Application of attenuated total reflectance Fourier transform infrared spectrometry to the determination of sodium percarbonate in washing powder detergent

In this paper, a novel and precise analytical procedure has been developed for quantitative determination of sodium percarbonate (SPC) in washing powder. The method is based on the partial least squares (PLS) treatment of data obtained by attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectrometry in wavenumber region of 1435-1342 cm⁻¹. The statistical parameters such as R², RSD, SEC and SECV have been evaluated, and number of factors, number of scan and the resolution have been optimized. In this method R² and RSD for five independent analyses of a 0.552 g per 100 g solution of SPC, SEC for 10 standard samples and SECV for five validation samples were 0.998, 1.011, 0.002 and 0.039 respectively.Results obtained for six different commercial washing powders compared well with those obtained with a standard method.     

Sol–gel coating of cellulose fibres with antimicrobial and repellent properties

Multifunctional, water and oil repellent and antimicrobial finishes for cotton fibres were prepared from a commercially available fluoroalkylfunctional water-born siloxane (FAS) (Degussa), nanosized silver (Ag) (CHT) and a reactive organic–inorganic binder (RB) (CHT). Two different application procedures were used: firstly, one stage treatment of cotton fabric samples by FAS sol (i), as well as by a sol mixture constituted from all three precursors (Ag–RB–FAS, procedure 1S) (ii), and secondly, two stage treatment of cotton by Ag–RB sol and than by FAS sol (Ag–RB + FAS, procedure 2S) (iii). The hydrophobic and oleophobic properties of cotton fabrics treated by procedures (i)–(iii) before and after consecutive (up to 10) washings were established from contact angle measurements (water, diiodomethane and n-hexadecane) and correlated with infrared and XPS spectroscopic measurements. The results revealed that even after 10 washing cycles cotton treated with Ag–RB + FAS (2S) retained an oleophobicity similar to that of the FAS treated cotton, while the Ag–RB–FAS (1S) cotton fibres exhibited a loss of oleophobicity already after the second washing, even though fluorine and C–F vibrational bands were detected in the corresponding XPS and IR spectra. The antibacterial activity of cotton treated by procedures (i)–(iii) was tested by its reduction of the bacteria Escherichia coli and Staphylococcus aureus following the AATCC 100-1999 standard method and EN ISO 20743:2007 transfer method. The reduction in growth of both bacteria was nearly complete for the unwashed Ag–RB and Ag–RB–FAS (S1), but for the unwashed Ag–RB + FAS (S2) treated cotton no reduction of S. aureus and 43.5 ± 6.9% reduction of E. coli was noted. After the first washing, the latter two finishes exhibited nearly a complete reduction of E. coli but for the Ag–RB treated cotton the reduction dropped to 88.9 ± 3.4. None of the finishes retained antibacterial properties after 10 repetitive washings. The beneficial and long-lasting low surface energy effect of FAS finishes in the absence of Ag nanoparticles, which led to the “passive” antibacterial properties of FAS treated cotton fabrics, was established by applying the EN ISO 20743:2007 transfer method. The results revealed a reduction in bacteria of about 21.9 ± 5.7% (FAS), 13.1 ± 4.8% (Ag–RB–FAS (S1)) and 41.5 ± 3.7% (Ag–Rb + FAS (S2)), while no reduction of the growth of bacteria was observed for cotton treated with Ag nanoparticles after 10 repetitive washings. The physical properties (bending rigidity, breaking strength, air permeability) of finished cotton samples were determined, and showed increased fabric softness and flexibility as compared to the Ag–RB treated cotton, but a slight decrease of breaking strength in the warp and weft directions, while air permeability decreased for all type of finishes.     

Some aspects on the kinetics of etherification in the preparation of CMC

Carboxymethylcellulose (CMC) was prepared from nine commercial dissolving pulps with different origins, viscosities and S₁₈-values. The rate of the etherification reaction and the final DS were studied with respect to the influence of pulp composition, pulp viscosity and S₁₈-value, and with respect to the sodium hydroxide and sodium monochloro-acetate charges. The possible influence on the final DS-value of the CMC of the washing procedure after the etherification was also investigated.     

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).     

Aerosol-OT-gamma-alumina admicelles for the concentration of hydrophobic organic compounds in water

A novel admicelle composing of a dialkylated anionic surfactant, di-2-ethylhexyl sodium sulfosuccinate (Aerosol-OT, AOT) and gamma-alumina was prepared by mixing them in acidic aqueous solution. The amount of the maximum sorption of AOT on 1 g of alumina at pH 2 was ca. 130 mg. By comparing the fluorescence spectra of N-phenyl-1-naphthylamine in different solvents, the solvent property of AOT-gamma-alumina admicelles was corresponding to that of toluene or diethyl ether. Thus, the AOT-gamma-alumina admicelles had greater hydrophobicity than SDS-gamma-alumina admicelles having similar hydrophobicity to 1-octanol or ethyl acetate. Hydrophobic organic compounds, chlorophenols having more than three chloro substituents, octylphenol, nonylphenol, dibutyl phthalate was almost quantitatively (98% or more) collected onto AOT admicelles composing of 1.5 g gamma-alumina and 150 mg AOT. The greater collection yields rather than those in SDS-admicellar system were ascribable to greater hydrophobicity and stability of AOT admicelles. After the 500-fold concentration, traces (nM) of organic contaminants in water samples were successfully detected with an HPLC having a photometric detector.