Sulfur, analysis Fluorescence

Coal can be analyzed by thermogravimetry (TG), oxygen combustion bomb, total sulfur analysis, x-ray fluorescence (XRF), atomic absorption (AA) spec-... 

Chemical analysis a sodium thiosulfate volumetric method for Cu, x-ray fluorescence for Zn, carbon and sulfur analysis (LECO CS-344) and a benzidine hydrochloride precipitation method for S04 X-ray diffraction for the measurement of Cu crystallite size and bulk component analysis scanning electron microscope (Phillip SEM-5Q5) XPS spectrometer (KRATOS XSAM 800). 

KEYWORDS rapid sulfur analysis, gasoline analysis, diesel analysis, ultra low sulfim in diesel, combustion/oxidation UV-fluorescence detection, fast on-line/at process sulfur determination... 

There are about 20 laboratory based ASTM standard test methods available for the determination of sulfur in various petroleum products and lubricant samples [6]. These utilize diverse analytical techniques and have applicability range sparming from m% to low mg/kg levels. However, at the very low end of sulfur analysis there are only three or four test methods which can adequately determine sulfur in such fuels. These lab-based standard test methods include ASTM D 2622 - wavelength dispersive X-ray fluorescence, D 3120 - oxidative microcoulometry, D 5453 - combustion UV-fluorescence, and D 6920 - oxidative combustion electrochemical detection methods. Without a doubt, the most widely used two methods out of these in oil industry laboratories are D 2622 and D 5453. Studies have shown that at truly ultra-low levels of sulfur only D 5453 can deliver accurate and precise results. This conclusion has... 

The production laboratory at the Herculaneum smelter performs quality analytical work for all the processes. The laboratory equipment includes a spark emission spectrophotometer, inductively coupled plasma atomic emission spectrometer, wavelength dispersive X-ray fluorescence spectrometer, sulfur analysis equipment, and wet chemistry equipment. The laboratory conducts the analysis for all process materials, including sinter, blast furnace slag, lead bullion, all finished lead products, and environmental samples. 

The sample is pyrolyzed in an 80/20 mixture of oxygen and nitrogen at from 1050 to 1100°C the combustion gases are analyzed by iodine titration or by UV fluorescence. Up to 20% of the sulfur can escape analysis, however. 

Principal component analysis has been used in combination with spectroscopy in other types of multicomponent analyses. For example, compatible and incompatible blends of polyphenzlene oxides and polystyrene were distinguished using Fourier-transform-infrared spectra (59). Raman spectra of sulfuric acid/water mixtures were used in conjunction with principal component analysis to identify different ions, compositions, and hydrates (60). The identity and number of species present in binary and tertiary mixtures of polycycHc aromatic hydrocarbons were deterrnined using fluorescence spectra (61). 

The chemical composition of particulate pollutants is determined in two forms specific elements, or specific compounds or ions. Knowledge of their chemical composition is useful in determining the sources of airborne particles and in understanding the fate of particles in the atmosphere. Elemental analysis yields results in terms of the individual elements present in a sample such as a given quantity of sulfur, S. From elemental analysis techniques we do not obtain direct information about the chemical form of S in a sample such as sulfate (SO/ ) or sulfide. Two nondestructive techniques used for direct elemental analysis of particulate samples are X-ray fluorescence spectroscopy (XRF) and neutron activation analysis (NAA). 

It is of interest to examine the development of the analytical toolbox for rubber deformulation over the last two decades and the role of emerging technologies (Table 2.9). Bayer technology (1981) for the qualitative and quantitative analysis of rubbers and elastomers consisted of a multitechnique approach comprising extraction (Soxhlet, DIN 53 553), wet chemistry (colour reactions, photometry), electrochemistry (polarography, conductometry), various forms of chromatography (PC, GC, off-line PyGC, TLC), spectroscopy (UV, IR, off-line PylR), and microscopy (OM, SEM, TEM, fluorescence) [10]. Reported applications concerned the identification of plasticisers, fatty acids, stabilisers, antioxidants, vulcanisation accelerators, free/total/bound sulfur, minerals and CB. Monsanto (1983) used direct-probe MS for in situ quantitative analysis of additives and rubber and made use of 31P NMR [69]. 

