Interference of trace amounts of nitrilotriacetic acid in ethylenediaminetetraacetic acid with the spectrophotometric determination of niobium as the niobium—edta—pyrocatechol complex

The effects of 10^-2–10 mol-% NTA in the EDTA used in this determination are reported. Satisfactory results are possible only if the NTA contamination is less than 0.05% ($\text{w}\text{w}$). Even analytical-grade EDTA from some sources may be grossly contaminated.     

Determination of aluminum and silicon in biological materials by inductively coupled plasma atomic emission spectrometry with electrothermal vaporization

An atomic emission spectrometric method is described for the determination of trace elements in microvolume samples especially of biological materials. Based upon the arrangement of a commercial electrothermal vaporizer and a 40-MHz inductively coupled plasma, the direct determination of aluminum and silicon in human body fluids such as urine and serum and aluminum in hemodialysis solution is performed. The instrumental system involves vaporizing the sample from a modified graphite electrode followed by atomization and excitation of the vapors in the ICP discharge. Compromise experimental conditions are reported and calibration functions compared. Limits of detection in 5-μl samples were 8 pg Al and 2.5 ng Si, and after preconcentration of Al with a poly(acrylamidoxime) resin, the detection limit was 1 pg Al. Recovery of 5 μg $\text{Si}\text{ml}$ and 10 ng $\text{Al}\text{ml}$ from aqueous and synthetic standards was 80–85% and 96–103%, respectively.     

Anodic stripping determination of mercury in air with a glassy carbon electrode

A technique for stripping determination of mercury traces in air employing a glassy carbon electrode is described. The sample is passed at 2 liters min^?1 for 2 hr through an absorber containing 0.2 M potassium permanganate and 10% $\text{w}\text{v}$ sulfuric acid (1:1). After reduction with hydroxylamine hydrochloride, the determination is carried out in 0.12 M potassium thiocyanate at pH 2.0 ± 0.2 in the presence of 0.2 ppm of cupric ions. Calibration curves were found to be linear in the range 20 ppb-1 ppm Hg(II) in the cell. The accuracy of the method was tested over simulated samples and it was found to be better than 95%; the relative standard deviation was 5% or less. The limit of detection of mercury in air was approximately 10 μg m^?3.     

The optimization of an ICP injection technique and the application to the direct analysis of small-volume serum samples

The optimization and the analytical properties of an injection technique for the analysis of small-volume samples (50–200 μl) by inductively coupled plasma atomic emission spectroscopy (ICP-AES) are described. Samples are injected into a small funnel connected to a concentric glass nebulizer. A 3 kW argon/nitrogen ICP with power stabilization is used as excitation source. When operating the nebulizer at an argon pressure of 5 bar, relative detection limits for calcium, copper, iron, magnesium and zinc (0.2–50 $\text{ng}\text{ml}$) are a factor of 2 to 10 higher when compared with ICP methods using continuous nebulization. However, the full power of detection of the injection method is obtained at a 50 μl sampling volume. Matrix effects caused by sodium salt concentrations of 5 $\text{g}\text{l}$ are lower than 10%. Relative standard deviations s_r,(I_X) ranged from 0.03 to 0.07. The method was applied to the sequential determination of trace elements (copper, iron and magnesium) in human serum samples after a 1 + 4 dilution with Herrmann solution. The accuracy of the method is illustrated by the analysis results for calcium, copper, iron, magnesium and zinc in a series of test serum samples.     

Fast neutron activation analysis of bulk coal samples for alumina,silica and ash

The fast neutron activation technique was applied to bulk samples (≈11 kg) of Australian black coal. The determination of alumina is based on the reaction ²⁷Al(n,p)-²⁷Mg by counting the 0.844-MeV peak (t_{$\text{1}\text{2}$} = 9.4 min). Silica is determined by means of the reaction ²⁸Si(n,p)²⁸Al; the 1.78-MeV peak (t_{$\text{1}\text{2}$} = 2.3 min) is counted and a correction for the interference from alumina is applied. The ash content is based on the correlation between ash and the sum of alumina and silica. The accuracies (1 SD) for the determination of alumina, silica and ash were 0.52% Al₂O₃, 0.79% SiO₂ and 1.02% ash, respectively. The ash, alumina and silica contents of the samples were in the ranges 8.8–37.5%, 1.3–10.3% and 6.4–22%, respectively.     

