N,N-二甲基苯胺-对氨基二甲替苯胺氧化偶联反应催化分光光度法测定铬(Ⅵ)

在pH=3.2乙酸-乙酸钠缓冲介质中,研究了铬(Ⅵ)催化过氧化氢氧化对-氨基二甲替苯胺盐酸盐和N,N-二甲基苯胺的氧化偶联反应及其机理,建立了催化光度法测定痕量铬(Ⅵ)的新方法.该方法线性范围为0～0.12 mg/L;检出限为1.0×10-7 g/L;相对标准偏差为0.12%,直接用于水中铬(Ⅵ)的测定,结果满意.     

Spectrophotometric methods for the determination of labetalol hydrochloride in pure and dosage forms

Simple and sensitive Spectrophotometric methods for the determination of labetalol hydrochloride are described. The first two are based on the oxidative coupling reaction of labetalol hydrochloride withp-N,N-dimethyl-phenylenediamine dihydrochloride (method A, _max 685 nm) and 3-methyl-2-benzothiazolinone hydrazone hydrochloride (method B, _max 545 nm) in the presence of sodium hypochlorite and eerie ammonium sulphate as oxidants, respectively. The third depends on the formation of an ion-association complex of labetalol hydrochloride with suprachen violet 3B at pH 1.3, which is extracted into chloroform (method C, _max 565 nm). The methods obey Beer's law and the precision and accuracy of the methods were checked against the B.P. reference method and the relative standard deviations were in the range 0.35–0.52%. These methods are applied to the determination of labetalol in dosage forms.     

Development and Validation of Spectrophotometric Methods for the Determination of Cefetamet in Pharmaceutical Dosage Forms

Two simple and sensitive spectrophotometric methods for the determination of cefetamet in either pure form or in its pharmaceutical formulations were described. The method Ⅰ is based on the interaction of 3-methylbenzo[d]- thiazolin-2-one hydrazone （MBTH） with cefetamet in the presence of freshly prepared ferric chloride in a neutral medium. The resulting blue colored product has λmax at 628 nm. The method Ⅱ describes the reduction of ferric ion by the drug to ferrous ion followed by a complex formation reaction with 1,10-phenanthroline （1,10-phen） to form an orange red colored chromogen exhibiting 2max at 510 nm. The products are stable for more than 5 and 8 h respectively. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed methods. Both methods are highly reproducible and have been applied to a wide variety of pharmaceutical preparations and the results are comparable with those of official methods.     

Voltammetric and Spectrophotometric Determination of Nizatidi ne in Pharmaceutical Formulations

 Two methods are described for quantitative determination of nizatidine. The first is a cathodic stripping voltammetric method which is based on the accumulation of the compound at the hanging mercury drop electrode. The adsorptive stripping response was evaluated with respect of accumulation time, potential, concentration, pH and other variables. A linear calibration graph was obtained over the range 3.0×10⁻⁸–1.0×10⁻⁶ M with a detection limit 3.0×10⁻⁸ M after a 20s accumulation time at −0.2 V accumulation potential. On the other hand, it was found that the detection limit could be lowered to 1.0×10⁻⁸ M after 180s accumulation time at −0.2 V accumulation potential. The relative standard deviation was in the range 1.2−2.0% for six measurements. The tolerance amounts of the common excipients have also been reported. The second is a spectrophotometric method which is based on the formation and extraction of the ion-pair complex formed between nizatidine and either bromocresol green or bromothymol blue. The extracted colored ion-pair complexes absorb at 416 nm. The effect of different factors such as: type of organic solvent, pH, reagent concentration, number of extraction times, shaking time, temperature and the tolerance amount of the common excipients have been reported. The calibration graph was linear in the range 6.0×10⁻⁷–1.8×10⁻⁵ M with a detection limit of 6.0×10⁻⁷ M and molar absorptivity of 2.1×10⁴ lċmol⁻¹ċcm⁻¹ when using bromocresol green, while the calibration graph was linear in the range 3.0×10⁻⁷–1.1×10⁻⁵ M with a detection limit of 3.0×10⁻⁷ M and molar absorptivity of 3.2×10⁴ lċmol⁻¹ċcm⁻¹ when using bromothymol blue. The spectrophotometric methods offer alternative methods with reasonable sensitivity, selectivity and accuracy with relative standard deviation in the range 2.1−6.0% and 1.2−4.7% (for six measurements) when using bromothymol blue and bromocresol green, respectively. The proposed two methods were applied for the determination of nizatidine in commercially available dosage forms. A comparison between the voltammetric and the extraction-spectrophotometric methods was also reported. Received April 19, 1999. Revision August 30, 1999.     

