtained are interesting and give us real possibility to reach optimum conditions for the formation of the ion pair. As the proposed method is free from interferences from major constituents of water, it has been successfully applied to the determination of anionic surfactant contents in wastewaters samples collected from Algiers bay.

Liquid–liquid microextraction and spectrophotometric determination of anionic surfactants using Astra Phloxine FF

A novel and simple procedure for determination of anionic surfactants has been developed. The method is based on the reaction of sodium dodecyl sulphate (SDS) with Astra Phloxine FF reagent at pH 3–8, followed by liquid–liquid microextraction of the formed ion associate into an organic phase containing a mixture of carbon tetrachloride and dichloroethane (4:1, v/v) and subsequent UV-Vis detection at 555 nm. The calibration plot was linear in the range 0.006–0.29 mg L−1 of SDS. The limit of detection (LOD), calculated based on 3s, is 0.002 mg L−1. The method was applied to the determination of anionic surfactants in real wastewater samples.

Cobalt phthalocyanine as a novel molecular recognition reagent for batch and flow injection potentiometric and spectrophotometric determination of anionic surfactants

Cobalt(II) phthalocyanine [Co(II)Pc] is used as both an ionophore and chromogen for batch and flow injection potentiometric and spectrophotometric determination of anionic surfactants (SDS), respectively. The potentiometric technique involves preparation of a polymeric membrane sensor by dispersing [Co(II)Pc] in a plasticized PVC membrane. Under batch mode of operation, the sensor displays a near-Nernstian slope of −56.5 mV decade −1, wide response linear range of 7.8 × 10 −4 to 8.0 × 10 −7 mol L −1, lower detection limit of 2.5 × 10 −7 mol L −1 and exhibits high selectivity for anionic surfactants in the presence of many common ions. Under hydrodynamic mode of operation (FIA), the slope of the calibration plot, limit of detection, and working linear range are −51.1 mV decade −1, 5.6 × 10 −7 and 1.0 × 10 −3 to 1.0 × 10 −6 mol L −1, respectively. The spectrophotometric method is based on the use of [Co(II)Pc] solution in dimethylsulfoxide (DMSO) as a chromogenic reagent. The maximum absorption of the reagent at 658 nm linearly decreases with the increase of anionic surfactant over the concentration range 2–30 μg mL −1. The lower limit of detection is 1 μg mL −1 and high concentrations of many interfering ions are tolerated. Flow injection spectrophotometric measurements are carried out by injection of the surfactant test solution in a stream of the reagent in DMSO. The sample throughput, working range and lower detection limit are 25–30 samples h −1, 4–60 and 2 μg mL −1, respectively. The potentiometric and spectrophotometric techniques are applied to the batch and flow injection measurements of anionic surfactants in some commercial detergent products. The results agree fairly well with data obtained using the standard methylene blue spectrophotometric method.

Micro-pumping flow system for spectrophotometric determination of anionic surfactants in water

A novel procedure has been developed for spectrophotometric determination of anionic surfactants in water using a solenoid micro-pump as fluid-propulsion device. The proposed method is based on substitution of methyl orange (MO) by anionic surfactants in the formation of an ion-pair with the cetyl pyridine ion (CPC+) at pH 5.0. The flow network comprised four solenoid micro-pumps which, under microcomputer control, enabled sample and reagent introduction, and homogenisation in the reaction zone. The system is flexible and simple to operate and control, and sensitive and precise. The analytical plot for the anionic surfactant was linear between 1.43x10(-6) and 1.43x10(-5) mol L(-1) (0.5 to 5.0 mg L(-1); R=0.997, n=5). The relative standard deviation was 0.8% (n=11) for a sample containing 5.74x10(-6) mol L(-1) (2 mg L(-1)) surfactant. The limit of detection was 9.76x10(-8) mol L(-1) (0.034 mg L(-1)) and the sampling throughput was 60 determinations per hour. The results obtained for washing-water samples were comparable with those obtained by use of the reference method, and no significant differences at the 95% confidence level were observed.

