AUTOMATION IN SAMPLE TREATMENT

The Prelude" Workstation, which is capable of automating solid sample treatments and includes options such as weighing, mixing, filtration and solid-phase extraction of samples for automatic insertion into HPLC systems, transfer to UV-Vis spectrophotometers and gathering in an EasyFill Sample Collection Module. 

Arce, L., Rios, A., and Valcarcel, M., Flow injection capillary electrophoresis coupling to automate online sample treatment for the determination of inorganic ions in waters, J. Chromatogr. A, 791, 279-287, 1997. 

Some of the variety of techniques described In the literature have resulted in the commercialization of modules independent of the chromatograph and providing it with different degrees of automation. Such modules are based on extraction (both liquid-liquid and solid-liquid), sorption (adsorption, ion exchange), vaporization, filtration (simple or through molecular sieves) or dialysis processes, or on chemical derivatization techniques. Some of these preliminary operations are better suited to HPLC, others to GC and the remainder equally to both. Only those involving the reduction of human Intervention to some extent are described here. This is a wide topic, so a comprehensive treatment is beyond the scope of this book. Below are described some representative examples of both HPLC and GC. Many of the systems described are based on the continuous separation systems dealt with in Chapter 4, devoted to the automation of sample treatment. The foundation of continuous and segmented flow analysers plays a major role in this context. 

Gas chromatography (GC) is an outstanding tool for the analysis of volatile, semivolatile and nonpolar compounds. Automation of sample treatment prior GC analysis is the bottleneck in GC analysis. It is of utmost interest to avoid laborious and time-consuming operations as well as sample contamination. 

Several proposals dealing with automation of sample treatment coupled to chromatography have been made in the last few years (Miro et ah, 2011). The connection between the flow-based system and the chromatograph can be accomplished at-line, inline, or online. At-line connection is the simplest as no physical attachment exists between the automatic flow system and the chromatograph, requiring the transport of treated sample container to the chromatograph autosampler, for instance. Online hyphenation requires that the treated sample is automatically directed to the separative column, via an injection... 

It is obvious that the simpler a method of analysis, the easier it will be to automate. Non-destructive methods which involve a minimum of sample treatment are the most attractive. X-ray fluorescence, for example, has been successfully applied to the continuous monitoring and control of process streams. However, the scope of automated analysis is wide and methods have been designed with a basis in nonspecific properties (pH, conductance, viscosity, density) as well as those characteristic of the che-... 

Water (drinking, surface, saline, domestic, and industrial waste) (EPA Method 335.4) Reflux-distillation of sample absorption of released HCN in NaOH treatment with chloramine-T, pyridine barbituric acid Semi-automated spectrophotometry (total cyanide) 0.02 ppm 95 (average) EPA 1993h... 

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. 

Egorov, O. B., O Hara, M. J., and Grate, J. W., Microwave-assisted sample treatment in a fully automated flow-based instrument Oxidation of reduced technetium species in the analysis of total technetium-99 in caustic aged nuclear waste samples, Anal. Chem., 76, 3869-3877, 2004. 

One analytical technique especially suited to pesticide analysis is high performance liquid chromatography (HPLC), and one particular version of it is called FAST-LC (an acronym for Fully Automated Sample Treatment for Liquid Chromatography). It is the various aspects of this automated sample treatment which will be considered in this report. 

One of the most successful applications of microsystem technology is the use of pTAS in diagnostics [332-335]. Microreactors have been integrated into automated analytical systems, which eliminate errors associated with manual protocols. Furthermore microreactors can be coupled with numerous detection techniques and pretreatment of samples can be carried out on the chip. In addition, analytical systems that comprise microreactors are expected to display outstanding reproducibility by replacing batch iterative steps and discrete sample treatment by flow injection systems. The possibility of performing similar analyses in parallel is an attractive feature for screening and routine use. 

Delgado Zamarreno MM, Sanchez Perez A, Bustamante Rangel M, and Hernandez Mendez J. Automated analysis for vitamin E in butter by coupling sample treatment-continuous membrane extraction—liquid chromatography with electrochemical detection. Anal. Chim. Acta 1999 386 99-106. 

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