Average Molar Absorption Research Articles

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.

Novo método espectrofotométrico para determinação de Hg (II) em amostras de peixe

A simple, sensitive and selective spectrophotmetric method is presented for the rapid determination of mercury (II) at trace levels using 2-mercapto-5-methylbenzimidazole (MMBI) as a new spectrophotometric reagent (lambdamax = 320 nm) in a slightly basic (0.04 M Britton-Robinson (BR) buffer, pH 8.0) aqueous solution. The reaction is instantaneous and the absorbance remains stable for over 24 hours. The average molar absorption coefficient was found to be 2.71 x 104 L mol-1 cm-1. The stoichiometric composition of the chelate is 1:1 (Hg:MMBI). Considerable excesses of copper, zinc, lead and cadmium do not interfere in the determination. The method developed allowed the determination of mercury in the range of 2 x 10-6 to 4 x 10-5 mol.L-1 with good precision, accuracy and the detection limit was 9.9 x 10-7 mol.L-1 of Hg. The method was successfully applied to fish samples and the results were evaluated and compared with classic atomic absorption spectrometry (AAS). The relative standard deviations for the samples analyzed were between 7.2 and 33% (n = 5), while the errors were between 1.63 and 11.6. The method was found to be sensitive, selective and was used for the determination of mercury in fish with satisfactory results.

A Rapid Spectrophotometric Method for the Determination of Trace Level Lead Using 1,5-Diphenylthiocarbazone in Aqueous Micellar Solutions

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 simple spectrophotometric method for the determination of cobalt in industrial, environmental, biological and soil samples using bis(salicylaldehyde)orthophenylenediamine

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 simple spectrophotometric method for the determination of trace level lead in biological samples in the presence of aqueous micellar solutions

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 Spectrophotometric Determination of Trace Level Mercury Using 1,5-Diphenylthiocarbazone Solubilized in Micelle

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 simple spectrophotometric method for the determination of cadmium in industrial, environmental, biological and soil samples using 5,7-dibromo-8-hydroxyquinoline.

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 rapid spectrophotometric method for the determination of mercury in environmental, biological, soil and plant samples using diphenylthiocarbazone

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−1 and 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−1 and 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 for the determination of copper in industrial, environmental, biological and soil samples using 2,5-dimercapto-1,3,4-thiadiazole.

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 rapid spectrophotometric method for the determination of molybdenum in industrial, environmental, biological and soil samples using 5,7-dibromo-8-hydroxyquinoline.

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)).

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 Sandell's sensitivity were found to be 4.93×10 4 l mol −1 cm −1 and 15 ng cm −2 of Pb, respectively. Linear calibration graphs were obtained for 0.1–40 μg ml −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 μg ml −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 μg ml −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 H2SO4 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 4.23×104 l mol−1 cm−1 and 10 ng cm−2 of Vv, respectively. Linear calibration graph were obtained for 0.1–30 μg ml−1 of Vv: 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 μg ml−1 of Vv. 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 μg ml−1).

ＳＯ２を含有する火力発電所排ガスからのＣＯ２の除去技術

For CO2 removal from flue gases containing SO2 at thermal power plants, secondary alkanolamine with high molecular weight (abb. HIA) was selected as an absorbent because of low utility consumption. SO2 forms sulfite salt in absorbent and it is oxidized with O2 to form the sulfate. These salts called Heat Stable Salts (HSS) reduce CO2 removal ratio. On the other hand, the sulfite consumes O2 in the absorbent and the resistance to oxidation of HIA can be expected. We estimated the relationship between concentration of HSS and CO2 removal ratio, and the resistance to oxidation of HIA absorbent by the presence of SO2 in treated gas. Based on these results, pilot testing (flue gas capacity: 1, 000 Nm3/h, CO2 removal ratio: 90%) was carried using coal oil mixture-fired power plant flue gas for continuous 2, 000 hours (accumulating time of 2, 441 h) to evaluate the resistance to oxidation and regeneration heat of HIA.Oxalic acid by oxidative degradation was accumulated 0.0095% after completion of pilot testing, and its amount was 0.1 times as low as that of LNG-fired flue gas. Furthermore, four kinds of cyclic amines were detected by GC-MS analyses and three of them were compounds by oxidative degradation. Their amounts of the mixture were spectrophotometrically determined to be 0.19% based on a reasonable assumption of the average molar absorptivity of the mixture. Average oxidation rate of the mixture was estimated 8.8x10-5%/h. This was 0.4% of the total loss of HIA.Regeneration heat of HIA was 20% as low as that of the conventional absorbent even in the case of accumulation of HSS up to 2% as the reduced concentration of H2SO4.

