The determination of quartz in clay materials

The quartz contents (maximum, 4 wt.%) of four clay materials and a tourmaline were determined by differential thermal analysis, by X-ray diffraction and by chemical analysis. The results are used to make a critical comparison of these three methods. DTA gives a better precision than X-ray diffraction analysis. The chemical method is judged unreliable in that feldspar and mica, present as minor components, are recorded in part as quartz.     

The low-temperature quartz resonator method for determination of the enthalpy of sublimation

A low-temperature quartz resonator method for determining the enthalpy of sublimation has been described. A quartz crystal cooled to the temperature of liquid nitrogen becomes a sensitive microbalance. The method permits the value of ΔH_sub to be obtained within 4–5 h and is especially useful in measuring ΔH_sub values of substances with low saturated vapour pressures. The following values of ΔH_sub were received for standard substances: benzoic acid, ΔH_sub = (90.8±0.6) kJ mol^?1 at 293–319 K: naphthalene, ΔH_sub = (72.3±0.8) kJ mol^?1at 293–331 K.     

Ion chromatographic determination of trace level phosphorus in purified quartz

Trace levels of phosphorus in purified quartz are determined by ion chromatography. In situ reagent purification, matrix digestion and oxidation of phosphorus to orthophosphate ion are carried out simultaneously in a vapour phase digestion (VPD) assembly using a mixture of HF, HNO3 and H2O2. A drastic reduction (475 times) in phosphate blank from reagents (HF/H2O2) was achieved in the VPD through in situ purification of the reagent. The residues remaining after volatilisation (solvent/matrix), mostly consisting of insoluble phosphate/fluoride salts of divalent and trivalent cations, were solubilised by ion-exchange dissolution. Phosphate was analysed on the IonPac AS17 column with suppressed conductivity detection. The results of the ion chromatography (IC) method were compared with a spectrophotometric method. Accuracy was evaluated by analysing a certified reference material (silicon, NIST 57a). The method detection limit was 0.05 microg g(-1).     

Grafting of swelling clay materials with 3-aminopropyltriethoxysilane

The grafting reaction between a trifunctional silylating agent and two kinds of 2:1 type layered silicates was studied using FTIR, XRD, TGA, and 29Si CP/MAS NMR. XRD patterns clearly indicate the introduction of 3-aminopropyltriethoxysilane (gamma-APS) into the clay interlayer. In the natural montmorillonite, gamma-APS adopts a parallel-bilayer arrangement, while it adopts a parallel-monolayer arrangement in the synthetic fluorohectorite. These different silane arrangements have a prominent effect on the mechanism of the condensation reaction within the clay gallery. In natural montmorillonite, the parallel-bilayer arrangement of gamma-APS results in bidentate (T2) and tridendate (T3) molecular environments, while the parallel-monolayer arrangement leads to monodentate (T1), as indicated by 29Si CP/MAS NMR spectra. This study demonstrates that the silylation reaction and the interlayer microstructure of the grafting products strongly depend on the original clay materials.     

ICP-AES法同时测定石英砂中的痕量元素

采用微波溶样，并通过条件试验，建立了微波溶样ICP－AES法同时测定石英砂中13种痕量元素的分析方法并已应用于实际样品的分析，方法的相对标准偏差≤10％，加标回收率为90％－107％。     

The determination of microgram quantities of sulphide in biological materials

Several methods for the estimation of microgram quantities of sulphide in biological material and enzymatic reaction mixtures were investigated- The optimum conditions for separation of sulphide by isothermal distillation are given. The formation of méthylène blue is recommended for the spectrophotometric determination of sulphide; modifications are described to improve the reliability and sensitivity of the method.     

Migration of134Cs and85Sr in clay materials

Retardation mechanisms of¹³⁴Cs and⁸⁵Sr have been investigated. Batch determination of distribution coefficientK _d have been carried out for various values of factors affecting retardation such as solid-liquid ratio, particle size, composition of solid phase. Various types of bentonites and mixtures of bentonites with sand have been also studied.     

