Sample handling solid samples

Diffuse-reflectance MIRS has found a number of applications for dealing with hard-to-handle solid samples, such as polymer films, fibers, or solid dosage forms. Reflectance MIR spectra are not identical to the corresponding absorption spectra, but sufficiently close in general appearance to provide the same level of information. Reflectance spectra can be used for both qualitative and quantitative analysis. Basically, reflection of radiation may be of four types specular, diffuse, internal, and attenuated total. 

There are several techniques for handling solid samples. The "best" technique again depends on the particular application one has, If there is a suitable solvent, one can dissolve the solid... 

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. 

The application of FTIR spectroscopy to the analysis of milk has been investigated, and its performance compared to that of conventional filter-based instrumentation [22]. Calibration of the FTIR spectrometer for the determination of fat, protein, lactose, and total solids was performed through the use of PLS. The FTIR method using modified Nicolet 510 research spectrometer was able to provide a four-component analysis of milk in 12 seconds per sample and met the AOAC specifications for milk analysis [22]. The results of this study demonstrated that the use of FTIR spectroscopy would allow payment laboratories to analyse for more components and with appropriate sample handling gain sample throughput speed. A commercial version of an FTIR milk analyser is presently on the market in Europe. An FTIR method for the direct determination of water in milk has also been reported [23]. 

GF-AAS methods combine a very high atomization efficiency with a 100-1000 fold increase in sensitivity compared to the conventional flame technique. For this reason and also because of the capability of handling solid samples as well as samples which normally requires sample pretreatment, GF-AAS is one of the most popular methods in trace and ultratrace element determinations in clinical chemistry. 

These methods may be used for liquid samples or solid samples which are soluble. They are especially useful for handling liquid samples containing only a small number of micro-organisms, when it becomes necessary to process large volumes. 

Porro, T. J. Pattacini, S. C. Sample Handling for Mid-Infrared Spectroscopy, Part 1 Solid and Liquid Sampling, Spectroscopy 1993, 8(7), 40-47. 

Solid-Bottom Basket Centrifuges SmaUer-scale, solid-bottom batch basket centrifuges are available for small test samples, when the sample cannot tolerate mechanical handling or when the traces of solids remaining in a more automated centrifuge would be subject to decomposition or spoilage. 

A major advantage of static SIMS over many other analytical methods is that usually no sample preparation is required. A solid sample is loaded directly into the instrument with the condition that it be compatible with an ultrahigh vacuum (10" —10 torr) environment. Other than this, the only constraint is one of sample size, which naturally varies from system to system. Most SIMS instruments can handle samples up to 1-2 inches in diameter. 

For the application of flame spectroscopic methods the sample must be prepared in the form of a suitable solution unless it is already presented in this form exceptionally, solid samples can be handled directly in some of the non-flame techniques (Section 21.6). 

INAA is well suited to study homogeneity of small samples because of its dynamic range of elemental sensitivity. The technique allows for the use of small solid samples, with the smallest usable sample size in the range of 0.5 mg to i mg as determined by handling and blank considerations. The INAA analytical procedure is well understood and characterized with mathematical relationships. Its analytical uncertainties can be sufficiently controlled and can be well determined for a particular procedure. This allows the calculation of the contribution of material heterogeneity to the uncertainty budget based on experimental data. 

Nondestructive radiation techniques can be used, whereby the sample is probed as it is being produced or delivered. However, the sample material is not always the appropriate shape or size, and therefore has to be cut, melted, pressed or milled. These handling procedures introduce similar problems to those mentioned before, including that of sample homogeneity. This problem arises from the fact that, in practice, only small portions of the material can be irradiated. Typical nondestructive analytical techniques are XRF, NAA and PIXE microdestructive methods are arc and spark source techniques, glow discharge and various laser ablation/desorption-based methods. On the other hand, direct solid sampling techniques are also not without problems. Most suffer from matrix effects. There are several methods in use to correct for or overcome matrix effects ... 

The DEP ends with a filament wire onto which a drop of sample is deposited. After evaporation to dryness, the probe is introduced into the source of the mass spectrometer and is rapidly heated to a temperature that can reach 1000°C. This probe is ideal for the study of high molecular weight or polymeric components. It is mostly dedicated to the analysis of samples in the liquid state. Although a small solid fragment of matter may be placed on the filament, this critical operation may lead to the loss of the sample, especially if it is particularly small. To avoid such a difficult handling, the sample may be ground and homogenised in a mini-mortar and then made into suspension with a few drops of appropriate solvent (Scalarone et al., 2003). 

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