Solid sampling techniques

Solid sampling techniques for ICP emission spectrometry need to be calibrated by very carefully characterized RMs or CRMs, if available. For example, the determination of Pb by vaporization of very small sample amounts into an ICP source was shown to be independent from matrix effects by using different CRMs for cahbra-tion (Ohls 1989). 

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 ... 

Table 8.36 Main element analytical solid sampling techniques and typical sample mass...

Isolation and identification of pyrazine alkaloids (Table III) have been achieved in most cases by a combination of gas chromatography and mass spectrometry (35,36,38,69,97,142). Methyl-, 2,3,6-trimethyl-, and tetramethylpyrazines (23a, 21a, and 22a) from the melon fly are identified by utilizing a solid sampling technique in conjunction with gas chromatography-mass spectroscopy (147). Methylpyrazines show the molecule ion as a base peak. Fragmentation proceeds mainly by the loss of HCN or CH3CN from the molecular ion (141). Eth-... 

The introduction of Fourier Transform Infrared Spectroscopy (FTIR) brought along a number of typical solid sample techniques. DRIFTS (Diffuse Reflectance Fourier Transform Infrared Spectroscopy) is probably most commonly known. Another technique, developed specifically for measuring solid, opaque samples is PAS (Photo Acoustic Spectroscopy). This accessory is less known, probably due to its high cost and its rather difficult modus operandi. 

Mixed Gas Plasmas. Water loading can be reduced by a desolvation system (condenser or membrane separator) only if the vast majority of the water can be removed. One way to eliminate the introduction of water into the plasma during measurement of the analyte signals is with electrothermal vaporization, laser ablation, or other direct solid sampling techniques. Mixed gas plasmas,... 

Metal Content. Calcium, sodium, and boron contents of paper samples were determined by using a direct solid-sampling technique in conjunction with flameless atomic absorption spectroscopy (20,24). A Varian Techtron AA-6 spectrophotometer was employed with a model 90 carbon rod atomizer. In addition to the direct solid-sampling technique, calcium content was also determined by digesting samples with concentrated hydrochloric acid for 30 min. 

Chalmers JM, Mackenzie MW (1988) Solid Sample Techniques. In Mackenzie MW (ed) Advances in Applied Fourier Transform Infrared Spectroscopy. Wiley, Chichester, p 105 Chalmers JM, Willis HA, Cowell GM, Spragg RA (1982) Perkin Elmer Infrared Bulletin 99 Champion JP (1977) Can J Phys 55 1802... 

Atsuya I, Itoh K, Ariu K. 1991. Preconcentration by coprecipitation of lead and selenium with nickel-pyrrolidine dithiocarbamate complex and their simultaneous determination by internal standard atomic absorption spectrometry with the solid sampling technique. Pure Appl Chem 63(9) 1221-1226. 

Atsuya 1, Itoh K, Akatsuka K and Jin K (1987) Direct determination of trace amounts of arsenic in powdered biological samples by atomic absorption spectrometry using an inner miniature cup for solid sampling technique. Eresenius J Anal Chem 326 53-56. 

Solid sampling techniques enable direct analysis of the homogenised tissues. A number of such applications for analysing solid biological tissues have been reported (Chakrabarti et al., 1980 Lundgren and Johansson, 1974, Nordahl, 1990). However the dried tissue invariably needs to be solubilised for trace element analysis using techniques requiring the sample in a solution form (Fry and Denton, 1977 Hohl et al., 1989). 

If the sample is a solid, dissolution is required prior to flame AAS. This slows the process and opens the opportunity for contamination during the various handling steps. It would be very convenient if there were a way to introduce solid samples directly into the flame. Papers have occasionally appeared in the literature but no solid sampling technique for flame AAS has been found to be generally acceptable for biological samples. 

A method applied for placenta tissue and compared with a solid sampling technique has been published by Herber et al. (1985). 

Developments in MIR spectrometers, particularly Fourier-transform (FT) techniques, have enabled the use of a variety of solid sampling techniques which overcome the disadvantages of classic IR-sampling techniques. Classic sampling techniques [30], such as alkali halide pellet preparation (with KBr or KCl) or mineral oil mull preparations, require a mechanical treatment of the sample and may thus induce solid-solid transformations or desolvations. 

General solid sampling technique can be used in the infrared analysis. However, improvement has been made in actual operation based on the features of the polymer. Mr. 

Other solid sampling techniques While in an article such as this, it is not possible to cover all mid-infra-red sampling techniques two other methods that have been used significantly in analytical spectroscopy applications are photoacoustic spectroscopy and emission spectroscopy. 

There are many benefits to the solid sampling technique including the fact that the entire sample is used, there is no dilution or contamination with... 

As stated before, the concentration of the element selected as internal reference must be known in advance. There are different possibilities to comply with this requisite (1) previous analysis of the sample, ideally using a fast nondestructive solid sampling technique capable of providing reliable values for elements found at high levels, such as SEM-EDX [62,71,75,76], a strategy that is very common (2) on occasions, the concentration of the main matrix constituent might be known with sufficient accuracy from the stoichiometry of the material or from historical information [48,66] or can be assumed... 

The sample introduction is performed at atmospheric pressure and allows for easy coupling to sample introduction systems for different states of matter [12,25]. Liquid and gaseous samples can be introduced directly. Unless specific solid sampling techniques are used. 

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