Simple IC Method for the Analysis of Phenols from Metrohm

Phenol also known by its old name of carbolic acid was isolated by the German Chemist Friedlieb Ferdinand Runge in the 1830's from coal tar and is a toxic, colorless crystalline solid. It has the chemical formula C₆H₅OH and the structure is a hydroxyl group bonded to a phenyl ring; it is thus an aromatic compound. Phenol today is used in a wide range of intermediate products and can be made from the partial oxidation of benzene or benzoic acid.

Phenol has been in production since the 1860s. One of the early uses for phenol was as an antiseptic and it was used by Sir Joseph Lister also known as 'The Father of Modern Surgery' in his pioneering techniques of antiseptic surgery, though the skin irritation caused by continual exposure to phenol eventually led to the substitution of aseptic germ-free techniques in surgery. An interesting fact is that surgical gloves were first used to protect doctor's hands from phenol burns. Lister decided that the wounds themselves had to be thoroughly cleaned and he then covered the wounds with a piece of lint covered in carbolic acid.

Towards the end of the 19th century, industrial scientists found new uses for phenol in the synthesis of dyes, aspirin and one of the first explosives picric acid. Phenol-methanal (formaldehyde) resins are the basis of the oldest plastics, and are still used to make low cost thermosetting plastics such as melamine and bakelite that are used in electrical equipment. These resins are also used extensively as bonding agents in manufacturing wood products such as plywood and MDF.

Phenol had a sinister use during the Second World War when injections of phenol were used as a means of rapid execution by the Nazis. Phenol injections were given to thousands of people in concentration camps at Auschwitz-Birkenau. Injections were administered intravenously originally into the arm, but later direct injection into the heart to induce instantaneous death was preferred. One of the most famous inmates at Auschwitz to be murdered by carbolic acid injection was Saint Maximilian Kolbe, a Catholic priest who volunteered to undergo three weeks of starvation and dehydration in the place of another inmate and who was finally injected with carbolic acid so that the Nazis could make more room in their holding cells.

Phenol is also used in the preparation of cosmetics including sunscreens, hair dyes and skin toning preparations. Compounds containing the phenol group can be used to prevent ultraviolet light induced damage to hair and skin due to the UV absorbing properties of the aromatic ring of the phenol. It is also used in cosmetic surgery as an exfoliant to remove layers of dead skin. It is also used in phenolization or phenol matricectomy, a surgical procedure used to treat an ingrown toe nail in which it is applied to prevent re-growth of the nail.

Phenol is highly corrosive to body tissue and burns the skin on contact but because of its local anesthetic effect it may not be felt immediately. Damage to lung tissue can occur if the vapour is inhaled. It is moderately toxic and can be absorbed into the body by ingestion, inhalation and contact. At low levels it is an irritant and may cause liver damage at higher doses. Phenol affects the central nervous system and symptoms of exposure can include muscle weakness and tremors, loss of coordination, paralysis, convulsions, coma and respiratory arrest. It may also be a carcinogen but this is not proven and phenol remains un-classified.

Phenol is used mainly as a chemical intermediate, which is converted into a whole range of other substances. Phenol has uses in molecular biology in the separation of genetic material (nucleic acids) from proteins.

Phenol and many substituted phenols are natural components of many substances (e.g. tea, wine and smoked foods) and phenol is also emitted from the combustion of fossil fuels and tobacco. Bacteria in the environment quickly break down phenol and so levels in air, waters and soils are generally very low.

Strict emission levels and handling routines are in place for workers involved in the production and use of phenol. It is thus important to have a control on the use of phenol containing products and their discharges so a reliable means of ensuring that consent limits are not breached.

Metrohm have developed a simple method for the analysis of four different phenols using the technique of Ion Chromatography (IC) in a variety of different matrices as long as the sample can be solved into the mobile phase. With this method it is possible to determine the quantities of phenol, cresol, dimethylphenol and trimethylphenol in less than 16 minutes.

The separation of the four phenols is performed using a potassium nitrate/sulfuric acid/methanol mobile phase with a C18 separation column with Pulsed Amperometric Detection (PAD) using a glassy carbon electrode. By applying three different working potentials in sequence the working electrode is cleaned and regenerated after measurement preventing fouling and the Metrohm flow cell is completely maintenance free.

The 871 Advanced Bioscan extends range of IC applications available from Metrohm. The heart of the 871 Advanced Bioscan is the PAD cell with built-in injector and column heater. Instrument control is via the IC Net software. The Bioscan can be used with a standalone pump to form a standalone PAD detection system or it can be integrated into a standard IC setup (e.g. 850 Professional IC or Advanced Modular IC) so that the instrument is capable of analyzing anions and cations also for maximum versatility. The measuring cell of the 871 Advanced Bioscan and the insulated column oven form a single unit that is optimally protected against environmental influences.

As an option the MagIC Net Software can also be used for manipulation of the results (IC Net is used only to start-up the hardware); operation of the instrument is performed from MagIC Net in terms of running samples, calibration of standards and all the chromatographic raw data goes into the MagIC Net database where the determinations can be reported or exported either manually or automatically into an external package. Shutdown of the IC hardware can also be performed from directly from MagIC Net.

Some of the features that MagIC Net will provide for IC operation:-

• Definable control cards for monitoring chromatographic parameters (retention times, resolution, theoretical plates etc) over time.
• Improved integration algorithm and manipulation of calibrations and standards (bracketing, check standards, blank subtraction).
• Monitoring of the lifetime of eluents and IC consumables (such as filters, guard column, piston seals etc) to prevent instrument down time.
• Numerous options for manipulation of results from the database; reprocess, overlay multiple determinations for reporting, import/export the determinations and view the history.
• Configuration of running the instrument to "One Button" IC for novice operation.