The determination of authigenic quartz in porous sedimentary rocks by means of differential scanning calorimetry

The DSC method is used to characterize diagenetic transformations of porous sedimentary rocks by measuring the reversible high-low inversion of quartz crystals. For this, ten specimens of authigenic quartz from cavities in sand-and limestones have been studied, avoiding any influence of mechanical treatment on the inversion behaviour. The method shows to be very sensitive in determining disordered parts of quartz crystals, using the interrelationship between the degree of structural disorder and the decrease of the inversion temperature. The application of the method for the purpose of prospection for hydrocarbons, sulfides or phosphates is shortly discussed. Dedicated to Professor Lisa Heller-Kallai on the occasion of her 65^th birthday     

Phosphorus determination in biological materials

Summary An analysis scheme for the spectrophotometric determination of phosphorus as phosphate in biological materials has been worked out. The wet digestion of the sample was carried out in Kjeldahl flasks by a mixture of perchloric and nitric acids. The relative standard deviation (RSD) of the obtained results is not more than 1% for amounts up to 30 g. The method was applied to various biological materials.     

Several modified piezoelectric quartz crystals for determination of omethoate

A chromatographic method for the determination of transition metals in human hair samples is described. The method involves the separation of Cu, Pb, Zn, Ni, Co, Cd and Mn in a C18 column coated with sodium hexadecane-sulfonate (SHS) and spectrophotometric detection (520 nm) after post-column reaction of the eluted metals with 4-(2-pyridylazo)-resorcinol (PAR). The eluent was a 100 mM tartrate solution adjusted to pH 3.1 with a 2 M sodium hydroxide solution (flow-rate=1.0 ml min(-1)). A good separation of the eluted metals (specially for Cu/Pb and Zn/Ni) has been achieved. The detection limits, expressed as mug l(-1), were 2.2 (Cu), 8.0 (Pb), 2.8 (Zn), 1.5 (Ni), 1.5 (Co), 12.0 (Cd), and 1.4 (Mn). A microwave-assisted closed vessel acid digestion procedure with HNO(3)+HClO(4) (4+1 ml) was used for the hair samples solubilisation. Nineteen hair samples were analysed with the proposed method. The results were in good agreement with those obtained by atomic absorption spectrometry (AAS).     

Synthesis of clay nanocomposite materials by light-induced crosslinking polymerization

Different types of nanocomposite materials have been synthetized within seconds at ambient temperature, by photoinitiated crosslinking polymerization of epoxy, vinyl ether and acrylate-based resins containing a small amount (3 wt%) of an organoclay filler. The curing process was followed quantitatively by infrared spectroscopy through the decrease upon UV exposure of the IR bands characteristic of the functional groups. The silicate nanoparticles were found to have no effect on the polymerization kinetics. The UV-cured nanocomposites proved to be more flexible and impact resistant than the corresponding microcomposites. This method of synthesis of nanocomposites presents the advantages associated with the UV-curing technology, namely a solvent-free resin transformed rapidly at ambient temperature into a chemically resistant material, with a minimum consumption of energy.     

The determination of low levels of polonium-210 in environmental materials

A method is presented for the determination of polonium-210 at very low levels in the presence of many different ions. Essentially quantitative recoveries were obtained in 60 min by deposition on to a silver plate in a special holder from 50 ml solution at 85–90° with sodium citrate present.     

The investigation of coating materials for the detection of nitrobenzene with coated quartz piezoelectric crystals

Powdered activated charcoal, quadrol tetrabase and polyethylene glycol (PEG)-400 and -750 are used as coatings on 15-MHz quartz piezoelectric crystals for the detection of nitrobenzene in air. The response to nitrobenzene over the range 2–10 ppm (2–10 × 10^?6 mol mol^?1)_was almost linear for all the coatings except charcoal which exhibited marked non-linearity, as well as greater sensitivity than the other coatings. The charcoal response was linear over the range 0.7–7.6 ppm nitrobenzene. For the other coatings, sensitivity increased in the order tetrabase < quadrol < PEG-400 < PEG-750.     

