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A new spectrophotometric reagent, N,N'-bis(salicylidene)-ethylenediamine (Salen), has been synthesized and characterized through novel reaction techniques. A very simple, ultrasensitive, and nonextractive spectrophotometric method has been developed for the determination of the picotrace amount of cobalt (II) using Salen. Salen undergoes a reaction in a slightly acidic solution (0.001-0.003 M H2S04) with cobalt in 20% ethanol to give a light orange chelate, which has an absorption maximum at 459 nm. The reaction is instantaneous, and the absorbance remains stable for over 24 hours. The average molar absorption co-efficient and Sandell’s sensitivity were found to be 6.04×105 L/mol.cm and 5.0 ng/cm2 of Co, respectively. Linear calibration graphs were obtained for 0.001-40 mg/Lof Co with a detection limit of 0.1 µg/L and RSD of 0-2 %. The stoichiometric composition of the chelate is 1:1 (Co:Salen). A large excess of over 60 cations, anions and some common complexing agents such as chloride, azide, tartrate, EDTA, SCN- etc. do not interfere in the determination. The developed method was successfully used in the determination of cobalt in several Certified Reference Materials (Alloys, steel, bovine liver, human hair, drinking water, sewage sludge, soil, and sediments) as well as in some environmental waters (Potable and polluted), biological fluids (Human blood, urine, and milk), soil samples, food samples (Vegetables, rice, and wheat) and pharmaceutical samples and solutions containing both cobalt (II) and cobalt (III) as well as complex synthetic mixtures. The results of the proposed method for assessing biological, soil, food and vegetable samples were comparable with ICP-OES and AAS were found to be in excellent agreement. The method has high precision and accuracy (s = ±0.01 for 0.5 mg/L).

A very simple, ultra-sensitive and highly selective non-extractive spectrophotometric method for the determination of trace amounts of lead using 5,7-dibromo-8-hydroxyquinoline (DBHQ) has been developed. DBHQ reacts in a slightly acidic (0.0006-0.0025 M HCl) aqueous solution with lead (II) in 30% ethanolic media to produce highly absorbent a greenish-yellow chelate which has an absorption maximum at 390 nm. The reaction is instantaneous and the absorbance remains stable for over 24 h. The average molar absorption co-efficient and Sandal’s sensitivity were found to be 6.16 x 105 L mol-1cm-1 and 5 ng cm-2 of lead (II), respectively. Linear calibration graphs were obtained for 0.01- 60.0 mg L-1 of lead (II) having detection limit of 1.0 μg L-1 and RSD 0-2%. The stoichiometric composition of the chelate is 1:2 (Pb: DBHQ). A large excess of over 60 cations, anions and complexing agents (like, chloride, phosphate, azide, tartrate, oxalate, SCN- etc.) do not interfere in the determination. The developed method was successfully used in the determination of lead levels in several Standard Reference Materials (alloys, steels, natural water, bovine liver, human urine and hair) as well as in some environmental waters (potable and polluted), biological samples (human blood, urine and hair), soil samples, food samples (vegetables, rice, wheat) solutions containing both lead (II) and lead (IV) and complex synthetic mixtures. The results of biological and food analyses by the spectrophotometric method were found to be in excellent agreement with those obtained by AAS.