Rapid determination of nicotinic acid by immobilized lactobacillus arabinosus

A rapid determination of aicotinic acid by using immobilized Lactobacillus arabinosus and a combined glass electrode is reported. L. arabinosus is immobilized in agar gel. The optimum agar concentration is from 2–2.5% ($\text{w}\text{v}$) and the optimum bacterial concentration in the agar gel matrix is 10 mg wet cells ml^-1. The relationship between the potential difference and the logarithm of the nicotinic acid concentration is linear over the range 5 X 10^-8–5 X 10^-6 g ml^-1. The assay requires only 1 h; potentials are reproducible with an average relative error of 5%. The growth of L. arabinosus in agar gel matrix is observed in the medium containing nicotinic acid. Immobilized L. arabinosus is stable for 30 days.     

Determination of trace metals in aluminium oxide by electrothermal atomic absorption spectrometry with direct injection of aqueous suspensions

Trace amounts (10^-5–10^-6% $\text{w}\text{w}$) of Ca, Cr, Cu, Fe, Na and Pb in aluminium oxide can be determined by graphite-furnace a.a.s. with injection of stirred sample suspensions into the tube. Calibration is possible either with Al₂O₃ standards for peak height and peak area measurements, or with standard solutions containing no aluminium for peak area measurements (except for copper). The analytical signals do not depend on the quantity of applied sample (0.02–1 mg Al₂O₃). Relative standard deviations are 2–6%.     

Fluorimetric determination of danthron in pharmaceutical tablets and in urine

A simple, rapid determination is reported for danthron (1,8-dihydroxyanthraquinone) in pharmaceutical tablets. In a flow-injection system, danthron is reduced by sodium dithionite in $\text{1}\text{1}$ methanol/borate buffer to give a fluorescent complex. Linearity ranges from 30 μg ml^?1 to below 0.1 μg ml^?1. In urine samples, danthron is separated from other fluorescing species by reversed-phase high-performance liquid chromatography before its reduction by dithionite in a post-column reactor. Urine preparation requires no extraction. Spiked urine samples were studied in the working range of 0.02–2.0 μg ml^?1 danthron.     

Observations on the reaction between nitric acid and brucine.

The macroporeus resin XAD-7 gives a fast rate of uptake of copper when used as a support for LIX-64N; it is superior to cellulose powder and other macroporous resins. The rate of uptake is satisfactory up to loadings of 60% ($\text{w}\text{w}$), and the use of purified LIX-65N or the addition of LIX-63 gives no improvement in rate. The use of toluene as a diluent reduces the rate of extraction. Elution curves for copper show negligible tailing, and rapid separations of copper from other metals by selective absorption are demon- strated. Copper can be concentrated from very dilute solution at a flow rate of 50 ml min^-1, and a 99% recovery is obtained. The method has been applied to the rapid determination of copper in brass and bronze.     

Effects of radiation and chain ends on fatigue behaviour of polystyrene

Fatigue lifetimes, under a given alternating stress amplitude, have been determined for a series of linear and branched polystyrenes. The branched polymers were obtained by a crosslinking reaction using γ-irradiation from a Co⁶⁰ source. By control of irradiation time, a series of branched samples of progressively increasing weight average molecular weight ($\text{M}$_w), with little change in number average molecular weight ($\text{M}$_n, were obtained. From comparison of fatigue data for these irradiated and branched samples with fatigue data obtained on a series of linear polystyrenes of increasing molecular weight, it may by concluded that appreciable increases in fatigue endurance can be achieved by increase in $\text{M}$_n and reduction in chain end density. For the irradiated samples, whether irradiated in air or in vacuum, fatigue lifetimes were comparable to or less than lifetimes to fracture for the unirradiated polymer, even though significant increases in $\text{M}$_w had occurred. It is suggested that the improved fatigue performance with increase of $\text{M}$_n is a consequence of increased craze stability resulting from the greater degree of chain entanglement and the smaller proportion of chain end defects.     

Neutron activation analysis of high-purity selenium : Part II. Determination of tellurium

Neutron activation determination of 15–25 p.p.b. of tellurium in selenium can be done by irradiating 100-mg samples for 4 days at a neutron flux of 6$\text{.}\text{?}$10¹² n. cm^-2.sec^-1. The daughter isotope of ¹³¹Te,¹³¹I is separated by distillation and extracted into carbon tetrachloride. Finally the silver iodide precipitate is measured by β,γ -coincidence counting. The standard deviation is 3–7%.     

