Analysis Of Cationic Surfactants Research Articles

Evaluating solid phase (micro-) extraction tools to analyze freely ionizable and permanently charged cationic surfactants

Working with and analysis of cationic surfactants can be problematic since aqueous concentrations are difficult to control, both when taking environmental aqueous samples as well as performing laboratory work with spiked concentrations. For a selection of 32 amine based cationic surfactants (including C8- to C18-alkylamines, C14-dialkyldimethylammonium, C8-tetraalkylammonium, benzalkonium and pyridinium compounds), the extraction from aqueous samples was studied in detail. Aqueous concentrations were determined using solid phase extraction (SPE; 3 mL/60 mg Oasis WCX-SPE cartridges) with recoveries of ≥80% for 30 compounds, and ≥90% for 16 compounds. Sorption to glassware was evaluated in 120 mL flasks, 40 mL vials and 1.5 mL autosampler vials, using 15 mM NaCl, where the glass binding of simple primary amines and quaternary ammonium compounds increased with alkyl chain length. Sorption to the outside of pipette tips (≤20% of total amount in solution) when sampling aqueous solutions may interfere with accurate measurements. Polyacrylate solid phase microextraction (PA-SPME) fibers with two coating thicknesses (7 and 35 μm) were tested as potential extraction devices. The uptake kinetics, pH-dependence and influence of ionic strength on sorption to PA fibers were studied. Changing medium from 100 mM Na+ to 10 mM Ca2+ decreases Kfw with one order of magnitude. Results indicate that for PA-SPME neutral amines are absorbed rather than adsorbed, although the exact sorption mechanism remains to be elucidated. Further research remains necessary to establish a definitive applicability domain for PA-SPME. However, results indicate that alkyl chain lengths ≥14 carbon atoms and multiple alkyl chains become problematic. A calibration curve should always be measured together with the samples. In conclusion, it seems that for amine based surfactants PA-SPME does not provide the reliability and reproducibility necessary for precise sorption experiments, specifically for alkyl chain lengths beyond 12 carbon atoms.

ANALYSIS OF IONIC SURFACTANTS BY HPLC WITH EVAPORATIVE LIGHT SCATTERING DETECTION AND CHARGED AEROSOL DETECTION

High-performance liquid chromatography was employed for the separation of five cationic surfactants and seven anionic surfactants. Detection method was compared with evaporative light scattering detector and charged aerosol detector. Acclaim surfactant and Capcell pak C18 column were selected for the study of separation efficiency. The elution behavior of surfactants on Acclaim surfactant column appeared as both hydrophobic and ionic interactions. In contrast, Capcell pak C18 column showed only hydrophobic interaction. In the case of cationic surfactants, good separation was achieved on an Acclaim surfactant column with methanol-0.1 M ammonium formate (pH 5) eluent. Additionally, anionic surfactants showed good separation results on Acclaim surfactant column with acetonitrile-0.1 M ammonium formate (pH 5) eluent. Optimum separation condition was applied to analysis of cationic surfactants as an antistatic agent in polybutyl acrylate adhesive. In the case of spiked calibration standards into polybutyl acrylate, precision (% RSD) and recovery (%) of five cationic surfactants ranged from 0.6 to 12.8% and from 92.3 to 112.9% for within-a-day assay (intra-batch, n = 3) and from 1.4 to 9.0% and from 97.8 to 111.3% for day-to-day assay (inter-batch, n = 3). The results showed acceptable linearity, precision, and recovery without interfering peaks.

Determination of homologues of quaternary ammonium surfactants by capillary electrophoresis using indirect UV detection

This investigation describes the simultaneous separation of two major non-chromophoric quaternary ammonium surfactants, alkyltrimethyl- and dialkyldimethylammonium compounds (ATMACs and DADMACs, respectively), by capillary electrophoresis (CE) using indirect UV detection. The most effective separation conditions was 10 mM phosphate buffer with 57.5% tetrahydrofuran and 3 mM sodium dodecyl sulfate (SDS) at pH 4.3, and the sample hydrodynamic injection of up to 20 s at 1 psi (approximately 60 nl), and an applied voltage of 25 kV ( 1 psi=6.9 kPa). Specially, the selection of an appropriate chromophore and an internal standard (I.S.) to improve the peak identification and quantitation was systematically investigated. Decylbenzyldimethyl ammonium chloride (C 10-BDMA +C −) as a chromophore with 3 mM sodium dodecyl sulfate provided the best detectability for all homologues. The reproducibility of the migration time and quantitative analysis can be improved by using tetraoctyl ammonium ion as an internal standard, giving the relative standard deviation (R.S.D.) less than 0.8% for the relative migration times, and 2.5–5.5% for the relative peak areas. A good linearity of CE analysis was obtained in the range of 1.0–20 μg/ml with r 2 values of above 0.999. The analysis of cationic surfactants in commercial products of hair conditioners and fabric softeners was also performed. Electrospray mass spectrometric method was applied to evaluate the CE method, and the compatible results were obtained.

