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.

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.

Estimating Aluminum Leaching into Meat Baked with Aluminum Foil Using Gravimetric and UV-Vis Spectrophotometric Method

Baking meat by wrapping them in Aluminum (Al) foil is common in many countries. The excessive use of Al foil in baking and the disagreement about using Al foils were the motivation to do this study especially after the 2007 WHO/FDA Report. In this investigation, a gravimetric and a UV-Vis spectrophotometric method are used to estimate Aluminum (Al) leaching into meat baked by wrapping in Al foil. Three kinds of meat were used fish, cow stakes and chicken. The importance of Al exposure area was neglected by many studies. Five factors affecting Al leaching into meat are studied (baking temperature, baking time, additives, Al exposure area and weight of meat). The effect of cooking times (20, 40, 60 minutes) at 180℃ and cooking temperatures (160℃, 180℃, 200℃) at 60 minutes on the amount of Al leaching were evaluated. It was found that Al leaching into meat increased with increasing temperature, baking time, additives and Al exposure area. Moreover, Al exposure area was more effective than the weight of the meat. The Al leaching was highest in fish and lowest in chicken. Comparing the present results with the Provisional Tolerance Weekly Intake of Al approved by WHO/FDA, it shows that Al leaching into meat baked by wrapping in Al foil may add considerable doses into the diet. Continuous monitoring of Al foil used for baking meat is recommended.

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

这研究为测量海水的化学需氧量(货到付款) 学习了一个新 Spectrophotometric 方法。在这个方法， COD 用一个分光光度计被测量而不是与钠 thiosulphate 滴定。测量波长被选择是三个标准葡萄糖答案的 470 nm，和 COD (货到付款 = 0.5， 1.5 和 2.5 mgL^(-1), 分别地) 并且二件海水样品(从南方黄海和 Jiaozhou 海湾) 我们分别地使用 Spectrophotometric 方法和 titrimetric 方法的 remeasured。结果证明 Spectrophotometric 方法比 titrimetric 方法有点好。Spectrophotometric 方法的相对标准差(RSD ) 是不到 2.7% ，并且海水样品的恢复从 96.3% ～ 103.8%。另外， Spectrophotometric 方法有象快速那样的另外的优点，操作简洁，分析 automatization，等等。Thereforethe Spectrophotometric 方法能被用来与令人满意的结果测量海水的 COD。

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.

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.

Quality Control of Tramadol in Kisangani: Development, Validation, and Application of a UV-Vis Spectroscopic Method

Context: Substandard and falsified medicines are circulating in low-income countries mostly without any control. We availed a simple and not expensive UV-Vis spectroscopic method to evaluate the quality of tramadol in Kisangani before and during the Covid-19 period. Methods: For the analytical quantitative method, an experimental design was applied to set up the optimal levels of the selected factors, namely, pH of dissolution medium, type of cuvette, and wavelength. Taking into account the capsule pharmaceutical formulation within 80 - 120 μg·mL-1 concentration range, we analyzed 89 tramadol samples from pharmacies and hospitals of the six Kisangani municipalities. Results: pH showed a significant effect on absorbance, whereas quartz cuvette and wavelength did not. A typical 100 μg·mL-1 tramadol solution gave an absorbance of 0.64 at 272 nm. Validation highlighted a matrix effect observed with a 6% bias. A correction factor of 0.9372 allowed to improve the accuracy profile, which were then totally included within the 10% acceptance limits. Quality control revealed that 25 samples out of 89 were not compliant in terms of manufacturing license, registration status in DRC and content as well. Conclusion: This study showed that the strengthening of analytical strategy in Kisangani is a need.

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).

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。

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。

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。

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%。

碱性高锰酸钾三波长分光光度法测定维生素B6的含量

基于在氢氧化钠介质中高锰酸钾与维生素B6可发生氧化还原反应产生绿色的锰酸钾,显色产物最大吸收波长分别位于420 nm和600 nm,同时使高锰酸钾褪色,褪色波长位于525 nm,提出了高锰酸钾三波长可见分光光度测定维生素B6含量的新方法。在以上三波长下,维生素B6浓度的线性范围分别为2~14 mg·L^(-1)、2~14 mg·L^(-1)和2~18 mg·L^(-1)。本研究所拟方法成功地测定了维生素B6原料药、片剂和注射液的含量,结果与紫外光度法所测一致。

全自动流动注射仪测定水中的阴离子表面活性剂

选用全自动流动注射分析仪测定水中阴离子表面活性剂的含量,实验结果表明:在0~2 mg/L范围内,体系信号响应值(峰面积)与水中阴离子表面活性剂的含量具有较好的线性(相关系数r值为0.9996),检出限为0.003 mg/L,精密度和正确度较高,有证标准物质相对误差低于10%,样品加标回收率良好。该方法分析快速、操作简单、环境友好,可用于水中阴离子表面活性剂的测定。

两种氨氮在线分析方法的质控结果及影响因素

选用2023年泸州市4个水质自动站的氨氮在线分析仪质控数据,分析了水杨酸分光光度法和氨气敏电极法两种方法的准确性和稳定性以及影响因素。结果表明,水杨酸分光光度法的准确性和稳定性较好,但抗浊度干扰能力较弱,应严格执行水样预处理措施,加强仪器日常清洗维护;氨气敏电极法的线性范围和抗浊度干扰能力较好,但受半透膜的质量、电解质的浓度、加热温度的波动及电极本身的老化程度的影响,系统误差较大,应定期对仪器检查并及时更换耗材。