SPTを用いた重液分離の一例：

A solution of sodium polytungstate (SPT) is used as a heavy liquid in global soil studies. This reagent has found wide use because it is nontoxic, incombustible, well soluble, environmentally safe, and of low viscosity. There is a relatively simple and accessible method for its regeneration. The reagent contains no carbon compounds, which is important for studying organic matter with the use of carbon isotopes. However, some chemical properties of SPT should be taken into consideration to ensure the obtainment of incoherent and sorbed solid-phase forms of organic matter. A modification of granulodensimetric fractionation is described that allows separating the solid-phase fractions of soils without changes in the content and isotope composition of the organic carbon and organic nitrogen in the separated material.

Two methods for separating dinoflagellate cysts from marine sediments were compared: panning and sodium polytungstate (SPT). After pretreatment with the SPT solution, Protoperidinium species had a high germination rate and cell growth rate. The germinated cells grew continuously, even in a low nutrient environment. Alexandrium cysts did not germinate, because their germination is usually active in winter. Using SPT solution, the separation process was easier, quicker, and caused much less eye fatigue than the panning method. Therefore, SPT solution offers a convenient way of pretreating dinoflagellate cysts for separation and analysis.

Bone density is considered one of the many factors influencing bone structure and DNA preservation. For this reason, it is of interest in fields such as anthropology, palaeontology, and genetics. This study describes a method for bone density assessment by gradient centrifugation in Sodium Poly-Tungstate (SPT) solutions (from 2.1 to 2.6 g/cm3). Fifty milligrams of bone powder (size range of 20–50 µm) were used, with an average recovery of 89.9 (IC = 3.3% at 95% of probability). In the first phase of the experiment, the protocol was applied to ten femurs: three exhumed from the WWII mass grave of Ossero, three aged (43–50 years old) femurs from a museum collection and four fresh controls. In the subsequent phase, the analysis was extended to three petrous bones, three metacarpals, and three metatarsals exhumed from the WWII mass grave. The SPT density gradient profiles revealed marked differences among the three femur sample sets: more than 80% of the powder from control femurs was recovered in fractions with a density ≤ 2.2 g/cm3, whereas approximately 45% of the femurs from the mass grave showed a density > 2.6 g/cm3. The remaining three aged femurs displayed peculiar density patterns. Among the other bone types, metatarsals showed the lowest density values, followed by petrous bones and metacarpals. To detect degradation signatures, all nineteen bone powders were also analysed by ATR-FTIR. The femurs from the mass grave exhibited spectral features consistent with mineral recrystallisation and degradation of the organic phase, whereas the other three aged femurs showed peculiar spectral profiles; metacarpals, petrous bones and metatarsals showed intermediate spectra. PCA was applied to SPT and ATR-FTIR data, revealing correlations that support the SPT method as a novel tool for bone quality assessment. Although based on a limited sample size, this preliminary work demonstrates that SPT gradient analysis is an effective, low-cost, rapid and reliable method for assessing bone density, with potential applications in different disciplines studying aged bone samples. Lastly, principal component analysis (PCA) revealed a correlation between bone density and the yield of DNA recovered from the ten femoral specimens.

Soil samples from a rainforest, a papaya plantation, a pure Brachiaria humidicola pasture and a B. humidicola/Desmodium ovalifolium mixture were analyzed for fertility parameters. Soils were sieved to >100 µm and the organic matter light fraction was obtained by 1.8 g mL−1 density separation in a sodium polytungstate solution which was subsequently incubated under anaerobic conditions. The effect of different density agents (sodium polytungstate, Ludox and sodium iodide) on mineralization was also tested on a temperate and a tropical soil and on maize tissue.