An environmentally friendly multicommutated alternative to the reference method for anionic surfactant determination in water

It has been developed a fully mechanized procedure for the spectrophotometric determination of anionic surfactants in water expressed in terms of SDS concentration. The reference method, based on the reaction of SDS with methylene blue (MB) followed by extraction in chloroform, was mechanized in order to reduce the consumption of organic solvents. The system was based on the multicommutation approach and provided a 35 times reduction of the waste production without sacrificing the figures of merit of the method in terms of sensitivity and repeatability, for a dynamic linear range from 0.2 to 1.7 mg l −1. Results obtained for washing water samples were comparable with those obtained using the reference method and no significant differences, at 95% confidence level, were observed. Other useful characteristics are a solvent consumption of 0.7 ml per determination, a sampling throughput of 40 determinations per hour, a relative standard deviation of 5.9% ( n = 10) for a sample containing 2 × 10 −6 mol l −1 (576 μg l −1) surfactant and a limit of detection of 6.1 × 10 −9 mol l −1 (1.7 μg l −1).

Flow injection spectrophotometric determination of anionic surfactants using methyl orange as chromogenic reagent.

A flow injection(FI) spectrophotometric method for the determination of anionic surfactants was developed on the basis of the competition for the cationic surfactant cetyl pyridine (CP+) chloride between the acidic dye methyl orange (MO) and anionic surfactants. In a pH 5.0 medium the cation of cetyl pyridine (CP+) reacts with dissociated methyl orange (MO-) to form an ion-associate complex, causing a blue shift of lambda(max) from 465 nm for MO- to 358 nm for the CP+ x MO- associate. The MO- in the ion-associate complex can be quantitatively substituted by such anionic surfactants as sodium dodecyl benzene sulfonate (DBS) or sodium lauryl sulfate (LS), leading to an increase in the absorbance measured at 465 nm. This increased absorbance value is proportional to the concentration of anionic surfactants. Various chemical and physical parameters for the FI spectrophotometric method were optimized, and interference-free levels were examined. At the optimized conditions, Beer's law was obeyed in the range 1.4 approximately 25 mg/L sodium DBS for an injected sample volume of 180 microL, and a detection limit of 0.22 mg/L for sodium DBS was achieved at a sampling rate of 90 h(-1). Eleven determinations of a 16 mg/L sodium DBS solution gave a RSD of 0.4%. The proposed method has successfully been applied to the determination of anionic surfactant concentration in waste water and in detergents.

Spectrophotometric determination of anionic surfactants in aqueous and environmental water samples with cationic dyes

The applicatiliby of the extractive spectrophotometric method using three different cationic dyes as the chromogenic reagent for indentification and quantification of anionic surfactants in aqueous solutions and environmental samples was comparatively investigated. The inteferences due to the ions Cl−, NO3 −, Ca++, Mg++ and Fe3+ were examined as well as the effect of pH. The recoveries ranged from 95 to 104% for sea water samples.

Spectrophotometric determination of anionic surfactants in sea-water based on ion-pair extraction with bis[2-(5-trifluoromethyl-2-pyridylazo)-5-diethylaminophenolato]cobalt(III) as counter ion

A simple and sensitive spectrophotometric method was developed for the extraction and spectrophotometric determination of low levels of anionic surfactants in sea-water. Anionic surfactants are extracted into toluene as an ion-pair with bis[2-(5-trifluoromethyl-2-pyridylazo)-5-diethylaminophenolato]cobalt(III){[Co(CF3-PADAP)2]+} and the absorbance of the organic phase is measured at 560nm. The cobalt complex cation is inert and stable over a wide pH range, and has a large molar absorption coefficient (Iµ= 1.06 × 104 m2 mol–1 at 573 nm in water and Iµ= 5.83 × 103 m2 mol–1 at 560 nm in toluene). The Beer–Lambert law was obeyed over the concentration range 0.01–0.4 mg dm–3 of sodium dodecyl sulfate (SDS) and the detection limit was 0.005 mg dm–3 on a 3σb basis. The relative standard deviations for artificial sea-water spiked SDS were about 2%. Electrolytes in sea-water do not interfere. The proposed method is simpler and more sensitive than the conventional Methylene Blue method even when the degradation products of anionic surfactants are present. The method was applied to the determination of anionic surfactants in sea-water samples without interference from matrix substances.

