Qualitative Identification of Propylene Tetramer Alkylbenzene Sulfonate and Alkylphenol Polyoxyethylene in Laundry Powders

B.1 Principle

Infrared absorption spectrum characteristic peak is adopted in this text to qualitatively identify the compositions of the sample.

As alkyl-chain of propylene tetramer alkylbenzene sulfonate has branches, the CH3symmetrical deformation vibration absorption peak splits into two sub-peaks,which are 1,380 cm-1(7.25 μm) and 1,370 cm-1(7.30 μm).While linear alkylbenzene sulfonate only has a 1,380 cm-1absorption peak which doesn’t split here. The CH2rocking vibration absorption peak of propylene tetramer alkylbenzene sulfonate is obvious at 800 cm-1to 700 cm-1(12.5 μm to 14.4 μm).

Alkylphenol polyoxyethylene has typical arene characteristics. C-H stretching vibration absorption peak centers at 3,100 cm-1to 3,000 cm-1(3.23 μm to 3.33 μm). –C=C– stretching vibration absorption peaks center at 1,610 c m-1to 1,590 cm-1(6.21μm to 6.29 μm), 1,520 cm-1to 1,490 cm-1(6.58 μm to 6.71 μm) and show medium intensity absorption at 1,250 cm-1(8.0 μm). The characteristics of absorption peaks above have significant differences with those of fatty alcoholpolyoxyethylene ether.

B.2 Reagents

B.2.1 Trichloromethane

B.2.2 Ethanol, anhydrous.

B.2.3 Petroleum ether, boiling range 30 ℃ to 60 ℃.

B.2.4 Neutral alumina (for chromatography), particle size between 75 μm and 150 μm (40 mesh/cm to 80 mesh/cm), activated at 800 ℃ for 4 hours.

B.3 Apparatus

Ordinary laboratory apparatus and

B.3.1 Infrared spectrophotometer, wave numbers of 4,000 cm-1to 650 cm-1(wavelength range 2.5 μm to 15 μm), with sodium chloride or potassium bromide absorption cell.

B.3.2 Chromatography column, internal diameter about 10 mm, 400 mm long.

B.4 Procedure

B.4.1 Preparation of chromatography column

Weigh 20 g of activated neutral alumina (B.2.4), suspended in 30 mL of petroleum ether (B.2.3). Introduce the suspension into the chromatography column and discharge the petroleum ether until the liquid level reaches the alumina surface. Pass 30 mL of trichloromethane (B.2.1) through the column to replace all the petroleum ether. Discharge the trichloromethane until the liquid level is about 2 cm above the top of the alumina surface. Keep in reserve.

B.4.2 Separation of surfactants

Weigh about 3 g of laundry powders sample in a 100 mL beaker, and extract the surfactants fromlaundry powders by 50 ml of trichloromethane (B.2.1). Separate the insoluble matter with a filter paper, and receive the filtrate in an 80 mL beaker. Heat and concentrate the filtrate to less than 20 mL. Introduce the concentrated filtrate into the chromatography column (B.4.1). Pass 130 mL of trichloromethane (B.2.1) to elute the nonionic surface active agents, and collect the eluate in a 200 mL beaker. Evaporate the solvent, dry and keep in reserve.Pass 150 mL of 50% ethanol-water solution to elute the anionic surface active agents, and collect the eluate. Evaporate the solvent, dry and keep in reserve.

B.4.3 Infrared spectra analysis

Analyze the nonionic surface active agents and anionic surface active agents separated respectively and get the corresponding infrared absorption spectrum.Infrared absorption spectrum of propylene tetramer alkylbenzene sulfonate, linear alkylbenzene sulfonate, alkylphenol polyoxyethylene and fatty alcohol-polyoxyethylene ether are shown.

Figure B.1 Infrared absorption spectrum of propylene tetramer alkylbenzene sulfonate

Figure B.2 Infrared absorption spectrum of sodium n-alkyl benzene sulfonate

Figure B.3 Infrared absorption spectrum of alkylphenol polyoxyethylene

Figure B.4 Infrared absorption spectrum of fatty alcoholpolyoxyethylene ether

B.5 Identification of infrared absorption spectrum and determination of results

With propylene tetramer alkylbenzene sulfonate existing, the CH3symmetrical deformation vibration absorption sub-peaks will appear at 1,380 cm-1(7.25 μm)and 1,370 cm-1(7.30 μm), and CH2rocking vibration absorption peak will appear at 760 cm-1(13.16 μm)(Theintensity of the peak is stronger than that of linear alkylbenzene sulfonate).

With alkylphenol polyoxyethylene existing, there will be typical arene characteristic absorption peaks in the infrared absorption spectrum, which center at 3,100cm-1to 3,000 cm-1(3.23 μm to 3.33 μm), 1,610cm-1to 1,590 cm-1(6.21 μm to 6.29 μm), and 1,520cm-1to 1,490 cm-1(6.58 μm to 6.71 μm), and show medium intensity absorption at 1,250 cm-1(8.0 μm).

Based on the infrared absorption spectrum, identify if there are propylene tetramer alkylbenzene sulfonate and alkylphenol polyoxyethylene in laundry powders or not.