Fiber optic-linear array detection spectrophotometry in combination with dispersive liquid-liquid microextraction for simultaneous preconcentration and determination of palladium and cobalt.

A new combined method including fiber optic-linear array detection spectrophotometry (FO-LADS) and dispersive liquid-liquid microextraction (DLLME) was developed using a cylindrical micro-cell for simultaneous preconcentration and determination of different species. DLLME and FO-LADS methods have good matching conditions for being combined since FO-LADS is a suitable method for the determination of analytes in low volume of the remained phase obtained after DLLME. DLLME technique was successfully used as a sample preparation method. In this preconcentration method, an appropriate mixture of ethanol (the disperser solvent) and 1,2-dichlorobenzene (the extraction solvent) was injected rapidly into the water sample containing palladium and cobalt after complex formation using 1-(2-pyridylazo)-2-naphthol (PAN) reagent. After phase separation, 50 microL of the sedimented phase containing enriched analytes was determined by FO-LADS. The ordinary and first derivative absorption spectra were obtained for optimization and simultaneous determination of palladium and cobalt, respectively. Under the optimum conditions, the calibration graphs were linear in the range of 2-100 microg L(-1) and 1-70 microg L(-1) with detection limit of 0.25 microg L(-1) and 0.2 microg L(-1) for palladium and cobalt, respectively. The relative standard deviations (R.S.D.s, n = 5) were lower than 4%. The enhancement factors of 162 and 165 were obtained for palladium and cobalt, respectively. The proposed method was compared with other methods and applied to the analysis of several real and synthetic samples with satisfactory results.

Determination of organophosphorus pesticides in water samples by single drop microextraction and gas chromatography-flame photometric detector.

In this paper we have developed single drop microextraction (SDME) with modified 1.00 microl microsyringe, followed by gas chromatography with flame photometric detector (GC-FPD) for determination of 13 organophosphorus pesticides (OPPs) in water samples. By using a 1.00 microl microsyringe the repeatability of drop volume and injection were improved, because of using maximum volume of microsyringe and no dead volume. On the other hand, the modification of needle tip caused increasing cross section of needle tip and increasing adhesion force between needle tip and drop, thereby increasing drop stability and achieving a higher stirrer speed (up to 1700 rpm). The method used 0.9 microl of carbon tetrachloride as extractant solvent, 40 min extraction time, stirring at 1300 rpm and no salt addition. The enrichment factor of this method ranged from 540 to 830. The linear ranges were 0.01-100 microg/l (four orders of magnitude) and limits of detection were 0.001-0.005 microg/l for most of analyte. The relative standard deviation (RSD%) for 2 microg/l of OPPs in water by using internal standard was in the range 1.1-8.6% (n = 5). The recoveries of OPPs from farm water at spiking level of 1.0 microg/l were 91-104%.

Anodized aluminum wire as a solid-phase microextraction fiber.

The efficiency of anodized aluminum wire was investigated as a new fiber for solid-phase microextraction (SPME). Aluminum wires were anodized by direct current in a solution of sulfuric acid at room temperature and were conditioned at 300 degrees C for 30 min. These fibers were used for the extraction of some aliphatic alcohols, BTEX, and petroleum products from gaseous samples. The extracted analytes were transferred to a GC injector using an (inhouse-designed) SPME syringe that also allowed for an easy change of SPME fibers. The results obtained prove the ability of anodized aluminum wire as a new fiber for sampling of organic compounds from gaseous samples. This behavior is due most probably to the porous layer of aluminum oxide, which is formed on the metal surfaces. In this work, the optimum conditions for the preparation and conditioning of fibers and the extraction of analytes from gaseous samples were obtained. In the optimum conditions, one fiber was used in several equal analyses and the relative standard deviations were below 5% (n = 5). However, fiber-to-fiber reproducibility was 8% (n = 5). This fiber is firm, inexpensive, and durable and can be prepared simply.

Determination of anthraquinones in rhubarb roots, dock flowers and senna leaves by normal-phase high performance liquid chromatography.

A normal-phase high performance liquid chromatography using a 5-microm Spherisorb-CN column (250 x 4.6 mm i.d.) has been used for determination of the monomeric anthraquinones and their glycosides present in rhubarb roots, senna leaves and dock flower. The effects of various parameters were studied and the conditions for the extraction of the anthraquinones from herbal samples and their chromatographic separation were optimized. The nature and the quantity of anthraquinones and their conjugates were determined with a good precision and accuracy.