Abstract
There is a growing need to develop mass spectrometric methods for the characterization of oil sands naphthenic acids (structural formulae described by C~n~H~2__n__+z~O~2~ where n is the number of carbon atoms and โzโ is referred to as the โhydrogen deficiencyโ and is equal to zero, or is a negative, even integer) present in environmental samples. This interest stems from the need to better understand their contribution to the total acid number of oil sands acids; along with assessing their toxicity in aquatic environments. Negativeโion electrospray ionization has emerged as the analytical technique of choice. For infusion samples, matrix effects are particularly evident for quantification in the presence of salts and coโelutants. However, such effects can be minimized for methods that employ chromatographic separation prior to mass spectrometry (MS) detection. There have been several advances for accurate identification of classes of naphthenic acid components that employ a range of MS hyphenated techniques. General trends measured for degradation of the NAs in the environment appear to be similar to those obtained with either lowโ or highโresolution MS. Future MS research will likely focus on (i) development of more reliable quantitative methods that use chromatography and internal standards, (ii) the utility of representative model naphthenic acids as surrogates for the complex NA mixtures, and (iii) development of congenerโspecific analysis of the principal toxic components. ยฉ 2008 Wiley Periodicals, Inc., Mass Spec Rev 28:121โ134, 2009