Adsorption and dynamics of sodium alkylbenzenesulfonates on alumina

Deuterium nuclear magnetic resonance (²H NMR) spectroscopy was used to probe the molecular motion of sodium alkylbenzenesulfonates on γ-alumina in aqueous solutions. Two homologs with a single and a double chain were employed to compare the adsorption characteristics at various coverages. Sodium decylbenzenesulfonate-d₄ (SDBS-d₄) was chosen as a single-tailed surfactant. Motionally narrowed (single) resonances were observed from this single-chained homolog on the surface and no discrete quadrupolar splitting was found in any of the concentration ranges investigated. The spectra indicated relatively restricted molecular motion at low coverages, but relatively free motion as the adsorption amounts increased. A double-tailed homolog, sodium 4-(1′-heptylnonyl)benzenesulfonate-d₄ (SHBS-d₄), also showed a single resonance at low coverage on alumina. However, at full coverage, a discrete powder pattern overlapped a single resonance, indicating the formation of a liquid crystal-like molecular environment at the alumina/water interface. In this report, we summarize our recent investigations of the dynamics of the surface-adsorbed surfactants and discuss the differences in the adsorption behavior of the single- and double-chained homologs.     

A metallic furnace atomizer in hydride generation atomic absorption spectrometry: Determination of bismuth and selenium

A flow injection hydride generation system with a metal furnace atomizer (Inconel 600® alloy) was employed for Bi and Se determination. The presented methods have linear ranges up to 200 and 500 μg L^− 1 for Bi and Se, respectively, with good linearities (r² = 0.9997 and 0.9974, respectively). The limits of quantification obtained according to IUPAC recommendations were 2.3 μg L^− 1 for Bi and 6 μg L^− 1 for Se, and the relative standard deviations (N = 6) based on Bi and Se analytical responses from real samples were 2.7% and 10%, respectively. Accuracy evaluations were based on certified materials such as SRM 361, SRM 363, and SRM 364 (steel alloys) for Bi, Mess-3 (marine sediment), SRM 397 (human hair), and Bio-Rad2 — 69042 (urine) for Se. Good agreements between the results were obtained at the 95% confidence level, according to the t-test.     

毛细管电泳测定双氯芬酸钠制剂中的双氯芬酸钠

建立了制剂中双氯芬酸钠毛细管电泳高频电导分析法,并用于氯芬黄敏片及双氯芬酸钠肠溶片中双氯芬酸钠的测定。对电泳介质的种类、浓度以及操作电压和进样量等影响因素进行了优化。实验采用5mmol/L乳酸为缓冲溶液,22.0kV为分离电压,可在9min内实现对双氯芬酸钠的分离检测。在最佳实验条件下,双氯芬酸钠的线性范围为0.4~100μg/mL,检出限为0.1μg/mL。成功地检测了氯芬黄敏片及双氯芬酸钠肠溶片的有效成分双氯芬酸钠,回收率为92.4%~103.0%。     

Determination of thallium by electrothermal atomic absorption spectrometry with a metal atomizer

Summary Electrothermal atomization of thallium in a molybdenum microtube atomizer is described. The addition of a low flow rate of hydrogen to argon purge gas resulted in higher peak absorption. In the presence of thiourea the addition of hydrogen did not alter the peak absorption value in pure argon, although the peak temperature shifted to lower region. A high heating rate of the atomizer was recommended for higher peak absorption and improvement of interferences from concomitants. The interferences by concomitants at 50 ng level were modified with thiourea. Modification with thiourea was effective even for interferences from 500 ng of cadmium, zinc or copper, while it was insufficient for 500 ng of calcium, magnesium, chromium, bismuth or lead. Provided the atomization of thallium was carried out at high heating rate and on addition of thiourea as a matrix modifier, the interference from chloride (500 ng) was modified. The absolute sensitivity (0.0044 abs) for thallium was 1.2 pg.

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Thalliumbestitmmung durch AAS mit elektrothermischer Atomisierung in einem metallischen Atomizer

Zusammenfassung Zur AAS-Bestimmung von Thallium wird eine Molybdän-Mikroröhre als Atomizer empfohlen. Zusatz von geringeren Wasserstoffmengen zum Argongas ergab eine höhere Absorption. In Gegenwart von Thioharnstoff erfolgte durch Wasserstoff-Zugabe keine Änderung des Absorptionswertes in reinem Argon, obwohl die Peaktemperatur in einen niederen Bereich verschoben wurde. Für höhere Absorption und zur Verminderung von Störungen durch Begleitelemente wurden höhere Erhitzungsgeschwindigkeiten empfohlen. Störungen durch Begleitelemente im Bereich von 50 ng konnten mit Thioharnstoff verringert werden. Die Zugabe von Thioharnstoff erwies sich ebenfalls als wirksam für 500 ng Cadmium, Zink oder Kupfer, während sie für dieselben Mengen an Calcium, Magnesium, Chrom, Bismut oder Blei ungenügend war. Mit hoher Erhitzungsgeschwindigkeit und Thioharnstoffzusatz konnte eine Störung durch Chlorid im Bereich von 500 ng reduziert werden. Die absolute Empfindlichkeit für Thallium (0,0044 abs) betrug 1,2 pg.