Some N-alkyl-naphthylazo pyridinium salts as new reagents for the spectrophotometric determination of anionic surfactants

Eleven pyridinium azo dyes with straight-chain alkyl groups CnH2n+1−(n=6−18) and bromoalkyl groups BrCmH2m−(m=6−12) were synthesized with the intention of developing reagents for the determination of low levels of anionic surfactants in an aqueous medium. The effect of the alkyl chain length of these reagents on the reactivity with anionic surfactants such as sodium dodecylsulphate (SDS), sodium linear-dodecylbenzenesulphonate (DBS), sodium dodecylsulphonate (DS) and sodium laurate (SL) was studied. It was found that the alkyl chain length played an important role in the formation of ion associates and the composition of the ion associates formed. These reagents were classified into four groups with respect to the reactivity with anionic surfactants. The first group (n,m=6) reacts only with DBS. The second group (n,m=8) reacts with SDS, DBS and DS. The third group (n,m=10, 12) reacts with SDS, DBS and DS; however, the colour intensity of the DBS-ion associate was unstable. The fourth group (n=14, 16, 18) reacts with all anionic surfactants examined, and the composition of the ion associates with SDS and DS was 2:1 ([reagent]/[surfactant]) though that of the ion associates of the three reagent groups mentioned above was 1:1. The optimal conditions for the determination of anionic surfactants in river water with 1-octyl-4-(4-aminonaphthylazo)-pyridinium bromide was examined. The calibration graph was linear up to 3×10−6 mol/l, and the apparent molar absorptivity of the ion associate was 3.8×104 l mol−1 cm−1 (at 427 nm). The relative standard deviation for 2.4×10−6 mol/l SDS was 4.9%. Recoveries of 88–107% were found for 8.0×10−7 mol/l SDS in river water samples.

Interaction of hydrophobic anions with cationic dyes and its application to the spectrophotometric determination of anionic surfactants

The change in absorption spectra of Ethyl Violet solution on addition of anionic surfactants in an aqueous solution was used for the determination of anionic surfactants. This change is caused by the hydrophobic interaction between the bulky dye and the detergent. The contribution from the substituents of the cationic dyes and anionic surfactants to the hydrophobicity is discussed. The calibration graph is linear over the concentration range from 4 × 10–6 to 4 × 10–5 mol dm–3. The molar absorption coefficient for lauryl sulfate is 1.76 × 103 m2 mol–1 at 700 nm.

Batchwise and Flow-Injection Methods for the Spectrophotometric Determination of Anionic Surfactants with 4-(4-N,N-Dimethylaminophenylazo)-2-methylquinoline

solvent-extraction Spectrophotometric method for the determination of anionic surfactants in water was developed with -(4-N, N-dimethylaminophenylazo)-2-methylquinoline (MQ) by batchwise and flow-injection techniques. The ion associates of MQ with anionic surfactants extracted into an organic phase showed a blue shift of the maximum absorption wavelength; their molar absorptivities were 4.5×10(4)l mol(-1) cm(-1) at 560nm. In the batchwise method, a 40-fold extraction concentration was possible. In the 20-fold concentration, the calibration graph was linear at concentration ranging from 1×10(-8)M to 7.5×10(-7)M of anionic surfactants, and the mean absorbances of the reagent blank and the 5×10(-7)M anionic surfactant (dodecylsulfate : LS(-)) were 0.024 and 0.518, respectively; the relative standard deviation for 10 measurements of 5×10(-7)M LS(-) was 0.28%. Foreign ions generally existing in river water did not interfere with the determination. This solvent-extraction spectrophotometric method was satisfactorily applied to a flow-injection method. The reagent MQ was recycled and repeatedly used at least for 7 months, and the efficiency of the reagent has not changed during at least this period.

