A solvent extraction technique for the isotopic measurement of dissolved copper in seawater

Stable copper (Cu) isotope geochemistry provides a new perspective for investigating and understanding Cu speciation and biogeochemical Cu cycling in seawater. In this work, sample preparation for isotopic analysis employed solvent-extraction with amino pyrollidine dithiocarbamate/diethyl dithiocarbamate (APDC/DDC), coupled with a nitric acid back-extraction, to concentrate Cu from seawater. This was followed by Cu-purification using anion-exchange. This straightforward technique is high yielding and fractionation free for Cu and allows precise measurement of the seawater Cu isotopic composition using multi-collector inductively coupled plasma mass-spectrometry. A deep-sea profile measured in the oligotrophic north Tasman Sea shows fractionation in the Cu isotopic signature in the photic zone but is relatively homogenised at depth. A minima in the Cu isotopic profile correlates with the chlorophyll a maximum at the site. These results indicate that a range of processes are likely to fractionate stable Cu isotopes in seawater.     

A study on the seasonal variation of the essential oil composition from Plectranthus hadiensis and its antibacterial activity

The chemical composition and seasonal variation of the essential oil from the aerial parts of Plectranthus hadiensis grown during the rainy and summer seasons in the Western Ghats of India was analysed by GC–MS technique. The analysis of rainy season oil led to the identification of 31 compounds, representing 96.4% of the essential oil and the winter season oil led to 25 compounds, representing 95.1% of the oil. Most of the compounds were sesquiterpenes and oxygenated monoterpenes. The major components of the rainy season oil were L-fenchone (30.42%), β-farnesene (11.87%), copaene(11.10%), 2,3-dimethyl hydroquinone (10.78%), α-caryophyllene(8.41%) and piperitone oxide (3.94%) and of the summer season oil are L-fenchone (31.55%), copaene(11.93%), β-farnesene (10.45%), 1,8-naphthalenedione, 8a-ethylperhydro (10.06%), α-caryophyllene(6.36%), piperitone oxide (5.79%) and limonene(4.63%). Antibacterial activity of the essential oil of P. hadiensis was tested using zone of inhibition and minimum inhibition concentration methods. Both the oils inhibited the organisms and showed the zone of inhibition in the range of 20–35 mm with MIC values between 32 and 64 mg/dL.     

Application of routine estimation of Pb isotopic ratios by inductively coupled plasma mass spectrometry for studying the Pb origin in hair of children living in polluted areas. A pilot study

The analysis of ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb and ²⁰⁸Pb isotope ratios for environmental Pb markers (leaded gasoline, air-borne particulate matter, house window dust) and hair of children was undertaken by the routine quadrupole inductively coupled argon plasma mass spectrometry (Q-ICP-MS). Hair samples collected from 10-year-old children living in Krakow in 1995 and 35 randomly selected children, aged 11, both sexes were included in the current study. Air-borne particles were collected by PM-2.5 (an aerodynamic diameter dac <2.5 μm) and PM-10 (fraction with an dac <10 μm) samplers in the proximity of steel factories situated near Krakow. Imprecision of routine estimations was approximately 0.6–0.7% or less, and was the lowest for the ²⁰⁷Pb/²⁰⁸Pb ratio (approx. 0.2%). These conditions were sufficient to distinguish Pb from air-borne dust from that in gasoline or window dust. No differences were found between Pb in PM-2.5 and PM-10 particles. The associations of the Pb in the these environmental sources and that in hair of children were discussed. The relationships of the Pb isotope ratios and other parameters related to environmental pollution were also analyzed. The analysis of distribution of the ²⁰⁷Pb/²⁰⁸Pb ratio in the hair of children, provided some evidence of the fact that hair lead of approximately 20% of the investigated population could arise from gasoline, while the Pb from air-borne dust and remaining sources can be attributed to approximately 80% of the population.     

Comparison of log k′ — solvent composition relationships in thinlayer and column chromatography for systems of the type: Silanized silica — water + methanol

Relationships between log k' values of polynuclear hydrocarbons and composition of water/methanol mixtures were determined for HPTLC on RP-18 silica and for HPLC using RP-2 silica. In spite of differences in the adsorbents used, a good correlation between HPLC and TLC parameters was found. In the TLC experiments, a sandwich tank with a modified solvent distributor was used. It has been reported that thin-layer chromatography is a good technique for the preliminary optimization of column chromatographic separations [1–5]. So far, the comparison of TLC and HPLC has been mainly restricted to silica as the adsorbent. Since TLC plates precoated with silanized adsorbents recently became commercially available, it seemed interesting to compare the chromatographic parameters obtained for the “reversed phase” systems with the two techniques (see also ref. 6).     

Solvent effects on extraction of potassium picrate with benzo-18-crown-6. A new equation for the determination of ion-pair formation of crown ether-metal salt complexes in water

In order to determine the ion-pair formation constant of a crown ether-metal salt 1:1:1 complex in water, an equation is derived from regular solution theory and its predictions are verified experimentally by the solvent extraction method using benzo-18-crown-6 (B18C6), potassium picrate (KA), and various diluents of low dielectric constant. The distribution constants of B18C6 itself and the overall extraction constants of KA with B18C6 were determined at 25±0.2°C. The distribution constants of the neutral K(B18C6)A complex were calculated from these data. The literature value for the complex-formation constant of K(B18C6)⁺ in water and the ion-pair formation constant (K _K(B18C6)A ) for K(B18C6)A in water determined in this study were log K _K(B18C6)A =3.12±0.23 at 25°C). The distribution behavior of B18C6 and K(B18C6)A is explained in terms of regular solution theory. The molar volumes V (cm³·mol^–1) and solubility parameters (cal^1/2-cm^–3/2) are as follows: V _B18C6 =249±36; V _K(B18C6)A =407±56; _B18C6 = 11.5 ± 0.5; and _K(B18C6)A = 11.5 ± 0.5.