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.

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.

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.

Application of Total Error Strategy in Validation of Affordable and Accessible UV-Visible Spectrophotometric Methods for Quality Control of Poor Medicines

In the framework of fighting against the poor quality medicines sold in developing countries using classical analytical methods easily accessible in those countries, four UV-Visible spectrophotometric methods for one antimalarial (quinine) and two antibiotics (amoxicillin and metronidazole) have been developed and validated according to the total error strategy using the accuracy profiles as a decision tool. The dosing range was 2 - 10 μg/mL (for quinine sulfate in tablet), 4 - 12 μg/mL (for quinine bichlorhydrate in oral drop-metronidazole benzaote in oral suspension) and 15 - 35 μg/mL (for amoxicillin trihydrate in capsule). The validated methods were then applied in determining the content of some analogous medicines sold in the Democratic Republic of Congo. Thus, the proposed UV-Visible spectrophotometric methods are simple and suitable to quantify quinine, amoxicillin and metronidazole in different pharmaceutical forms.

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）.

Quick and Simple Spectrophotometric Method of Identification of the Thermal State of Meat on the Basis of Composition and Content of Free Nucleotides

At present, there is no method for identifying meat frozen in a thermal state acceptable for production control. The role of free nucleotides in the processes of refrigeration and storage of meat, affecting the structural and mechanical properties of muscle tissue, the formation of taste and its biological value is known. In this article we compared methods for identifying the thermal state of meat based on the determination of the composition and content of free nucleotides by high-performance liquid chromatography (HPLC) and spectrophotometry [SF]. High-purity reference substances were used: free nucleotides—ATP, ADP, AMP, IMP and nucleosides-inosine and hypoxanthine. It has been experimentally established that the characteristic peaks of the absorption spectra for extracts of free nucleotides of meat frozen depended from thermal state of meat. The content of ATP is 21.8 times higher in meat frozen in a fresh state, and the amount of IMF is 12.3 times lower than in meat frozen after cooling. The results of studies of meat frozen using the HPLC method and the developed SF method show the adequacy of the data obtained by both methods. SF-method based on the determination of the optical density of the extracts of free nucleotides is recommended to justify the choice of technological process meat defrost modes.

A Novel Spectrophotometric Method for Determination of Five 1,4-Dihydropyridine Drugs in Their Tablets and Capsules Using Vanillin Reagent

A selective and new spectrophotometric method is described for determination of five 1,4 dihydropyridine drugs (1,4- DHP);namely nifedipine (NIF), nicardipine (NIC), nimodipine (NIM), felodipine (FEL) and amlodipine (AML). The method is based on a coupling reaction between the cited drugs and vanillin reagent in acidic condition. Under optimized conditions, the red coloured products were measured at 500 nm for NIF, NIC, NIM and FEL or at 479 nm for AML. Molar absorptivities were ranged from 0.575 × 104 - 1.065 × 104 l·mol-1·cm-1, Beer’s law was obeyed at 5 - 70 μg/mL concentration range and the limit of detection was ranged from 0.150 - 1.500 μg/mL. The proposed method was successfully extended to pharmaceutical preparations tablets and capsules and comparison by Student’s t-test and variance ratio F-test showed no significant difference.

Spectrophotometric Determination of Fluoride in Groundwater Using Resorcin Blue Complexes

New simple and sensitive spectrophotometric determination of fluoride in drinking groundwater has been developed using aluminium-resorcin blue complex. The method is based on the reaction of fluoride with the coloured complex to produce colourless aluminium fluoride complex and releasing of the free ligand. The relationship of the reaction of flu-oride with the complex is sixth-order polynomial function. The reaction reaches equilibrium at fluoride concentration of 0.054 mM. The equilibrium constant (Keq) was calculated as 1.12 × 1014. Beer-Lambert law is obeyed in the range 0.0 - 0.024 mM of fluoride (0.0 - 1.0 mg·L-1). The molar absorptivity at 502 nm is 6.45 × 103 L·mol-1·cm-1. Fluoride concentration higher than 1.0 mg·L-1 can be measured after proper dilution. The sensitivity, detection limit, quantitation limit, and the percentage recovery of 0.75 mg·L-1 fluoride for the method were found to be 0.357 μg·ml-1., 0.07 mg·L-1, 0.2 mg·L-1, and 101.1 respectively.

Copper and Mercury in Food, Biological and Pharmaceutical Samples: Spectrophotometric Estimation as Cu(DDTC)₂

An alternative spectrophotometric method was optimized and validated for the estimation of mercury using diethyldithiocarbamate (DDTC), a common reagent, widely used for the preconcentration and isolation of metal ions in complex matrices followed by their estimation by varied techniques. Diethyldithiocarbamate forms yellow Cu(DDTC)2 with copper and white Hg(DDTC)2 with mercury (having d10 system) which are extracted in CCl4. The UV-visible spectrum of Cu(DDTC)2 is very stable at pH 5.0 and has a maximum absorption (λmax) at 435 nm. Hg(DDTC)2 is more stable than Cu(DDTC)2. Estimation of mercury is based on a quantitative displacement of Cu(II) of Cu(DDTC)2 with the addition of mercury followed by the measurement of reduced absorbance. Primarily, method was optimized and validated for the estimation of copper. Therefore, simultaneous determination of Cu(II) and Hg(II) in mixture is proposed fractionating the extract. The molar specific coefficient (ε) for the mercury was 1.4 × 104 mol﹣1·L·cm﹣1 and for copper was 3.16 × 105 mol﹣1·L·cm﹣1 at 435 nm. The detection limits of Cu2+ and Hg2+ were 0.023 μg·mL﹣1 and 0.029 μg·mL﹣1, respectively. The calibration curve shows good linearity of 0.02 - 12.0 and 0.02 - 15.0 μg·mL﹣1 for the Cu2+ and Hg2+ determination, respectively. Proposed technique was applied to food, biological and pharmaceutical samples for the determination of Cu(II) and Hg(II).

DETERMINATION OF STABILITY CONSTANTS OF THE COORDINATION COMPOUNDS OF Au(Ⅲ)-2-MERCAPTOPYRIDINE-1-OXIDE AND METHYL DERIVATIVES——METHOD OF DUAL-WAVELENGTH CORRESPONDING SOLUTIONS

In this paper,we report the deductive formula used for the method of dual-wavelength corresponding solutions under condition of having ligand interference and the stability constants of three new coordination compounds [AuL_2]^+determined with this method.The stability of the three compounds,the necessity of controlling pH in experimental systems and the advantage of this method are discussed in detail.

Spectrophotometric Characterization of the Complex Generated in Solution for the Reaction of H[Ru(III)Cl₂(H₂EDTA)] Complex with AETS Modifier Agent

Spectrophotometric method was used to evaluate the kinetic of the complex formation from the reaction between H[Ru(III)Cl2(H2EDTA)] and the modifier agent [3-(2-aminoethyl)aminopropyl] trimethoxysilane (AEATS) (μ = 0.50 mol.dm-3 with NaCF3COO, 298.15 K), in pseudo-first order conditions. These studies showed that the reactions are successives producing several species influenced by the concentrations ratio. The electronics spectrum of all solutions showed a band in 457 nm with variable molar absorptivity (ε).

丁二烯中阻聚剂TBC测试方法的研究

通过对工业用丁二烯中微量特丁基邻苯二酚(TBC)的测定方法分光光度法和气相色谱法进行了方法原理、仪器条件、校准曲线等对比研究,试验结果表明,两种方法不存在显著性差异,气相色谱法较分光光度法具有操作简捷、准确度高、重复性好的特点。

重铬酸盐法与快速消解分光光度法测定化学需氧量的对比

文章通过对重铬酸盐法和快速消解分光光度法检出限、精密度、正确度和不同行业的实际样品的分析,以及操作过程中的试剂前处理、操作步骤、消解时间、计算公式、产生废液量及实验效率的比较,着重讨论了两种检测方法的准确性与适用性。经分析可知,两种检测方法对实际水样中COD的测定结果相近。检出限、精密度、正确度均符合检测方法的要求,结果无明显差异。快速消解分光光度法所用试剂无需前处理、仪器操作简单、消解时间短、实验结果直接读取无需计算且产生废液量少,实验效率更高,在大批量快速检测或突发检测中的适用性远高于重铬酸盐法。

分光光度法与活菌计数法测定副鸡禽杆菌菌液浓度的相关性研究

为建立一种快速测定副鸡禽杆菌菌液浓度的方法,本研究选取副鸡禽杆菌血清A、B和C型代表性菌株(CVCC254株、CVCC257株和CVCC256株),培养制备菌液,分别在450、540、600、650 nm波长测定其吸光度值(OD值),同时测定活菌计数值。回归分析两组数据,获取回归方程及标准曲线,分析回归方程的测定系数(R^(2))和标准曲线的点线离散度,确定最适测定波长。再选取不同培养时间点(10、12、14、16、18、20 h)的菌液,在最适波长下测定其OD值并代入回归方程获取活菌数,同时采用活菌计数法获取活菌计数值,将两组数据使用SPSS 17.0软件进行统计分析,进一步验证分光光度法与活菌计数法测定菌液浓度的相关性。结果显示,3株菌液在600 nm波长测定的OD值与活菌计数值之间均呈最佳的线性关系,确定其菌液浓度最适测定波长均为600 nm,其回归方程分别为y=14.302x-0.1441(R^(2)=0.9962)、y=14.464x-0.2746(R^(2)=0.995)和y=14.681x-0.01326(R^(2)=0.9989),y为活菌计数值(×10^(8)CFU/mL),x为OD600值。3株培养至衰退期前的菌液在600 nm波长测定的OD值代入回归方程计算获得的活菌数值与其活菌计数值无显著差异(P>0.05)。研究结果表明,衰退期前副鸡禽杆菌菌液的分光光度法与活菌计数法具有良好的相关性。因此,该分光光度法可用于快速测定衰退期前副鸡禽杆菌菌液浓度。

