New sample preparation technologies are being proposed all of the time. Many are novel and interesting but will never have
a big impact on the sample preparation scene. Some, however, have been remarkably successful, such as solid-phase microextraction,
QuEChERS, and stir-bar sorbent extraction. Over the next few installments of "Sample Prep Perspectives," we will examine some
newer sample preparation approaches that may have the potential to break away from the field and become mainstay techniques.
This first installment features techniques that have been introduced in the past and are now being used in new application
Although sample preparation is an important part of this analytical cycle, it doesn't always get the respect that the separation
and measurement instrumentation and the data handling aspects receive. Oftentimes, the task of sample preparation is delegated
to the junior staff members who employ decades-old technology that is often manual, time-consuming, and uses a large amount
of glassware and other devices. Some of the older technologies use copious amounts of solvent that must eventually be disposed
of, creating expense and safety issues. Because of the use of multiple sample preparation steps in an attempt to simplify
and isolate the desired analytes from a complex matrix, errors tend to creep into the assay and analyte recoveries may suffer.
These observations and concerns cause many to consider sample preparation as the last bottleneck in the analytical laboratory.
In addition, sample preparation doesn't always receive the attention of the academic community because they consider the technologies
dealing with preparing the sample to be simplistic and mundane and not real science. Nevertheless, if samples are not representative
of the original source and are not collected, transported, and stored properly and considerable care is not taken in handling
and preparing the sample in the laboratory then all the great analysis that takes place after the sample is presented to the
instrument is for naught.
Despite all these obstacles, the need for faster, simpler, solvent-free, automatable sample preparation still exists. Because
of the vast improvements in other parts of the analytical cycle, especially in the chromatographic analysis and detection
(for example, mass spectrometry [MS]), there have been great strides in reducing the volume of sample required. This sample
volume reduction in turn presents further challenges such as the need for more careful sampling but on the positive side results
in a corresponding reduction in the amount of solvent and other chemicals needed for preparing the sample. The result is a
reduction in overall sample preparation time and the cost of purchase and disposal of chemicals. Miniaturized sample preparation
techniques such as solid-phase microextraction (SPME), single-drop microextraction, hollow-fiber membrane extractions, and
microextraction by packed sorbent (MEPS) have been introduced that decrease solvent requirements by 100-fold or more. On the
other hand, some of these newer technologies require more time for equilibration and thus there is a tradeoff in speed versus
I have been writing about sample preparation for some time and tend to collect articles and manufacturer's literature on sample
preparation techniques that have been published or introduced that could become the next mainstream technique like SPME or
QuEChERS (quick, easy, cheap, efficient, rugged, and safe). In this installment and in two future installments of "Sample
Prep Perspectives" I will cover a number of technologies that could "cross the chasm" and become more widely used. In formulating
these presentations, I divided the technologies into three categories:
- Existing technologies that have found new and different application areas from their original intent;
- New media that could be more useful in liquid–solid extractions (to be covered in a future installment); and
- New approaches to sample preparation that could bring added value (to be covered in a future installment).