Spectrophotometric determination of anionic surfactants in tap and river waters with 1-(10-bromodecyl)-4-(4-aminonaphthylazo)-pyrimidinium bromide

A new cationic dye, 1-(10-bromodecyl)-4-(4-aminonaphthylazo)-pyridinium bromide, was synthesized and evaluated as a new reagent for the determination of anionic surfactants. The reagent reacts with anionic surfactants, such as sodium dodecylsulphate and sodium dodecylbenzenesulphonate, to produce an ion associate in an aqueous medium. The colour change occurs simultaneously, and the colour development is very stable. This makes it possible to determine anionic surfactants directly by spectrophotometry without solvent extraction. The stoichiometric ratio of the ion associate was found to be 1:1 by the mole ratio method. The calibration graph was linear up to 2.5×10−6 mol/l. The apparent molar absorptivity of the ion associate was 5.3×104 l mol−1 cm−1 (at 595 nm). The relative standard deviation (n=10) for 1.2×10−6 mol/l sodium dodecylsulphate was 4.9%. The proposed method was applied to the determination of anionic surfactants in tap and river waters.

Spectrophotometric determination of anionic surfactants in water after solvent extraction coupled with flow injection

Anionic surfactants in water were determined by a spectrophotometric method involving flow injection coupled with solvent extraction. Eight cationic dyes were examined with several extraction solvents. Of the pairs of cationic dye and extraction solvent investigated, Methylene Blue and 1,2-dichlorobenzene were the most efficient. The ion associate formed between an anionic surfactant and Methylene Blue was extracted into the organic phase, the absorbance of which was measured at 658 nm. The carrier stream was distilled water and the reagent stream consisted of a cationic dye, sodium sulphate and acetate buffer (pH 5). A phase separator with a poly(tetrafluoroethylene) porous membrane (0.8 µm pore size) was used to separate the organic phase. The sampling rate was 20 samples per hour. The calibration graphs were linear up to 3 × 10–5M(8.7 mg l–1) or 7 × 10–5M(20.2 mg l–1) of anionic surfactant when the injection volumes were 300 and 100 µl, respectively. The relative standard deviation (n= 10) was 0.9% when 300 µl of 2.1 × 10–6M(610 µg l–1) sodium dodecylsulphate were injected. The detection limit corresponding to a signal to noise ratio of 3 was 1 × 10–8M(5 µg l–1) for the injection of 300 µl of sodium dodecylsulphate. The proposed method was used to determine anionic surfactants in river water.

Spectrophotometric determination of anionic surfactants with 1-(4-bromomethylbenzyl)-4-(4-diethylaminophenylazo)-pyridinium bromide.

A new cationic dye, 1-(4-bromomethylbenzy1)-4-(4-diethylaminophenylazo)-pyridinium bromide, with anionic surfactants such as laurylbenzenesulfonate(LBS) and laurylsulfate (LS), reacts to form ion-associates extractable into benzene. The concentration of the surfactants can be determined by measuring the absorbance of extracts at 545 nm. Calibration curve obeyed Beer's law over the range 0.222.2×10-5mol dm-3 (in benzene) of the surfactans. The apparent molar absorptivity of the ion-associates is 34000 dm3 mol-1 cm-1. The procedure for surfactant determination is as follows : In a 30 ml stoppered test tube, place 25 ml of sample solution, 1 ml of 4.9×10-4 mol dm-3 reagent and 1 ml of phosphate buffer solution (pH 7). Add 5 ml of benzene, and shake the test tube for 5 min mechanically and allow to stand for 15 min. Measure the absorbance of the benzene phase at 545 nm with glass cells of 1-cm path-length. The relative standard deviation for 1.1×10-6 mol dm-3 LBS was 3.4%.