The determination of chlorine in organic materials by combustion and microcoulometry

A combustion apparatus capable of burning both solid and liquid samples is described. The samples were vaporized in helium and then burned in humid oxygen. Oxygen was then used to burn non-volatile residues within the vaporization chamber. The use of cheap, disposable vaporization chambers eliminated carryover from one analysis to the next. The application of this instrument to the determination of organochlorine-containing samples is described. The moist effluent hydrogen chloride from the combustion was condensed and the chloride content was determined by microcoulometry. Pure solutions of high-boiling inorganic chlorides did not evolve chloride but the addition of an amino acid resulted in evolution of all of the chloride present.     

The determination of chromium in biological materials by atomic absorption spectroscopy

Biological samples were mineralized with a mixture of nitric, sulfuric, and perchloric acids. The chromium was oxidized to chromium(VI) followed by extraction into methyl isobutyl ketone in the cold. The ketone extract was aspirated into a fuel-rich hydrogen-air flame, and the absorption recorded using the 357.9 nm line of chromium. The limit of detection for chromium was found to be 10 p.p.b. Tissue chromium levels of normal albino rats were determined. Increased chromium values were observed for animals maintained on a high chromium diet compared to those fed a deficient diet.     

The determination of zirconium in biological materials by photon activation analysis

Non-destructive photon activation analysis with 30-MeV bremsstrahlung has been applied for the determination of zirconium in biological materials. The materials investigated were the NBS SRMs Orchard Leaves and Bovine Liver, and various tissues of rats. The detection limits of this method for a 2 h irradiation are 0.1 g for Orchard Leaves, 0.04 g for Bovine Liver and animal tissues. The zirconium contents of animal tissues obtained in this work appear to be significantly lower than the values reported earlier. New data on zirconium in the NBS SRMs are presented.     

The determination of iodine in biological and environmental standard reference materials

Iodine is an element with excellent intrinsic sensitivity when determined by thermal neutron activation. However, in most real samples, the preponderance of chlorine and bromine, relative to iodine, makes the direct determination of iodine virtually impossible. Over the past 20 years, there probably have been as many publications on the separation of iodine as there have been for any other radionuclide. Upon review, however, the methods are essentially the same. After irradiation, the samples are subjected to a rapid destructive process to free the iodine from the matrix and then the iodine is separated from the other halides either by liquid-liquid extraction or by liquid ion exchange. Both of these procedures are, however, rather complex and do not effect a complete separation of the halides in one pass. In the work presented here, a simple procedure is described for the quantitative separation of iodine from chlorine. The procedure utilizes a gas phase separation on hydrated manganese dioxide with iodine collected on silvered quartz wool. The described procedure has been used for the determination of iodine in numerous new and old SRM's at the NBS.     

The identification and determination of various triazine herbicides in biological materials

Summary The methods known today for the determination of triazine herbicides in biological materials are discussed. Analytical methods such as thin-layer and gas chromatography are dealt with as examples of specific analytical methods. Two examples using partitioning procedures, hydrolysis and photometric determination are described. These latter methods are less specific but are suitable for routine determinations where the spray history of the crops is known.

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Zusammenfassung Die heute bekannten Methoden zur Bestimmung von Triazin-Herbiciden in biologischen Materialien werden diskutiert. Spezifische Nachweis-Methoden unter Anwendung von Dünnschicht- und Gas-Chromatographie schließen sich an. Die weiterhin beschriebenen Beispiele beruhen auf der Verteilungsmethode, Hydrolyse und photometrischen Bestimmung. Diese letzten Verfahren sind zwar weniger spezifisch, eignen sich jedoch zur routinemäßigen Erfassung von Triazin-Herbiciden in Proben bekannter Triazin-Applikation.