Thin Layer chromatographic analyses of pesticides in a soil ecosystem

Silica gel 60, silica gel 60 F254, and aluminium oxide as adsorbents were used to investigate their suitability for the analysis and detection of the pesticides: nitrofen, atrazine, diuron, dioxacarb, propoxur, propanil, carbaryl and cypermethrin in soil ecosystem using ethyl acetate, chloroform, dichloromethane and ethyl acetate/chloroform (1:1) as developing solvents. O-tolidine and potassium iodide reagent were used for the detection of the pesticides. Rf values obtained for the pesticides using the silica gel 60-ethyl acetate, silica gel 60 F254-ethyl acetate, silica gel 60-chloroform, silica gel 60 F254-chloroform, silica gel 60 – (1:1) ethyl acetate/chloroform and silica gel 60 F254 – (1:1) ethyl acetate/chloroform systems generally were within the stipulated range of 0.4 –0.8. Rf values obtained for the pesticides using silica gel 60-dichloromethane and silica gel 60 F254-dichloromethane systems were very low except for cypermethrin and nitrofen. Analysis with aluminium oxide coated plates gave a heavy yellow background with the detection reagent making visualization of spots difficult. Aluminium oxide coated plate is, therefore, not recommended when o-tolidine plus potassium iodide is used as detection reagent

Comparison of two detection methods in thin layer chromatographic analysis of some herbicides in a Coastal Savanna Soil in Ghana

o-tolidine plus potassium iodide and photosynthesis inhibition detection methods were investigated for the analysis of three triazine herbicides (atrazine, ametryne, simazine) and two urea herbicides (diuron, metobromuron) in a coastal savanna soil using thin layer chromatography to compare the suitability of the two methods for the study of the herbicides. This was done by spiking 5 g of the soil sample with specific amount of the herbicide standards to generate herbicide-soil concentration of 40.24, 41.46, 40.28, 39.90 and 40.64 ìg/g for atrazine, ametryne, simazine, diuron and metobromuron, respectively. Extraction was performed with acetone/hexane mixture (4:1) and the detection limit of each herbicide was then determined. In all, the photosynthesis inhibition method performed better for both the triazine and the urea herbicides, while the o-tolidine plus potassium iodide method was suitable for only the triazine herbicides. With the photosynthesis inhibition method, detectability in the range of 0.004–0.008 ± 0.002 ìg/g was attained for the herbicides using the unclean extracts. In the case of o-tolidine plus potassium iodide method, detectability of 0.008–0.406 ± 0.02 ìg/g was obtained. With the clean up extracts detectability in the range of 0.025–0.162 ± 0.004 ìg/g was obtained using the photosynthesis inhibition method. However, metobromuron was not detected in the cleaned up extracts when o-tolidine plus potassium iodide detection method was used. For the methods described, clean up with SPE cartridge, equipped with C-18, is not critical to obtain the desired results

Effect of hydrofluoric acid on acid decomposition mixtures for determining iron and other metallic elements in green vegetables.

The efficiency of acid mixtures, HNO3 - HCIO4 -HF, HNO3 - HCI - HF, HNO3 - HCIO4 and HNO3 - HCl in the decomposition of four edible green vegetables, Gboma (Solanum macrocarpon), Aleefu (Amaranttius hibirid-us), Shoeley (Hibiscus sabdariffa) and Ademe (Corchorus olitorius), for flame Atomic Absorption Spectromet-er analysis of Fe, Mn, Mg, Cu, Zn and Ca was studied. The concentrations of Fe were higher (120.61 – 710.10 mg/kg), while the values of Cu were lower (2.31 – 4.84 mg/kg) in all the samples. The values of concentration for Fe were more reproducible when HF was included in the decomposition mixtures. There were no significant differences in the concentrations of the other elements when HF was included in the acid mixture as compared to the acid mixtures without HF. Therefore, the inclusion of HF in the acid decomposition mixtures would ensure total and precise estimation of Fe in plant materials, but not critical for analysis of Mn, Mg, Cu, Zn and Ca. Performance of the decomposition procedures was verified by applying the methods to analyse Standard Reference Material IAEA-V-10 Hay Powder. Journal of Applied Science and Technology Vol. 12 (1&2) 2007: pp. 84-8

Neutron Activation Analysis of Chitin And Chitosan Extracted From Local Sea Crab Shells

Multielemental determinations in Chitin and Chitosan powders extracted from exoskeletons of local crab shells using Instrumental Neutron Activation Analysis (INAA) technique are reported. The samples were initially irradiated in a neutron thermal flux of 5 x 1011 n.cm-2s-1 in the 30kW Miniature Neutron Source Reactor (MNSR) at the Ghana Atomic Energy Commission (GAEC).Using a combination of short, medium and long irradiation schemes, fourteen elements were identified and quantified of which twelve (Al, Ca, Cl, Mg, Mn, Co, Cr, Cs, Eu, Fe, Sb, and Sc) were common to both samples. The study shows that these samples are rich sources of minor and major elements important for nutrition and growth in both plants and animals. Journal of the Ghana Science Association Vol. 9 (2) 2007: pp. 38-4

Radiation Processing And Characterization Of Chitin And Chitosan Extracted From Crab Shells

The extraction and characterization of Chitin and Chitosan from crab shells (Callinectes sp.) obtained locally in Ghana is presented. The shells were finely milled and soaked in 10 % dilute hydrochloric acid (HCl) for 48 hr followed by de-proteinization using 2M sodium hydroxide (NaOH) solution for 24 hr to obtain Chitin. The Chitin was refluxed at 100 oC in 50 % NaOH for 7 hr to yield Chitosan. The Chitin and Chitosan were characterized by determining the de-acetylation, viscosity and average molecular weights. The degree of de-acetylation was determined to be 89.7 %. The viscosity of Chitosan in dilute acetic acid was measured and the average molecular weight estimated. The average molecular weight of dry gamma irradiated (up to 100kGy) Chitosan samples decreased with increasing dose. The results have been discussed in terms of radiation induced degradation of solids. Journal of the Ghana Science Association Vol. 9 (2) 2007: pp. 18-2