     

Effect of different butanols on the adsorption of sodium dodecylsulfate on alumina

The adsorption of sodium dodecylsulfate onto alumina from aqueous solutions (0.3 M NaCl) was determined in the presence of short-chain alcohols,i.e.,1-, 2-,iso-, andtert-butanol. All adsorption isotherms of the surfactant show the same trend upon the addition of the different short-chain alcohols. The isotherm reaches its saturation level at lower surfactant equilibrium concentrations than without alcohol, and the saturation adsorption density level decreases. The reason for these changes is attributed mostly to the lowering effect of butanols on the critical micelle concentration of sodium dodecylsulfate in the aqueous bulk phase, but also the competitive adsorption of the alcohols is considered.     

Determination of sodium in sodium amalgam by measurement of the thermo-electric potential

Summary A fast method for the determination of the sodium content of sodium amalgam is based on the almost linear part of the relationship between the thermo-electric potential (T.E.P.) and the sodium content. An apparatus was constructed which has been successfully used in a mercury-brine electrolysis plant for several months. The speed of analysis is 120 samples/h. The mean deviation is ± 5% for the sodium content range of 0.1 to 0.4% by weight.

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Bestimmung von Natrium in Natriumamalgam durch Messung des thermoelektrischen Potentials

Zusammenfassung Das beschriebene Verfahren zur schnellen Messung des Natriumgehalts von Natriumamalgam beruht auf dem nahezu linearen Teil der Beziehung zwischen dem Thermoelektrischen Potential (T.E.P.) und dem Natriumgehalt. Die entwickelte Apparatur ist seit mehreren Monaten bei einer Anlage zur Chloralkali-Elektrolyse in Gebrauch. 120 Proben können in 1 h gemessen werden. Der mittlere Fehler beträgt ± 5% bei einem Natriumgehalt von 0,1–0,4 Gew-%.

     

Electrothermal atomization from metallic surfaces: Part 2. Atom formation Processes in the tungsten-tube atomizer

A modified carbon rod atomizer (Varian M-63) is used to study the mechanism of atom formation of Al, Ba, Co, Pb, Ni and V in a tungsten-tube atomizer by a combined thermodynamic—kinetic approach. The atomizer is made from two profiled tungsten strips held in two copper supporting electrodes and forming a cylindrical cavity (5 mm long, 4 mm i.d.). Appearance temperatures and atomization energies are compared with those obtained for a graphite-tube atomizer. The major pathways leading to gaseous atoms are thermal dissociation of the metal oxide (or hydroxide) and reduction of the metal oxide followed by the atomization of free metal, depending on the protecting atmosphere (argon or argon—hydrogen mixture) and analyte.     

Determination of the iron content of aluminate liquors from the Bayer alumina process by neutron activation analysis

The behaviour of iron in the Bayer process has been investigated by neutron activation analysis and Ge(Li) spectrometry, using bauxite samples of various origin. The amount of iron impurities in alumina was found to be independent of the origin of the bauxites. Alumina is contaminated by iron in the process of decomposition of aluminate liquors; regardless whether iron is present in ‘dissolved’ form or as a floating impurity, it will pass into the alumina almost completely.     

Determination of dicyclohexylamine in sodium cyclamate

Dicyclohexylamine is determined in sodium cyclamate at levels of concentration down to the order of 1 ppm by measurement of the yellow colour of the chloroform extract of its Bromophenol Blue complex.     

Determination of sodium ion diffusion coefficients in sodium vanadium phosphate

Carbon-coated Na₃V₂(PO₄)₃ (NVP) was prepared by a standard sol–gel procedure. The apparent diffusion coefficients of sodium ions in the rhombohedral NVP have been determined by different techniques such as galvanostatic intermittent titration technique (GITT) and cyclic voltammetry (CV). It was found that the apparent diffusion coefficients range from 6?×?10^?13 cm² s^?1 to 2?×?10^?15 cm² s^-1. These sodium ion apparent diffusion coefficients follow a similar trend as observed for lithium ions in the closely related monoclinic modification of Li₃V₂(PO₄)₃, demonstrating a minimum at the potential where the ion extraction/insertion occurs.     