Figure 7.2 shows a typical TLC plate. Some components are visible to the naked eye, but others may need to be visualized. Commonly this can be achieved under a UV light if the compounds themselves fluoresce, or if they alter the behavior of the fluorescent binder. It is also possible to spray the plate with dye or oxidize the compounds with sulfuric acid to make them visible, although the last method will result in the destruction of the sample. Once identified, areas of the stationary phase can be scraped from the inert plate and solvent extracted to yield the separated components for further analysis, if needed. 

False-negative results arising from disturbance of normal peak ratios of the analyte ions may be overcome by a variety of means including reinjection of the same derivative on another column, application of an alternative derivatization technique, and/or performing a second analysis with a different method. Thus, the identity, for example, of an illegal hormone residue in a suspect sample has been given by a series of different events including two values for the ratio to the front in two-dimensional HPTLC, a characteristic fluorescence after sulfuric... 

In liquid chromatographic analysis of quinolone antibacterials, most popular is the fluorometric detector due to the inherent fluorescence of these drugs and the advantages in terms of selectivity and sensitivity that this detector offers (Table 29.6). Fluorometric detection after postcolumn derivatization with sulfuric acid has also been reported (203). However, quinolones exhibit also remarkable ultraviolet absorption and are therefore ideal for direct determination without derivatization. Detection can be performed in the wavelength range of 254-295 nm. 

H. Mana and U. Spohn, Sensitive and Selective Flow Injection Analysis of Hydrogen Sulfite/Sulfur Dioxide by Fluorescence Detection with and without Membrane Separation by Gas Diffusion, Anal. Chem. 2001, 73, 3187. 

An ongoing study of sulfur materials taken from an Icelandic Norse-trading site context (55) has used this combination of simultaneous co-incident X-ray micro-fluorescence and micro-diffraction analyses. The compositional data from the fluorescence results are used to constrain the multi-phase analysis of the diffraction data. This approach reduces the requirement for accuracy in the... 

The use of ligand exchange has been examined for the analysis of PTH (phenylthio-hydantoin) amino acids separated on silica gel plates [92]. The method is an extension of the procedure developed for organophosphate pesticides [84]. The chromatoplate is sprayed with a solution of palladium(II) chloride and calcein. Palladium complexes with calcein to form a non-fluorescent chelate. However, in the presence of many sulfur-containing compounds, such as PTH-amino acids, the palladium is displaced from the complex liberating free calcein which gives an intense fluorescence. This method is capable of determining 0.1-nmole amounts of PTH-amino acids. 

X-ray fluorescence analysis (ASTM D-4326) is a rapid, simple, and reasonably accurate method of determining the concentration of many minor and trace elements in whole coal. The method is dependent on the availability of suitable standards. Although the major elements in coal (carbon, hydrogen, oxygen, and nitrogen) cannot be analyzed by x-ray fluorescence, most other elements at levels greater than a few parts per million (ppm) are readily determined. Sulfur should be determined by an alternative method (ASTM D-1757). 

The OPA method is based on the formation of a highly fluorescent isoindole derivative by reaction with o-phthalaldehyde and 2-aminoethanol in mildly basic aqueous solution (331. The advantage of this technique is that a large variety of thiols and other reduced sulfur compounds can be detected at subnanomolar to nanomolar concentrations. Its disadvantage is that the fluorescent derivative, which preserves the thiol in its reduced stage, is unstable and must be formed just prior to injection. These characteristics preclude the delayed analysis (e.g., in the laboratoiy) of large numbers of samples collected in the field. 

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