基于万古霉素高效还原Ag纳米粒子体系的分光光度法检测

万古霉素(vancomycin,Van)是临床实践中常用的抗生素,其用于预防传染病,但在环境水微量污染物检测中常常被忽略。利用溶剂热反应过程中Ag+选择性氧化Van中酚类羟基团特性,开发了一种利于分光光度法检测废水中Van的方法。探讨了反应温度和时间等对氧化还原反应的影响,建立了Van质量浓度(concentration,C)与Ag纳米粒子溶液吸光度(absorbance,A)之间的线性关系。发现C与A呈双线性关系:在线性浓度范围为1~15μg/mL时,线性关系为A_(1)=0:0017+0:012C_(1),检测限为0.5μg/mL;在20~40μg/mL时,A_(2)=0:11+0:0055C_(2)。该方法成功应用于废水中Van检测,回收率为96.0%~104.5%,废水中可能存在其他物质或颗粒,干扰了Van的测量,导致回收率计算结果超过100%。

2,2-联氮-二(3-乙基-苯并噻唑-6-磺酸)(ABTS)和N,N-二乙基对苯二胺(DPD)显色分光光度法测定水中微量高碘酸盐的对比

高碘酸盐(IO_(4)^(-),PI)因具有强氧化性和化学稳定性,被广泛应用于环境污染物的氧化降解,然而传统的PI分析方法具有操作复杂、费用高和检出限高等缺点,不适用于常规分析.因此如何快速、准确、低成本测定水中微量PI备受环境领域研究者的关注.本研究基于2,2-联氮-二(3-乙基-苯并噻唑-6-磺酸)(ABTS)和N,N-二乙基对苯二胺(DPD)与PI氧化显色的原理,建立了两种利用分光光度法测定水中低浓度PI的方法.结果表明,当pH=3.0时,ABTS与PI的反应化学计量系数接近1:2,最大吸光值在415 nm处,标准曲线线性范围为0—20μmol·L^(-1)(R^(2)>0.997),灵敏度为(6.45±0.03)×10^(4)L·mol^(-1)·cm^(-1),检出限和定量下限分别为1.1×10^(-8)mol·L^(-1)和3.3×10^(-8)mol·L^(-1);当pH=6.5时,DPD与PI的反应化学计量系数为1:2,最大吸光值在551 nm处,标准曲线线性范围为0—40μmol·L^(-1)(R^(2)>0.998),灵敏度为(2.11±0.08)×10^(4)L·mol^(-1)·cm^(-1),检出限和定量下限分别为3.7×10^(-7)mol·L^(-1)和1.23×10^(-6)mol·L^(-1).最后,研究了水中常见共存离子、腐殖酸、实际水质背景对PI测定的影响以及加标回收率,发现两种方法均具有良好的抗干扰性、稳定性和检测精度.本研究结果表明两种方法可准确、快速、低成本测定水中微量PI浓度并具有较好的应用前景.

基于四氰合镍(Ⅱ)配合物的紫外吸收快速测定废水中氰化物

基于四氰合镍(Ⅱ)配合物在267.6 nm、285.4 nm、309.0 nm有特征吸收的特性,建立了紫外光度法快速测定废水中氰化物的新方法。当底液中氢氧化钠、硫酸镍、氨浓度分别为0.04 g/L、1.0 mmol/L、0.8 mol/L时,氰化物(CN-)与二价镍快速反应生成四氰合镍(Ⅱ)配合物,A_(267.6)、A_(285.4)、A_(309.0)分别与0.16 mg/L~6 mg/L、0.46 mg/L~15 mg/L、2.7 mg/L~80 mg/L的氰化物呈现良好的线性关系(R>0.999),且三个线性范围相互重叠,因此可采用紫外光度法快速测定0.16 mg/L~80 mg/L的氰化物,检出限为0.05 mg/L。该方法能与标准方法(HJ 484-2009)中的预蒸馏程序直接对接,用于焦化废水、黄金冶炼废水中氰化物的测定,回收率在95.2%~103.3%之间,相对标准偏差小于2.6%。

扩散分光光度法测定玉米果实中的氟

本方法使用塑料密封盒进行扩散,利用氢氧化钠薄膜吸收玉米果实样品中的氟。对玉米果实样品和国家标准物质中的氟化物含量进行分析测定,最终确定0.11μg/g为检出限,相对误差RE小于5%,相对标准偏差RSD小于5%,该方法优点为简单快速,分析测定的结果准确可靠,可以用于大批量玉米果实样品中痕量氟的分析测定。

乙酰丙酮分光光度法测定啤酒中的甲醛含量

本研究重点探讨乙酰丙酮分光光度法在测定啤酒中甲醛含量方面的科学应用与实用价值。依托该技术精确、稳定的分析特性,研究展现了其在食品安全监测领域的卓越性能及应用潜力。经由严谨的实验设计与数据处理,该法在微量甲醛检测方面展示出显著优势。本研究旨在为啤酒行业提供一种科学、精确的甲醛定量分析手段,有益于提升产品安全品质,并对保障消费者利益提供技术支持。