Determination of Maneb Residues,in Tomatoes,by Spectrophotometric Method of Acid Hydrolysis,Through Multivariate Calibration

ABSTRACT

In this work, a chemometric method was applied through multivariate calibration, PLS (Partial Least Squares), to establish the analysis of ethylenebisdithiocarbamates residues in tomatoes samples by the hydrolysis method. The algorithm used to implement the PLS in the MatLab environment on IBM-compatible personal computer, was obtained from chemometrics package PLS_ToolBox. In samples with elevated levels of Maneb the univariate calibration showed similar results to the multivariate calibration. However, in samples with lower levels of residues increases occurred in the order of 15 to 47% in the levels detected by the multivariate calibration. In addition, there was a significant decrease in the standard deviations, in relation to those obtained, when the method of univariate calibration was used. The levels of contamination by Maneb found in tomatoes samples were below the maximum established by the Brazilian legislation.     

Determination of acetaldehyde in saliva by gas-diffusion flow injection analysis

The consumption of ethanol is known to increase the likelihood of oral cancer. In addition, there has been a growing concern about possible association between long term use of ethanol-containing mouthwashes and oral cancer. Acetaldehyde, known to be a carcinogen, is the first metabolite of ethanol and it can be produced in the oral cavity after consumption or exposure to ethanol. This paper reports on the development of a gas-diffusion flow injection method for the online determination of salivary acetaldehyde by its colour reaction with 3-methyl-2-benzothiazolinone hydrazone (MBTH) and ferric chloride. Acetaldehyde samples and standards (80 μL) were injected into the donor stream containing NaCl from which acetaldehyde diffused through the hydrophobic Teflon membrane of the gas-diffusion cell into the acceptor stream containing the two reagents mentioned above. The resultant intense green coloured dye was monitored spectrophotometrically at 600 nm. Under the optimum working conditions the method is characterized by a sampling rate of 9 h⁻¹, a linear calibration range of 0.5–15 mg L⁻¹ (absorbance = 5.40 × 10⁻² [acetaldehyde, mg L⁻¹], R² = 0.998), a relative standard deviation (RSD) of 1.90% (n = 10, acetaldehyde concentration of 2.5 mg L⁻¹), and a limit of detection (LOD) of 12.3 μg L⁻¹. The LOD and sampling rate of the proposed method are superior to those of the conventional gas chromatographic (GC) method (LOD = 93.0 μg L⁻¹ and sampling rate = 4 h⁻¹). The reliability of the proposed method was illustrated by the fact that spiked with acetaldehyde saliva samples yielded excellent recoveries (96.6–101.9%), comparable to those obtained by GC (96.4–102.3%) and there was no statistically significant difference at the 95% confidence level between the two methods when non-spiked saliva samples were analysed.     

Spectrophotometric determination of clozapine in pharmaceuticals

New Spectrophotometric methods for the assay of clozapine (CZP) in pure and dosage forms are described. Method A is based on the oxidative coupling reaction of CZP with 3-methyl-2-benzothiazolinone hydrazone hydrochloride (MBTH) in the presence of ceric ammonium sulphate to form a coloured species (_max 570 nm). Method B is also based on the oxidative coupling reaction of CZP withP-,N,N-dimethylpheny-lenediamine dihydrochloride (DMPD) in the presence of sodium hypochlorite to form a coloured species (_max 690 nm). Method C is based on the formation of coloured charge-transfer complex between CZP and chloranilic acid (_max 540 nm). Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 2–25, 10–120 and 15–300 g/ml for methods A, B and C, respectively. The validity of the proposed methods was tested by analysing pharmaceutical dosage forms containing CZP and the relative standard deviation values were within 1.0%.     

2,6-二碘-4-硝基偶氮胂分光光度法测定微量铋

研究了显色剂 2 (2 胂酸基苯偶氮 ) 7 (2 ,6 二碘 4 硝基苯偶氮 ) 1,8 二羟基 3,6 萘二磺酸与铋的显色反应。在 0 .6mol LHClO4 介质中 ,试剂与铋生成的深色络合物 ,最大吸收波长 6 33nm ,摩尔吸光系数为1 2 0× 10 5L·mol- 1 ·cm- 1 ,灵敏度高 ,常见的金属离子允许量大 ,选择性好。Bi 0～ 0 .8mg L范围内符合比耳定律 ,以NaCl褪色试样空白为参比 ,分光光度法测定纯铜及铜合金中的微量铋 ,方法简便 ,结果可靠     