Mixed aggregate-based acid-induced cloud-point extraction and ion-trap liquid chromatography–mass spectrometry for the determination of cationic surfactants in sewage sludge

Alkyl ammonium surfactants were extracted and concentrated from sludge samples using the acid-induced cloud-point extraction (ACPE) technique. Reversed-phase liquid chromatography–electrospray ionization in positive ion mode ion-trap mass spectrometry was then used for the separation, quantitation and identification of single homologues of the cationic surfactants. Variables affecting the ACPE efficiency were optimized using a spiked activated sludge. Total method recoveries ranged from 91 to nearly 100%. Detection limits for cationics in the sludge were between 40 and 75 ng/g. The analysis of cationic surfactants in activated and dehydrated sludge collected from two different sewage treatment plants revealed the presence of dialkyldimethyl, alkylbenzyldimethyl and alkyltrimethyl ammonium in the concentration range from 0.1 to 34 mg/kg. Alkylpyridinium surfactants were not detected. The persistence of alkyl ammonium surfactants in sewage sludge after treatments applied at municipal sewage plants was confirmed.

Analysis of Cationic Surfactants in Environmental Aqueous Matrices by New Isfet Devices.

Three new ISFET devices (ion-selective field effect transistor) based on polymeric selective membranes sensitive to cationic surfactants have been fabricated and characterised. These new sensors use a PVC-sebacate matrix incorporating benzyldimethyl-hexadecylammonium reineckate, dodecyltrimethyl-ammonium reineckate and hexadecylpyridinium phosphotungstate, respectively, as exchanger. A complete electroanalytical characterisation of new cationic ISFETs has been performed and the analytical results compared with those obtained using other sensors such as ISEs equipped with the same exchanger or using a biosensor responsive to cationic and anionic surfactants. Determinations of cationic surfactants in authentic aqueous matrices of environmental interest have been carried out using the new sensor with the best performance. Furthermore, the critical micellar concentration (CMC) of some cationic surfactants has also been evaluated.

Analysis of cationic surfactants by capillary electrophoresis

Capillary zone electrophoresis was applied to the analysis of N-benzyl-N-alkyl-N,N-dimethylammonium chloride compounds with different alkyl chain lengths (C 12C 18) by direct UV detection. A tetrahydrifuran-containing buffer was used to prevent the occurrence of micellization and adsorption of the surfactants, thereby yielding adequate separations according to their free-form electrophoretic mobilities. Resolution, theoretical plate number, reproducibility and precision were ascertained. Finally, the electrophoretic method was applied to the quantitative determination of an industrial mixture of C n -benzyl surfactants.

Analysis of Cationic Surfactants in Household Products by High Performance Liquid Chromatography with Nitrogen Chemiluminescence Detection

Abstract For compounds containing less than 10% (wt./wt.) nitrogen, the sensivity of nitrogen chemiluminescence detection is limited to concentrations of greater than 0.1 mg/mL under typical operating conditions. For determinations of nitrogen containing surfactants in household products, such sensitivity is not prohibitive due to the high levels of surfactant added to the formulations and is potentially offset by the advantage of the detector's specificity towards nitrogen containing compounds. Lauryl/myristyl monoethanolamide is detected without interfence in a variety of dishwashing liquids and n-methyl glucosamides are detected in liquid laundry detergents. Replicate injections of a single dishwashing liquid preparation indicate a quantitative reproducibility of 8% rsd for lauryl/myristyl monoethanolamide. Performance comparable to HPLC with UV detection has been achieved for methyl neodecanamide in an all purpose cleaner.

Analysis of Cationic Surfactants

Analysis of Cationic Surfactants

Analysis of cationic surfactants by mass spectrometry/mass spectrometry with fast atom bombardment

Analysis of cationic surfactants by mass spectrometry/mass spectrometry with fast atom bombardment

The analysis of cationic surfactants

AbstractLong‐chain cationic surfactants have become a very important class of industrial chemicals. These useful oleochemicals are usually based on vegetable oils and animal fats. They have many applications which include fabric softeners, antistatic agents, organo clays, emulsifiers, germicides, flotation, chemicals, corrosion inhibitors and foam depresents. The fatty quaternary ammonium compounds (quats) are by far the most important of this group of the commerical compounds. However, the fatty amine salts and amine oxides must also be classified as cationic surfactants. Although not as widely used as quats, they have special properties and uses which are often unique and useful. The various analytical methods used for these chemicals serves several objectives, including routine quality control, identification and characterization, determination in mixtures and formulations, determination at use level, and determination in the environment. In general, the objective of the analysis will determine what method will be used. Routine quality control procedures will most often use wet methods or some simple instrumental techniques. Identification and characterization of unknown cationic samples often require the most sophisticated of instrumental and chromatographic methods. Use level and environmental samples usually must be analyzed using the most sensitive methods. Often, colorimetric analysis is adequate. These samples often must undergo rigorous separation and celan‐up techniques before the method of choice can be used. The methodology for the analysis of fatty amines, amine oxides and quaternary ammonium compounds is reviewed with the various analytical objectives in mind. However, the main emphasis is placed on the quats.

Potentiometric titration of thiols, cationic surfactants and halides using a solid-state silver—silver sulphide electrode

A rugged, low resistance silver-silver sulphide solid-state electrode for determining pharmaceuticals as authentic samples or in dosage forms by potentiometric titration is described. Sodium tetraphenylborate, mercury(II) acetate and silver nitrate (0.01) M were employed as titrants in the analysis of cationic surfactants (cetylpyridinium chloride, benzethonium chloride, benzalkonium chloride and chlorhexidine salts), antithyroid drugs (methimazole and propylthiouracil) or sodium halides respectively.