The present study was conducted to assess the toxic and heavy metals concentrations in water at different locations of the Karnafuli River. The assessment was carried out for various toxic and heavy metals concentrations in three seasons during pre-monsoon, monsoon and post-monsoon seasons for various continuous monitoring during the hydrological year 2014-2016. The statistical methods of sampling were used for collecting samples from different points of Karnafuli River. The samples were collected in high and low tide conditions. Since the water quality is expected to vary with season, multiple samples were collected at an interval of 2 to 3 weeks. The work has been carried out by traveling to the sampling sites for collection required water samples and the estimation of water discharge and determination of basic parameters of the sites. Samples were preserved with suitable preservation and transported to the laboratory. Standard methods were followed to determine the toxic and heavy metals concentrations. In the present study, seasonal variation hydrochemical character of Karnafuli River water has been evaluated and assessed the suitability of water for human & animal′s consumption, irrigation and industrial purposes. The study stress to access various essential heavy metals concentrations including arsenic, cadmium, cobalt, chromium, copper, iron, lead, manganese, nickel and zinc. Toxic and heavy metals concentrations were studied such as As, Cd, Co, Cr, Cu, Fe, Pb, Mn, Ni and Zn were found in variation from (0.01 - 0.05)-mgL-1, (0.12 - 0.75)-mgL-1, (0.01 - 0.013)-mgL-1, (0.051 -0.063)-mgL-1, (0.012 - 0.25)-mgL-1,(0.006 - 4.844)-mgL-1, (0.036 - 0.07)-mgL-1, (0.015 - 0.845)-mgL-1, (0.02 - 0.097)-mgL-1, (0.013 - 0.8)-mgL-1 respectively. The average of maximum heavy metals concentrations studied was found higher than those of the World Health Organization (WHO), Department of Environment (DoE) and BSTI drinking water guidelines. The laboratory finding of water quality parameters were also compared with the recommended values set by DoE and BSTI. From Pearson correlation program, significant positive and negative correlations were found in different parameters. These assessment data indicated that the water quality of Karnafuli River are highly polluted which are continuously polluting the coastal zone, sea and the Halda river of Chittagong. The environmental impact of water quality of Karnafuli River has been discussed. A strategic water quality management plan has been proposed.

The present study was conducted to assess the physicochemical characteristics of water quality parameters concentrations in water at different locations of the Karnafuli River. The assessment was carried out for various physicochemical parameters in three seasons during pre-monsoon, monsoon and post-monsoon seasons for various continuous monitoring during the hydrological year 2014-2015. The statistical methods of sampling were used for collecting samples from different points of Karnafuli River. The samples were collected in high and low tide conditions. Since the water quality is expected to vary with season, multiple samples were collected at an interval of 2 to 3 weeks. The work has been carried out by traveling to the sampling sites for collection required water samples and the estimation of water discharge and determination of basic parameters of the sites. Samples were preserved with suitable preservation and transported to the laboratory. Standard methods were followed to determine the physicochemical water quality parameters. In the present study, seasonal variation hydro-chemical character of Karnafuli River water has been evaluated and assessed the suitability of water for human & animal′s consumption, irrigation and industrial purposes. The study stress to access various essential physical and chemical parameters including pH, conductivity, salinity, total dissolved solid (TDS), total suspended solid (TSS), turbidity, alkalinity, acidity, dissolved oxygen (DO), sulfate, biological oxygen demand (BOD), Chemical demand oxygen (COD), nitrate, phosphate, chloride, total- hardness. The average of maximum parameters studied both physical and chemical were found higher than those of the World Health Organization( WHO), Department of Environment (DoE) and BSTI drinking water guidelines. The laboratory finding of water quality parameters were also compared with the recommended values set by DoE and BSTI. From Pearson correlation program, significant positive and negative correlations were found in different parameters. These assessment data indicated that the water quality of Karnafuli River are highly polluted which are continuously polluting the coastal zone, sea and the Halda River of Chittagong. The environmental impact of water quality of Karnafuli River has been discussed. The result provided data to understand and quantify the threat of the impact of climate change on river water resources of greater Chittagong region. The result also provided data for water quality of Karnafuli River water resources of greater Chittagong region to match national and international standard for drinking, agriculture, industrial and livestock requirements. The assessment data can be used to help the determination the efficacy of existing water quality policies to help analysts determine the need for and likely consequences of new policies. The assessment data can be supplied to the proper Govt. authority for making new national and appropriate preventive measures. The assessment can be increased the awareness of the people of the risk and affected areas so that they could ready to face the disaster due to climate change, from the investigation it can be concluded that the water quality of Karnafuli River is being affected by pollution hazard. The delay of the application of the legal frame work as well as stakeholder awareness aggravates the situation by continually reducing the water quality in the river. A strategic water quality management plan has been proposed.

