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  • Author or Editor: Ali Mohammad x
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Three methyl groups containing quaternary ammonium compounds have been separated and identified by thin-layer chromatography using green solvents. Silica gel G and n-butanol-40% aq. ethylene glycol-ethyl acetate (6:4:1) have been found the most favorable for the resolution of three cationic surfactants (cetrimonium chloride-benzyl trimethylammonium chloride-tetramethylammonium hydroxide). Densitographic separation pattern has been presented. The limits of detection for cetrimonium chloride, benzyl trimethylammonium chloride, and tetramethylammonium hydroxide have been determined. The mobility trend of separated surfactants was also examined by replacing n-butanol with other alcohols. Chromatographic parameters like ΔR F, separation factor (α), and resolution (R S) for the separation have been calculated. The effect of the presence of foreign substances such as metal cations, metal anions, amino acids, and vitamins as impurities on separation has been examined. The proposed method has been successfully applied for the identification of cetrimonium chloride in commercially available shampoo sample.

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Aqueous micellar bile salt, sodium deoxycholate (NaDC) solution as additive in acetonitrile (ACN) in the ratio (1:5 ν/ν) was identified as the most favorable mobile phase for on-plate identification and resolution of three series of common sugars (disaccharide, pentose and hexose) on commercially available high performance silica gel plates. Effect of mobile phase composition and the presence of heavy metal cations as impurities in the analyte sample have been investigated to optimize experimental conditions for the separation. The lowest possible amount of all sugar on high-performance thin-layer chromatography (HPTLC) plate has been determined at nanogram level. This method was successfully applied for identification and separation of sugars in pharmaceutical formulations [cough syrup (Honitus), multivitamin syrup (Becozinc)] and biological matrix (human blood).

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Thin-layer chromatography (TLC) of fifteen amino acids was performed using silica gel and alumina impregnated with micellar solutions of cetrimide and cetylpyridinium chloride as stationary phases and aqueous solutions of dextrose as mobile phases. TLC system comprising of silica gel impregnated with micellar solution of cetrimide (5.0 mM) as stationary phase and 40% ( w/v ) aqueous solution of dextrose as mobile phase was found the most favourable for the separation of amino acids. Impregnation of silica gel with the micellar solution of cetrimide brings about a substantial change in the mobility of lysine. Separation of lysine (ketogenic) from arginine (glucogenic) is important physiologically. Surface modification of silica gel on impregnation, as indicated by FTIR and SEM studies, was responsible for improved chromatographic performance. The effect on the separation of the presence in the sample of heavy metal cations, as impurities, was examined. Limits of detection for lysine and arginine were 0.17 μg and 0.12 μg, respectively. For validation, the stability of the mixture and the reproducibility of the chromatographic properties Δ R F , separation factor ( k ), and resolution ( R S ) were calculated. The proposed method is simple, rapid, and free from use of volatile organic solvents.

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A new spray reagent has been used for TLC detection and spectrophotometric quantification of dichlorvos after extraction with ethanol from bluish tinged maize grains. Silica gel G as stationary phase with cyclohexane-acetone-methanol 8:3:0.5 (ν/ν) as mobile phase was identified as the best TLC system for detection and migration (R F) of dichlorvos. On alkaline hydrolysis dichlorvos forms dimethylphosphoric acid and dichloroacetaldehyde; the latter reacts with 2-thiobarbituric acid to give a sharp pink spot. The reagent is selective for dichlorvos, and does not react with other organophosphorus, organochlorine, carbamate, and synthetic pyrethroid insecticides. The constituents of viscera (amino acids, peptides, proteins, etc.) and grain do not interfere with the test. The lower limit of detection on silica TLC plates was 18 μg. The absorbance maximum (λ max) of the pink color formed by dichlorvos was 500 nm. A plot of absorbance against concentration was a straight line passing through the origin and obeying the Beer-Lambert law in the concentration range 50–350 μg mL−1. The method has been used for identification of dichlorvos in cereals, pulses, vegetables, and fruit.

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A thin-layer chromatographic system comprising a silica layer impregnated with nonionic surfactant (2% Cween 80) as stationary phase and double-distilled water as mobile phase was identified as the most favorable system for mutual separation of the water-soluble vitamins thiamine, cyanocobalamin, and ascorbic acid. The presence of inorganic anions and metal cations as impurities in the sample, the effect of different solvents of the analyte, and the effects of pH of sample and mobile phase were examined for separation of the three-component mixture. It was possible to separate microgram amounts of thiamine from milligram amounts of cyanocobalamin and vice versa. The stability of the mixture of thiamine, cyanocobalamin, and ascorbic acid; the relative standard deviation of the R F values of separated components of the mixture; and the lowest detectable amounts of the three vitamins were determined. The proposed thin-layer chromatographic method is suitable for identification and separation of thiamine, cyanocobalamin and ascorbic acid in drug samples.