ABSTRACTIdentifying and tackling recrystallization is a critical factor in the reliable radiocarbon (14C) dating of carbonates, since exogenous carbon can be incorporated and thus mask the real age of the samples. Vermetids are among the most important bioindicators used for paleo sea-level reconstruction, and the accuracy of their chronology can significantly impact sea-level curves. Age differences larger than 1 14C kyr before and after acid etching, combined with X-ray diffraction (XRD) analysis that indicates a significant amount of calcite still remains in the shell, led us to apply the previously developed carbonate density separation protocol (CarDS). Using a solution of sodium polytungstate, with density of 2.80 g/cm3, we successfully separated different carbonate fractions for a set of 10 vermetid samples from the coast of Rio de Janeiro, southeast of Brazil. Each separation was verified by XRD analysis and the 14C concentrations of different fractions were compared. The results show that the calcite fraction in the studied vermetid samples varied from 12 to 63% and aragonite fraction ages are up to 2 14C kyr older than the raw samples, thus confirming the efficacy of CarDS in removing young carbonates and the importance of density separation to vermetids prior to accelerator mass spectrometry (AMS) dating.

The use of quartz is critical to the electron spin resonance (ESR) dating of sediments and fault gouges. The germanium center (Ge center) in quartz is a commonly used color center employed in ESR signal measurement. Although Ge center signals in quartz can be detected using an ESR spectrometer, they are weak and sometimes undetectable. Impurities in quartz grains can further aggravate these deficiencies and may even invalidate any attempt to repeat ESR ages due to the deficiencies evident in the processes used in sample preparation. Using sieving, carbonate-organic matter removal, water flotation, magnetic separation, heavy liquid separation, and HF solution etching, we separated quartz, feldspar (plagioclase), mica, and the heavy minerals and measured the ESR signal in each of them to examine the impact of impurities within mineral grains on the ESR signals. From the ESR spectra, we observed intense ESR signals in feldspar and the heavy minerals and weak signals in mica at the same positions as the Ge center in the quartz. The ESR signals in the feldspar proved to be the most intense and overrode the peaks exhibited by the Ge center in the quartz. Feldspar is commonly associated with quartz in sediments, but it is difficult to separate it from quartz as their colors, specific gravities, and magnetic properties are similar. Any ESR signal in quartz containing foreign minerals would therefore be likely to be heavily disturbed by the signals from these foreign minerals, particularly from the feldspar and heavy minerals. ESR signals in the feldspar decreased similarly to those in the quartz when exposed to sunlight, declining by 70%–80% after being exposed for 50 h. Such declination was more obvious in high-altitude areas than in low-altitude areas. Our results indicate that highly pure quartz is required when dating; we would therefore strongly suggest that the procedures for the purification of quartz grains should include floating, heavy liquid separation, and HF solution etching to remove the feldspar, heavy minerals, and any remnant magnetite. Such a procedure would guarantee that the signal that is measured comes from the quartz alone, allowing repeatable measurements using the same spectrometer as well as valid comparisons between the spectrometries derived from different spectrometers.

Several iron ore occurrences are placed in the island of Crete and especially in the prefectures of Chania and Rethymno (Western Crete), some of which have been occasionally exploited. The aim of the present study is the mineralogical examination and the investigation of mineral processing potential of an iron ore occurrence located in the area of Skines village near to the city of Chania. The investigated iron ore occurrence form lenses which are placed within the contact of the phyllitequartzite of Phyllite-Quarzite-Series (PQS) of Crete and the overlaid limestones. The major minerals of the iron ore are goethite, hematite and quartz, while the less common are muscovite, lepidocrocite, gibbsite, talc and pyrite. The ore microscopy exanimation indicated that an extended epigenetic ferruginisation process has taken place. In general, mineral processing by using heavy liquid and magnetic separation did not give satisfactory results, except for the size fraction -1+0,250 mm of the heavy liquid and the magnetic products of size ftactions -8+4 mm, -4+1 mm and -1+0,250 mm. Ore microscopy examination of the different size fractions indicated that the difficulties in mineral processing are closely related to the ore liberation.