Mechanism of cobalt atomization from different atomizer surfaces in graphite-furnace atomic-absorption spectrometry

The mechanism of cobalt atomization from different atomizer surfaces in graphite-furnace atomic-absorption spectrometry has been investigated. The atomizer surfaces were pyrolytically coated graphite, uncoated electrographite, and glassy carbon. The activation energy of the rate-determining step in the atomization of cobalt (taken as the nitrate in aqueous solution) in a commercial graphite furnace has been determined from a plot of log k_s vs. 1/T (for T values greater than the appearance temperature), where k_s is a first-order rate constant for atom release, and T is the absolute temperature. The activation energy E_a, can be correlated either with the dissociation energy of CoO_(g) or with the heat of sublimation of Co_(s), formed by carbon reduction of CoO_(s), the latter being the product of the thermal decomposition of Co(NO₃)₂. The mechanism for Co atomization seems to be the same for the pyrolytically coated graphite and the uncoated electrographite surfaces, but different for the glassy carbon surface. The suggested mechanisms are consistent with the chemical reactivity of the three atomizer surfaces, and the physical and thermodynamic properties of cobalt and its chemical compounds in the temperature range involved in the charring and atomization cycle of the graphite furnace.     

Determination of manganese in natural waters by atomic absorption spectrometry with a carbon tube atomizer.

A method is described for the accurate and precise determination of alumina and silica in bauxites with the aid of a ²²⁷Ac-Be isotopic neutron source with a total neutron output of 10⁸ n s^-1. Three ores can be analysed in triplicate within 4 h, including the determination of the natural radioactivity of the ores. Samples are pellets pressed from a mixture of 4.5 g of powdered bauxite and 0.9 g of a wax as pelleting agent. The special flux distributions of the source allow irradiations at very different fast-to-thermal flux ratios without cadmium neutron absorbers. The drying and water re-uptake of bauxite and the natural radioactivity in these ores are discussed. The method was tested with several certified standards. A relative precision of 0.7% for the alumina determination was obtained for triplicate analyses. Vanadium is the only interfering element, the concentration of which should be determined separately or estimated; a correction procedure is given.     

Determination of gold in biological materials by electrothermal atomic absorption spectrometry with a molybdenum tube atomizer

Electrothermal atomic absorption spectrometry (ETA-ASS) of gold with a molybdenum tube atomizer has been investigated. A sensitive ETA-AAS method was developed. The gold absorption signal became higher with the heating rate of the tube atomizer and as the ratio of hydrogen in the argon purge gas decreased. The optimal heating rate and the optimal gas flow rate were 5.5 C/msec and Ar 480 ml/min + H(2) 20 ml/min, respectively. The absolute characteristic mass (the mass of element giving 0.0044 abs.) of gold by the atomizer was 1.8 pg and the detection limit was 130 pg/ml (3S/N). These values were > 10 times better than those obtained with graphite atomizers, ICP and ICP-MS. The interferences caused by large amounts of interferents were evaluated. The addition of thiourea served to eliminate severe interferences. The recovery of spiked gold in biological materials was in the range of 101-106%.     

Determination of135Cs in sodium from an in-pile loop by activation analysis

Several months after shut-down,¹³⁷Cs and¹³⁴Cs were the main activities in coolant residues from an in-pile sodium loop where a fuel pin had failed at 40000 MWd/t burn-up, FR2-reirradiation of coolant residues increased¹³⁴Cs and generated¹³⁶Cs, thus indicating the presence of stable¹³³Cs and of long-lived¹³⁵Cs in the samples. The amount of¹³⁵Cs calculated from¹³⁶Cs activities was of the same quantity as the number of¹³⁷Cs atoms.     

硝普钠分光光度法测定头孢噻肟钠

建立了测定头孢噻肟钠的新方法,碱性溶液中硝普钠与头孢噻肟钠生成了化学计量比为2∶1的产物,其最大吸收波长λmax=525 nm,表观摩尔吸光系数3.9×103L.mol-1.cm-1。头孢噻肟钠在0.91~200μg/mL浓度范围内与吸光度呈现良好线性关系,线性回归方程A=0.010+0.00816ρ(μg/mL),线性相关系数r=0.9994,检出限(3σ/k)为0.62μg/mL。方法可用于药物样品和血清中头孢噻肟钠含量的测定。     

Determination of trace amounts of chromium by atomic absorption spectrometry with a tantalum filament atomizer

The sample solution containing chromium was vaporized and atomized from a tantalum filament by electrical heating into an argon stream within an absorption chamber. The interference of various metals on the atomic absorption spectrometry of chromium was investigated. Interferences were minimized by using a high filament temperature. The flameless atomizer was used for the determination of chromium in steel at a filament temperature of 2150°; with the steels investigated no matrix effect was observed, and the accuracy and precision were satisfactory.     

Determination of gadolinium in sodium borate glasses

A method for the determination of gadolinium in sodium borate glasses is described which utilizes the 312-nm fluorescence of gadolinium under 273-nm excitation. A linear dependence of fluorescence on concentration is found for the concentration range 10-20000 ppm. Quenching of gadolinium fluorescence by samarium is examined.