Situ Elemental Analysis

Requirements for SEC in process control or HTS are speed (faster than conventional SEC 10 min/sample), less maintenance, and very high robustness [269]. Also process analysis with SEC was described [270,271]. In a moderately sized chemical plant it is often possible to conduct many more analyses per unit time by TLC-HPTLC than by GC or HPLC. 

On-line HPLC can be used for characterisation of raw materials, analysis of the composition of 

Polymer characterisation by on-iine SEC has been described [279]. On-line SEC analysis of low-MW polymers and additives in a process area has been published [280]. The ability to obtain rapid status information concerning blend tank component ratios enables reduction in holding time and an increase in precision in comparison to off-line wet chemical testing procedures. For coating process control and quality evaluation of polymeric automotive coatings a variety of techniques (HPLC/SEC, TA, ATR-FTIR) are used [281]. 

Principles and Characteristics In Chp. 8 of ref. [113a] we discussed elemental analysis modes in which the sample was approached to the elemental analysis tool. Mobile spectrometers are more suitable for in situ or on-line monitoring. Various such tools have recently been developed, as portable XRF and LIES A . X-ray fluorescence (XRF) analysis may be based on either electron or radio-isotope excitation. Compact, rugged, and reliable on-line XRF analysers based on radioisotope excitation have been described [25]. On-line (micro-)XRF analysers need very little if any sample preparation compared to many other techniques. Of prime importance is that the surface at the cell window represents the whole sample stream. The instruments are capable of excellent on-line performance for many applications such as process liquids, slurries, solids (e.g., polymer pellets), powders, and others. Process control XRF allows simultaneous determination of up to 32 elements. 

XRF is being used increasingly in a works environment for QC type applications [282,283], for example to measure the level of additives in oil, or of metals or other elements in a polymer. The advantage is that sample preparation is minimal because 

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SECONDARY ION MASS SPECTROMETRY TECHNIQUE AS A FUNDAMENTAL TOOL FOR IN SITU ELEMENTAL ANALYSIS... 

The reactions of the conjugate base of 2-nitropropane, used as the lithium or tetraalkylammonium salt, have been described for a number of 2-nitro-5-X-thiophenes (X = H, I, NOz, CMe2N02) and for 2,4-dinitrothio-phene. They generally display a complex pattern leading to several products. Only for 2-nitrothiophene and 2,4-dinitrothiophene has evidence for the formation of (7-adducts 137 and 138, respectively, been recorded.178 Adduct 138 has in fact been isolated as the tetramethylammonium salt and characterized by elemental analysis and NMR spectroscopy, whereas 137 has been detected in situ. The NMR data are reported in Table XX. H-NMR chemical shifts... 

Based on TGA and elemental analysis, up to one in 20 nanotube carbons (5 %) has been found to possess an aryl addend [174], For the preparation of PS-CNT nanocomposites, the same authors functionalized SWCNTs by in-situ generation of a diazonium compound from 4-(10-hydroxydecyl)aminobenzoate [175], From rheology data it was suggested that the reinforcement and dispersibility of the thus functionalized SWCNT-composites were improved over PS composites with pristine SWCNTs. 

The UV-absorption method, with which quantitative determination of DNA in tissue sections can be done, provided the inspiration for the development of x-ray spectrographic methods at the end of the 1940s. The quantitative x-ray analysis methods were developed to provide quantitative elementary analysis on a histochemical and cytochemical scale, that is, quantitative elemental analysis of tissues in situ and at a subcellular level. Engstrom1 formulated how the problem could be attacked in the following way ... 

From the discussion of ex situ spectroscopic techniques earlier in the chapter it is clear that other products of the interaction between incident beam and the surface can be detected. One of these is backscattered electrons (BSE) which give an image in which heavy elements lead to high backscattering (white areas) and light elements lead to low backscattering (black areas). Thus a very qualitative form of elemental analysis can be performed by BSE detection. 

Elemental analysis was carried out by inductively coupled plasma using a TJA IRIS-HR spectrometer after dissolving the compounds in a minimum amount of hydrochloric acid. X-ray diffraction spectra (XRD) were recorded on a Siemens D-500 diffractometer with a graphite-filtered CuKa radiation (1,5405 A). ESR spectra were recorded at 77 K using an ER 200 tt Brucker spectrometer. An ASAP 2000 Micrometries apparatus measured specific surface areas by nitrogen adsorption at 77K after degassing the samples in situ at 353 K for 4h. 

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