二溴羟基苯基荧光酮－溴化十六烷基三甲铵分光光度法测定微量铑

本文提出了分光光度测定铑的新方法。在ｐＨ＝５．８～６．７的磷酸盐缓冲介质中，铑与二溴羟基苯基荧光酮－溴化十六烷基三甲铵反应生成的配合物最大吸收峰位于６１０ｎｍ，对比度为８０ｎｍ，表观摩尔吸光系数为１．２９×１０￣５Ｌ·ｍｏｌ￣（－１）·ｃｍ￣（－１）。铑浓度在０～５．０μｇ／１０ｍＬ范围内符合比尔定律。经离子交换分离消除贱金属等的干扰后，可用于二次合金中微量铑的测定，结果满意。     

Determination of protonation- and metal complex stability constants for a chelating monomer and its immobilized in polymer resin

An improved method is described for the calculation of complex stability constants for metal–ligand complexes considering ligands immobilized in resin phase. The applicability of it has been proved for N′-benzylethylene diamine N,N,N′-triacetic acid monomer (BEDTA) and for the ion exchange resin developed in the authors laboratory immobilizing this with styrene divinyl benzene. Calcium and magnesium metal ion complexes were investigated. Electrochemical and flame photometric measurements were used to collect equilibrium concentration data. The procedure worked out included the measurement of the quantity of resin bound water. Using these and the other experimentally gathered values and the improved way of calculation metal ligand complex stability constants were determined in aqueous media. Ion exchange chromatographic separation of calcium and magnesium ions was performed with a resin containing column for separation and optimized eluent.     

微波消解和固相萃取光度法测定氰化渣中痕量钯

根据 2_(2_喹啉偶氮 )_5_二甲氨基苯甲酸 (QADMAB)与钯的显色反应及C18固相萃取小柱对显色络合物的固相萃取 ,并结合微波消解样品 ,建立了一种测定氰化渣中痕量钯的方法。即在pH为 3 5的HAc_NaAc缓冲介质中 ,溴化十六烷基三甲胺 (CTMAB)存在下 ,QADMAB与钯反应生成 2 1稳定络合物 ,该络合物可被C18小柱萃取富集 ,富集的络合物用乙醇洗脱后用光度法测定 ,在乙醇介质中体系λmax=63 0nm ,ε=1 2 0× 1 0 5L·mol-1·cm-1。钯含量在 0 0 1～ 1 5mg L内符合比尔定律 ,方法用于氰化渣中钯含量的测定 ,结果令人满意。     

A Facile Procedure for the oxidative Coupling of 2-Naphthol and 2-Naphthalenethiol in Solid State

l,lLBi-2-naPhtholshavebeenwidelyappliedasimportantchiralauxiliariesandligands..tinorganicchemistry'.TheconversionofthiolstothecorrespondingdisulphidesisofintCrestbothfromabiological'andpracticalpointofview.ForthesynthesisofbinaPhtholsanddisulphides,theoxidativecouplingofnaphtholsandthiolshaslongbeenarecognisedmethodofchoice.Variousoxidantscanbringaboutthecouplingofnaphthols'andthiols4insolution,buttheyoftenleadtolowyieldsorsufferfromdisadvantagesduetotheinsolubilityofoxidant,naPhthoIandthiol…     

Aerobic Oxidative Coupling of Resveratrol and its Analogues by Visible Light Using Mesoporous Graphitic Carbon Nitride (mpg‐C3N4) as a Bioinspired Catalyst

The first aerobic oxidative coupling of resveratrol and its analogues by mesoporous graphitic carbon nitride as a bioinspired catalyst with visible light has been developed. With this method, δ‐viniferin and its analogues were synthesized in moderate to high yield. The metal‐free conditions, visible‐light irradiation, and the ideal oxidant, molecular oxygen, make this coupling reaction environmental friendly and practical.     

藉聚2-丙烯胺缩-3-(4-甲酰基苯偶氮)-4,5-二羟基-2,7-萘二磺酸分光光度法测定生物体液、食品和饮品中的镁

聚2-丙烯胺缩3－（4-甲酰基苯偶氮）-4，5-二羟基-2，7-萘二磺酸（PA-FPNS）在pH11．5的磷酸盐介质中．与镁（Ⅱ）形成一蓝色络合物，其最大吸收位于604nm，表观摩尔吸光系数ε=5．7×104L·mol-1·cm-1，线性范围为0．01～0．35mg／L，至少稳定12h。考察了30多种共存离子的影响，在所测样品中它们不干扰，无需掩蔽或分离即可直接测得其中的镁。     

高效液相色谱法同时测定土壤中毒死蜱残留及其有毒代谢物3,5,6-TCP

通过对色谱分离条件优化、提取体系建立和固相色谱小柱筛选,建立了用弗罗里硅土固相萃取小柱净化高效液相色谱法同时测定土壤中毒死蜱农药残留及其有毒代谢物3,5,6-TCP.方法加标回收率在59％～87％之间,检测限为0.0005～0.03 μg/g,日内回收率标准偏差RSD≤4.3％,日间回收率标准偏差RSD≤4.9％,方法...     

