Analysis of microsample

There are advantages to direct solid sampling. Sample preparation is less time consuming and less prone to contamination, and the analysis of microsamples is more straightforward. However, calibration may be more difficult than with solution samples, requiring standards that are matched more closely to the sample. Precision is typically 5% to 10% because of sample inhomogeneity and variations in the sample vaporization step. 

Natelson, S. Automatic analysis of microsamples contained in capillaries with a microsample dispenser. Microchem. J. (1968), 13, 433 - 458. 

The use of a desolvating system improves the sensitivity and can extend the matrix effect with respect to conventional sample introduction apparatus.85 The current trend is towards total consumption systems. Fundamental studies concerning the analysis of microsamples with common micronebulizer based systems have been reviewed by Todoli and Mermet.85... 

Infrared analyses are conducted on dispersive (scanning) and Fourier transform spectrometers. Non-dispersive industrial infrared analysers are also available. These are used to conduct specialised analyses on predetermined compounds (e.g. gases) and also for process control allowing continuous analysis on production lines. The use of Fourier transform has significantly enhanced the possibilities of conventional infrared by allowing spectral treatment and analysis of microsamples (infrared microanalysis). Although the near infrared does not contain any specific absorption that yields structural information on the compound studied, it is an important method for quantitative applications. One of the key factors in its present use is the sensitivity of the detectors. Use of the far infrared is still confined to the research laboratory. 

The final application of FTIR to be discussed is the analysis of microsamples. A major problem encountered in the infrared examination of microsamples is the reduction in energy reaching the detector (3). The sensitivity of FTIR proved beneficial in work performed in support of metabolite studies of thiofanox. Samples were prepared by dissolving the compound in a small amount of solvent (10-20 pi), followed by withdrawing the solution into a syringe. The tip of the syringe was coated with a small amount of KBr, and the solution was slowly released... 

The more recent success achieved with Delves cup and heated graphite sources for microsample applications in AAS has widened the applicability of AAS to include major-element analysis of microsamples and trace-element analysis of macrosamples. The range of sensitivities now available affords relatively easy analysis of samples of airbpme materials over the full range of concentrations important in studies of air pollution and occupational health problems. 

Apart from continuous sample aspiration also flow injection and discrete sampling can be applied (see Section 3.1), both of which deliver transient signals. In the latter case 10-50 pi aliquots can be injected manually or with a sample dispenser into the nebulization system, as was first proposed by Ohls et al. [125] and described by Bemdt et al. (see Ref. [126]). The approach is especially useful for preventing clogging in the case of sample solutions with high salt contents, for the analysis of microsamples as required in semm analysis or when aiming at the... 

Electrothermal vaporization (ETV) in addition to its features for the analysis of microsamples, in ICP-MS has the additional advantage of introducing a dry analyte vapor into the plasma. Hence, it has been found to be useful for elements for which the detection limits are high as a result of spectral interferences with cluster ions. In the case of 56 Fe, which is subject to interference by 40ArO+, Park et al. [529] showed that the detection limit could be improved considerably by ETV. For similar reasons the direct insertion of samples in ICP-MS leads to the highest absolute power of detection (detection limits in the pg range and lower [530, 531]). 

The successful application of the CFD method in combination with subsequent gas chromatographic separation and the use of an BCD has resulted in the extensive development of this technique. However, other CFD methods aimed at obtaining derivatives that can be selectively detected by other selective detectors (e.g., sodium thermionic, flame photometric) have not been developed adequately, despite their obvious promise. It seems that the high selectivity of the method should be used for the elaboration of selective methods of functional group analysis in order to identify compounds at the picogram level. This is especially pertinent to the analysis of microsamples on capillary columns. 

The analysis of microsamples and coupling ICP with different liquid separation techniques require low-consumption introduction systems. In principle, for standard-sized analytical columns, the flow rate in liquid... 

Many samples occur naturally in solid form and a number of advantages can be gained if solid samples are introduced directly into the plasma source. Pretreatment or dissolution steps are not required, and contamination from reagents is minimized. Dilution errors are also eliminated and sample losses are avoided. Sample preparation is the most time-consuming step in conventional plasma spectrometry when samples are introduced in solution form into the plasma. The direct analysis of solid samples reduces reagent and manpower costs. Improved absolute detection limits may be obtained, analysis of microsamples or localized segments of samples are possible, and the sample vaporization, atomization, and excitation steps may be separated and optimized. 

Possibility of analysis of microsamples, better compatibility with MS detectors... 

Perkin Elmer and Spectra-Tech are two major suppliers of FT-IR microscopes (see Appendix 1). Spectra-Tech supply four types of microscopes ranging from the most expensive research microscope, to an analytical microscope, to a laboratory microscope, to the relatively low cost spectroscope designed for routine transmission analysis of microsamples. Grazing angle microscopy of monomolecular films can also be carried out using the Spectra-Tech microscope. 

Radionuclides are used in many subdivisions of analytical chemistry (see Table 1). Of major importance are radiotracers in methodological and pathway studies, isotope dilution analysis (IDA), radioimmunoassay, and nuclear activation analysis (AA) (- Activation Analysis) [66]. They are all especially suited to analyze the extremely small amounts of substances encountered in ultra-trace analysis or in trace analysis of microsamples. 

Anatoliy Aleksandrovich Kaplin (October 20, 1937-July 27, 1989) (Fig. 5.4.3.4) has developed SV for the determination of traces in semiconductor and other high-purity materials [51]. He was an excellent organizer, not only of research work (he has supervised 20 PhD theses) but also of conferences, e.g., of four All-Union Conferences on Stripping Voltammetry in Tomsk (1973,1982,1986,1990) under the chairmanship of Stromberg. Parallel to Ye. Ya. Neyman who worked in Moscow, Kaplin started to study the formation of complex amalgams, intermetaUic compounds in mercury, and solid solutions under the conditions of SV. Anodic currents of such systems were described by Kaplin on the basis of regular solution thermodynamics. Kaplin defended his doctoral thesis entitled Inverse voltammetric analysis of microsamples, crystal layers and films before a conunission in Moscow. 

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