Solvents are substances that dissolve other substances without chemically modifying them. Even with water being the most common solvent according to this definition, the generic term is generally applied to a large number of other industrially used substances, most of them organic (i.e. containing hydrocarbon), that belong to no particular group of substances. Various alcohols and ethers, for instance, as well as aliphatic, aromatic or halogenated hydrocarbons, are used as solvents.
Solvents are used in the production of paints, varnishes and adhesives, in the rubber and textile industry as well as in cleaning agents and other household products. Since most solvents are volatile, they evaporate within a few hours or days. The use of solvents is therefore subject to regulations concerning their emission into the environment and occupational health and safety regulations (ventilation, protective clothing).
Solvents in foodstuffs
In the food manufacturing industry, the migratory ability of solvents used in food contact materials is a critical issue, i.e. when substances migrate from the packaging into the food itself. Solvents are frequently contained in the coatings of packaging material and other food contact materials, since they are used to make the components of binding agents flowable and processable.
Carrier solvents, by contrast, are added to food directly in order to facilitate blending with other additives. These include 1,2-propanediol (propylene glycol) which has been approved for chewing gum and aromas only and is declared as E 1520, or triethyl citrate (E 1505) which has been approved for aromas and egg white powder.
Furthermore, so-called extraction solvents are required for extraction processes that aim to gain or remove certain substances from food, e.g. natural aromas. Declaration is not required, although residual concentrations may be contained in the product. Dichloromethane, for instance, is used to remove caffeine, bitters and irritants from coffee (permitted residual concentration 2 mg/kg) or tea (5 mg/kg). The permitted residual concentration in aromas is 0.02 mg/kg. Hexane is used as an extractant for cooking oils, cocoa butter and aromas and in the production of defatted protein products. All permitted extraction solvents and their maximum residual concentrations are specified in the German Regulations on Processing Aids (THV) that translate Directive 88/344/EEC into German law.
Benzene in soft drinks
Recently, reports about the carcinogenic solvent benzene in non-alcoholic soft drinks had come to light. In 2005 the German Federal Institute for Risk Assessment had published a statement pointing to the fact that the preservative benzoic acid (E 210) may turn into benzene in the presence of ascorbic acid (E 300, vitamin C). There is currently no limit value for benzene in beverages. The Drinking Water Ordinance specifies a permitted maximum value of 1 µg/l, which had been exceeded in some soft drinks, as detected in analyses commissioned by a TV magazine. When assessing the resulting hazard potential, unavoidable benzene concentrations from other sources must be taken into account. According to a counterstatement of the beverage industry, e.g., every person takes in several hundred micrograms of benzene via the air each day.
ifp Institut für Produktqualität analyses solvents in foods and packaging material. Analysis is done by means of headspace gas chromatography with a mass-selective detector (MSD) and a deuterated internal calibration standard.
The range of analysis comprises: