Determination of Aliminium, Chrominium, Iron and Selenium Chelates in Drinking Water at Tikreet City by Gas Liquid Chromatography Technique with Electron Capture Detector

Aluminum (III) ,and chromium (III) were chelated with trifluoroacetylacetonate (TFA), determined by gas liquid chromatography (GLC) with electron capture detector (ECD), while iron (III) was treated similarly ; but their chromatography suffered from number of practical difficulties . The technique was reliable for aluminum; although very sensitive was quite time consuming. Selenium was converted to the 4-chloropiazselenol and extracted into toluene for analysis. The Se (VI) was first reduced to Se (IV) by adding HCl and HBr with heating for more than 2 hours at 100 Co. Estimation of selenium by gas liquid chromatography with ECD considers very sensitive technique allowing pictogram (10 ̄12gm) amount of selenium can be determined. The analysis of the sample (Drinking water at Tikreet city) was shown that the level of Al, Cr, Fe, Se in water below the detection limit of GLC with ECD.


Introduction
The application of gas chromatography to metal determination requires that the metal compounds which are usually ionic be converted to volatile compounds this can then be subjected to gas chromatographic separation and measurement [1].
The formation of volatile compounds{Equations (1) and (2)} are an important aspect of the analytical technique, it is necessary that the metal cheated be formed quantitatively , rapidly and also be easy to extract into organic solvents in order to facilitate injection in gas chromatography .The determination of metal cheated by gas chromatography is dependent upon the choice of support, stationary phase and the type of detector [2].It is clear that all the fluorinated and chlorinated complexes form cheated with trivalent metals such as Al, Cr, Fe and tetravalent element (Se) which afford detection limits in the anagram range [2] .
based on the measurement of the amount of metal complexes formed by reaction of metal with an appropriate reagent in acid media , followed by extraction into toluene [3] .The introduction of second electrophone into the molecule such as chloride considerably improves the sensitivity allowing pictogram (10¯¹² gm) amount of selenium to be determined [4] .Iron (III) and molybdenum (VI) interfere in the estimation of selenium with these reagent, but the interference can be overcome by addition of EDTA in both cases.Vanadium (V) interferes with the metal cheated and unfortunately EDTA does not eliminate the interference [5].The level of selenium in blood was determined by using GLC with ECD [6] ; In present work , selenium in water was estimated by forming piazselenol with chelating agent after reduction of Se (VI) to Se (IV) by heating with concentrated HCl and extraction into toluene [7] .Many workers [8] have been used gas chromatography of metals chelates for determination of aluminum, chromium and iron in different sample matrix; therefore these metals cheated have been used later in the present work for estimation of Al, Cr, Fe and Se in water.

Results
All glassware was washed with water, detergent solution, rinsed with tap water and placed in a tank of 40% v/v aqueous nitric acid for at least 4 hours before use.The apparatus was then rinsed with distilled water , followed by double distilled water (DDW) and either dried by air drying or oven dried when required for immediate use .Syringes were immersed in acetone and ultrasonicated every day before injection was made.
The "Analar" grade reagent were used; nitric acid , hydrochloric acid , selenium dioxide , chromium nitrate , Aluminum nitrate , Ferric Chloride , Trifluoroacetonate and 1,2 diamino-4-chlorobenzene .Selenium Piazselenol Equimolar amount of (0.04 M) diamine hydrochloride salt and selenium (IV) as SeO2 were mixed together in (0.2 M) HCl .The mixture was allowed to stand at room temperature for one hour, the solid piazselenols were filtered off through a glassfiber filter paper and the damp solids recrystalized from 95% ethanol-acetate [12] The Varian Masspectrometer mode 151 in Baghdad water directorate was used in this study, the mass spectra illustrated below;

Gas Chromatographic Studies
Stock solution of aluminum, chromium and iron (1000 µg/ml) prepared individually by dissolving known amount of the complexes in toluene.Further dilutions were carried out to prepare standard solution.A good response was obtained for the aluminum and chromium complexes using chromatographic conditions and typical chromatogram obtain is shown is Fig. (2).No response was observed from the ECD for the iron complex, but it is suggested that the metal complex decomposed on the Column (13).Selenium (IV) stock solution (1000 µg/ml) was prepared by dissolving 0.1405 gm of selenium dioxide in 10 ml of concentrated nitric acid and diluted to 100 cm³ with double distilled water.Working solution were prepared by dilution of stock solution with 5% v/v nitric acid.For the extracted standards 1.00-5.00µg of Se (IV) were pipettes from 2µg/ml and 1 ml of 0.5% (w/v) the di-amine hydrochloride was added.After standing for two hours, chloropiazselenol were extracted with 25ml of toluene after shaking for five minutes [14].5 µl of the sample was injected under the conditions listed in

Determination of Al, Cr, Fe and Se in Water
An attempt was carried out to determine aluminum in drinking water in Tikreet city by GLC using solvent extraction method [15], a water sample (1500 ml) was placed in a separating funnel, then 50 ml of acetate buffer was added followed by 0.1M TFA (10ml) in toluene [16] .The organic layer was washed with 6M NH4OH (twice) and diluted to 25cm³ with toluene.The chromatogram did not show any peaks for aluminum in sample.The same procedure were used for the determination of chromium, again no signal for Cr (III) in the chromatogram The reduction of Se (VI) to Se (IV) is carried out by heating 1500ml of water sample with mixture of concentrated hydrochloric acid (5 ml) and hydrobromic acid (2.5 ml) by boiling gently for 15 minutes.After cooling to room temperature (2 ml) of 1M NH2OH.HCl are added to reduce the excess bromine.The aqueous layer was transferred to flask, (2 ml) of the 0.5% (w/v) 1,2 diamino-4chlorobenzene were added and the mixture allow to stand for four hours at room temperature, with the aid of 5-10 cm³ of DDW.The solution was extracted with 10ml of toluene after shaking for five minutes, 5µl of organic phase was injected into gas chromatography with ECD, but no signal for Se(IV) in chromatogram{Fig(3)}

Fig ( 1 )Fig
Fig (1) illustrates the molecular weight of metal complexs and the fragmentation pattern as following ;(Fig 1a) +