Effects of Standing Time during Pretreatment on the Nitrite Concentration Detected by Spectrophotometric Method

Food safety problems caused by excessive nitrite addition have been frequently reported and the detection of nitrite in food is particularly important. The standing time during the pretreatment of primary sample has a great influence on the concentration of nitrite tested by spectrophotometric method. In this context, three kinds of food samples are prepared, including canned mustard, canned fish and home-made pickled water. A series of standing times are placed during the sample pretreatments and the corresponding nitrite contents in these samples are detected by spectrophotometric method based on N-ethylenediamine dihydrochloride. This study aims to find out a reasonable standing time during the pretreatment of food sample, providing influence factor for precise detection of nitrite.

A New Spectrophotometric Method for Measuring COD of Seawater

This research studied a new spectrophotometric method for measuring the chemical oxygen demand （COD） of seawater. In this method, the COD was measured using a spectrophotometer instead of titrating with sodium thiosuiphate. The measuring wavelength was selected to be 470 nm, and the COD of three standard glucose solutions （COD = 0.5, 1.5 and 2.5 mgL^-1, respectively） and two seawater samples （from the South Yellow Sea and Jiaozhou Bay） were measured using the spectrophotometric method and titrimetric method respectively. The results showed that the spectrophotometric method was somewhat better than the titrimetric method. The relative standard deviation （RSD） of the spectrophotometric method was less than 2.7%, and the recovery of seawater samples ranged from 96.3% to 103.8%. In addition, the spectrophotometric method has other advantages such as expeditiousness, operation simplicity, analysis automatization, etc. Therefore the spectrophotometric method can be used to measure the COD of seawater with satisfactory results.

Simultaneous Determination of Iron and Manganese in Water Using Artificial Neural Network Catalytic Spectrophotometric Method

A new analytical method using Back-Propagation (BP) artificial neural network and kinetic spectrophotometry for simultaneous determination of iron and magnesium in tap water, the Yellow River water and seawater is established. By conditional experiments, the optimum analytical conditions and parameters are obtained. Levenberg-Marquart (L-M) algorithm is used for calculation in BP neural network. The topological structure of three-layer BP ANN network architecture is chosen as 15-16-2 (nodes). The initial value of gradient coefficient μ is fixed at 0.001 and the increase factor and reduction factor of μ take the default values of the system. The data are processed by computers with our own programs written in MATLAB 7.0. The relative standard deviation of the calculated results for iron and manganese is 2.30% and 2.67% respectively. The results of standard addition method show that for the tap water, the recoveries of iron and manganese are in the ranges of 98.0%-104.3% and 96.5%-104.5%, and the RSD is in the range of 0.23%-0.98%; for the Yellow River water (Lijin district of Shandong Province), the recoveries of iron and manganese are in the ranges of 96.0%-101.0% and 98.7%-104.2%, and the RSD is in the range of 0.13%-2.52%; for the seawater in Qingdao offshore, the recoveries of iron and manganese are in the ranges of 95.3%-104.8% and 95.3%-104.7%, and the RSD is in the range of 0.14%-2.66%. It is found that 21 common cations and anions do not interfere with the determination of iron and manganese under the optimum experimental conditions. This method exhibits good reproducibility and high accuracy in the determination of iron and manganese and can be used for the simultaneous determination of iron and manganese in tap water and natural water. By using the established ANN- catalytic spectrophotometric method, the iron and manganese concentrations of the surface seawater at 11 sites in Qingdao offshore are determined and the level distribution maps of iron and manganese are drawn.

Solid-phase extraction of trace Au(Ⅲ) with SDG and determination by the catalytic spectrophotometric method

The new catalytic kinetic spectrophotometric method for Au（III） determination was developed and validated. It was based on the catalytic effect of gold on the oxidation of sudan red III by ammonium peroxodisulfate （（NH4）2S2O8） with nitrilo triacetic acid as an activator in microemulsion and H2SO4 medium. Under optimum conditions, there was the linearity of the calibration curve in the concentration range from 0 to 20 μg/L Au（Ⅲ） at 520 nm. The relative standard deviation was 3.0% with a correlation coefficient of 0.9986. The detection limit achieved was 9.75 × 10^-5 μg/mL. A new method using a column packed with sulfhydryl dextrose gel （SDG） as a solid-phase extractant has been developed for the preconcentration and separation of Au（Ⅲ） ions. The method has been applied to the determination of trace gold with satisfactory results.

Rapid Estimation on the Sperm Concentration in Boar Semen by Spectrophotometric Method

[ Objective] To establish the standardized spectrophotometric method to determine boar sperm concentration. [ Method ] The relation- ships between absorbance （A）, transmittance （T） and sperm concentration （C） of different wavelengths （450, 550, 650 nm） were compared. [ Result] The maximum sperm concentration detected by absorbance presented an upward trend with the increase of the wavelengths, 202 mitliorVml （450 nm）, 224 million/ml （550 nm） and 235 mUlion/ml （650 nm）, respectively, but the stability of repeated measurement was decreased. With the increase of sperm dilution times, the stability of repeated measurement of transmittance was reduced, and when dilution times were more than 10 times （450 nm）, 6 times （550 nm） and 4 times （650 nm）, differences appeared between the observed values of repeated measurement. [ Con- clusion] Wavelength at 450 nm was found to be the most sensitive and reliable, and sperm concentration presented cubic functional regression rela- tionship or power functional regression relationship with absorbance or transmittance, respectively. The regression equation for the standard curve at 450 nm was C400 = 0.48A3 - 0.76A2 ＋ 0.67A - 0.066 （ R = 0.951 ） and C400 = 1.657T -0.108. 8 （ R = 0.940）.

THE STUDY ON DETERMINATION OF SELENIUM WITH POTASSIUM BUTYL XANTHATE

A simple and fast ultraviolet spectrophotometric method was used to determineselenium (Ⅳ) through the formation, separaion and quantitative determination of potassium butylxanthae -selenium complex. The complex absorbed light sharply at 375 nm. The optimum acidity ofthe complex formation was between pH 3.4 - 4.0. The absorption value was no change in 120 minutesafter the comlex was extracted by Carbon tetraChioride. The sensitivity of the colour reation was 0.2ng cm-2, The content of selenimp (Ⅳ) was within 0-30 μg and linear rclation was good,Y=0.07X＋0.025, relevent coefficient r＝0.9997. A great quantity of I, Cu, Co, the and SO4-2, PO4-3contained in .the Sample had no effect on the results ofdetenninion when seldsum was determined.When content of Fe was over l00gμg/ml and Zn was over 180μg/ml, there was diotance to the determination, but the disturbance was rem0ved by adding EDTA. When making use of the method todetermine containin seldsum additivef Cv =6.85, rate of recovery was 97.2%, wild jujubef;Cv=3.22,rate of recovery was 90. 1%, soil Samlef Cv=4.64, rate of recovery was 86.2%. The method for sensitivity measured was apprtoate to 2, 3-diamino naphthalene (DAN) fluorescence method.

Synthesis of Different Ligand Complex Mo (VI) with Stillbazo and Cetylpyridinium Chloride

The complex of molybdenum (VI) with stilbene-2,2’-disulfonic acid-4,4’’bis (azo-1’’)-3’’, 4’’ dioxybenzene (stillbazo) in the presence of a cationic surfactant cetylpyridinium chloride (CPCl) was studied spectrophotometrically. It was found that in the presence of CPCl, a mixed-ligand complex with a component ratio of 1:2:4 is formed. The effect of pH, time, temperature, the concentration of reagents, and CPCl in the formation of homogeneous ligand and mixed-ligand complexes were studied. The stability constants (lgβk = 86 × 108) and the molar absorption coefficient of the mixed-ligand complex (εк = 11,835) were determined. It was found that Beer’s law is observed at a concentration of 0.05 - 17.00 μg/ml. A method has been developed for the spectrophotometric determination of molybdenum (VI) in complex industrial facilities.

Catalytic Kinetic Spectrophotometric Method for Determination of Phosphate Ion

The kinetic method for the determination of phosphate microamounts was described. The developed method is based on catalytic effect of phosphate on sodium pyrogallol-5-sulphonate （PS） by dissolved oxygen. The reaction was followed spectrophotometrically by measuring the rate of change in the values of the absorbance of the oxidation product at 437 nm. The optimum reaction conditions are PS （0.44×10^-3 mol·L^-1） and HClO4 （3.6×10^-6 mol·L^-1） at 25 ℃. Following this procedure, phosphate can be determined with a linear calibration graph up to 0.23 μg·mL^-1. The interference effect of several species was also investigated and it was found that the most common cations and anions did not interfere with the determination. The developed procedure was successfully applied to the determination of phosphate in natural waters and soil.

Evaluating the Efficiency of Cadmium Removal by Alginate Hydrogels from Water Using 5,7-Dibromo-8-hydroxyquinoline as a Complexing Reagent

Cadmium toxicity in wastewater is a rising concern due to industries like batteries,metallurgy,electroplating,plastic stabilizers,and pigments.The quantitative detection of Cd^(2+)and its remediation from wastewater samples are of major concern from an environmental point of view.In the present work,an effective spectrophotometric method has been reported using 5,7-dibromo-8-hydroxyquinoline(DBHQ)as a complexing agent for Cd^(2+).This method has advantages like using recyclable,less toxic solvents and easy sample preparation.The limit of detection,limit of quantification,and sensitivity of the proposed method were found to be 33.30,36.70 mg L^(−1),and 2×10^(−3),respectively.The DBHQ method was validated using atomic absorption spectroscopy,and the recovery percentage was more than 98%.These results indicate that DBHQ can be effectively used for monitoring Cd^(2+)in aqueous systems.The method developed was further employed for monitoring Cd^(2+)adsorption on calcium alginate(AL)hydrogels.Batch adsorption studies were done to optimize parameters of Cd^(2+)removal using AL hydrogels,and the data obtained were used for kinetic and thermodynamic studies.Kinetic studies indicated that the pseudo-first-order model showed better fitting,and thermodynamic studies showed Freundlich-like adsorption.The maximum adsorption capacity of Cd^(2+)on AL hydrogels was found to be 56.45 mg g^(−1).The validation studies of DBHQ were performed using statistical analysis methods like t-tests and one-way variance.