Modern Extraction Techniques

摘要

"Where shall I start?" asked Piglet. "How about at the beginning," Pooh replied. (The Adventures of Winnie the Pooh, A. A. Milne). Preparing an inaugural biennial review covering a field as broad as "extraction" or "sample preparation" is a rather daunting task. Where does one begin? How should the topic be defined? What combination of breadth versus depth is needed? After careful consideration, this biennial review addresses "modern extraction methods" applied as analytical sample preparation tools. Even with this limitation, a significant level of discretion needs to be used in this subjective review. The review covers those articles abstracted during the calendar years of 2002 and 2003, with preference given to articles introducing new forms of analytical extraction and fundamental developments in extraction and related methodologies. Applications discussed are only those that are unique. Following the rapid development of analytical techniques in the post-World War II era, increasing demands are placed on sample quality, and thus extraction as a sample preparation tool-akin to the computer-programming mantra "garbage in, garbage out." These demands include sample integrity, throughput, and compatibility with subsequent analysis. Thus, during this review period, trends in analytical extraction have been a movement toward less (organic) solvent consumption, faster extraction time, improved quantification (i.e., higher recoveries, better reproducibility, and a drive to ever lower method detection limits), and automation. In many instances, the underlying goals are achieved through miniaturization, including the direct coupling of extraction procedures to small-scale separation and analysis methods. Improved extraction selectivity is often a secondary goal since analytical selectivity is typically achieved through subsequent separations methods, selective analytical methods, or both.