A New Absorbance Ratio Derivative Spectrophotometry for the Simultaneous Determination of a Binary Mixture Containing Phenol and Resorcin

It is the most important problem of spectrophotometric analysis to determine two or more components in the same sample simultaneously without previous separation. In this respect, the absorbance derivative spectrophotometry is an analytical technique of great utility and offers greater selectivity than normal spectrophotometry. Recently, Salinas et al developed the absorbance ratio derivative spectra. The absorption spectrum of the mixture is divided by the absorption spectrum of a standard solution of one of the two or more components, and the first derivative of the ratio spectrum is obtained. The concentration of active component is then determined from a calibration graph obtained by measuring the amplitude at point corresponding to the minimum or maximum wavelength. In this way, the sensitivity of method is greatest.     

Non-Extractive Simultaneous Spectrophotometric Determination of Trace Quantities of Palladium(II) and Tungsten(VI)

A second order derivative spectrophotometric method has been developed for the simultaneous determination of Palladium(II) and Tungsten(VI) using 3,4-dihydroxybenzaldehyde isonicotinoylhydrazone (3,4-DHBINH) as a new complexing agent. The Pd(II) reacts with 3,4-DHBINH in the pH range from 3 to 7 to form green colored solution. The absorbance calibration curves were constructed for palladium(II) at 362 nm (0.53～6.40 μg/ml) and tungsten(VI) at 374 nm (0.92～11.40 μg/ml). The metal ions interfere with each other in determination of zero order as well as the first order spectrophotometry. The optimum condition for maximum color development and other analytical parameters were evaluated. The method was applied successfully for the determination of palladium in hydrogenation catalyst and tungsten in industrial waste water samples.     

Comparison of purge and trap GC/MS and spectrophotometry for monitoring petroleum hydrocarbon degradation in oilfield produced waters

Results of using a field spectrophotometer and its appropriate protocols as a surrogate method for an oilfield produced water treatment process is presented. Methylene chloride extractions of the produced water before and after treatment maintained a yellow color pigment that was directly proportional to the hydrocarbon concentration. From this, an absorption spectrum and standard curve were developed. A resultant linear plot of the standard curve indicated that there is an excellent correlation (r²=0.9847) between the varying concentrations and the associated absorbance values at a wavelength of 400 nm. Total n-alkane concentration comparisons between the laboratory GC/MS analysis and the spectrophotometry analysis generated data of similar accuracy and precision at concentrations ranging from 1 to 137 mg/l (alpha=0.05). Linear comparisons between GC/MS and spectrophotometric coefficients were near unity, with the constant being near zero, with a correlation coefficient (r²) of 0.99. Based on this study, spectrophotometry is a complimentary method to GC/MS for determining total n-alkane concentrations in oilfield produced water samples.     

Simultaneous determination of tin, germanium and molybdenum by diode array detection-flow injection analysis with partial least squares calibration model

Simultaneous determination of tin, germanium and molybdenum in food samples has been established by flow injection-charge coupled detector (CCD) diode array detection spectrophotometry with partial least squares (PLS) algorithm. The method was based on the chromogenic reaction of metal ions and salicylflurone in the presence of cetyltrimethyl ammonium bromide. The overlapping spectra of these complexes are collected by CCD diode array detector and the multi-wavelength absorbance data are processed using partial least squares algorithm. The reaction conditions and analytical parameters of flow injection analysis have been investigated. The method was applied to directly determine Ge, Mo and Sn in several food samples after digestion with satisfactory results. The recoveries of spiked samples were 80.0-102.0% for tin, 86.3-92.0% for germanium and 83.2-95.2% for molybdenum, and the relative standard deviations for samples were 4.4-7.8%. Molybdenum in certified reference material of cattle liver was determined by the proposed method (n=8). The differential values between determined and guarantee values were within the given uncertain value ranges (t=1.687, P>0.05 for t-test). The samples of mung bean, kelp and pork liver were analyzed by the proposed method and inductively couple plasma-atomic emission spectroscopy (ICP-AES) method. The determination results of the two methods are in good agreement. The sampling rate is 30 samples h⁻¹.     

快速测定蜂王浆中蜂王酸的分光光度法研究

本文提出了用差示分光光度法和一阶导数分光光度法测定蜂王浆中蜂王酸的含量，差示光谱最大测定波长为（＋）２２８．０ｎｍ；一阶导数光谱测定波长为（＋）２０４．５ｎｍ和（－）２３３．５ｎｍ。线性范围为０－２０μｇ／ｍｌ（差示分光光度法）和０－１５μｇ／ｍｌ（一阶异数分光光度法）。二法在实际测定中具有操作简便，快速和准确度高等优点。     

Synthesis of 4-aza analog of ramelteon: a novel tricyclic 1,6,7,8-tetrahydro-2H-cyclopenta[d]furo[2,3-b]pyridine derivative as melatonin receptor ligand

The 4-aza analog of ramelteon (−)-1, a novel tricyclic 1,6,7,8-tetrahydro-2H-cyclopenta[d]furo[2,3-b]pyridine derivative, was synthesized via the intramolecular inverse electron demand Diels-Alder reaction followed by fluoride-induced desilylation-cyclization.     

Simultaneous Spectrophotometric Determination of Hydrochlorothiazide and Pharmaceutical Preparations

Abstract

We developed three methods for the simultaneous determination of amiloride (AMI) and hydrochlorothiazide (HCT): zero-crossing, derivative quotient spectra with normalized divisor and multiple linear regression (MULTIC) methods. The two first methods use the derivative spectrophotometry, and the last one uses the absorbance measurement. The three methods were used to determine both compounds in synthetic mixtures and pharmaceutical preparations with errors less than 5% and 15%, respectively.     

Facile entry into the 3H,9H-bis[1,2,4]triazolo-[1,5-a:5′,1′-d][1,3,5]triazinium (5/6/5 tricyclic NNN) system

A facile, one-pot reaction between 3,4,5-triamino-1,2,4-triazole (guanazine) and cyanogen bromide provides a new high-nitrogen example of the 3H,9H-bis[1,2,4]triazolo[1,5-a:5′,1′-d][1,3,5]triazinium system, the 2,3,5,6-tetraamino-9-imino derivative (3) as a quaternary bromide salt.     

Structure of tetra-o-tolylgermanium

A full X-ray structure analysis of tetra-o-tolylgermanium, C₂₈H₂₈Ge, has been performed. Unlike the corresponding tetraphenyl derivative, this molecule loses its D_2d symmetry due to steric hindrance. The mean value of the GeC bond is 2.166 Å.     

Second Derivative Spectrophotometric Determination of p-Aminophenol in the Presence of Paracetamol

Abstract

A second derivative spectroscopic method for the determination of p-aminophenol in paracetamol powder is described. Second derivative absorbance (d²A/dλ²) values were measured at 223.8 nm (Δ = 4.2 nm) where p-aminophenol showed derivative responses obeying Beer's Law but paracetamol had negligible derivative absorption. The concentrations of p-aminophenol solutions prepared in 0.1 N HCl (0.12–7.61 mcg/ml), containing constant amounts of paracetamol (20 mcg/ml) related linearly with the d²A/dλ² values and gave a straight line (r = ?0.9999). The method allowed determination of 0.5% to 38% of p-aminophenol in paracetamol without prior separation, it is rapid, precise and accurate.     

Highly stereoselective addition of organozinc reagents to pentopyranose derived glycals: effect of protecting group and assignment of C-glycoside stereochemistry

The nucleophilic addition of ethyl 3-propionylzinc iodide to a variety of differently protected pentopyranose derived d-glycals 6a-g proceeds with good to high levels of diastereoselectivity to provide the corresponding β-C-glycosides 7. The stereochemistry of the para-nitrobenzoate derivative 7d has been confirmed by X-ray crystallography, and the stereochemistry of the other β-C-glycoside products has been correlated to 7d. The stereochemical outcome observed supports the earlier suggestion by Isobe that through-space effects are important in stabilising and controlling the reactivity of the intermediate oxonium species represented by 11.     

用傅立叶红外光谱测定泌尿系结石中的草酸钙

对泌尿系结石的组成进行结构分析,为分析结石病的产生原因及预防复发提供参考,在临床诊断和治疗上具有重要意义.傅立叶红外光谱是研究泌尿系结石构造的一种较理想的分析手段.用红外光谱仪定量分析泌尿结石中草酸钙采用的内标法、吸光度比值法和一阶导数法进行了比较,建立的分析方法可以简便对草酸钙混合结石中一水草酸钙(COM)和二水草酸钙(COD)进行定量测定,分析结果可初步满足临床诊断的要求.     

