Solid sampling automation

Soxhlet extraction and automated Soxhlet extraction are described in this section. Soxhlet extraction was named after Baron Yon Soxhlet, who introduced this method in the mid-nineteenth century. It had been the most widely used method until modern extraction techniques were developed in the 1980s. Today, Soxhlet is still a benchmark method for the extraction of semivolatile organics from solid samples. Automated Soxhlet extraction (Soxtec being its commercial name) offers a faster alternative to Soxhlet, with comparable extraction efficiency and lower solvent consumption. 

Magnesium deficiency has been long recognized, but hypermagnesia also occurs (Anderson and Talcott 1994). Magnesium can be determined in fluids by FAAS, inductively coupled plasma atomic emission spectrometry (ICP-AES) and ICP-MS. In tissue Mg can be determined directly by solid sampling atomic absorption spectrometry (SS-AAS) (Herber 1994a). Both Ca and Mg in plasma/serum are routinely determined by photometry in automated analyzers. 

Difficult matrix introduction (DMI) is another recently introduced way of automating trace analysis in complex and dirty matrices [101]. The technique may be used for both liquid and dirty solid samples. In DMI a sample extract or sample matrix (solid) is introduced directly into a microvial in the injector. Volatiles are desorbed directly... 

Hybrid systems which have been used to determine metals in solids include ETV-ICP, spark-MIP, spark-flame, arc-flame, laser-flame, laser-ETA and laser-DCP. ETV-ICP-MS is a solid sampling process which is automated, multi-element with high detection power, and amongst the best currently achieved. 

Equipment for automated Kjeldahl determinations of organic nitrogen in water and solid samples is supplied by Tecator Ltd. Their Kjeltec system 1 streamlines the Kjeldahl procedure resulting in higher speed and accuracy compared to classical Kjeldahl measurements. 

ASE—also referred to as pressurized fluid extraction (PFE)—offers an order of magnitude of additional reductions in solvent use with faster sample processing time, and with the potential of automated, unattended extraction of multiple samples. Briefly, with ASE a solid sample is enclosed in a cell containing an extraction solvent after the cell has been sealed, the sample is permeated by... 

Supercritical fluid extraction (SFE) utilizes the unique properties of supercritical fluids to facilitate the extraction of organics from solid samples. Analytical scale SFE can be configured to operate on- or off-line. In the online configuration, SFE is coupled directly to an analytical instrument, such as a gas chromatograph, SFC, or high-performance liquid chromatograph. This offers the potential for automation, but the extract is limited to analysis by the dedicated instrument. Off-line SFE, as its name implies, is a stand-alone extraction method independent of the analytical technique to be used. Off-line SFE is more flexible and easier to perform than the online methods. It allows the analyst to focus on the extraction per se, and the extract is available for analysis by different methods. This chapter focuses on off-line SFE. 

Table 3.15 summarizes the advantages and disadvantages of various extraction techniques used in the analysis of semivolatile organic analytes in solid samples. They are compared on the basis of matrix effect, equipment cost, solvent use, extraction time, sample size, automation/unattended operation, selectivity, sample throughput, applicability, filtration requirement, and the need for evaporation/concentration. The examples that follow show the differences among these techniques in real-world applications. 

A number of solid-phase automated immunoassay analyzers have been used for performing immunoassays. Table 5 (96) provides useful information on maximum tests that can be mn per hour, as well as the maximum number of analytes per sample. A number of immunoassay methods have been found useful for environmental analysis (see Automated INSTRUMENTATION). 

The Solid Sample Store is an automated sample bank facilitating storage and random access retrieval of glass vials containing powder samples. The preparation of the HTS library starts with the tedious process to prepare new solutions from the solid-compound collection. The Solid Sample Store assembles and provides the powder samples for the preparation of the HTS master solutions of defined molar concentration in pure, water-free DMSO. It is also used for the supply of powder samples to medicinal chemistry and biology labs. 

Finally, the development of automated methods for wet decomposition of solid samples without human participation can only be achieved with the use of a robotic station [183]. Nevertheless, a number of auxiliary energies and commercially available modules can facilitate and/or accelerate this time-consuming step of the analytical process (i.e., obtain the analyte(s) from a solid sample in the form of a solution). 

M.Q Luque de Castro and J.L. Luque-Garcia, Acceleration and Automation of Solid Sample Treatment, Eisevier, Amsterdam, 2002. 

Volume 24 Acceleration and Automation of Solid Sample Treatment... 

Many of the previous problems have been partly solved with the implementation of new instrument developments and improvements in analytical methodology over the past two decades. Progress in three different lines (viz. the design of graphite atomizers specially adapted for handling solid samples, the automation of solid sample insertion and the use of stable-temperature platform furnaces) has helped overcome some of the drawbacks of solid sampling with electrothermal atomizers and vaporizers. 

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