M. Jamaluddin Ahmed

Spectrophotometric determination of aluminium by morin

A direct spectrophotometric method for the determination of aluminium with morin has been developed. Morin reacts in slightly acidic 50% ethanolic media (0.0001-0.0015 M H(2)SO(4)) with Al to give a deep-yellow chelate which has an absorption maximum at 421 nm. The average molar absorptivity and Sandells sensitivity were found to be 5.3 x 10(3) l mol(-1) cm(-1) and 5 ng of Al cm(-2), respectively. The reaction is instantaneous and absorbance remains stable for 48 h. The colour system obeys Beers law from 10 ng ml(-1) to 5.0 mug ml(-1) of Al; the stoichiometric composition of the chelate is 2:3 (Al:morin). The interference from over 50 cations, anions and complexing agents has been studied at 0.1 mug ml(-1) of Al. The method was applied successfully to some certified reference material samples (alloys and steels), environmental waters (inland and surface), biological samples (human blood, urine and gallstone), soils and complex synthetic mixtures.

Spectrophotometric determination of lead in industrial, environmental, biological and soil samples using 2,5-dimercapto-1,3,4-thiadiazole.

A very simple, ultra-sensitive and fairly selective non-extractive spectrophotometric method for the determination of trace amounts of lead with 2,5-dimercapto-1,3,4-thiadiazole (DMTD) has been developed. DMTD reacts in slightly acidic (0.0015-0.01 M HCl) aquatic media with lead(II) to give a greenish-yellow chelate, which has an absorption maximum at 375 nm. The reaction is instantaneous and absorbance remains stable for 24 h. The average molar absorption coefficient and Sandells sensitivity were found to be 4.93x10(4) lmol(-1)cm(-1) and 15 ngcm(-2) of Pb, respectively. Linear calibration graphs were obtained for 0.1-40 mugml(-1) of Pb; the stoichiometric composition of the chelate is 1:2 (Pb-DMTD). The interference from over 50 cations, anions and complexing agents has been studied at 1 mugml(-1) of Pb. The method developed was used successfully in the determination of lead in several standard reference materials (alloys and steels), environmental waters (potable and polluted), biological samples (human blood and urine), soil samples, solutions containing both lead(II) and lead(IV) and complex synthetic mixtures. The method has high precision and accuracy (S=+/-0.01 for 0.5 mugml(-1)).

Spectrophotometric method for determination of vanadium and its application to industrial, environmental, biological and soil samples

The very sensitive, fairly selective direct spectrophotometric method for the determination of trace amount of vanadium (V) with 1,5-diphenylcarbohydrazide (1,5-diphenylcarbazide) has been developed. 1,5-diphenylcarbohydrazide (DPCH) reacts in slightly acidic (0.0001-0.001 M H(2)SO(4) or pH 4.0-5.5) 50% acetonic media with vanadium (V) to give a red-violet chelate which has an absorption maximum at 531 nm. The average molar absorption coefficient and Sandells sensitivity were found to be 4.23 x 10(4) l mol(-1) cm(-1) and 10 ng cm(-2) of V(v), respectively. Linear calibration graph were obtained for 0.1-30 microg ml(-1) of V(v): the stoichiometric composition of the chelate is 1:3 (V: DPCH). The reaction is instantaneous and absorbance remain stable for 48 h. The interference from over 50 cations, anions and complexing agents has been studied at 1 microg ml(-1) of V(v). The method was successfully used in the determination of vanadium in several standard reference materials (alloys and steels), environmental waters (potable and polluted), biological samples (human blood and urine), soil samples, solution containing both vanadium (V) and vanadium (IV) and complex synthetic mixtures. The method has high precision and accuracy (s=+/-0.01 for 0.5 microg ml(-1)).

A Rapid Spectrophotometric Method for the Determination of Cobalt in Industrial, Environmental, Biological, Pharmaceutical and Soil Samples Using Bis(5-bromosalicylaldehyde)orthophenylenediamine

A very simple, ultra-sensitive and fairly selective spectrophotometric method is presented for the determination of cobalt at trace levels using bis(5-bromosalicylaldehyde)orthophenylenediamine (BBSOPD). The method is based on the reaction of nonabsorbent BBSOPD in a slightly acidic (0.001–0.0025 M H2SO4 or pH 3.4–4.0) and 50% N,N-dimethylformamide media with cobalt(II) to produce a highly absorbent orange colored chelate-product with an absorption maximum at 473 nm. The reaction is instantaneous and the absorption remains stable for 24 h. The average molar absorption coefficient and Sandell’s sensitivity were found to be 5.84 × 104 l mol-1 cm-1 and 9.0 ng cm-2 of cobalt(II), respectively. Linear calibration graphs were obtained for 0.02–4.0 mg l-1 of Co(II). The stoichiometric composition of the chelate is 1:1 (Co(II):BBSOPD). A large excess of over 50 cations, anions and complexing agents do not interfere in the determination. The method was successfully used for the determination of cobalt in several standard reference materials (steels and alloys), environmental waters (potable and polluted), biological samples (human blood and urine), pharmaceutical and soil samples and solutions containing both cobalt(II) and cobalt(III) as well as some complex synthetic mixtures. The method has high precision and accuracy.

A simple spectrophotometric method for the determination of trace levels of molybdenum in industrial, environmental, biological and soil samples using benzoylacetone-benzoylhydrazone

A very simple, ultra-sensitive and highly selective non-extractive spectrophotometric method for the determination of trace amounts of molybdenum(VI) in solution using benzoylacetone-benzoylhydrazone (Bzac-BH) has been developed. Bzac-BH reacts in a slightly acidic solution (0.0003–0.002 M H2SO4) with molybdenum(VI) to give an orange chelate which has an absorption maximum at 447 nm. The reaction is instantaneous and the absorbance remains stable for over 12 h. The average molar absorption co-efficient and Sandells sensitivity were found to be 6.3 × 105 L mol−1 cm−1 and 15 ng cm−2 of molybdenum(VI), respectively. Linear calibration graphs were obtained for 0.05–2 mg L−1 of molybdenum(VI). The stoichiometric composition of the chelate is 1 : 1 (Mo : Bzac-BH). A large excess of over 50 cations, anions and complexing agents (such as chloride, phosphate, azide, thiosulfate, thiourea, SCN−, etc.) do not interfere with the determination. The developed method was successfully used in the determination of molybdenum levels in several Standard Reference Materials (alloys and steels) as well as in some environmental waters (inland and surface), biological samples (human blood and urine), soil samples, solutions containing both molybdenum(V) and molybdenum(VI) and complex synthetic mixtures. The method has high precision and accuracy (s = ±0.01 for 0.5 mg L−1).

A highly selective and sensitive spectrophotometric method for the determination of selenium using 2-hydroxy-1-napthaldehyde-orthoaminophenol

A very simple, ultra-sensitive and highly selective non-extractive spectrophotometric method for the determination of trace amounts of selenium using 2-hydroxy-1-napthaldehyde-orthoaminophenol (HNA-OAP) has been developed. HNA-OAP reacts in slightly acidic (7 × 10−6 to 3.5 × 10−5 M H2SO4) aquatic media with selenium(IV) in 40% N,N-dimethylformamide (DMF) to produce a highly absorbent orange red chelate, which has an absorption maximum at 509 nm. The absorbance intensity of the metal–chelate reaches a constant value (after heating for 5 min at 45 ± 5 °C) within 15 min and remains stable for over 24 h. The average molar absorption coefficient and Sandells sensitivity were found to be 6.30 × 105 L mol−1 cm−1 and 10 ng cm−2 of Se, respectively. Linear calibration graphs were obtained for 0.02–7.0 mg L−1 of Se, having a detection limit of 1.0 μg L−1, the quantification limit of the reaction system was found to be 10 μg L−1, and the RSD was 0–2%. The stoichiometric composition of the chelate is 2 : 3 (Se : HNA-OAP). A large excess of over 60 cations, anions and complexing agents does not interfere in the determination. The method was applied successfully in the determination of selenium in several standard reference materials (alloys, steels, sediments, tea and bovine liver) as well as in some environmental waters (portable and polluted), biological samples (human blood, urine and hair), soil samples, food samples, pharmaceutical samples, solutions containing both selenium(IV) and selenium(VI) and complex synthetic mixtures. The method has high precision and accuracy (s = ±0.01 for 0.5 mg L−1).

A highly sensitive and selective spectrofluorimetric method for the determination of manganese at nanotrace levels in some real, environmental, biological, soil, food and pharmaceutical samples using 2-(α-pyridyl)-thioquinaldinamide

A very simple, ultra-sensitive and highly selective non-extractive spectrofluorimetric method is presented for the determination of manganese at nano-trace levels using 2-(α-pyridyl)-thioquinaldinamide (PTQA). PTQA has been proposed as a new analytical reagent for the direct non-extractive spectrofluorimetric determination of manganese(VII). This novel fluorimetric reagent, PTQA becomes oxidized in a slightly acidic (0.0125–0.05 M H2SO4) solution with manganese(VII) in absolute ethanol to produce a highly fluorescent oxidized product (λex = 319 nm; λem = 373 nm). Constant and maximum fluorescence intensities were observed over a wide range of acidity (0.0125–0.05 M H2SO4) for the period between 5 min and 24 h. Linear calibration graphs were obtained for 0.01–800 μg L−1 of Mn, having a detection limit of 1 ng L−1; the quantification limit of the reaction system was found to be 10 ng L−1 and the RSD was 0–2%. A large excess of over 60 cations, anions and complexing agents do not interfere in the determination. The developed method was successfully used in the determination of manganese in several standard reference materials (alloys, steels, hair and sediments) as well as in some environmental waters (potable and polluted), biological samples (human blood, urine and hair), soil samples, food samples (vegetables, fruits, tea, rice, and wheat), fertilizer samples and pharmaceutical samples (multivitamin-mineral tablets and syrup), solutions containing both manganese(II) and manganese(VII) speciation and complex synthetic mixtures. The results of the proposed method for assessing biological, food and vegetables samples were comparable with AAS and ICP-MS and were found to be in excellent agreement.