Volume 45, Issue 3

Attenuated total reflectance Fourier transform infrared spectrometry was applied for determination of tetraacetylethylenediamine (TAED) in commercial laundry powder samples. Investigating different spectral regions, 1724–1670 cm −1 was selected as the best region. Spectroscopic data were compared with gas chromatography results, demonstrating reliability of the proposed method, higher accuracy and precision. Standard error of estimation (SEE), standard error of prediction (SEP), correlation coefficient (R 2 ) and root mean square error of prediction (RMSEP) was 0.022, 0.031, 0.998 and 0.138 in the selected spectral region, respectively.

The critical micellar concentrations (cmc) of cationic alkyltrimethylammonium bromides (C 10 TAB – C 16 TAB) and of anionic alkyl sulfates (SDS, technical grade Sulfopon 12G and Sulfopon 1214G) were determined using specific conductivity and surface tension measurements. While the cationic surfactants were purified, the anionic surfactants were used as received. In the former case, surface tension and conductivity measurements lead to the same cmc values. In the latter case, measuring the specific conductivities (bulk property) proved to be superior compared to measuring the surface tensions (surface property) because the presence of highly surface active impurities creates a pronounced minimum in the surface tension isotherm, which makes it impossible to determine an accurate value for the cmc. On the other hand, these impurities do not influence the conductivities, i. e. that the conductivities can be used to determine cmc values of impure and technical grade ionic surfactants, respectively. Moreover, an evaluation of the specific conductivities allows for the determination of the degree of micelle ionization (α) of the ionic surfactant solutions and thus provides additional useful information.

Electrocatalytic hydrogenolysis and hydrogenation of 4-halophenols, 4-chloroaniline and chloronitrobenzene have been investigated in aqueous media using different surfactant agents on two kinds of cathodes investigated on, Raney nickel electrode and carbon electrode.

As clouding in drugs causes high concentration of drug at a particular site which may prove harmful to the body, the clouding behaviour of a tricyclic phenothiazine drug promazine hydrochloride (PMZ) in aqueous solutions has been studied in the presence of surfactants and ureas. The cloud point (CP) decreases with increase in pH due to deprotonation of the drug molecules. Addition of non-ionic and cationic (conventional as well as Gemini) surfactants increased the CP whereas anionic surfactants showed a peaked profile. The urea family additives influenced the CP in both ways that depended whether they contain >C=O or >C=S moiety: the former interacts with the micelles and lowers the CP while the latter (due to its electropositive character) may not interact and hence CP increases. Dye solubilization results indicate micellar growth with the addition of surfactants in PMZ solutions. The results are interpreted taking cognizance of mixed micelle formation, hydrophobic interactions, and/or change in solvent structure.

The surface activity of newly nonionic hydroxyl mixed ether surfactants HME n at air/water and solid/water interfaces was studied as a function of ethoxylation degree (n-value). The characteristics of this series of nonionic surfactant, including surface tension, critical micelle concentration cmc, adsorption onto hydrophilic saponite clay and hydrophobic Teflon are reported. The surface tension results indicate that cmc, surface tension after γ cmc , and the minimum surface area per adsorbed HME-surfactant molecule A min are all increased with n-value. Results of static light scattering are in agreements with those obtained using surface tension method. For HME-surfactants, strong adsorption measured by surface tension onto the hydrophilic synthetic clay mineral saponite. This result was also observed by atomic force microscopy AFM for HME 9.7 onto hydrophilic mica surface. On the other hand, the adsorption of HME-surfactant onto hydrophobic polytetraflouroethylene PTFE (Teflon) is less than that measured onto saponite. However, the adsorption at both surfaces has the same dependency on n-value.

The gradually increasing detergents consumption in Germany since 1950 resulted in higher emissions of their ingredients to the environment. The first generation of mineral oil-based surfactants, tetrapropylene benzene sulfonate (TPS), exhibited poor biodegradability and caused public environmental concerns. These prompted Henkel in 1958 to start a systematic measurement of some main detergent constituents in the river Rhine in Germany. Since then, a number of monitoring activities regarding the determination of detergent ingredients concentrations and freights in rivers and waste water treatment plants (WWTP) followed. This paper summarizes 50 years experience at Henkel in monitoring of detergent ingredients in the aquatic environment. The long-term monitoring results on the river Rhine provides an impressive record of the development of the environmental burden by surfactant emissions and of the gradual improvement of river water quality over time. The reasons for the changes are discussed. Further monitoring activities on WWTPs have shown for the first time, that domestic wastewater treatment plants (DWTP) are similarly suitable for the removal of surfactants like municipal ones. The good removal of prominent organic detergent ingredients was shown by several time-proportional sampling campaigns in municipal WWTPs. Finally the positive impact of the modernisation of a municipal WWTP on the chemical and biological water quality on a small river creek is reported over the time period of 7 years. All of the reported studies indicate a low environmental burden due to the use of detergents ingredients today. The learnings from the different activities in environmental monitoring by Henkel have contributed to a solid understanding of the fate of detergent ingredients in the environment. This in turn was the prerequisite for development of reliable exposure prediction models. Today, Henkel employs both, environmental monitoring and modeling instruments, for assessing the environmental exposure of chemicals.