Multi-walled carbon nanotube modified with 1-buthyl 3-methyl imidazolium hexaflouro phosphate supported on sawdust as a selective adsorbent for solid phase extraction of Bi(III).

Multi-walled carbon nanotube (MWCNT) was dispersed and loaded with 1-buthyl 3-methyl imidazolium hexaflouro phosphate ([BMIM]PF(6)), supported on sawdust and used as a new adsorbent for preconcentration of trace amount of bismuth. In this method, Bi(III) ions are retained by the adsorbent in a column after formation of negative complex with iodide. BiI(4)(-) complexes are retained on MWCNT-[BMIM]PF(6) through the electrostatic interactions with positive charge of imidazolium ion. The adsorbed complex is eluted from the column with a solution of nitric acid and determined by flame atomic absorption spectrometry (FAAS). The effect of various parameters, such as pH, sample volume, concentration and volume of nitric acid as eluent, iodide concentration in sample solution, and interfering ions was investigated in order to achieve highest sensitivity. The calibration graph was linear in the range of 4-300 ng mL(-1) for Bi(III) in the initial solution. The limit of detection based on 3S(b) was 2.3 ng mL(-1) for Bi(III). The relative standard deviation for ten replicate measurements of 20 and 80 ng mL(-1) was 2.3 and 0.98%, respectively. The method was applied to the determination of Bi(III) ions in river water, tap water and drug samples.

Simultaneous cloud point extraction and spectrophotometric determination of carmoisine and brilliant blue FCF in food samples.

A novel simultaneous cloud point extraction method for the determination of carmoisine and brilliant blue FCF by spectrophotometry has been developed. The method is based on the cloud point extraction of carmoisine and brilliant blue FCF from aqueous solution using Triton X-100, diluting the extracted surfactant rich phase with water and measuring the absorbance at 522 and 640 nm for carmoisine and brilliant blue FCF, respectively. The effects of different parameters such as pH, concentration of surfactant and temperature on the cloud point extraction of both dyes were investigated and optimum conditions were established. Linear calibration curves were obtained in the range of 0.02-3.50 µg mL(-1) for carmoisine and 0.05-3.50 µg mL(-1) for brilliant blue FCF under optimum conditions. Detection limit based on three times the standard deviation of the blank (3S(b)) was 0.017 and 0.016 µg mL(-1) (n=10) for carmoisine and brilliant blue FCF, respectively. The relative standard deviation (RSD) for 0.1 µg mL(-1) was 4.14 and 3.30% (n=10), for carmoisine and brilliant blue FCF, respectively. The method was applied to the simultaneous determination of the dyes in different food samples.

Silica gel-polyethylene glycol as a new adsorbent for solid phase extraction of cobalt and nickel and determination by flame atomic absorption spectrometry.

In this paper a novel solid phase extraction method to determine Co(II) and Ni(II) using silica gel-polyethylene glycol (Silica-PEG) as a new adsorbent is described. The method is based on the adsorption of cobalt and nickel ions in alkaline media on polyethylene glycol-silica gel in a mini-column, elution with nitric acid and determination by flame atomic absorption spectrometry. The adsorption conditions such as NaOH concentration, sample volume and amount of adsorbent were optimized in order to achieve highest sensitivity. The calibration graph was linear in the range of 0.5-200.0ngmL(-1) for Co(II) and 2.0-100.0ngmL(-1) for Ni(II) in the initial solution. The limit of detection based on 3S(b) was 0.37ngmL(-1) for Co(II) and 0.71ngmL(-1) for Ni(II). The relative standard deviations (R.S.D.) for ten replicate measurements of 40ngmL(-1) of Co(II), and Ni(II) were 3.24 and 3.13%, respectively. The method was applied to determine Co(II) and Ni(II) in black tea, rice flour, sesame seeds, tap water and river water samples.

Solid phase extraction of cadmium on 2-mercaptobenzothiazole loaded on sulfur powder in the medium of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and cold vapor generation-atomic absorption spectrometric determination.

A novel solid phase extractor for preconcentration of cadmium at ng L(-1) levels has been developed. Cadmium ions were retained on a column packed with sulfur powder modified with 2-mercaptobenzothiazole (2-MBT) in the medium of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim](+)PF(6)(-)) ionic liquid. The presence of ionic liquid during modification of sulfur enhanced the retention of cadmium ions on the column. The retained cadmium ions were eluted with 2 mol L(-1) solution of HCl and measured by cold vapor generation-atomic absorption spectrometry (CVG-AAS). By using reaction cell-gas liquid separator (RC-GLS), gaseous cadmium vapors were produced and reached the atomic absorption spectrometer, instantaneously. The influence of different variables on both processes of solid phase extraction and CVG-AAS determination of cadmium ions was investigated. The calibration curve was linear in the range of 10-200 ng L(-1)of cadmium in the initial solution with r=0.9992 (n=8) under optimum conditions. The limit of detection based on three times the standard deviation of the blank (3S(b), n=10) was 4.6 ng L(-1). The relative standard deviation (R.S.D.) of 25 and 150 ng L(-1) of cadmium was 4.1 and 2.2% (n=8), respectively. The procedure was validated by the analysis of a certified reference material (DORM-3), water and fish samples.

An optical chemical sensor for thorium (IV) determination based on thorin.

A selective method for the determination of thorium (IV) using an optical sensor is described. The sensing membrane is prepared by immobilization of thorin-methyltrioctylammonium ion pair on triacetylcellulose polymer. The sensor produced a linear response for thorium (IV) concentration in the range of 6.46 x 10(-6) to 9.91 x 10(-5)mol L(-1) with detection limit of 1.85 x 10(-6)mol L(-1). The regeneration of optode was accomplished completely at a short time (less than 20s) with 0.1 mol L(-1) of oxalate ion solution. The relative standard deviation for ten replicate measurements of 2.15 x 10(-5) and 8.62 x 10(-5)mol L(-1) of thorium was 2.71 and 1.65%, respectively. The optode membrane exhibits good selectivity for thorium (IV) over several other ionic species and are comparable to those obtained in case of spectrophotometric determination of thorium using thorin in solution. A good agreement with the ICP-MS and spiked method was achieved when the proposed optode was applied to the determination of thorium (IV) in dust and water samples.

Solid phase extraction of mercury on sulfur loaded with N-(2-chloro benzoyl)-N'-phenylthiourea as a new adsorbent and determination by cold vapor atomic absorption spectrometry.

This paper reports sulfur powder loaded with N-(2-chloro benzoyl)-N'-phenylthiourea as a new solid phase extractor for determination of ultra trace amounts of mercury. The mercury ions were retained on a mini-column filled with the solid phase at a flow rate of 16 mL min(-1). The retained Hg(II) ions were eluted with 3 mol L(-1) solution of HCl and measured by cold vapor atomic absorption spectrometry (CV-AAS). The mercury vapors were generated by a homemade Reaction Cell-Gas Liquid Separator (RC-GLS). The effect of different variables such as pH, sample flow rate, amounts of ligand loaded on sulfur and SnCl2 concentration was investigated. Calibration curve was linear in the range of 0.02-1.20 microg L(-1) with r=0.9991 (n=8). The limit of detection (LOD) based on three times the standard deviation of the blank was 0.012 and 0.003 microg L(-1) when 250 and 1000 mL sample volumes were used, respectively. The relative standard deviation (R.S.D.) for determination of 0.04 and 1.00 microg L(-1) of Hg(II) was 3.9 and 1.2% (n=8), respectively. The method was successfully applied to determine Hg(II) in water and marine samples.

Solid phase extraction of lead and cadmium using solid sulfur as a new metal extractor prior to determination by flame atomic absorption spectrometry.

A new method using a mini-column packed with sulfur as a new solid phase extractor has been developed for simultaneous preconcentration of lead and cadmium in water samples prior to flame atomic absorption spectrometric determinations. The effects of various parameters such as pH, flow rate of sample and eluent, type and concentration of eluent, sample volume, amount of adsorbent and interfering ions have been studied. The calibration graph was linear in the range of 10-300 and 1-20 ng mL(-1) for lead and cadmium, respectively. The limit of detection based on three times the standard deviation of the blank (3S(b)) was 3.2 and 0.2 ng mL(-1) (n=10) for lead and cadmium, respectively. A preconcentration factor of 250 was achieved in this method. The proposed procedure was applied to the determination of metal ions in tap, river and wastewater samples.

Determination of mercury in water and fish samples by cold vapor atomic absorption spectrometry after solid phase extraction on agar modified with 2-mercaptobenzimidazole.

A novel solid phase extraction method for the determination of mercury has been developed. The Hg(II) ions were retained on a mini-column packed with agar powder modified with 2-mercaptobenzimidazole at a flow rate of 6 mL min(-1). The retained Hg(II) ions were eluted with 3 mol L(-1) solution of HCl and measured by cold vapor atomic absorption spectrometry (CV-AAS). The effect of different variables such as pH, sample flow rate, amounts of 2-mercaptobenzimidazole loaded on agar and SnCl(2) concentration was investigated and optimum conditions were established. The calibration curve was linear in the range of 0.040-2.40 ng mL(-1) with r=0.9994 (n=8). The limit of detection based on three times the standard deviation (3S(b)) (n=10) obtained under optimum conditions was 0.02 ng mL(-1). The relative standard deviation (R.S.D.) for the determination of 0.4 and 2.0 ng mL(-1) of Hg(II) was 2.6 and 1.9% (n=8), respectively. The method was successfully applied to determine Hg(II) in water, wastewater and fish samples.

