Douglas E. Raynie

Douglas E. Raynie

"Sample Prep Perspectives" editor Douglas E. Raynie is a Department Head and Associate Professor at South Dakota State University. His research interests include green chemistry, alternative solvents, sample preparation, high-resolution chromatography, and bioprocessing in supercritical fluids. He earned his PhD in 1990 at Brigham Young University under the direction of Milton L. Lee. Raynie is a member of LCGC's editorial advisory board. Direct correspondence about this column via e-mail to LCGCedit@mjhlifesciences.com.

Articles by Douglas E. Raynie

Douglas E. Raynie explores formal and informal training opportunities that may be available to educate all chemists in the fundamentals of necessary laboratory sample preparation skills.

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Solid-phase microextraction (SPME) was introduced nearly 30 years ago and since that time has matured into a widely used tool in the arsenal of sample preparation techniques. Simultaneously, it has spawned a host of related techniques where sorbent coatings are placed on stir bars, magnetic particles, vial walls, and so on. Over the past few years, several advances in SPME have been developed, including increasing the sorbent surface area available for extraction, accommodating direct analysis by mass spectrometry (MS), and sorbent overcoating to resist fouling by sugars, lipids, and other macromolecules present in some sample types. These advances are discussed in this month’s instalment. The use of SPME for microsampling of biological systems, so-called bio-SPME, will be the focus of Part 2.

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Confusion exists on the quantitative nature of headspace sampling, because it is an equilibrium-based technique when done in the static mode, but not necessarily in the dynamic mode. To aggravate matters further, the concentrations of headspace compounds in common applications, like foods, flavours, or petroleum distillates, can easily vary by an order of magnitude or more. Thus, what defines quantitative may depend largely on the goals of the analysis. This month we’ll take a look at headspace sampling and its quantitative nature.

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Too often, analysts follow prescribed methods, including the processing of “blanks”, without fully understanding the rationale behind the various steps. This month we’ll look at the types of blanks used in an analytical procedure and why they are used. We will focus on those defined by U.S. regulatory agencies.

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During the developmental stages of chromatography, the use of sample derivatization was prevalent either to render difficult-to-separate analytes ready for chromatography or to improve analyte detectability. As chromatography techniques advanced, including detection, the need for derivatization was less pronounced. Today, there is a resurgence of interest in derivatization schemes; however, the new generation of separation scientists is not as well-versed in these reactions. Some of this resurgence is for newer purposes, such as combining two or more derivatizations for the analysis of multiple compound classes, or to develop greener approaches. In this month’s instalment, we explain the use of chemical derivatization in the separation sciences, generally, and in sample preparation specifically.

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Traditional extraction methods for food samples, such as liquid–liquid extraction and Soxhlet extraction, are often time-consuming and require large amounts of organic solvents. Therefore, one of the objectives of analytical food safety studies currently has been the development of new extraction techniques that can improve the accuracy and precision of analytical results and simplify the analytical procedure.

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Perhaps the largest source of error with sampling and sample preparation, especially with solid and semisolid samples, is the sample heterogeneity. Generally, sample heterogeneity is managed by sample homogenization, such as grinding and mixing, as well as use of an appropriately large sample size. Incremental sampling methodology (ISM) involves structured composite sampling and a processing method to create an unbiased estimate of the mean concentration of soil contaminants. Hence, ISM is emerging as a preferred methodology for conducting field environmental sampling. In this month’s instalment of “Sample Preparation Perspectives”, we describe the application of ISM to laboratory subsampling protocols.

Traditional extraction methods for food samples, such as liquid-liquid extraction and Soxhlet extraction, are often time-consuming and require large amounts of organic solvents. Therefore, one of the objectives of analytical food safety studies currently has been the development of new extraction techniques that can improve the accuracy and precision of analytical results and simplify the analytical procedure.

Blood is perhaps the most widely used sample fluid in bioanalysis. Dried blood spots (DBS) have been used with clinical samples for over 50 years but are recently seeing a resurgence of interest. DBS hold several advantages associated with the use of small sample sizes obtained via finger pricks, reduction biohazard, and more. In the previous installment, we gave an overview of microsampling in bioanalysis. This month, we will dig deeper into bioanalysis using DBS.

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Blood is perhaps the most widely used sample fluid in bioanalysis. Dried blood spot (DBS) sampling has been used in clinical applications for more than 50 years, but it is recently seeing a resurgence of interest. DBS sampling holds several advantages associated with the use of small sample sizes obtained via finger pricks, including simplicity and biohazard reduction. In the previous instalment, we gave an overview of microsampling in bioanalysis (1). This month, we dig deeper into bioanalysis using DBS sampling.