A new kinetic-spectrophotometric method is proposed for the determination of copper (Ⅱ). The method is based on the catalytic effect of copper (Ⅱ) on the oxidation of weak acid brilliant blue dye (RAWL) by hydrogen ...A new kinetic-spectrophotometric method is proposed for the determination of copper (Ⅱ). The method is based on the catalytic effect of copper (Ⅱ) on the oxidation of weak acid brilliant blue dye (RAWL) by hydrogen peroxide. The copper (Ⅱ) can be determined spectrophotometrically by measuring the decrease of absorbance of RAWL at λ = 626 nm using the fix-time method. The optimum reaction conditions are as follows: pH 7.20, buffer solution NaOH-KH2PO4, RAWL (200 mg L-1) 5.00 mL, H2O2 (30%) 0.50 mL, reaction temperature 80℃ and reaction time 20 min. The linear range of this method is between 0 μg L-1 and 12 μg L-1 and the limit of detection is 0.011 μg L-1, the relative standard deviation (RSD) in five replicate determinations for 2 and 8 μg L-1 copper (Ⅱ) are 3.2% and 2.3%, respectively. Twenty ions do not interfere in the determination of copper (Ⅱ). The method has been applied satisfactorily to the determination of copper (Ⅱ) in freshwater samples (tap water and Yellow River water from Lijin, Shandong, China) and seawater samples (from the South China Sea), the recovery rates are 98.0%, 102.5% and 96.0%, respectively.展开更多
A novel method for on-site determination of trace iron was developed using membrane preconcentration and spectrophotometric detection. Fe（II）-ferrozine complex was reacted with cetyltrimethylammonium bromide （CTAB...A novel method for on-site determination of trace iron was developed using membrane preconcentration and spectrophotometric detection. Fe（II）-ferrozine complex was reacted with cetyltrimethylammonium bromide （CTAB） to form a Fe（II）-ferrozine-CTAB paired compound, which was collected on a membrane by filtration under vacuum. The membrane was immersed in 2 mL of ethanol-nitric acid and the absorbance of the solution measured for quantitative analysis. Various factors affecting the iron collection and determination were investigated. With different sample preconcentration volumes, the range of determination was broadened to 0.5-120 ~tg/L. The detection limit of this method reached 0.19 ktg/L and the recoveries were between 97.2 and 109% when the concentration enrichment was about 45. The relative standard deviation （n = 7） was 1.9% for samples containing 10 ~g/L Fe. Twelve seawater samples were analyzed on-site using the proposed method, and two were also analyzed in inductively coupled plasma mass spectrometry. No significant difference was shown between the two methods by the Student＇s t-test. The method has also been used on-site for iron enrichment experiments with phytoplankton and concluded to be simple, accurate and inexpensive.展开更多
A new kinetic spectrophotometric method has been developed for the determination of vanadium（V）.The method is based on the catalytic effect of vanadium（V）on the oxidation of weak acid brilliant blue dye（RAWL）by ...A new kinetic spectrophotometric method has been developed for the determination of vanadium（V）.The method is based on the catalytic effect of vanadium（V）on the oxidation of weak acid brilliant blue dye（RAWL）by KBrO3 using the citric acid as activation reagent.The obtained optimum conditions are：c（RAWL）= 1×10-4 molL-1,c（KBrO3）= 3×10-2 molL-1,c（citric acid）=9×10-3 molL-1,pH = 2.50,the reaction time being 7.0min and the temperature being 25.0℃.Under the optimum conditions,the proposed method allows the determination of vanadium（V）in the range of 0-70.0ng mL-1 and the detection limit is down to 0.407 ng mL-1.For standard vanadium（V）solution determination,the recovery efficiency is in the range of 98.5%-102% and the RSD ranges from 0.76%-1.25%.Moreover,it is demonstrated that most cations and anions do not interfere with the determination of vanadium（V）under the analytical condition.The new method was successfully applied in the determination of vanadium（V）in fresh water and seawater samples with satisfactory results.Vanadium（V）in the seawater samples from Qingdao offshore was determined using the method and the distribution of vanadium（V）was mapped.Compared with other instrumental analytical methods,the proposed method shows good selectivity,sensitivity,simplicity,lower cost and rapidity.It can be employed on shipboard easily.展开更多
