Sulfur-specific detection

Jensen et al. [125] investigated an HPLC/ICP-MS (inductively coupled plasma mass spectrometry) with sulfur-specific detection, as a method for obtaining metabolite profiles for omeprazole administered as a 1 1... 

Jensen et al. [125] investigated an HPLC/ICP-MS with sulfur-specific detection, as a method for obtaining metabolite profiles for omeprazole administered as 1 1 mixture of 32S- and 34S-labeled material. Analysis based on the monitoring of the chromatographic eluent at either m/z 32 or m/z 34 was not successful due to insufficient sensitivity caused by interferences from polyatomic ions. However, reaction of sulfur with oxygen in the hexapole collision cell, combined with monitoring at m/z 48 (for 32S) or m/z 50 (for 34S), provided a facile method for metabolite profiling. Detection at m/z 48 was superior in sensitivity to detection of m/z 50. 

Evans, E. H. Wolff, J.-C. Eckers, C. 2001. Sulfur-specific detection of impurities in cimetidine drug substance using liquid chromatography coupled to high resolution inductively coupled plasma mass spectrometry and electrospray mass spectrometry. Anal. Chem., 73,4722-4728. 

The use of high-resolution inductively-coupled plasma MS was used for the sulfur-specific detection of cimetidine impurities. The stmcture of most of the impurities was subsequently confirmed by LC-ESI-MS [67]. 

ICP-MS and on-hne LC-ICP-MS are primarily used for element speciation in environmental, food-related, and clinical applications. Its use in metabolism stndies is more recent [66-67], Bromine-specific detection by LC-ICP-MS in conjnnction with LC-MS has been apphed to selectively find the bromine-containing metabolites of 4-bromoaniline [66] in rat mine, while chlorine and sulfur-specific detection was applied in a metabohte stndy on diclofenac [67], Pharmaceutical applications of LC-ICP-MS were reviewed [68],... 

Although analytical SFC was demonstrated in the early 1960s, it has only been in recent years that the availability of adequate high resolution packed and capillary SFC columns and instrumentation has led to renewed interest in the technique. Plasma emission is a natural development because of its use in GC and HPLC. A surfatron MIP sustained in helium has been employed for SFC detection, giving sulfur-specific detection at 921.3 nm with a 25 pg s limit for thiophene [28]. An argon high efficiency MIP has been interfaced with packed column SFC and the separation and detection of ferrocene and derivatives achieved with iron specific detection. Methanol modifier concentrations to 5% were tolerated in the carbon dioxide mobile phase [29]. 

Microcoulometric titration is used as the detection mode in some commercial sulfur-specific analysers. Sulfur in PP and waxes (range from 0.6 to 6 ppm S) were determined by means of an oxidative coulometric procedure [537]. The coulometric electrochemical array detector was used for determining a variety of synthetic phenolic antioxidants (PG, THBP, TBHQ, NDGA, BHA, OG, Ionox 100, BHT, DG) in food and oils [538],... 

Element-specific detection combined with capillary GC has become a key technique in the chemical communication studies of our laboratory. An effective detector of this type is based on the microwave plasma emission (Wylie and Quimby 1989), with a tunable selectivity for several elements and a prominent sensitivity for sulfur-containing compounds, which is significantly greater than... 

Like pesticides, heavy metals are traditionally tested by enzyme inhibition or modulation of catalytic activity. Several metalloproteins behave as chelators for specific metals with no known catalytic reactions. Such heavy metal binding sites exist in metallothioneins and in various protein elements of bacterial heavy metal mechanisms and have been exploited for specific detection through affinity events. Nevertheless and as previously mentioned, bacterial resistance mechanisms can also be linked to catalytic pathways. For instance, c5rtochromes c3 and hydrogenases from sulfate and sulfur reducing bacteria [284,285] are well suited for bioremediation purposes because they can reduce various metals such as U(V) and Cr(VI) [286,287]. Cytochrome c3 has been reported to catalyse Cr(VI) and U(VI) reduction in Desulfovibrio vulgaris [288,289], suggesting... 

A buffer mixture of ammonium sulfate and sulfuric acid can also be employed for the elution of aluminum. Its specific detection is carried out via derivatization with Tiron (4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt) with subsequent photometry of the complex formed at a wavelength of 313 nm (Fig. 3-160). In an acidic sulfate medium aluminum ions exist as A1S04+ ions depending on the hydrogen ion and sulfate ion concentration. The parameter determining retention is, in this case, the ammonium sulfate concentration. 

The use of nitrogen- or sulfur-specific detectors for GC enables small quantities of nitrogen- or sulfur-containing molecules to be detected. 

A spectrophotometric technique has been used for quantifying pg/mL levels of free and acid-labile (chemically bound) carbon disulfide in the blood of rats (Lam and DiStefano 1982, 1983). This technique is based on measuring the absorbance at 430 nm of a yellow cupric diethyldithiocarbamate complex that is formed by reacting carbon disulfide in blood with Viles reagent in the presence of acid and heat. A headspace sampler connected to GC equipped with a sulfur-specific flame photometric detector (FPD) has been developed for measuring low levels of free and acid-labile carbon disulfide in the blood of shift workers exposed to carbon disulfide (Campbell et al. 1985). A detection limit of 15.2 pg of carbon disulfide/L of blood was achieved. Concentrations of free and acid-labile carbon disulfide have also been determined by GS/MS (Brugnone et al. 1993, 1994 Perbellini et al. 1994). 

Specific detection reagents are used for the preliminary identification of glycolipids.The most useful reagents are the resorcinol-HCI spray for gangliosides and the orcinol-sulfuric acid spray for neutral glycolipids and gangliosides. 

The use of electrolytic conductivity detectors (HECDs, also known as Hall detectors) for the analysis of organic sulfur compounds is limited, probably because they require high maintenance. The electrolyte must be kept extremely clean and its sulfur specificity is limited by high concentrations of cotrapped carbon dioxide. Despite these problems, HECD performed well in the sulfur detection mode. ... 

It is apparent that elemental sulfur species that are suspected to cause silver corrosion can be detected at the appropriate levels that contribute to the fuel gauge issue. Of course, the ability to make a rapid total sulfur measurement is extremely useful in many circumstances. For instance, in a process plant upset, speciation of sulfur may be desirable only when a total sulfur specification is exceeded. In those circumstances, it is desirable to be able to simply change operating conditions back and forth between total sulfur and speciated sulfur analysis, and this is achievable using LTMGC. 

For observing the sulfur-containing isothiocyanates in GC, specific detectors can be employed. The use of an electron capture system has been described [48]. A sulfur-specific photometric detector might even be more useful in order to improve sensitivity and selectivity. A nitrogen-selective detection system has been used recently for the same purpose [59]. 

Volatile and aromatic components Separation of volatile components is achieved on either fused silica capillary columns or packed columns. Individual volatile components are detected with a FID and identified by the use of reference standards. Methods using specific detectors, such as the NPD, sulfur-specific flame photometric detector, and mass-selective detector (MSD) have also been used. The MSD has the additional advantage of providing structural identification of the individual components. 

There are a number of other GC detectors commercially available. Photoionization detectors (PIDs) are primarily used for the selective, low-level detection of the compounds which have double or triple bonds or an aromatic moiety in their structures. Electrolytic conductivity detectors (ELCDs) are used for the selective detection of chlorine-, nitrogen-, or sulfur-containing compounds at low levels. Chemiluminescence detectors are usually employed for the detection of sulfur compounds. The atomic emission detectors (AEDs) can be set up to respond only to selected atoms, or group of atoms, and they are very useful for element-specific detection and element-speciation work. 

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