Depth profiles of arsenic in semiconductor silicon by chemical etching and non-dispersive atomic fluorescence spectrometry with hydride generation

An improved non-dispersive atomic fluorescence spectrometric determination of arsenic by sodium tetrahydroborate reduction is described. A new burner on which a small argon-hydrogen-entrained air flame can be maintained at a low hydrogen flow rate (0.15 1 min^-1) is reported. The detection limit ($\text{S}\text{N}$ = 2) is 10 pg of arsenic, and the analytical working curve is linear over four decades of concentration from the detection limit. The system is applied to depth profiling of arsenic in silicon slices. The silicon is anodized, the silica film is removed by hydrofluoric acid and the arsenic in the etching solution determined. The depth of silicon removed is measured by determining the silicon content in the etching solution by inductively-coupled plasma atomic emission spectrometry. The method permits determinations of ?10¹⁸ atoms As cm^-3 in 30-nm sections of a silicon slice with a diameter of 5.1 cm.     

The determination of titanium in iron and steel by atomic absorption spectrometry

A method has been developed for the determination of titanium by atomic absorption spectrometry in a wide range of iron and steels containing <1% aluminium. Interferences are overcome by the addition of aluminium to sample and standard solutions. The accuracy and reproducibility of the method have been established at the 0.05,0.15 and 0.50% levels with British Chemical Standard samples. The procedure is time-saving, particularly as aluminium may be determined on the same initial 2% ($\text{w}\text{v}$) sample solution.     

Proprietes dielectriques d'une serie de polyoxyethylene (POE) presentant des masses moleculaires lentement variables (200 ≤ Mw ≤ 4 × 106)

In this paper, we present dielectric results for samples of POE (polyethyleneoxyde) divided into three classes. Compounds of low molecular weight ($\text{M}{}_{\mathrm{w}}\text{< 1000}$) show very weak absorption at lower temperatures. At higher temperatures (below the melting point), there appears a very important peak (stronger for lower $\text{M}{}_{\mathrm{w}}$) which corresponds to the supercooled phase. Compounds of intermediate molecular weight ($\text{1000 ≤}\text{M}{}_{\mathrm{w}}\text{≤ 10}{}^5$) show a β relaxation near 250 K (bis$\text{M}{}_{\mathrm{w}}\text{? 3000}$) which is due to the movement of chain-ends in the amorphous phase. This process increases with the importance of that part of the structure formed of shorter lamellae, thus explaining the marked diminution of this absorption for higher molecular weight compounds (the shorter lamellae cannot be obtained for $\text{M}{}_{\mathrm{w}}\text{> 4000}$). The α relaxation (obtained for T > 300 K) is perturbed by an important conduction; however, we have found a peak and a shoulder at lower frequencies, due to shorter and longer lamellae respectively. The shoulder is also present for high molecular weight compounds ($\text{M}{}_{\mathrm{w}}\text{≥ 0.1–10}{}^6$). At lower temperatures, they display a very broad γ absorption, superposed at higher frequencies with a β relaxation. The nature of this β relaxation is different from that observed for the intermediate molecular weight compounds.     

Determination of tungsten by direct current plasma atomic emission spectrometry

The determination of tungsten in steels and alloys with the three-electrode direct current plasma (DCP) “spectrajet” was investigated. The relative intensities of 17 spectral lines of tungsten and several possible interfering lines of its concomitants are listed. WI 400.875 nm is normally best suited, because the background produced by iron and acid is low and easily compensated for by using a blank solution. The limit of detection c_l in steels is 2 × 10^?3% W for 10 $\text{mg}\text{ml}$ of sample. The line W I 407.436 nm is preferred in the presence of much titanium. For the purpose considered the DCP provides about the same power of detection as the more expensive inductively coupled plasma (ICP), but its observation zone is less well buffered against influences from the matrix.     

Dilute solutions of nylon 12—II. Relationship between intrinsic viscosity and molecular weight

Samples of poly(12-dodecanelactam) (polylaurolactam, nylon 12) with $\text{M}$_n 1 × 10³?33 × 10³ were prepared. Polymerizations initiated with water or with lauric acid proceeded under conditions for minimum changes in end-group concentration. Values of $\text{M}$_n were calculated from the end-group content and $\text{M}$_n from light scattering in the mixture m-cresol/60 vol% of 2.2,3,3-tetrafluoropropanol. From measurements of intrinsic viscosity in m-cresol, the relationship [n] ? $\text{M}$_n was established in the given range of $\text{M}$_n. The relationship [n] ? $\text{M}$_w for $\text{M}$_w from 3.3 × 10³ to 125 × 10³ has been established.     