文摘A new kinetic-spectrophotometric method is proposed for the determination of copper (Ⅱ). The method is based on the catalytic effect of copper (Ⅱ) on the oxidation of weak acid brilliant blue dye (RAWL) by hydrogen peroxide. The copper (Ⅱ) can be determined spectrophotometrically by measuring the decrease of absorbance of RAWL at λ = 626 nm using the fix-time method. The optimum reaction conditions are as follows: pH 7.20, buffer solution NaOH-KH2PO4, RAWL (200 mg L-1) 5.00 mL, H2O2 (30%) 0.50 mL, reaction temperature 80℃ and reaction time 20 min. The linear range of this method is between 0 μg L-1 and 12 μg L-1 and the limit of detection is 0.011 μg L-1, the relative standard deviation (RSD) in five replicate determinations for 2 and 8 μg L-1 copper (Ⅱ) are 3.2% and 2.3%, respectively. Twenty ions do not interfere in the determination of copper (Ⅱ). The method has been applied satisfactorily to the determination of copper (Ⅱ) in freshwater samples (tap water and Yellow River water from Lijin, Shandong, China) and seawater samples (from the South China Sea), the recovery rates are 98.0%, 102.5% and 96.0%, respectively.
基金Supported by State Key Laboratory of Marine Environmental Science(MEL)Funds(No.MELRI1001)
文摘A novel method for on-site determination of trace iron was developed using membrane preconcentration and spectrophotometric detection. Fe（II）-ferrozine complex was reacted with cetyltrimethylammonium bromide （CTAB） to form a Fe（II）-ferrozine-CTAB paired compound, which was collected on a membrane by filtration under vacuum. The membrane was immersed in 2 mL of ethanol-nitric acid and the absorbance of the solution measured for quantitative analysis. Various factors affecting the iron collection and determination were investigated. With different sample preconcentration volumes, the range of determination was broadened to 0.5-120 ~tg/L. The detection limit of this method reached 0.19 ktg/L and the recoveries were between 97.2 and 109% when the concentration enrichment was about 45. The relative standard deviation （n = 7） was 1.9% for samples containing 10 ~g/L Fe. Twelve seawater samples were analyzed on-site using the proposed method, and two were also analyzed in inductively coupled plasma mass spectrometry. No significant difference was shown between the two methods by the Student＇s t-test. The method has also been used on-site for iron enrichment experiments with phytoplankton and concluded to be simple, accurate and inexpensive.
文摘A new kinetic spectrophotometric method has been developed for the determination of vanadium（V）.The method is based on the catalytic effect of vanadium（V）on the oxidation of weak acid brilliant blue dye（RAWL）by KBrO3 using the citric acid as activation reagent.The obtained optimum conditions are：c（RAWL）= 1×10-4 molL-1,c（KBrO3）= 3×10-2 molL-1,c（citric acid）=9×10-3 molL-1,pH = 2.50,the reaction time being 7.0min and the temperature being 25.0℃.Under the optimum conditions,the proposed method allows the determination of vanadium（V）in the range of 0-70.0ng mL-1 and the detection limit is down to 0.407 ng mL-1.For standard vanadium（V）solution determination,the recovery efficiency is in the range of 98.5%-102% and the RSD ranges from 0.76%-1.25%.Moreover,it is demonstrated that most cations and anions do not interfere with the determination of vanadium（V）under the analytical condition.The new method was successfully applied in the determination of vanadium（V）in fresh water and seawater samples with satisfactory results.Vanadium（V）in the seawater samples from Qingdao offshore was determined using the method and the distribution of vanadium（V）was mapped.Compared with other instrumental analytical methods,the proposed method shows good selectivity,sensitivity,simplicity,lower cost and rapidity.It can be employed on shipboard easily.