A new spectrofluorimetric reagent 2-(α-pyridyl)-thioquinaldinamide (PTQA) has been synthesized and characterized through novel reaction techniques. A very simple, ultra-sensitive and highly selective non-extractive new spectrofluorimetric method for the determination of vanadium at Pico-trace levels using 2-(α-pyridyl)-thioquinaldinamide (PTQA) has been developed. PTQA has been proposed as a new analytical reagent for the direct non-extractive spectrofluorimetric determination of vanadium (V). This novel fluorimetric reagent, PTQA becomes oxidized in a slightly acidic (0.0035 - 0.0085 M H2SO4) solution within vanadium (V) in 20% ethanol to produce highly fluorescent oxidized product (λex = 319 nm; λem = 371 nm). Constant and maximum fluorescence intensities were observed over a wide range of acidity (0.0035 - 0.0085 M H2SO4) for the period between 5 min and 24 h. Linear calibration graphs were obtained for 0.001 - 600-μg·L-1 of V, having a detection limit of 0.3-ng·L-1; the quantification limit of the reaction system was found to be 3-ng·L-1 and the RSD was 0% - 2%. A large excess of over 60 cations, anions and complexing agents (like, chloride, phosphate, azide, tartrate, oxalate, SCN- etc.) do not interfere in the determination. The developed method was successfully used in the determination of vanadium in several Certified Reference Materials (alloys, steels, serum, bovine liver, drinking water, soil and sediments) as well as in some environmental waters (potable and polluted), biological fluids (human blood, urine, hair and milk), soil samples and food samples (vegetables, rice and wheat) solutions containing both vanadium (IV) and vanadium (V) speciation and complex synthetic mixtures. The results of the proposed method for assessing biological, food and vegetable samples were comparable with inductively coupled plasma optical emission spectroscopy (ICP-OES) and atomic-absorption spectrophotometer (AAS) was found to be in excellent agreement.

A very simple, ultra-sensitive, highly selective and non-extractive new spectrofluorimetric method for the determination of arsenic at pico-trace levels using 2-(α-pyridyl)-thioquinaldinamide (PTQA) has been developed. PTQA has been proposed as a new analytical reagent for the direct non-extractive spectrofluorimetric determination of Arsenic (V). This novel fluorimetric reagent, PTQA becomes oxidized in a slightly acidic (0.025 - 0.1 M H2SO4) solution with Arsenic (V) in absolute ethanol to produce highly fluorescent oxidized product (λex = 303 nm; λem = 365 nm). Constant and maximum fluorescence intensities were observed over a wide range of acidity (0.025 - 0.1 M H2SO4) for the period between 2 min and 24 h. Linear calibration graphs were obtained for 0.001 - 800-μgL-1 of As, having a detection limit of 0.1-ngL-1; the quantification limit of the reaction system was found to be 1-ngL-1 and the RSD was 0% - 2%. A large excess of over 60 cations, anions and complexion agents (like, chloride, phosphate, azide, tartrate, oxalate, SCN, etc.) do not interfere in the determination. The developed method was successfully used in the determination of arsenic in several Certified Reference Materials (alloys, steels, ores, human urine, hair, nails, bovine liver and sediments) as well as in some biological fluids (human blood, urine, hair, nail and milk), soil samples, food samples (vegetables, fruits, rice, corn and wheat), solutions containing both arsenic (III) and arsenic (V) speciation and complex synthetic mixtures. The results of the proposed method for assessing biological, food and soil samples were comparable with both ICP-OES & AHG-AAS and were found to be in excellent agreement.

Air pollution has significant effects on exacerbation of asthma, allergy and other respiratory diseases. There is a great need to implement control measures in most of the megacities of the world to improve air quality and hence protect public health. Like many other megacities in the world the ambient air quality of Chittagong is also being deteriorated day by day. Main sources of air pollution in this city are arising out of the emission from the motor-vehicles, industries, galvanisms, etc. Considering the severity of the problem, the current study plan was undertaken to measure the gaseous pollutants level in the air of different urban locations of Chittagong, the second largest city of Bangladesh. Atmospheric pollutants like gaseous (SO2, NO2), particulate matters (SPM) were determined in Chittagong city. Eight different sampling stations, Muradpur Circle, WASA Circle, G.E.C Circle, Proborthak Circle, Chawk Bazar Circle, Olongkar Circle, New Market Circle and Oxygen Circle were selected for sample collection and observations during the atmospheric year 2013 -2014. The objective of the study was to determine the concentrations of gaseous pollutants (SOx, NOx) and particulate matters (SPM, PM2.5 and PM10) to find out the variation of air pollutants in different locations of Chittagong city. The concentration of gaseous pollutants was found more at highly traffic areas. The highest concentration value of SO2, NO2and SPM was observed in highly traffic area at Muradpur Circle, Olongkar Circle & New Market Circle, respectively. The lowest concentration value was found in less traffic area at WASA Circle & Proborthak Circle. The average results of gaseous pollutants, particulate matters and trace metals have been compared to national and international standards. The value of SPM in air of Chittagong city is higher than that of TLV value recommended by WHO and DOE. The elemental concentrations (e.g. Cd, Co, Cr, Cu, Fe, Pb, Hg, Ni and Zn) of ambient air that collected at different locations in Chittagong city is exceeded the TLV. A strategic air quality management plan has been proposed.

A very simple and non-extractive spectrofluorometric method for the swift determination of aluminum at nano-trace levels using 2',3,4',5,7-pentahydroxyflavone (morin) has been developed. Morin reacts in a slightly acidic (0.005 - 0.025 M H2SO4) solution with aluminum in 20% ethanol to produce a highly fluorescent complex in aqueous solution, which has excitation and emission wavelengths of λex = 270 and λem = 565 nm, respectively. Linear calibration graphs were obtained for 0.01 - 800 μg L-1 of Al, providing a detection limit of 1 ng L-1. The limit of quantification of the reaction system was 10 ng L-1. The stoichiometric composition of chelate is 3:2 (Al:morin). The developed method was successfully used in the determination of aluminum in several Standard Reference Materials (SRM) as well as in some water, biological, hemodialysis solutions, food, pharmaceutical, soil sample, and complex synthetic mixtures. The results of the proposed method for biological and food analysis were found to be in excellent agreement with those obtained by AAS. The results of the proposed method for hemodialysis solutions were analogous with those obtained using the method described in British Pharmacopoeia within 95% confidence limits.

Chittagong is one of the major developing cities in Bangladesh; its area is rapidly increasing and a large number of populations live in Chittagong City Corporation (CCC). Majority of the people are using the groundwater as a prime source for their domestic needs, besides the CCC is supplying them with an allocation of treated water. Our research work has been focused on various essential physical and chemical parameters including color, odor, transparency, pH, conductivity, salinity, total dissolved solids (TDS), dissolved oxygen(DO), Chemical oxygen demand(COD), sulfate, nitrate, ammonia, orthophosphate, chloride, fluoride, M. alkalinity, P. alkalinity, hardness, calcium, magnesium, arsenic, iron, potassium, manganese, chromium, nickel, cadmium, lead silver, mercury and zinc of water samples from various districts of Chittagong region. An attempt has been made in this study to evaluate the groundwater quality of Chittagong region. Groundwater samples were collected from shallow wells, deep wells and hand pumps of different heavily industrialized and domestic blocks. The work has been confined to Chittagong region and districts. Since the water quality is expected to vary with season, multiple samples have been collected from 100 sites at an interval of 2 to 3 weeks in each district before and after monsoon for hydrological year 2016 -2018. The water samples have been analyzed using standard method for physicochemical parameters as prescribed by APHA, using standard techniques and compared with WHO drinking water quality standards. The laboratory findings of water quality parameters were also compared with the recommended values set by DoE and BSTI. The concentration of different constituents of most of the groundwater samples were within the permissible limits ofBSTI drinking water quality guideline except As, Cd and Pb. Results of water quality assessment identified the problem areas in respect of arsenic. The results also provided data to understand and quantify the threat of the impact of climate change on freshwater resources of this region. The results also provided data for water quality of groundwater resources of Chittagong area to match national and international standards for drinking, agricultural, industrial and livestock requirements. &nbsp

A very simple, ultra-sensitive and highly selective non-extractive spectrofluorimetric method for the determination of cadmium at ultra-trace levels using 2',3,4',5,7-pentahydroxyflavone(morin) has been developed. Morin reacts in a slightly acidic (0.0005-0.002 M H2SO4) aqueous solution with cadmium and to form intensely fluorescent chelate, which has high fluorescence intensity (lex =424 nm; lem=485 nm).The reaction is instantaneous and the fluorescent intensely remains stable for the period between 5 min and 24 h. Linear calibration graphs were obtained for 0.01- 600-μg L-1 of Cd, with an R2 = 0.99987, 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 0-3%. The stoichiometric composition of the chelate is 1:2 (Cd:morin). A large excess of over 60 captions, anions and complexing agents (like chloride, phosphate, azide, tartrate, oxalate, SCN- etc.) do not interfere in the determination. The developed method was successfully used in the determination of cadmium in several Standard Reference Materials (alloys, steels, sediments,human hair, bovine liver, freshwater, and rice flour) as well as in some environmental waters (potable and polluted), biological samples (human blood, urine and hair), tobacco samples, food samples (rice, wheat, cake, tea, cookies and shellfish),vegetables samples(radish, carrot, ginger, potato, tomato and cabbage),fertilizer samples, soil samples and complex synthetic mixtures. The results of the biological, food and vegetable analyses by spectrofluorimetric methods were found to be in excellent agreement with those obtained by AAS. The method has high precision and accuracy (s = ±0.01 for 0.5µgL-1). Keywords: Spectrofluorimetry; cadmium determination; morin.

A very simple, ultra-sensitive and highly selective non-extractive new spectrofluorimetric method is presented for the determination of cerium at pico-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 cerium(IV). This novel fluorimetric reagent, PTQA becomes oxidized in a slightly acidic (0.0005–0.0015 M H2SO4) solution with cerium(IV) in absolute ethanol to produce a highly fluorescent oxidized product (λex = 303 nm; λem = 370 nm). Constant and maximum fluorescence intensities were observed over a wide range of acidity (0.0005–0.0015 M H2SO4) for the period between 5 min and 24 h. Linear calibration graphs were obtained for 0.001–600 μg L−1 of Ce, having a detection limit of 0.1 ng L−1; the quantification limit of the reaction system was found to be 1 ng L−1 and the RSD was 0–2%. A large excess of over 60 cations, anions and complexing agents (like, chloride, phosphate, azide, tartrate, oxalate, SCN− etc.) do not interfere in the determination. The developed method was successfully used in the determination of cerium in several certified reference materials (alloys, steels, noodles, ores and sediments) as well as in some environmental waters (potable and polluted), biological fluids (human blood, urine and milk), soil samples, food samples (vegetable, rice, corn and wheat), bone samples (human, cow, bull, fish, hen, goat, sheep), solutions containing both cerium(III) and cerium(IV) and complex. The results of the proposed method for assessing biological, food and vegetables samples were comparable with ICP-OES and were found to be in excellent agreement.

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 Sandell's 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 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.

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 Sandell's 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 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 very simple, ultra-sensitive and fairly selective direct spectrophotmetric method is presented for the rapid determination of lead(II) at ultra-trace level using 1,5-diphenylthiocarbazone (dithizone) in micellar media. The presence of the micellar system avoids the previous steps of solvent extraction and reduces the cost and toxicity while enhancing the sensitivity, selectivity and the molar absorptivity. The molar absorptivities of the lead-dithizone complex formed in the presence of the cationic cetyltrimethylammonium bromide (CTAB) surfactants are almost ten times the value observed in the standard method, resulting in an increase in the sensitivity of the method. The reaction is instantaneous and the absorbance remains stable for over 24 h. The average molar absorption coefficient was found to be 3.99 x 10(5) L mol(-1) cm(-1) and Sandell's sensitivity was 30 ng cm(-2) of Pb. Linear calibration graphs were obtained for 0.06-60 mg L(-1) of Pb(II); the stoichiometric composition of the chelate is 1:2 (Pb:dithizone). The interference from over 50 cations, anions and complexing agents has been studied at 1 mg L(-1) of Pb(II). The method was successfully used in the determination of lead in several standard reference materials (alloys and steels), environmental water samples (potable and polluted), biological samples (human blood and urine), soil samples and solutions containing both lead(II) and lead(IV) and complex synthetic mixtures. The method has high precision and accuracy (sigma = +/-0.01 for 0.5 mg L(-1)).

A very simple, ultra-sensitive and fairly selective non-extractive spectrophotmetric method is presented for the rapid determination of mercury(II) at ultra-trace level using 1,5-diphenylthiocarbazone (dithizone) as a new micellar spectrophotometric reagent (lambdamax = 490 nm) in a slightly acidic (0.07 - 0.17 M H2SO4) aqueous solution. The presence of a micellar system avoids the previous steps of solvent extraction and reduces the cost, toxicity while enhancing the sensitivity, selectivity and the molar absorptivity. The reaction is instantaneous and the absorbance remains stable for over 24 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 5.02 x 10(4) L mol(-1) cm(-1) and 10 ng cm(-2) of Hg, respectively. Linear calibration graphs were obtained for 0.05 - 10 mg L(-1) of Hg; the stoichiometric composition of the chelate is 1:2 (Hg:dithizone). The method is characterized by a detection limit of 1 microg L(-1) of Hg. Large excesses of over 60 cations, anions and complexing agents (e.g. EDTA, tartrate, oxalate, citrate, phosphate, thiourea, azide, SCN-) do not interfere in the determination. The method was successfully applied to a number of environmental water samples (potable and polluted), biological samples (human blood and urine; milk and fish) and soils; solutions contained both mercury(I) and mercury(II) as well as complex synthetic mixtures. The method has high precision and accuracy (s = +/-0.01 for 0.1 mg L(-1)).

A very simple, ultra-sensitive and highly selective non-extractive spectrophotometric method for the determination of trace amount of cadmium using 5,7-dibromo-8-hydroxyquinoline (DBHQ) has been developed. DBHQ reacts in a slightly acidic solution with cadmium to give a deep greenish-yellow chelate, which has an absorption maximum at 396 nm. The average molar absorption co-efficient and Sandell's sensitivity were found to be 5.3 x 10(3) L mol(-1) cm(-2) and 20 ng cm(-2) of Cd, respectively. Linear calibration graphs were obtained for 0.1-30 microg mL(-1) of Cd. A large excess of over 50 cations, anions and some common complexing agents do not interfere with the determination. The method was successfully used in the determination of cadmium in several Standard Reference Materials as well as in some environmental waters, biological and soil samples.

A simple spectrophotometric method is presented for the rapid determination of copper at a trace level using 2,5-dimercapto-1,3,4-thiadiazole (DMTD) as a new spectrophotometric reagent. The method is based on the reaction of non-absorbent DMTD in a slightly acidic (0.002-0.014 mol dm(-3) sulfuric acid) aqueous solution with copper(II) to produce a highly absorbent greenish-yellow chelate product that has an absorption maximum at 390 nm. The reaction is instantaneous and the absorbance remains stable for 24 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 5.65 x 10(4) dm3 mol(-1) cm(-1) and 10 ng cm(-2) of CuII, respectively. Linear calibration graphs were obtained for 0.1-20 microg cm(-3) of CuII; the stoichiometric composition of the chelate is 1:2 (Cu:DMTD). A large excess of over 50 cations, anions and complexing agents (e.g. tartrate, oxalate, citrate, phosphate, thiourea, SCN-) do not interfere in the determination. The method was successfully used for the determination of copper in several Standard Reference Materials as well as in some environmental water samples, biological samples, soil samples and solutions containing both copper(I) and copper(II) and complex synthetic mixtures. The method has high precision and accuracy (s = +/-0.01 for 0.5 microg cm(-1)).

A novel high-performance liquid chromatographic method has been developed for the determination of stevioside in the leaves of the plant Stevia rebaudiana (Bertoni). An isocratic water-acetonitrile eluent was employed with a LiChrosorb NH 2 bonded silica column. The effluent was monitored by integrated pulsed amperometry in an alkaline medium (pH > 12) after adding sodium hydroxide post-column. Peak responses were linear from 1 to 100 mg L -1 , with a limit of detection of 0.3 mg L -1 . This method gave greater sensitivity and selectivity than UV detection.

A simple high sensitive, selective, and rapid spectrophotometric method for the determination of trace gold based on the rapid reaction of gold(III) with bis(salicylaldehyde)orthophenylenediamine (BSOPD) in aqueous and micellar media has been developed. BSOPD reacts with gold(III) in slightly acidic solution to form a 1:1 brownish-yellow complex, which has an maximum absorption peak at 490 nm in both aqueous and micellar media. The most remarkable point of this method is that the molar absorptivities of the gold-BSOPD complex form in the presence of the nonionic TritonX-100 surfactant are almost a 10 times higher than the value observed in the aqueous solution, resulting in an increase in the sensitivity and selectivity of the method. The apparent molar absorptivities were found to be 2.3 x 10 4 L mol-1 cm-1 and 2.5 x 10 5 L mol-1 cm-1 in aqueous and micellar media, respectively. The reaction is instantaneous and the maximum absorbance was obtained after 10 min at 490 nm and remains constant for over 24 h at room temperature. The linear calibration graphs were obtained for 0.1 -30 mg L-1 and 0.01 -30 mg L-1 of gold(III) in aqueous and surfactant media, respectively. The interference from over 50 cations, anions and complexing agents has been studied at 1 mg L-1 of Au(III); most metal ions can be tolerated in considerable amounts in aqueous micellar solutions. The Sandell's sensitivity, the limit of detection and relative standard deviation (n = 9) were found to be 5 ng cm-2, 1 ng mL-1 and 2%, respectively in aqueous micellar solutions. Its sensitivity and selectivity are remarkably higher than that of other reagents in the literature. The proposed method was successfully used in the determination of gold in several standard reference materials (alloys and steels), environmental water samples (potable and polluted), and biological samples (blood and urine), geological, soil and complex synthetic mixtures. The results obtained agree well with those samples analyzed by atomic absorption spectrophotometry (AAS).

Bis(salicylaldehyde)orthophenylenediamine (BSOPD) has been proposed as new analytical reagent for the direct non-extractive spectrophotometric determination of cobalt. It reacts with cobalt in slightly acidic (0.0002-0.001 M H(2)SO(4)) 50% 1,4-dioxanic medium to form a red-orange chelate with a molar ratio 1:1. The reaction is instantaneous and the maximum absorbance was obtained at 458 nm and remains constant for over 24h. The average molar absorption coefficient and Sandell's sensitivity were found to be 1.109 x 10(4)l mol(-1)cm(-1) and 20 ng cm(-2) of Co(II), respectively. Linear calibration graph was obtained for 0.1-15 mg l(-1) of Co(II) with a correlation coefficient value of 0.995 for Co-BSOPD complex. Large excess of 44 cations, anions and complexing agents do not interfere in the determination. The method was successfully used in the determination of cobalt(II) from synthetic mixture and certified reference materials for the purpose of validating the method and the results of analyses were found to be excellent agreement with those of actual values. This developed method was also used for determination of cobalt in some environmental waters (potable and polluted), biological (blood and urine) and soil samples and solution containing both cobalt(II) and cobalt(III). The results of the proposed method for biological samples were comparable with AAS and were found to be in good agreement. The method has high precision and accuracy (s=+/-0.01 for 0.5 mg l(-1)).

A very simple, ultra-sensitive and fairly selective new spectrophotometric method has been developed for the rapid determination of lead(II) at ultra-trace level using 1,5-diphenylthiocarbazone (dithizone) in presence of aqueous micellar solutions. The proposed method enabled the determination of lead down to µg l−1in human blood and urine in aqueous media without resource of any “clean-up” step. The most remarkable point of this method is that the presence of micellar system avoids the previous steps of solvent extraction and reduces the cost, toxicity while enhancing the sensitivity, selectivity and the molar absorptivity. The complex formation of lead in blood with dithizone was completed within a minute at room temperature and the absorbance remains stable for 24 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 3.99×105l mol−1 cm−1and 30 ng cm−2of Pb, respectively. Linear calibration graphs were obtained for 0.06–60 mg l−1of PbII; the stoichiometric composition of the chelate is 1:2 (Pb:dithizone). The interference from over 60 cations, anions and complexing agents has been studied at 1 mg l−1of PbII. The method was successfully used in the determination of lead in several biological samples (human blood and urine and bovine liver), solution containing both lead(II) and lead(IV) and complex synthetic mixtures. The results of biological analyses by the spectrophotometric method were in excellent agreement with those obtained by AAS. The results of lead concentration in biological samples were varied with age, sex and place which have been discussed.