The Colour Reaction of Mercury with 1-(6-Ethoxyl-2-benzothiazolyl)-3-(4-Nitrophenyl)-Triazene and its Application

Thetfiazenereagentswereusedforthedeterminationofcadmium,mercuryandzinc.Wehavesynthesizedthetriazenereagentscontainingheterocyclicring'-'.Recently,annewreagentEtOBTNPTwassynthesized.Becausethereagentcontainsanelectronpropellinggroup(-OCH,CH,)inoneendandanelectronwithdrawinggroup(-NO,)intheotherend,sotheconjugatesystemisenlargedinthemolecularstructure,thisresultinginadvantageofmigrationofelectroniccloud.ThesensitivityofthecolourreactionofEtOBTNPTwithmercuryissuperiortoothertfiazenereage…     

Kinetic Study of Peroxidase‐Catalyzed Coupling of Benzene‐1,4‐diamine and N‐(2‐Aminoethyl)naphthalen‐1‐amine: Development of Micromolar Hydrogen Peroxide Reaction System

A novel chromogenic method to measure the peroxidase activity using para‐phenylenediamine dihydrochloride (=benzene‐1,4‐diamine hydrochloride; PPDD) and N‐(1‐naphthyl)ethylenediamine dihydrochloride (=N‐(2‐aminoethyl)naphthalen‐1‐amine; NEDA) is presented. The PPDD entraps the free radical and gets oxidized to electrophilic diimine, which couples with NEDA to give an intense red‐colored chromogenic species with maximum absorbance at 490 nm. This assay was adopted for the quantification of H₂O₂ between 20 and 160 μM . Catalytic efficiency and catalytic power of the commercial peroxidase were found to be 4.47×10⁴ M ^?1 min^?1 and 3.38×10^?4 min^?1, respectively. The catalytic constant (k_cat) and specificity constant (k_cat/K_m) at saturated concentration of the co‐substrates were 0.0245×10³ min^?1 and 0.0445 μM ^?1 min^?1, respectively. The chromogenic coupling reaction has a minimum interference from the reducing substances such as ascorbic acid, L ‐cystein, citric acid, and oxalic acid. The method being simple, rapid, precise, and sensitive, its applicability has been tested in the crude vegetable extracts that showed peroxidase activity.     

新显色剂二溴羟基苯基荧光酮的氧化显色反应及双波长分光光度法测定废水中的铬

本文利用光度法和电位滴定法探讨了铬(Ⅵ)与二溴羟基苯基荧光酮(DBHPF)的显色反应,发现在酸性介质中为DBHPF的氧化显色反应。DBHPF曾成功地应用于钛钼钨锡等元素的测定。本文利用Cr(Ⅵ)与DBHPF的氧化显色反应,进一步研究了双波长分光光度法测定Cr(Ⅵ)的条件。应用拟定的新方法测定了电镀废水中的铬(Ⅵ)和总铬量,结果满意。     

Studies on Simultaneous Fluorescence-Spectrophotometric Determination of Ultratrace Niobium(V), Tantalum(V), and Zirconium(IV) Using Partial Least-Squares Algorithm

In the presence of cetyltrimethylammonium bromide, a cationic surfactant, highly sensitive molecular fluorescence reactions occur between Nb(V), Ta(V), and Zr(IV) ions and morin (3, 5, 7, 2′, 4′-pentahydroxyflavone) in acidic medium to form stable ternary micellar complexes. Their λ_ex(max)/λ_em(max)values are 421.0/492.2, 416.2/489.6, and 424.2/507.8 nm, respectively, and their λ_em(max)values are 490.5, 488.6, and 507.2 nm, respectively, at the same fixed λ_exof 420.5 nm, indicating their seriously overlapping fluorescence excitation spectra and fluorescence emission spectra. The linear ranges of their regression calibration curves are 0 to 0.20, 0 to 0.50, and 0 to 0.20 mg/liter, respectively, with 0.5 ng/ml for all of sensitivities. The simultaneous molecular fluorescence-spectrophotometric determination of ultratrace or trace Nb(V), Ta(V), and Zr(IV) without separation was made using a partial least-squares (PLS) algorithm and other algorithms. The optimum PLS computation conditions are wavelength point number of 25 and corresponding wavelength range from 450 to 550 nm oriented from λ_em500 nm to two sides at combined intervals of 2.5 and 5.0 nm at a fixed λ_exof 420.5 nm with an optimum calibration sample number of 14 and respective optimum abstracted factor numbers of 6, 4, and 3. With respect to both accuracy and precision of the obtained results, the PLS algorithm is superior to the ordinary least-squares algorithm.