Spectrophotometric determination of anionic surfactants by conversion of the leuco-bases of triphenylmethane dyes

A one-phase, one-reagent, spectrophotometric technique is reported for the detection and determination of anionic surfactants of the sulfonate and sulfate types. Both applications are based on conversion of the colorless leuco-bases of triphenylmethane dyes (Brilliant Green and methyl violet) to colored (quinoid) forms by the anionic surfactants. The quantitative method, in the absorption and reflectance modes, is applicable to anionic surfactants in the 0–1500 ppm range; the spectrophotometric procedure can be automated. Residual surfactant can be detected at the 0.01% level on the surface of cellulosic products.

Atomic Absorption Spectrophotometric Determination of Anionic Surfactants in Water

A simple and sensitive method for the determination of anionic surfactant in water was established by using atomic absorption spectrophotometry with graphite furnace atomizer. The proposed method was based on the atomic absorption spectrometric determination of cobalt in a chelate complex produced by the reaction of anionic surfactant with bis [2-(5-chloro-2-pyridylazo)-5-diethylaminophenolato] cobalt (III) chloride (Co-PADAP) proposed by Taguchi et al. A water sample (surfactant content <30μg) was taken in a beaker, adjusted to pH 1 with sulfuric acid and transferred into a separating funnel. One ml of 7.9×10-4M Co-PADAP solution was added to the sample solution and mixed for a few seconds. After allowed to stand for 1 min, 5.0 ml of benzene was added to the solution and shaked for 1 min. The benzene layer was subjected to atomic absorption spectrophotometry. The recoveries of sodium di-(2-ethylhexyl) sulphosuccinate as a standard compound added to various kinds of water were in the range of 92.0-110.0% and the coefficient variations were within 4.7%. The interference by ClO-could be eliminated by the addition of Na2SO3. There were high significant correlations between the proposed method and the methylene blue method or the Taguchi's colorimetric method. The assayed values of anionic surfactants in the water samples obtained from the rivers in Kobe city were distributed 0.026 mg/l and 2.562 mg/l.

Spectrophotometric determination of anionic surfactants with 1-methyl-4-(4-diethylamino-phenylazo)-pyridinimn iodide

Spectrophotometric determination of anionic surfactants with 1-methyl-4-(4-diethylamino-phenylazo)-pyridinimn iodide

Spectrophotometric determination of anionic surfactants in river waters using 1-(4-nitrobenzyl)-4-(4-diethylaminophenylazo)-pyridinium bromide

Nitro, bromo and methyl derivatives of 1-(benzyl)-4-(4-diethylaminophenylazo)pyridinium bromide were synthesised and evaluated as new cationic reagents for the determination of anionic surfactants. These reagents were very stable and reacted with anionic surfactants, such as alkylbenzene-sulphonate and alkylsulphate, to form a 1 : 1 stable ion associate, which was extracted into chlorobenzene in a single extraction. The apparent molar absorptivity of the ion associate of the 4-nitro derivative with sodium di(2-ethylhexyl)sulphosuccinate was 6.10 × 104 l mol–1 cm–1(at 573 nm) in chlorobenzene. 1-(4-Nitrobenzyl)-4-(4-diethylaminophenylazo)pyridinium bromide was used in the determination of µg l–1 levels of anionic surfactants in river water. The results were compared with the methylene blue method (Japanese Industrial Standard method) for river waters. This method is designed to determine anionic surfactant concentrations in solution.

Extractional spectrophotometric determination of anionic surfactants in waters with Remacrylblau B and Remacrylrot 2BL

The cationic dyes Remacrylblau B and Remacrylrot 2BL have been investigated as analytical reagents for the determination of anionic surfactants in waters. Extractional spectrophotometric procedures are proposed. The lowest quantity of anionic surfactant determinable (expressed as lauryl sulphate) when a 1-cm cell is used is 14 μg/l., with a standard deviation of 1 μg/l.

Spectrophotometric determination of anionic surfactants with Bindschedler's Green derivatives

Spectrophotometric determination of anionic surfactants with Bindschedler's Green derivatives