Automation, in sample preparation

Finally, no discussion of this topic would be complete without the mention of automation in sample preparation and its impact on this activity. Laboratory robotics initial focus was on the automation of sample preparation and is used in that way in many laboratories, but islands of automation have developed within certain organizations where certain portions of sample preparation such as SPE are automated. 

The automation of sample preparation is clearly a requirement if one wants to measure a reasonably high number of test compounds. While sample changers have been used for a long time in analytical NMR laboratories, sample preparation robots have been introduced only recently, especially in the field of biomolecular NMR. They offer the great advantage that the samples are freshly prepared under identical conditions and delivered to the NMR instrument in a just-in-time fashion. Thus, they circumvent the disadvan-... 

The use of robotics can be adopted also in sample preparation steps, in particular on-line SPE [7], This necessity is particular evident when small quantity of starting materials is available and the target molecules are present at low concentration levels. With the advent of miniaturization and automated procedures for samples handling, treatments and analysis, the lost of analytes due to a laboratory steps can be reduced. The reduction of analyte losses and the possibility to analyze even a total sample (no loss) leads to lower limits of detection (and consequently lower limits of quantification). Smaller volumes bring to obtain adequate sensitivity and selectivity for a large variety of compounds. In addition, on-line SPE requires low solvent consumption without the need to remove all residual water from cartridges, since elution solvents are compatible with the separation methods. 

Wells, D. A. and Lloyd, T. L., Automation of Sample Preparation for Pharmaceutical and Clinical Analysis, In Sampling and Sample Preparation for Field and Laboratory Fundamentals and New Directions in Sample Preparation, Pawliszyn, J., Ed., Vol. XXXVII, Elsevier Science, Amsterdam, Netherlands, pp. 837—868, 2002. 

Guillen, D.A., Barroso, C.G., and Perez-Bustamante, J.A., Automation of sample preparation as a preliminary stage in the high-performance liquid chromatographic determination of polyphenolic compounds in sherry wines, J. Chromatogr. A, 730, 39, 1996. 

The information in this chapter applies specifically to the first element sample preparation. The sample preparation steps are usually the most tedious and labor-intensive part of an analysis. By automating the sample preparation, a significant improvement in efficiency can be achieved. It is important to make sure that (1) suitable instrument qualification has been concluded successfully before initiation of automated sample preparation validation [2], (2) the operational reliability of the automated workstation is acceptable, (3) the analyte measurement procedure has been optimized (e.g., LC run conditions), and (4) appropriate training in use of the instrument has been provided to the operator(s). The equipment used to perform automated sample preparation can be purchased as off-the-shelf units that are precustomized, or it can be built by the laboratory in conjunction with a vendor (custom-designed system). Off-the-shelf workstations for fully automated dissolution testing, automated assay, and content uniformity testing are available from a variety of suppliers, such as Zymark (www.zymark.com) and Sotax (www.sotax.com). These workstations are very well represented in the pharmaceutical industry and are all based on the same functional requirements and basic principles. 

The robustness of a sample preparation technique is characterized by the reliability of the instrumentation used and the variability (precision) of the information obtained in the subsequent sample analysis. Thus, variations in controlled parameters and sequences are to be avoided. In sample preparation methods employing supercritical fluids as the extracting solvents, it has been our experience that minimal variations in efficient analyte recoveries are possible using a fully automated extraction system. The extraction solvent operating parameters under automated control are temperature, pressure (thus density), composition and flow rate through the sample. The precision of the technique will be discussed by presenting replicability, repeatability, and reproducibility data for the extraction of various analytes from such matrices as sands and soils, river sediment, and plant and animal tissue. Censored data will be presented as an indicator of instrumental reliability. 

Laboratory robotics represents an attractive approach for the automation of sample preparation and separation steps in radiochemical analysis, and for many years, such methods have been routinely used by laboratories serving the analytical needs of the International Atomic Energy Association.64 68-72 However, there are currently a limited number of published studies containing technical details on the radiochemical separations and how they were automated. Accordingly, the remainder of this chapter will focus on fluidic approaches. 

Scientists at PNNL have developed an automated radiochemical sample preparation-separation-detection system for the determination of total "Tc in nuclear-waste process streams.46 85 86 144145 This analyzer was designed to support a technetium removal process planned as part of the development of a nuclear-waste processing plant. The process stream composition is both complex and variable, with a high pH, high salt matrix. Depending on the source of the feed, the total base content, the concentration of organics, and complexant concentrations will vary, as will the aluminum, nitrate, nitrite, dichromate, and radionuclide composition. 

Structure Confirmation In the open-access LC/MS procedure described by Pullen and co-workers, the samples are directly introduced from solution for ease of automation and sample preparation. Chemists prepare samples in solvent to a suggested concentration range, then log the samples into the system. The sample log-in is done at any time during the continuous automated queue. Autosampler vials are used to hold the samples, and autosamplers are used to... 

There are several other factors that are important when it comes to the selection of equipment in a measurement process. These parameters are items 7 to 13 in Table 1.2. They may be more relevant in sample preparation than in analysis. As mentioned before, very often the bottleneck is the sample preparation rather than the analysis. The former tends to be slower consequently, both measurement speed and sample throughput are determined by the discrete steps within the sample preparation. Modern analytical instruments tend to have a high degree of automation in terms of autoinjectors, autosamplers, and automated control/data acquisition. On the other hand, many sample preparation methods continue to be labor-intensive, requiring manual intervention. This prolongs analysis time and introduces random/systematic errors. 

When considering automating the sample preparation steps and interfacing with chromatographic systems, laboratory robotics has been the method of choice. A laboratory robotics system has a robotic arm and controller, a computer linked to a controller or connected directly to the robotic arm, and application peripherals for performing specific functions in the application process. 

Maquille et al. [121], due to the physicochemical properties (i.e., polarity and ionization state) of the investigated drugs (opiates, amphetamine, cocaine and metabolites), concluded that LLE should be selected. To automate the sample preparation procedure, this team proposed urine extraction by supported liquid-liquid extraction (SLE), a promising technique that appeared in 1997 [122], which can be easily automated in a 96-well plate format. It has been demonstrated that matrix effect is significantly minimized. 

The analysis of phytochemicals is a tedious process involving several steps in which care must be taken to avoid degradation and contamination. Recent advancements in extraction, concentration, purification and analytical procedures of phytochemicals have been made, but additional developments are needed to assist in the identification and quantification of the diverse array of phytochemicals present in plants and foods, as well as metabolites in biological samples. Specifically there is a need to automate sample extraction, clean-up, and concentration steps to facilitate the screening of phytochemicals develop analytical methods with improved sensitivity, resolution and throughput that utilize less organic solvents and develop concentration and purification methods to produce analytical standards that are not available commercially. Continued advancements in sample preparation and analytical techniques will assist researchers in their quest to identify and quantify the vast array of phytochemicals present in plants... 

Luque de Castro, M.D., Luque Garcia, J.L. Automation of sample preparation. In Mester, Z., Sturgeon, R. (eds.) Sample Preparation for Trace Element Analysis, pp. 649-680. Elsevier, Amsterdam (2003)... 

As more and more samples are sent for analysis, automated procedures will be required. Improvements in instrumentation and software will facilitate the development of greater automation of sample preparation into a fully integrated analytical method. 

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