The thermal polymerization of styrene at temperatures up to 250°

The kinetics of the thermal polymerization of styrene have been studied over the range 60–250°. The overall energy of activation was 86 ± 2 kJ/mole, a value identical to that obtained for the thermal polymerization of styrene in diethyl adipate. As expected, the molecular weight of the polymer decreases with increase in the temperature of the polymerization, and the ratio $\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{M}{}_{\mathrm{<mtext>n</mtext>}}$ becomes greater than 2 for polymer formed at above 140°. The plot of log ($\text{1}\text{M}{}_{\mathrm{<mtext>n</mtext>}}$) against (absolute temperature)^?1 can be represented by two straight lines yielding 24.5 and 32,0 kJ/mole for the activation energies at temperatures below 120° and above 140°, respectively. The former value is in keeping with the molecular weight being controlled by chain transfer with monomer; the latter value would be that expected if the termination process controls the molecular weight of the polymer. Mark Houwink relationships between intrinsic viscosity and $\text{M}$_n and $\text{M}$_w have been found to apply to polymer samples when the molecular weight averages were determined by osmometry and by light scattering. However, deviations were found for low molecular weight material when measured using gel permeation chromatography. The K values were considerably lower, and the α values higher than reported in the literature.     

Studies of an inductively-coupled high-frequency argon plasma for optical emisson spectrometry—II: Compromise conditions for simultaneous multielement analysis

This paper deals with the experimental selection of conditions under which a low-power inductively-coupled plasma (ICP) can be operated so as to achieve a good compromise for simultaneous multi-element analysis. With the experimental facilities employed by the authors such conditions were found at a power of 0·7 kW, a carrier gas flow of $\text{1·31}\text{min}$ of argon, and an observation height of 15 mm. An outstanding detection power with detection limits below 1 $\text{ng}\text{ml}$ for 27 out of 32 representative elements and satisfactory suppression of ionization interference effects were simultaneously achieved.Modifications of a previously described ultrasonic nebulizer led to a higher rate of sample injection into the plasma, an improved overall reliability of the sample introduction device, and better reproducibility of spectral-line intensities (1·0–1·2% at concentrations 100 times the detection limits for 15-s integrations). Details of the construction of the ultrasonic nebulizer and its performance are provided and a simple theoretical treatment of the dependence of the aerosol ejection rate on the carrier gas flow and the size of the fog chamber is presented.Possible interelement interferences in the ICP are broadly classified.From the optimization experiments and application studies general conclusions regarding the usefulness of the ICP for both the accurate determination of a few elements and general overall analysis comprising a large number of elements are drawn.     

Polarography of disodium pentacyanonitrosylferrate(II): Part 2. Determination at Therapeutic Levels in Serum,Plasma, and Whole Blood

Disodium pentacyanonitrosylferrat(II) (sodium nitroprusside) is determined at therapeutic (ng ml^?1) levels in plasma, serum and blood with conventional and high-performance differential pulse polarography (d.p.p. and h.p.d.p.p.) at a dropping mercury electrode or a static mercury drop electrode. Serum or plasma (3 ml) is treated with perchloric acid containing 1 mg ml^?1 potassium hexacyanoferrate(II), centrifuged for 10 min and subjected to polarography. For spiked serum, calibration graphs are linear over the range 30–1000 ng ml^?1 sodium nitroprusside, regardless of the polarographic technique; the estimated detection limit is 15 ng ml^?1 (5 × 10^?8 M). Calculated therapeutic levels range from 100 to 1000 ng ml^?1. Similar results were obtained for spiked plasma. A similar procedure is suitable for whole blood and was used to study the in-vitro degradation of sodium nitroprusside (200 ng ml^?1) on incubation at 37°C. The in-vitro loss is rapid (t_{$\text{1}\text{2}$} ≈ 6 min) but meaningful in-vivo levels can be obtained when the blood is collected in a 0.9% sodium chloride solution at 0°C. Thiocyanate, the main metabolite of nitroprusside, and thiosulphate, which is a potential antidote for cyanide, do not interfere.     

Non-destructive proton activation analysis for nitrogen in refractory metals

The non-destructive determination of nitrogen in some refractory metals was studied by activation analysis with the ¹⁴N(p, n)¹⁴O reaction. The samples were irradiated with 12-MeV protons from a cyclotron. The proton beam intensity was normalized by means of a copper flux monitor. After chemical etching, the ¹⁴O activity (E_γ = 2313 keV, T_{$\text{1}\text{2}$} = 70.5 s) of the sample was measured by means of a Ge(Li) or NaI(Tl) detector. Standardization was carried out by the “average cross-section” method with nylon 6 as a nitrogen standard. The method gives a sensitivity of 0.4–30 μg g^?1 for analysis of Ta, W, Nb, and Ti, and 2000–4000 μg g^?1 for Zr, Ni and Mo.