Sulfur isotopes preparation

Sulfide grains sampled from the Type II veins in the high gold zones from two drill cores were prepared for sulfur isotope analysis. Pyrite samples (n=5) have average 5 S of 8.0 + 0.5 %o and a range of 7.6 - 8.3 7oo, whereas arsenopyrite (n=4) averages 7.9 + 0.5 %o and ranges between 7.3 - 8.4 %o (Fig. 3). 

D. Rumble, T.C. Hoering, J.M. Palin (1993) Preparation of SF for sulfur isotope analysis by laser heating sulfide minerals in the presence of Fj gas. Geochim. Cosmochim. Acta 52. 4499-4512... 

Figure 22. Sulfur isotope data for sulfides (closed symbols) and sulfates (open symbols) form Iberian Margin, Hess Deep, and MARK serpentinites. Data from Alt and Shanks (1998 and in preparation).

In addition to the 4 stable isotopes sulfur has at least 9 radioactive isotopes, the one with the longest half-life being which decays by activity (Kmax 0.167 MeV, 87.5 d). can be prepared by Cl(n,p), S(n,> ) or S(d,p) and is commercially available as SeicmcQt H2S, SOCb and KSCN. The radiation has a similar energy to that of C ( mav 0.155 MeV) and similar counting techniques can be used (p. 276). The maximum range is 300 min in air and 0.28 mm in water, and effective shielding is provided by a perspex screen 3-10 mm thick. The preparation of many - S-containii compounds has been... 

This new and novel method to study the photochemical degradation of Kevlar-29 fabric in air divides into four steps (1) fabric cleaning, (2) photolysis at specified temperature and time in 0.2 atm - 02, (3) preparation of the degraded (DMAc-soluble) sample surface for decarboxylation at 25° and 196°C in the concentrated sulfuric acid, and (4) the total carbon dioxide analyses by gas chromatography and the isotopic carbon dioxide ( °C02 and 48co2) ratios by GC-mass spectrometer. 

The chemistry of sulfur is a broad area that includes such chemicals as sulfuric acid (the compound prepared in the largest quantity) as well as unusual compounds containing nitrogen, phosphorus, and halogens. Although there is an extensive chemistry of selenium and tellurium, much of it follows logically from the chemistry of sulfur if allowance is made for the more metallic character of the heavier elements. All isotopes of polonium are radioactive, and compounds of the element are not items of commerce or great use. Therefore, the chemistry of sulfur will be presented in more detail. 

An important criticism of the use of combustion trains is that combustion is not site specific, that is all atoms in the analyte end up in the gas transferred to the IRMS. For studies of carbon isotope effects this is invariably C02. The question is especially important for carbon isotope analysis because analyte molecules of interest usually contain several different kinds of carbon atoms and therefore combustion methods average or dilute the IE s of interest. Should site specific isotope ratios be required another method of sample preparation (usually much more tedious) is necessary. Combustion methods, however, are frequently used to study nitrogen and sulfur IE s because many organic molecules are singly substituted with these atoms. Obviously, oxygen isotope effects cannot be determined using combustion trains because external oxygen is employed. Rather some type of pyrolytic sample preparation is required. 

All errors due to chemical preparation limit the overall precision of an isotope ratio measmement to usually 0.1-0.2%o, while modem mass spectrometer instrumentation enables a precision better than 0.02%c for light elements other than hydrogen. Larger uncertainties are expected, when elements present in a sample at very low concentration are extracted by chemical methods (e.g., carbon and sulfur from igneous rocks). 

Chemical preparation of the various sulfur compounds for isotopic analysis have been discussed by Rafter (1957), Robinson and Kusakabe (1975) among others. The gas generally used for mass-spectrometric measurement is SO2, although Puchelt et al. (1971) and Rees (1978) describe a method using SFs which has some distinct advantages it has no mass spectrometer memory effect and because fluorine is monoisotopic, no corrections of the raw data of measured isotope ratios are necessary. Comparison of 5 " S-values obtained using the conventional SO2 and the laser SFe technique has raised serious questions about the reliability of the SO2... 

Puchelt H, Sabels BR, Hoering TC (1971) Preparation of sulfur hexafluoride for isotope geochemical analysis. Geochim Cosmochim Acta 35 625-628 Quade J, Ceding TE (1995) Expansion of C4 grasses in the late Miocene of northern Pakistan evidence from stable isotopes in paleosols. Palaeogeogr Palaeoclimatol Palaeoecol 115 91-116... 

The A-nitroimidazolcs are stable for a time even in the presence of water, but treatment with concentrated sulfuric acid cleaves the N-nitro group, and strong base opens the ring. Much of the interest in such compounds is related to their multistep complex substitution reactions in which sequential nucleophilic addition of arylamines, ring opening, ring closure, nitroamide elimination, and rearomatization gives l-aryl-4-nitroimidazoles, e.g., 840 839. This method can also be used to prepare isotopically labeled imidazoles when labeled amino acids are used as the amine. 

To study the biosynthesis of thiophenes in Tagetes, S-labeled thiophene derivatives have been prepared by in vitro culture of Tagetes sp. 3. Different sources of isotopic sulfur were tested and the best results were achieved with Na2 S04- The resulting bithiophenes such as alkyne 12 are derived from triceapentaynene obtained from oleic acid <1995MI807, 1996JRN455, 1997MI175>. 

In the first place the discovery of the secretion of DHA-sulfate by the adrenal cortex in apparently major quantities suggested a hitherto completely unsuspected role of steroid sulfates in steroid biosynthesis and metabolism. Second, a number of steroid metabolites conjugated with two molecules of glucuronic or sulfuric acid were discovered, particularly in pregnancy urine, amniotic fluid, and in perfused placentofetal preparations. Finally, isotopic studies revealed several cases in which administered doubly labeled steroid conjugates were metabolized in the steroid part of the molecule without hydrolysis of the conjugate (e.g., D4, R5 cf. B5). 

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