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Adsorption of Zn(II) and Cd(II) ions on soil TLC plates was studied using aqueous solutions of surfactants as mobile phases. The effects of decomposition of soil organic matter, cation saturation, soil pH, and sewage sludge on the hR F values (or adsorption) of Zn(II) and Cd(II) were investigated. Among these conditions, soil pH was the most important factor affecting adsorption of Zn(II) and Cd(II) ions by soil layers. Aqueous solutions of cationic (cetyltrimethylammonium bromide, CTAB), nonionic ( t -octylphenoxydecaethoxyethanol, Triton X-100), and anionic (sodium dodecyl sulfate, SDS) surfactants at different concentrations (below, near, and above their critical micelle concentrations, CMC) were tested as mobile phases to examine their effect on the efficiency of adsorption of zinc(II) and cadmium(II) by soil stationary phases. Furthermore, the combined effect of surfactants and fertilizers on the adsorption characteristics of Cd(II) and Zn(II) was also investigated. Fertilizers such as KCl and CaCl 2 in SDS remain insoluble whereas MgCl 2 (1.0 m ) in SDS was highly viscous and causes difficulty during development of soil TLC plates. Addition of Cl-fertilizers to aqueous surfactant mobile phases led to increases in the hR F values (or reduced adsorption) of Zn(II) and Cd(II) ions on soil layers. Among the mobile phases examined, 1.0 M MgCl 2 in aqueous CTAB (at concentrations above the CMC) was found to be the best mobile phase for separation of Cd and Zn ions on soil layers. RSD of hR F values were calculated for both Zn(II) and Cd(II). Cd(II) was found to migrate through the soil layer more quickly than Zn(II). Thus, Zn(II) is strongly retained by the soil surface and Cd(II) is able to pass through the soil layer. The limit of detection of these metal ions was also determined.

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Thin-layer chromatography (TLC) of cationic and nonionic surfactants has been performed on soil, silica gel, alumina, and kieselguhr layers using aqueous solutions of ammonium sulfate and urea as mobile phases. Four stationary phases and fifteen mobile phases were used to examine the mobility of the surfactants and to discover the best TLC system for selective separation of dodecyltrimethylammonium bromide (DTAB) from multicomponent mixtures of other surfactants. The mobility of all the surfactants was insignificant on soil, alumina, and silica gel, irrespective of the nature of the mobile phase. Some of the surfactants were mobile on kieselguhr. Among the TLC systems studied, kieselguhr-0.1 m ammonium sulfate was best for achieving selective separation of DTAB from other surfactants. A salting-out effect on DTAB is reported. The stability of the mixture of surfactants on the plate and in solution was also examined. The limit of detection of DTAB was 0.3 μg per zone.

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Thin-layer chromatography of ten metal ions has been performed on pure soil layers; the mobile phases were aqueous organic and inorganic fertilizer solutions, solutions of aqueous inorganic fertilizer mixed with potassium, sodium, or calcium halide, and aqueous anionic sodium dodecyl sulfate (SDS) solutions with added iodides or chlorides of K, Na, or Ca. A novel mobile phase, 1:9 ( v/v ) 0.001 m SDS-NaCl, was identified for rapid separation of mixtures of Zn 2+ , Cd 2+ , and Hg 2+ .The metal cation mobility observed on pure soil layers with these mobile phases was compared with that obtained on organic-matter-free soil layers. A general trend toward increased metal ion mobility on organic matter-free soil layers was observed. Substitution of SDS by a cationic ( N,N,N -cetyl- N -trimethylammonium bromide) or a nonionic (Tx-100 or Brij 35) surfactant in the mobile phase hampered separation of Zn 2+ from Cd 2+ and Hg 2+ . The effect of inorganic additives (sodium molybdate, KSCN) and acids (oxalic, tartaric, and citric) on the mutual separation of Zn 2+ , Cd 2+ , and Hg 2+ was examined.

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Linguatula serrata (Fröhlich, 1789) is a ubiquitous parasite species belonging to pentastomids, which has been reported frequently from domestic herbivores of Iran. This study was carried out to elucidate the pathological changes caused by the nymphal stage of L. serrata in the mesenteric lymph nodes (MLNs) of goats. Jejunal and ileal MLNs of slaughtered goats infected with L. serrata were collected and fixed in 10% neutral formal saline. Histopathological changes included follicular necrosis accompanied by a loss of lymphocytes and oedematous cystlike spaces. Granulomatous lesions were formed by mononuclear cell infiltration and necrotic tissue. Some lymphocytes were apoptotic with chromatolysis. A more frequent vascular abnormality was vasculitis. These findings show that larval migration is the main factor to initiate trauma and cause irritation in the MLNs of goats. Since goats are habitual intermediate hosts in Iran, rigorous inspection of the MLNs of slaughtered goats is recommended in order to decrease the chance of human infection through the consumption of raw visceral organs of goats.

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