A simple, sensitive and highly selective direct spectrophotometric method for the determination of trace levels of mercury(II) in various samples is described. Diphenylthiocarbazone (dithizone) reacts in slightly acidic 50% aqueous 1,4-dioxane media (0.18–1.80 M sulphuric acid) with mercury(II) to give an orange chelate which has an absorption maximum at 488 nm. The average molar absorption co-efficient and Sandell's sensitivity were found to be 2.5×104l mol−1 cm−1and 0.015 μg of Hg(II) cm−2, respectively. The reaction is immediate and absorbance remains stable for over 24 h. Beer's law is obeyed for concentration range of mercury(II) between 0.1 μg ml−1and 25 μg ml−1; the stoichiometric composition of the chelate is 1 :2 (mercury : dithizone). The various analytical parameters, such as effect of time, acidity, reagent concentration and foreign species, were studied. The method was applied successfully to a number of environmental waters (portable and polluted), biological samples (human blood, urine and fish), soils, plant samples (potato, cabbage, lettuce, carrot and tomato), solutions containing both mercury(I) and mercury(II) and complex synthetic mixtures. The method is very simple and requires no solvent extraction or pre-concentration steps.

A simple spectrophotometric method is presented for the rapid determination of copper at a trace level using 2,5-dimercapto-1,3,4-thiadiazole (DMTD) as a new spectrophotometric reagent. The method is based on the reaction of non-absorbent DMTD in a slightly acidic (0.002-0.014 mol dm(-3) sulfuric acid) aqueous solution with copper(II) to produce a highly absorbent greenish-yellow chelate product that has an absorption maximum at 390 nm. The reaction is instantaneous and the absorbance remains stable for 24 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 5.65 x 10(4) dm3 mol(-1) cm(-1) and 10 ng cm(-2) of CuII, respectively. Linear calibration graphs were obtained for 0.1-20 microg cm(-3) of CuII; the stoichiometric composition of the chelate is 1:2 (Cu:DMTD). A large excess of over 50 cations, anions and complexing agents (e.g. tartrate, oxalate, citrate, phosphate, thiourea, SCN-) do not interfere in the determination. The method was successfully used for the determination of copper in several Standard Reference Materials as well as in some environmental water samples, biological samples, soil samples and solutions containing both copper(I) and copper(II) and complex synthetic mixtures. The method has high precision and accuracy (s = +/-0.01 for 0.5 microg cm(-1)).

A very simple, ultra-sensitive and highly selective non-extractive spectrophotometric method for the determination of trace amount of molybdenum(VI) using 5,7-dibromo-8-hydroxyquinoline (DBHQ) has been developed. 5,7-Dibromo-8-hydroxyquinoline reacts in a slightly acidic solution (0.05 - 1.0 M H2SO4) with molybdenum(VI) to give a deep greenish-yellow chelate which has an absorption maximum at 401 nm. The reaction is instantaneous and the absorbance remains stable for over 24 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 4.13 x 10(3) L mol(-1) cm(-1) and 7 ng cm(-2) of molybdenum(VI), respectively. Linear calibration graphs were obtained for 0.1 - 50 microg mL(-1) of molybdenum(VI). The stoichiometric composition of the chelate is 1:3 (Mo:DBHQ). A large excess of over 50 cations, anions and some common complexing agents (e.g. EDTA, oxalate, citrate, phosphate, thiourea, SCN-) do not interfere with the determination. The method was successfully used in the determination of molybdenum in several Standard Reference Materials (alloys, steels and waters) as well as in some environmental waters (inland and surface), biological samples (human blood and urine), soil samples, solution containing both molybdenum(V) and molybdenum(VI) and complex synthetic mixtures. The method has high precision and accuracy (S = +/-0.01 for 0.5 microg mL(-1)).

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 Sandell's 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 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 Sandell's 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 Beer's 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.