Spring 2008 Newsletter
Clean Green - Environmentally Friendly Surfactants
Detergents are chemical formulations designed to dissolve or disperse grease, grime, and dirt by making them water soluble. One basic concept in chemistry is “like dissolves like”, which means that structurally different molecules like oil and water do not mix. Although detergents are typically composed of various ingredients (e.g. builders, alkalis, complexing agents, etc.), the class of ingredients that give detergents their foam and grease cutting property are the surfactants, short for surface active agents.
Surfactants are bifunctional molecules that contain a hydrophilic (i.e. water loving) and a lipophilic (i.e. “grease” loving) group. This bifunctional property allows the surfactant molecules to group together to form micelles (pockets with a grease loving core) that can dissolve the grease, grime and dirt.
Synthetic surfactants have been developed over the past 100 years. The surfactant molecule can be tailored to control the chemical properties of the hydrophilic end (e.g. anionic, cationic, nonionic, etc.) and the hydrophobic end (e.g. chain length, branched, etc.). This control in design has created a large library for use in detergents.
An enormous amount of surfactants are produced globally each year. In fact, 5 billion pounds of linear alkylbenzenesulfonates (on of the most common surfactants) are produced annually. These surfactants go down the drain and into the water treatment facilities for processing.
Some surfactants that are highly effective at dissolving grease simply cannot be naturally broken down by microbes (i.e. they are not biodegradable). Ultimately, the environmental impact of these surfactants becomes worrisome as more and more are developed, used and disposed.
A standard surfactant type used in many cleansers and detergents are alkylphenol ethoxylates (APEs), with the most common members of the family being octylphenol ethoxylate and nonyl phenolethoxylate. APEs are versatile, non-ionic surfactants used for more than half a century in a variety of applications. They have excellent detergency, wetting, solubilization, and emulsification properties and are one of the lowest priced bulk surfactants on the market.
A drawback of APEs, though, is that they biodegrade very slowly and persist in the environment. They are made from alkyl phenols and ethylene oxide polymer chains, both derived from petrochemicals. Additionally, their biodegredation products are more toxic to marine life than the surfactants themselves. Very small amounts can cause harmful effects to the endocrine systems of animals.
Another example of a highly effective surfactant that persists in the environment is branched tetrapropylene aryl sulfonates (ABS). ABS was such an effective surfactant that it flooded the market soon after introduction. Over time, though, foaming was discovered in sewage treatment plans and even home faucets. ABS was identified as the culprit and the branched nature of the molecule was found to be the cause of the persistence. As a result, a linear version of the surfactant, linear alkylbenzenesulfonate (LAS), was developed. LAS is biodegradable, although slowly, and is currently one of the most commonly used surfactants.
The increasing awareness of our effects on the environment has caused consumers to demand more environmentally-friendly cleaning products. As a response, chemical manufacturers are producing several new surfactants that are more eco-friendly and that are derived from renewable resources.
Alkyl polyglycosides are a type of environmentally-friendly surfactant currently in use. These non-ionic surfactants are manufactured entirely from natural, renewable resources such as plant oils. They have great environmental compatibility and are highly biodegradable. Alkyl polyglycosides may be used in a wide variety of applications, from personal care products to household and industrial cleansers. The lipophile of alkyl polyglycosides is a fatty alcohol, which is derived from natural fats and oils found in plants. The hydrophile of the alkyl polyglycosides is a chain composed of glucose, which is also derived from plant oils.
Several manufacturers of cleaning products have keyed into consumers’ desire for more earth-friendly cleaners by introducing products that boast superior cleaning capabilities. Seventh Generation, Method, and GreenWorks are just a few of the companies that produce non-toxic, environmentally-friendly cleaners that are not tested on animals and are easily biodegradable. Their product lines include laundry detergents, all-purpose cleaners, dish soaps, hand and body soaps, kitchen and bathroom cleaners, and air fresheners.
Ingredients for these cleaning solutions come from natural, renewable resources. They do not use harsh petrochemical-derived surfactants and most of their products are even chlorine-free. A formulation for an environmentally-friendly cleaner may include coconut or corn derived surfactants, soda ash, corn alcohol, fragrances from lemons, and biodegradable preservatives.
Analyzing Cleaning Products
At Chemir, we analyze cleaning solutions for the presence and quantity of surfactants by a combination of techniques. For the identification of the general surfactant type, a Fourier Transform Infrared (FT-IR) spectrum is useful. The spectra indicate the chemical moieties present in the surfactant. For example, the presence of a polyethoxylated species, such as an APE, is indicated by an intense band in the FT-IR spectrum at approximately 1100 cm-1. Proton Nuclear Magnetic Spectroscopy (1H NMR) also provides valuable information about the chemical structure of a surfactant present in a cleaning solution.
The most powerful technique for full characterization of a surfactant is Liquid Chromatography with Mass Spectrometry (LC/MS). This technique separates the surfactant from other components of the cleaning solution and “weighs” the surfactant molecules. Obtaining the “weight” or molecular mass of the surfactant molecule allows for our chemists to identify the surfactant exactly.
Detailed information about the surfactant or surfactant blend can be gained from in-depth LC/MS analysis. For example, if several surfactants are present, each is separated and identified individually. If a surfactant contains a polymeric portion, such as a polyethylene glycol (PEG) chain, the exact chain lengths used in the surfactant can be deduced. In addition, when surfactants are made from either petrochemical or renewable resources, the hydrophobic portion (e.g. the alkylphenol or alkyl groups) are often a mixture of similar components. The exact components used in the mixture can be deciphered from LC/MS analysis. If further information is needed to definitively characterize a surfactant, Chemir has LC/MSn capabilities to fragment the surfactant molecules into their components.
The toolbox available to Chemir scientists makes the complicated process of identification, characterization, and quantitation of surfactants in either conventional or environmentally-friendly cleaning solutions possible.