There is currently great environmental interest in phenol analysis and phenol derivatives due to their high toxicity and wide industrial use. The Environmental Protection Agency (EPA) has compiled a list of eleven phenols that are considered to be priority pollutants. Phenol is ranked more hazardous than most chemicals in 4 out of 12 ranking systems. As the maximum allowable concentration for phenols in drinking water is around 1 ppb or lower, analytical techniques are required to measure in this range. To reach these low detection limits, traditional methods use a large volume of sample for extraction. The phenols are then extracted from the water using liquid-liquid extraction, solid phase extraction or carbon cartridges. The phenols in the final extract are then pre-concentrated by reducing the final volume of the extract by evaporation. This solvent evaporation step has, however, found to result in major losses of several chlorophenols. Phenols are then usually determined by use of chromatographic techniques such as HPLC or GC.
UIS Organic Laboratory developed a method for the extraction and analysis of phenols using Solid Phase Micro-extraction (SPME) and GC/MS. The potential of this method was demonstrated earlier (Varian Application Note No 11), using a 85-µm polyacrylate SPME fiber. The major advantages of this method are that it only requires a small sample volume (< 10 ml) and no tedious sample preparation in necessary. It is important to agitate or stir the sample during extraction to disrupt the depleted layer of water that tends to accumulate around the fiber during static sampling and increasing the amount of phenol absorbed in a given time. The method can also easily be automated with a CombiPAL or Varian 8200 AutoSampler. The only sample preparation required is to adjust the pH of the sample to 2.0, thus converting the phenols to the non-ionized acid state, and to saturate the sample with Na2SO4. The addition of salt has the effect of reducing the solubility of the phenols in water. After SPME extraction, phenols are analysed on a benchtop GC/MS. Analyte compounds are identified by comparing their measured mass spectra and retention times to reference spectra and retention times in a data base. Reference spectra and retention times for analytes are obtained by the measurement of calibration standards under the same conditions used for samples. The concentration of each identified component is measured by relating the MS response of the quantitation ion(s) produced by that compound to the MS response of the quantitation ion(s) produced by a compound that is used as an internal standard. The method is suitable for a variety of phenols, which efficiently partitioned from the water sample onto the SPME fiber and which were thermally stable for gas chromatography.
SPME-GC/MS is a fast, efficient and sensitive method for the routine determination of phenols in drinking water and other types of water samples of environmental interest. Phenols can be detected in the low ppb level with good precision and linearity, without any special sample pre-treatment or advanced MS techniques. It is, however, possible to increase the selectivity and sensitivity using an advanced detection technique such as tandem mass spectrometry (MS/MS) for this analysis.
The method includes the following compounds: