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.

Catalytic spectrophotometric determination of trace selenium in microemulsion after separation and enrichment by SDG

A new catalytic spectrophotometric method was developed for the determination of trace amount of Se（Ⅳ） in microemulsion medium. The method is based on the catalytic effect of traces of Se（Ⅳ） on the oxidation of 2＇,4＇-dichlorophenylfluomne （p-CPF） by potassium bromate with HNO3 as an activator in the presence of nonionic microemulsion medium. Under optimum conditions, the calibration graph is linear in the range of 0.4-15 μg·L^-1 of Se（Ⅳ） at 480 nm. The detection limit achieved is 9.86 × 10^-10μg·L^-1. Samples were dissolved and the obtained trace Se（Ⅳ） was separated and enriched by sulphydryl dextrane gel （SDG）. The method has been applied for determination of trace selenium with satisfactory results.

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.

Indirect Spectrophotometric Determination of Sulphide with the Complex of Cd(Ⅱ)-5-Br-PADAP-CPB

By the use of CPB, Cd(Ⅲ) forms a highly sensitive complex with 5-Br-PADAP in aqueous solution, molar absorptivity εis 1. 21 ×105 1. mol-1. cm-1.Trace amount of sulphide can be determined from its effect on the complex of Cd (Ⅲ)-5-Br-PADAP-CPB, sulphide in the range 0~3. 2 ×10-6mol dm-3 causes a decrease in absorption, that is a linear function of the concentration, For 13ng cm-3 sulphide, common metal ions such as Na+, K+, Ca2+, Mg2+, Al3+ and anions such as CO (24μg cm-3). S2O (22μg cm-3). PO (20μg cm-3) etc. do not interfere. A method for the indirect determination of sulphide in beer and in dustrial waste water with good selectivity and accuracy is described.

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.

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.

A Novel Spectrophotometric Method for Determination of Gabapentin in Pharmaceutical Formulations Using 2,5-Dihydroxybenzaldehyde

A highly simple, rapid, sensitive and selective method is developed for spectrophotometric determination of gabapentin in pure form as well as in pharmaceutical formulations. The method is based on the formation of a yellow Schiff base derived from the condensation of gabapentin drug (1-amino methyl) cyclo hexane acetic acid and 2,5-dihydroxybenzaldehyde (DHBA) exhibiting a maximum absorbance at 445 nm. The composition, molar absorptivity and effect of different excipient have been determined spectrophotometrically. Under optimized experimental conditions, Beer’s law is obeyed in the concentration range 2.57 - 37.25 μg/ml. The method is validated with respect to accuracy, precision, limit of detection and limit of quantification. The Sandell sensitivity, correlation coefficient and regression equation are calculated. The equilibrium constant and free energy change using Benesi-Hildebrand plot are also determined. The Schiff base derived from condensation of gabapentin with DHBA is also synthesized and characterized. The condensation reaction mechanism has been proposed.

New simple spectrophotometric method for determination of the binary mixtures(atorvastatin calcium and ezetimibe;candesartan cilexetil and hydrochlorothiazide) in tablets

A new simple spectrophotometric method was developed for the determination of binary mixtures without prior separation.The method is based on the generation of ratio spectra of compound X by using a standard spectrum of compound Y as a divisor.The peak to trough amplitudes between two selected wavelengths in the ratio spectra are proportional to concentration of X without interference from Y.The method was demonstrated by determination of two drug combinations.The first consists of the two antihyperlipidemics：atorvastatin calcium（ATV） and ezetimibe（EZE）,and the second comprises the antihypertensives：candesartan cilexetil（CAN） and hydrochlorothiazide（HCT）.For mixture 1,ATV was determined using 10 μg/mL EZE as the divisor to generate the ratio spectra,and the peak to trough amplitudes between 231 and 276 nm were plotted against ATV concentration.Similarly,by using 10 μg/mL ATV as divisor,the peak to trough amplitudes between 231 and 276 nm were found proportional to EZE concentration.Calibration curves were linear in the range 2.5-40 mg/mL for both drugs.For mixture 2,divisor concentration was 7.5 μg/mL for both drugs.CAN was determined using its peak to trough amplitudes at 251 and 277 nm,while HCT was estimated using the amplitudes between 251 and 276 nm.The measured amplitudes were linearly correlated to concentration in the ranges 2.5-50 and 1-30 μg/mL for CAN and HCT,respectively.The proposed spectrophotometric method was validated and successfully applied for the assay of both drug combinations in several laboratory-prepared mixtures and commercial tablets.

Solid-liquid Extraction Spectrophotometric Determination of Copper with 2,9-dimethyl-1,10-phenanthroline

Solid liquid extraction of copper ion (I) with 2, 9-dimethyl-1, 10-phenanthroline (neo-cuproine, DMP) into molten naphthalene followed by chloroform spectrophotometric determination has been studied experimentally. The ternary complex Cu(I)-DMP-ClO4 was extracted quantitatively into molten naphthalene in the range of pH from 5 to 6 at 85 C-. Absorbance was spectrophotometrically determined at 459 nm against the reagent blank after the solid naphthalene layer was anhydrously dissolved in chloroform. Beer's law is obeyed over a concentration range of 0.5-70 mug/mL. The molar absorptivity and Sandell's sensitivity are 1.0x10(4) L/(mol(.)cm) and 0.0099 mug(.)cm(2) respectively. In addition, the various conditions on determination and the interference of coexisted ions were discussed, and the method was applied to the determination of copper ion both in tea samples and cadmium sulfate reagents. The results are in good agreement with those obtained by ICP AES method.

Azeotropic mixture used for development and validation of Lornoxicam in bulk and its tablet dosage form by spectrophotometric method

A novel,safe,economic and sensitive method of spectrophotometric estimation has been developed using Azeoptropic mixture (water∶methanol:60∶40,v/v) for the quantitative determination of Lornoxicam,a practically water-insoluble drug.Hence,Lornoxicam stock solution was prepared in Azeoptropic mixture.Lornoxicam showed maximum absorbance at 383 nm.Beer's law was obeyed in the concentration range 4-24 μg/mL with regression coefficient of 0.999.The method was validated in terms of linearity (R2=0.999),precision (CV for intra-day and inter-day was 0.28 0.68 and 0.12-0.92,respectively),accuracy (98.03-100.59％ w/w) and specificity.This method is simple,precise,accurate,sensitive and reproducible and can be used for the routine quality control testing of the marketed formulations.

β－CORRECTION SPECTROPHOTOMETRIC DETERMINATION OF ALUMINIUM， USING THE AL（Ⅲ）－PF－OP REACTION

Aluminium has been determined by β-correction spectrophotometer with phenylfluorone (PF)and a non-ionic surfactant, emulsifying OP in PH 8 ammoniacal buffer solution. β-correction spectrophotometric method can eliminate completely the effect of excess PF to increase the analytical sensitivity and decrease error. The results have Shown that Beer's law was obeyed over the concentration range 0-15μg Al (Ⅲ)/25ml and the relative standard deviation was less than 3.3%.

Spectrophotometric Simultaneous Determination of Zinc(II), Manganese(II) and Iron(II) in Pharmaceutical Preparations Using OSC-PLS

This work reports the spectrophotometric simultaneous determination of zinc（Ⅱ）, manganese（Ⅱ） and iron（Ⅱ） in pharmaceutical preparation, using orthogonal signal correctionpartial least squares （OSC-PLS）. All the factors affecting on the sensitivity were optimized and the linear dynamic range for determination of these metals was found. The PLS modeling was used for the multivariate calibration of the spectrophotometric data. The OSC was used for preprocessing of data matrices and the prediction results of model. The experimental calibration matrix was designed by measuring the absorbance over the range 450-570 nm for 21 samples of 0.05-1.05, 0.10-1.10 and 0.05-1.05μg·mL^-1 of zinc（Ⅱ）, manganese（Ⅱ） and iron（Ⅱ）, respectively. The RMSEP for zinc（Ⅱ）, manganese（Ⅱ） and iron（Ⅱ） using OSC-PLS were 0.0164, 0.0132, 0.0146, respectively. The proposed method was successfully applied the determination of zinc（Ⅱ）, manganese（Ⅱ） and iron（Ⅱ） in pharmaceutical preparations.

SPECTROPHOTOMETRIC ANALYSIS OF MIXTURES OF TRACE METAL BY DOUBLE-SYSTEM AND MULTIVARIATE CALIRRATION

In this paper,a new method for simultaneous spectrophotometric analysis of multi- component with double-system was developed.The multivariate calibration method,principal component analysis-partial least squares(PCA-PLS),was described and applied to the processing of measurement data.A demonstration,simultaneous determination of cobalt,nickel,copper,zinc and iron with double-system(5-Br-PADAP and PAR as chromogenic chelate reagents,respectively) was given.The results showed that the method with douhle-system gave better precision than those with single system and MLR(in this paper,AKC method was selected)did not give satis- fied precision in any situation.

Spectrophotometric Determination of Trace Chromium(VI) in Mass Chromium(III)

The method for the sepration and determination of trace Cr(VI) exiting in mass Cr(III) has been researched. The method is highly sensitive and less interference, but is simple and useful for analysis trace Cr(VI).

SPECTROPHOTOMETRIC STUDY OF DDQ CHARGE-TRANSFER COMPLEXES WITH 1,10-PHENANTHROLINE AND ITS DERIVATIVES

1,10-phenanthroline and its derivatives can form charge-transfer complexes with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone(DDQ).The absorption spectra and conditions of complex formation,such as the reaction time,the quantity of DDQ, and the solvents, have been studied.After the HMO calculation of phenanthrolines,the molar absorptivities were found to depend on the substituents on the phenanthroline rings.

Study on the Spectrophotometric Determination of Rare Earths with a New Chromogenic Reagent Dibromo-p-methyl-chlorosulfonazo(DBMCSA)

A new method for the determination of cerium subgroup rare earths was studied and reported ill this paper. It was found that cerium subgroup rare earth elements react with DBMCSA in 0.6 mol/L hydrochloric acid medium to form stable blue complexes. The absorbances of equal amounts of cerium subgroup rare earths are close to each other at their maximum adsorptive wavelength (641 nm). Beer's law is obeyed for 0-20 mu g of I ars earths in 25 mi of solution. The method has been applied to the determination of the total amount of cerium subgroup rare earths in steel and cast iron samples with satisfactory results.

SPECTROPHOTOMETRIC STUDY OF BIMETALLIC TERNARY COMPLEX OF LANTHANUM——COPPER WITH ALIZARIN FLUORINE BLUE

The bimetallic ternary complex formation in the aqueous solution of La and Cu with alizarin fluorine blue (AFB) was studied by spectrophotometry.The ternary complex LaCu3(AFB)3 has maximum light absorption at 550nm.The colour reaction selectivity is fairly good and the method can be applied to the direct photometric determination of copper in lanthanum or some pure metals.A new mathematical approach to the treatment of spectrophotometric data for differentiation between mononuclear and polynuclear in solution is presented.The improvable fixed logarithm method is for complexes of the type MmBn(m=n) or MmBn(m=n).We report that La(Ⅲ) combines with AFB at pH 4.5 to form a single complex,withm=n=2,La2(AFB)2.

Liquid waveguide capillary cell for the spectrophotometric determination of nanomolar iodate concentrations in marine waters

A new spectrophotometric method based on a liquid waveguide capillary cell for an enhanced detection was developed to measure nanomolar iodate concentrations.This method has a detection limit and precision of 1-2 nmol/L,which is equivalent to 10%that of conventional methods,a recovery of 97.7%-104.0%,and a working range of 10-120 nmol/L.Water samples were collected from three estuaries and one coastal ocean for testing,and the proposed technique detected as low as 11 nmol/L and 18 nmol/L iodate in these samples.This newly developed method is helpful in understanding the biogeochemical cycle of iodine in nature.

STUDY AND APPLICATION OF SPECTROPHOTOMETRIC DETERMINATION OF MICRO AMOUNTS OF BISMUTH WITH MESO—TETRAKIS—(4—N—TRIMETHYL AMMONIUMPHENYL)PORPHINE

A new highly sensitive spectrophotometric method has been developed for the determination of micro amounts of bismuth (Ⅲ), based on the formation of Bi (Ⅲ)—meso—tetrakis—(4—N—trimethylammonium phenyl) porphine [T (4TMAP) P] complex. In the presence of Cd (Ⅱ), Bi(Ⅲ) reacts almost instantaneously with T (4TMAP)P in a 0. 6 mol/l NaAc—HAC buffer (PH5.8) at room temperature. The composition of the complex is T(4TMAP)P: Bi=1:1. The absorbance complex obeys Beer's law over the Bi(Ⅲ) concentration range 0.1—1.4 μg/ml. The linear relative coefficient γ is 0.9998. The apparent molar absorptivity was 1.75×10~5 1. mol^(-1). cm^(-1) at 463nm. The relative standard deviation of the method is 1.50％ for Bi(Ⅲ) 7ug/10ml (10 determinations). The interference of foreign ions has been examined. This simple and rapid method can be applied to the assay of Bi(Ⅲ) in some tablets directly.

SYNTHESIS OF MESO-TETRA (4-METHOXYPHENYL-3-SULFONATE) PORPHINE AND SPECTROPHOTOMETRIC STUDY OF COLOUR REACTION WITH COPPER

In this paper meso-tetra (4-methoxyphenyl-3-sulpho) Porphine (TMPPS_4) was synthesized and its colour reaction with copper was studied. It was found to be a highly sensitive and highly selective reagent for the direct spectrophotometric determination of ultramicro amount of copper. The apparent molar absorptivity of the complex is 3.72×10~5L/mol·cm. Beer's law is obeyed for Cu(Ⅱ)of 0～1.4μg/10ml. The interference of 21 different ions and 6 kinds of salts were examined and found to be minimal. The complex formation of Cu(Ⅱ) with TMPPS_4 is generally slow at room temperature<<25℃>, but the reaction can be accelerated in the presence of NH_2OH·>HCl and completed within 5min. At PH 5.2 the Soret band of TMPPS_4 overlaps almost completetely with that of the complex. Therefore, the complex formation is taken to completion at this PH. Then the Soret band of TMPPS_4 shifted away from that of the complex by acidification. This simple and rapid method has been successfully applied to the direct determination of Cu in Al-alloys, industrial water, foods and human hair.