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 2SO 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 × 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 μg 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 μg 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.

Non-extractive spectrophotometric determination of vanadium(v) in alloys and environmental, biological and soil samples using 5,7-dibromo-8-hydroxyquinoline.

An ultra-sensitive and highly selective non-extractive spectrophotometric method is presented for the rapid determination of vanadium(v) at trace levels using 5,7-dibromo-8-hydroxyquinoline (DBHQ) as a new spectrophotometric reagent (lambda max = 400 nm) in slightly acidic solution (0.00015-0.016 mol-1 sulfuric acid). The reaction is instantaneous and the absorbance remains stable for over 48 h. The average molar absorption coefficient and Sandell's sensitivity were found to be 6.1 x 10(3) l mol-1 cm-1 and 0.015 micrograms cm-2 of Vv, respectively. Linear calibration graphs were obtained for 0.1-20 micrograms ml-1 of Vv: the stoichiometric composition of the chelate is 1:3 (V:DBHQ). Large excesses of over 50 cations, anions and complexing agents (e.g., tartrate, oxalate, citrate, phosphate, thio-urea, SCN-) do not interfere in the determination. The method was successfully used in the determination of vanadium in several Standard Reference Materials (alloys and steels) as well as in some environmental waters (potable and polluted), biological samples (human blood and urine), soil samples and complex synthetic mixtures. The method has high precision and accuracy (s = +/- 0.01 for 0.5 micrograms ml-1).

Molybdenum(V) tetramer in sulphuric acid solution

The molybdenum(V) species in 2–9 M sulphuric acid solution were investigated by ESR and spectrophotometry. For 1 mM and 0.15 M molybdenum(V) in 9 M H 2SO 4 their ESR signals show considerable differences. The average molar absorption coefficient at 407 nm also shows a drastic change when the concentration of molybdenum(V) is changed. This difference was analyzed and the presence of a tetrameric molybdenum(V) species was deduced.

Spectrophotometric determination of Fe(III) with tiron in the presence of cationic surfactant and its application for the determination of iron in Al-alloys and Cu-based alloys

A sensitive Spectrophotometric method for the determination of iron with tiron and a cationic surfactant, cetylpyridinium chloride, at pH 5.6 is reported. The complex is extracted into a chloroform-propan-2-ol (4∶1) mixture and shows maximum absorbance at 520 nm. Beer's law is obeyed in the range 1–14 μg/ml with an average molar absorptivity of 15800 l mol−1 cm−1. The molar ratio as determined by Job's method for Fe:tiron:CPC is 1∶4∶3. Interferences by various ions are examined. Zr, Ti and Mo interfere heavily. The method is applied for the determination of iron in Al-based and Cu-based alloys, using appropriate masking agents.

Spectrophotometric determination of polyquaternium-1 with trypan blue by a difference procedure

A spectrophotometric method is described for the determination of polyquaternium-1 in a pharmaceutical solution. This method is based on a bathochromic shift of the trypan blue absorption which occurs when it is complexed with polyquaternium-1. The difference in absorption is measured at 680 nm with an apparent average molar absorptivity of 1.5 × 105 l mol–1 cm–1. Linearity is observed over the range 5–15 µg ml–1.

Effect of reabsorption on the concentration dependence of fluorescence lifetimes of chlorophyll a

The concentration dependence of mean fluorescence lifetimes of chlorophyll a in methanol was studied in the concentration interval 3 × 10 −6 − 7.3 × 10 −5 mol l −1 at room temperature. The values found experimentally were corrected for reabsorption of fluorescence using the average molar absorptivity ϵ F derived from spectral properties of overlapping fluorescence and absorption spectra of chlorophyll a.

Absorptivity and Solid State and Solution Fluorescence of Mixed Aflatoxin Standards Stored in Solution and as Dry Films

Abstract Mixed anatoxin B1, B2, G1, and G2 standards were stored 1 year in chloroform and benzene solutions and as dry films at 28 and – 18°C. Weighted average molar absorptivity and solution and TLC plate fluorescence were used as indices of deterioration. Changes in all three indices were greater for standards stored at 28°C than for those stored at –18°C. Storage at 28°C resulted in appreciable deterioration of dry film standards. Both solution and plate fluorescence were more sensitive indices than molar absorptivity for detecting changes in the properties of stored standards. A good correlation was obtained between anatoxin concentration as measured by UV molar absorptivity and the plate fluorescence of the stored standards. An accelerated storage study of anatoxins B1 and G1 stored 34 days in benzeneacetonitrile (98 + 2) at 51°C showed no detectable change in molar absorptivity or plate fluorescence.