Detecting organic vapors using a conductometric sensor prepared from Ardel®D-100 and graphite

The composites of graphite with Ardel^?D-100 which is a trademark of a polyester of bisphenol-A with terephthalic and isophthalic acid were used as a sensing material in a conductometric vapor sensor. The magnitudes of responses are increased in the order of benzene, isobutyl acetate, isoamyl acetate, ethyl benzene and chloro benzene. This suggests that Ardel^?D-100 can be used as a sensing material for chlorobenzene, ethyl benzene and isoamyl acetate. On the other hand, specific retention volumes of the sensed vapors on Ardel^?D-100 coated on graphite were determined by inverse gas chromatography at temperatures between 200 and 260 °C. The distribution coefficient, K _s of the vapors between stationary and mobile phases in the column was obtained. It was revealed for the first time that the logarithm of K _s of the solvents varies almost linearly with their responses based on conductometric resistance of the sensing polymer composite. Subsequently, the study suggests that gas chromatographic retention data can be used in prediction of the conductometric responses of a polymeric sensor to vapors. Correspondence: Ferdane Karaman, Department of Chemistry, Yildiz Technical University, 34220 Istanbul-Esenler, Turkey     

Determination of Some Heavy Metal Ions with a Carbon Paste Electrode Modified by Poly(glycidylmethacrylate‐methylmethacrylate‐divinylbenzene) Microspheres Functionalized by 2‐Aminothiazole

A carbon paste electrode modified with 2‐aminothiazole functionalized poly(glycidylmethacrylate‐methylmethacrylate‐divinylbenzene) microspheres was used for trace determination of mercury, copper and lead ions. After the open‐circuit accumulation of the heavy metal ions onto the electrode, the sensitive anodic stripping peaks were obtained by square wave anodic stripping voltammetry (SWASV)). Many parameters such as the composition of the paste, pH, preconcentration time, effective potential scan rate and stirring rate influence the response of the measurement. The procedures were optimized for most sensitive and reliable determinations of the desired species. For a 10‐min preconcentration time in synthetic solutions at optimum instrumental and experimental conditions, the detection limit (LOD) was 12.3, 2.8 and 4.5 μg L^?1 for mercury, copper and lead, respectively. The limits of detection may be enhanced by increasing the preconcentration time. For example, LOD of mercury and copper was 4.9 and 1.0 μg L^?1 for fifteen minutes preconcentration time. The sensitivity may also considered to be increased by using a more suitable electrode composition targeting the more conductive electrode with lesser amount of modified polymer for sub‐μg L^?1 levels of heavy metal ions. The optimized method was successfully applied to the determination of copper in tap water and waste water samples by means of standard addition procedure. The copper content found was comparable with the certified concentration of the waste water sample. The calibration plots for mercury and lead spiked real samples were also drawn.     

Comment on ＇Electronic Properties of Red P-Type T12S5 Single Crystals＇

Recently, Gamal et al. [Chin. Phys. Left. 22 （2005） 1530] reported the results of electrical conductivity, Hall effect and thermoelectric measurements on p-type T12S5 single crystals. From the experimental data for the temperature dependence of differential thermoelectric power, G amal et al. determined the values of 2.66 × 10^-41 kg and 2.50 × 10^-41 kg, respectively, for the effective masses of electrons and holes in p-type T12S5, which are about ten orders of magnitude smaller than the free electron mass （9.11 × 10^-31 kg）. We argue that the anomalously small values obtained for the effective mass of charge carriers in T12S5 have no physical significance.     

Comment on `Electronic Properties of Red P-Type Tl2S5 Single Crystals'

Recently, Gamal et al. [Chin. Phys. Lett. 22 (2005) 1530] reported the results of electrical conductivity, Hall effect and thermoelectric measurements on p-type Tl₂S₅ single crystals. From the experimental data for the temperature dependence of differential thermoelectric power, Gamal et al. determined thevalues of 2.66×10^-41kg and 2.50×10^-41kg, respectively, for the effective masses of electrons and holes in p-type Tl₂S₅, which are about ten orders of magnitude smaller than the free electron mass (9.11×10^-31kg). We argue that the anomalously small values obtained for the effective mass of chargecarriers in Tl₂S₅ have no physical significance.     

Relaxation and Miscibility of the Blends of a Poly (Ether Imide) (Ultem™) and a Phenol-A-Based Copolyester (Ardel™) by Inverse Gas Chromatography

Inverse gas chromatography (IGC) was used to analyze the secondary transition temperatures and the miscibility of binary mixtures of poly (ether imide) (Ultem™) and a copolyester of bisphenol-A with terephthalic and isophthalic acids (50/50) (Ardel™) in three compositions (25/50, 50/50 and 75/25). Retention diagrams of the mixtures of Ultem™ and Ardel™ for n-nonane, n-decane, n-butyl acetate and isoamyl acetate were obtained at temperatures between 60 and 285 °C. Second-order transition temperatures of the mixtures were determined according to the slope change in retention diagrams of the solvents. The glass transition temperatures of the mixtures suggested the miscibility of the polymers. Polymer–polymer interaction parameters of binary mixtures of the polymers were determined at temperatures between 260 and 285 °C by Flory–Huggins theory. The polymer–polymer interaction parameters were dependent on the solvent used. The small values of polymer–polymer interaction parameters close to zero suggest some weak interactions between the polymers in the mixture. It was concluded that it was possible to obtain more meaningful information related to the interactions of polymers in a mixture from IGC measurements, if binary polymer–solvent interaction parameters of the used solvent probes were around 0.5.