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ABSTRACT: Conventional oil and grease analysis that involves liquid-liquid extraction (LLE) has many disadvantages, which include poor reproducibility, emulsion formation, large solvent usage, and loss of volatile and semivolatile compounds during evaporation of the solvent. Therefore, an alternative method using octadecyl siloxane (C18) solidphase extraction (SPE) columns was developed to overcome these analytical problems. The amount of the solvent was reduced and more reproducible results were obtained using this C18 SPE method. The time required for analysis is approximately the same for both methods. Higher recovery of semivolatile compounds also was obtained. The proposed C18 SPE method was also found to be comparable to those obtained from commercially available columns. Water Environ. Res., 69, 368 (1997).
KEYWORDS: analysis, extraction, grease, oil, stormwater.
According to Standard Methods (APHA, 1995), oil and grease is defined as "any material or substance that is soluble in the solvent." It does not measure the presence of any specific compound but is an important analytical procedure for environmental samples. The conventional liquid-liquid extraction (LLE) procedure for oil and grease analysis is plagued by various analytical problems such as poor or inconsistent recovery, emulsion formation, usage of large solvent volume, and loss of volatile and semivolatile compounds during evaporation of the solvent. Stenstrom et al. (1986) reviewed the development of oil and grease analytical procedures and their disadvantages. An alternative method for the oil and grease analysis is needed to overcome these analytical problems and, more importantly, to avoid or reduce the use of solvents that may be greenhouse or smog-forming gases. Solid phase extraction (SPE) is one candidate procedure and has been used extensively during the past 20 years for sample preparation in the analysis of semiand nonvolatile organic compounds for both environmental samples and for drugs in the pharmaceutical industry. The advantages of using solid-phase extraction are reduced analysis time, cost and labor, and freedom from emulsion formation. Solvent usage is also much less.
The development in recent years of disposable columns with prepacked bonded silica has encouraged the use of solid-phase extraction for environmental and pharmaceutical applications. The most commonly used silica bonded adsorbents include octadecyl (C18), octyl (C8), ethyl (C2), cyclohexyl (CH), diol (OH) and cyanopropyl (CN). Two major uses of the SPE method are sample cleanup...