Understanding the microscale spatial distribution and mineralogical residency of Re in pyrite: Examples from carbonate-hosted Zn-Pb ores and implications for pyrite Re-Os geochronology

Improved density gradient separation techniques using sodium polytungstate and a comparison to the use of other heavy liquids

The hydrothermal addition of excess 40Ar at the lava flows from the early Jurassic in the Hartford Basin (Northeastern U.S.A.): Implications for the time scale

K-Ar age determinations were carried out on 12 volcanic rocks from the Noto Peninsula. Ages range from 8.64 to 27.9 Ma and are generally consistent with paleontological and stratigraphical data. Ages of volcanic rocks from the Anamizu Formation are grouped into two: 24-28 Ma in the northeast part and 16-17 Ma in the northwest part. Rocks from the Yanagida Formation give ages of 15.2 and 19.7 Ma, the former is slightly younger than expected by micropaleontological data. The Iwakurayama Rhyolite and the Kurosaki Volcanics are dated at 16.1 and 8.64 Ma, respectively.

40Ar/39Ar ages of volcanic rocks from offshore southern and peninsular California and the Southern California Borderland

Nine SHRIMP U/Pb ages on zircon and two Pb/Pb single zircon ages have been determined from Late Paleozoic volcanic rocks from Saxony and northern Bohemia. Samples came from the Teplice-Altenberg Volcanic Complex, the Meissen Volcanic Complex, the Chemnitz Basin, the Dohlen Basin, the Brandov-Olbernhau Basin, and the North Saxon Volcanic Complex. The Teplice-Altenberg Volcanic Complex is subdivided into an early Namurian phase (Mikulov Ignimbrite, 326.8 ± 4.3 Ma), thus older than assumed by previous studies, and a late caldera-forming phase (Teplice Ignimbrite, 308.8 ± 4.9 Ma). The age of the latter, however, is not well constrained due to a large population of inherited zircon and possible hydrothermal overprint. The Leutewitz Ignimbrite, product of an early explosive volcanic episode of the Meissen Volcanic Complex yielded an age of 302.9 ± 2.5 Ma (Stephanian A). Volcanic rocks intercalated in the Brandov-Olbernhau Basin (BOB, 302 ± 2.8 Ma), Chemnitz Basin (CB, 296.6 ± 3.0 Ma), Dohlen Basin (DB, 296 ± 3.0 Ma), and the North Saxon Volcanic Complex (NSVC, c. 300–290 Ma) yielded well-constrained Stephanian to Sakmarian ages. The largest Late Paleozoic ignimbrite-forming eruption in Central Europe, the Rochlitz Ignimbrite, has a well-defined middle Asselian age of 294.4 ± 1.8 Ma. Ages of palingenic zircon revealed that the Namurian-Westphalian magmatism assimilated larger amounts of crystalline basement that formed during previous Paleozoic geodynamic phases. The Precambrian inherited ages support the chronostratigraphic structure assumed for the Saxo-Thuringian Zone of the Variscan Orogen. The present results help to improve the chronostratigraphic allocation of the Late Paleozoic volcanic zones in Central Europe. At the same time, the radiometric ages have implications for the interbasinal correlation and for the geodynamic evolution of the Variscan Orogeny.

Potash-rich volcanic rocks and lamprophyres in western Shandong Province: 40Ar-39Ar dating and source tracing

Magnetic separations in biological systems have been used as alternative to gravitational or centrifugal separations. There are several advantages to using magnetically separable particles as supports for biological molecules such as enzymes, antibodies, and other bioaffinity adsorbents. For example, when magnetic particles are used as solid-phase supports in immobilized enzyme systems, the enzyme can be selectively recovered from the media, including media containing suspended solids, allowing recycling in enzyme reactors. The practical development of magnetic separations has been hindered by several critical properties of the magnetic particles developed thus far. For example, large magnetic particles (e.g., having a mean diameter in solution greater then 10 μm) respond to weak magnetic fields and magnetic field gradients; however, they tend to settle rapidly, limiting their usefulness for reactions requiring homogeneous conditions. Superparamagnetic particles coated with polymers capable of binding bioaffinity adsorbents have been prepared. Their used in the separation of biological molecules from, or directed movement of the molecules in, the surrounding medium is discussed and separation times and efficiency is compared to conventional protein processing methods.