Determination of Orange II in food samples after cloud point extraction using mixed micelles.

In this paper, a cloud point extraction method for the determination of trace amounts of Orange II by spectrophotometry is described. The method is based on the extraction of Orange II from aqueous solution using mixed micelles of non-ionic surfactant, Triton X-100 and cationic surfactant cetyltrimethyl ammonium bromide (CTAB) in acidic media. The extracted surfactant rich phase is diluted with water and its absorbance is measured at 484 nm by a spectrophotometer. The effects of surfactant, acid and salt concentration, incubation time and temperature were investigated. The calibration graph was linear in the range of 2.1-420 ng mL(-1) of Orange II in the initial solution with r=0.9991 (n=12). Detection limit based on three times the standard deviation of the blank (3S(b)) was 0.67 ng mL(-1) and the relative standard deviation (RSD) for 35 and 105 ng mL(-1) of Orange II was 1.20% and 1.49% (n=10), respectively. The method was applied to the determination of Orange II in different food samples.

Spectrophtometric determination of malachite green in fish farming water samples after cloud point extraction using nonionic surfactant Triton X-100.

A novel and sensitive cloud point extraction procedure for the determination of trace amounts of malachite green by spectrophotometry was developed. Malachite green was extracted at pH 2.5 mediated by micelles of nonionic surfactant Triton X-100. The extracted surfactant-rich phase was diluted with ethanol and its absorbance was measured at 630 nm. The effect of different variables such as pH, Triton X-100 concentration, cloud point temperature and time and diverse ions was investigated and optimum conditions were established. The calibration graph was linear in the range of 4-500 ng mL(-1) of malachite green in the initial solution with r=0.9996 (n=10). Detection limit based on three times the standard deviation of the blank (3S(b)) was 1.2 ng mL(-1) and the relative standard deviation (R.S.D.) for 20 and 300 ng mL(-1) of malachite green was 1.48 and 1.13% (n=8), respectively. The method was applied to the determination of malachite green in different fish farming and river water samples.

Kinetic spectrophotometric determination of Tween 80.

A novel kinetic spectrophotometic method for the determination of Tween 80 based on its interaction with 5(p-dimethylaminobenzylidene)rhodanine (PDR) in alkaline media is reported. The effect of variable on the rate of interaction of Tween 80 and PDR was investigated in order to establish the optimum conditions. The interaction was monitored spectrophotometically and change in absorbance (DeltaA) of PDR at 464nm at times of 30 and 270s was used as an analytical parameter. Tween 80 can be measured in the range of 2.5x10(-5) to 1.25x10(-3)M with detection limit of 1.5x10(-5)M. The relative standard deviation for eight replicate determinations of 2x10(-4) and 1x10(-3)M of Tween 80 solution was 4.08 and 3.88%, respectively. This method was used to determine Tween 80 in biscuit and multivitamin syrup.

Solid phase preconcentration of iron as methylthymol blue complex on naphthalene-tetraoctylammonium bromide adsorbent with subsequent flame atomic absorption determination.

A sensitive and selective preconcentration method for the determination of trace amounts of iron by atomic absorption spectrometry has been developed. Iron forms a complex with methylthymol blue at pH=3. This complex is retained by naphthalene tetraoctylammonium bromide adsorbent in a column with a height of about 2cm. The adsorbed metal complex is then eluted from the column with nitric acid and its iron content is determined by flame atomic absorption spectrometry (FAAS). The effect of different variables such as pH, reagent concentration, flow rate and interfering ions on the recovery of the analyte was investigated. The calibration graph was linear in the range 25-350ngml(-1) of iron in the initial solution with r=0.9994. The limit of detection based on 3S(b) criterion was 12ngml(-1) and the relative standard deviation for eight replicate measurements of 150 and 300ngml(-1) of iron was 3.1 and 1.8%, respectively. This procedure was successfully applied to the determination of iron in tap and sewage water samples.

Catalytic spectrophotometric determination of tungsten using the malachite green-Ti(III) redox reaction and a thiocyanate activator.

Thiocyanate was found to have a highly activating effect on the tungsten-catalyzed reaction of malachite green with Ti(III). A highly sensitive, selective and simple method was developed for the determination of tungsten based on this effect. The reaction rate was monitored spectrophotometrically by measuring the change in absorbance at 616 nm using a fixed time method. The effect of different parameters was studied and optimum conditions were established. The calibration graph was linear in the range of 1.2-10 and 10-80 ngml(-1). The detection limit was 0.15 ngml(-1) and relative standard deviation for ten replicate measurements of 1.2 ngml(-1) of tungsten was 1.8%. The proposed method was applied successfully for the determination of tungsten in hot spring waters.