Headspace solvent microextraction of trihalomethane compounds into a single drop

Headspace solvent microextraction (HSME) into a single drop is developed for the determination of six trihalomethanes, CH2Cl2, CHCl3, C4H9Cl, CCl4, C2HCl3, and C2Cl4, in aqueous solution. A drop of benzyl alcohol containing bromoform, as an internal standard, is used for extraction. The analytes are extracted by suspending a 3-microL drop directly from the needle of a microsyringe. The needle passes through the septum of a vessel, and the needle tip appears above the surface of the solution. After the prescribed extraction time, the drop is drawn back into the syringe. The syringe is then removed, and its content is injected directly into a gas chromatography column for analysis. The main parameters affecting the HSME process, such as stirring speed, microdrop volume, sample solution temperature, microsyringe needle temperature, sample volume, solution pH, extracting solvent, and ionic strength of the solution, are studied. Also, the linear range and precision of the method are examined.     

Radiotracer studies on ion-selective membranes based on poly(vinyl chloride) matrices

Radiotracer studies with (45)Ca, (89)Sr and (133)Ba have provided evidence that the permeation of magnesium, strontium and barium ions through PVC membranes containing Orion 92-20-02 liquid ion-exchanger is inhibited by their low affinity for the liquid ion-exchanger sites. Experiments with (7)Be indicate a strong affinity of the membrane for beryllium ions with corresponding inhibition of permeation. When acid is present in the solution on one side of the membrane, preferential permeation by protons may lead to transport of ions against their concentration gradient in order to maintain the balance of charge.     

Hydrocarbon polymer analysis by external MALDI fourier transform and reflectron time of flight mass spectrometry

The traditional solvent-based matrix-assisted laser desorption ionization (MALDI) preparation method has been used to analyze nonpolar polymers of various molecular weights. High resolution silver cationized oligomers with masses of up to 12 KDa were measured using 9.4 tesla Fourier transform mass spectrometry (FTMS) with an external ionization source. It was observed that when time-of-flight mass spectrometry was used, the spectra of polyethylene polymers showed abundant low mass fragment ions. However, these fragments were absent from the FTMS spectra.