A novel 2:1 cycloadduct of dimethyl acetylenedicarboxylate with 3,5-diphenyl-4-methoximino-4H-pyrazole 1,2-dioxide

Two equivalents of dimethyl acetylenedicarboxylate react with 3,5-diphenyl-4-methoximino-4H-pyrazole 1,2-dioxide in acetonitrile under reflux. The major product was shown by X-ray analysis to be a 5,8-epoxyisoxazolo[2,3-d]-[1,4]-diazepine derivative.     

Recent developments in derivative ultraviolet/visible absorption spectrophotometery

The instrumental development and analytical applications of derivative ultraviolet/visible region absorption spectrophotometry produced in the last seven years (since 1987) are reviewed.     

Benzimidazole Annulated New Heterocyclic Compounds: Synthesis of Polycyclic Pyrrole Derivatives

Several benzimidazolo[1,2‐a]pyrrole derivative s were obtained by reaction of benzimidazolo[1,2‐a]indeno[2,1‐d]pyrrole derivative with different reactants such as p‐toluenesulfonyl chloride, phenylthiocyanate, phenyl‐isothiocyanate, dimethylsulfate, and active methylene such as malononitrile, ethyl cyanoacetate, benzoyl acetonitrile, ethyl acetoacetate, and diethyl malonate. The newly synthesized products have been deduced on the basis of spectral and analytical data.     

关于透光率导数光谱用作定量分析的可行性

探讨了我率导数光谱（d^nT/dλ^n）与吸光度导数光谱（d^nA/dλ^n）的关系，并讨论了用d^nT/dλ^n作定量分析的可行性及其产生分析误差的原因以及最佳测量条件。     

Short asymmetric synthesis of (S,S)-PDP using l-prolinol derivative as economic starting material

(S,S)-PDP (5d) and its backbone (2S,2′S)-bipyrrolidine (1) have been extensively applied as the scaffold of various chiral ligands in catalytic asymmetric syntheses. In this study, new short asymmetric syntheses of these two important C₂-symmetrical nitrogen heterocycles have been accomplished employing economically available l-prolinol derivative 10 as the starting material. Excellent diastereoselectivity was achieved of the key Grignard addition to imine intermediate utilizing (S)-N-tert-butanesulfinamide as the chiral auxiliary.     

Number of species in complexation equilibria of o-, m- and p-CAPAZOXS with Cd, Co, Ni, Pb and Zn ions by PCA of UV-vis spectra

A critical comparison of the selected derivative principal component analysis (PCA) methods on the absorbance matrix data concerning the complexation equilibria between o-CAPAZOXS and Cd²⁺, Pb²⁺ and Zn²⁺ or m-CAPAZOXS and Cd²⁺, Co²⁺, Ni²⁺ and Zn²⁺ or p-CAPAZOXS and Cd²⁺ and Zn²⁺ at 25 °C is provided. As the number of complex species in a complex-forming equilibria mixture is an important step in spectral data treatment, the nine selected index functions for the prediction of the number of light-absorbing species that contribute to a set of spectra is critically tested by the PCA. An improved identification with the second SD(AE) or third derivative TD(AE) and derivative ratio function ROD(AE) for the average error criterion AE is preferred. After the number of various complexes formed the stability constants of species ML, ML₂ (and ML₃, respectively) type log β₁₁, log β₁₂ (and log β₁₃, respectively) for the system of o-CAPAZOXS (ligand L) with the metals (the standard deviation s(log β_pq) of the last valid digits is given in brackets) Cd²⁺ (6.39(5) and 11.51(9)), Pb²⁺ (4.24(2) and 9.01(2)) and Zn²⁺ (5.18(7) and 9.06(10)) and for the system of m-CAPAZOXS with Cd²⁺ (6.59(20) and 11.51(32)), Co²⁺ (7.19(6) and 12.19(8)), Ni²⁺ (7.64(7) and 13.39(12)) and Zn²⁺ (4.83(3) and 9.57(3)) and for the system of p-CAPAZOXS with Cd²⁺ (6.44(5), 10.99(10) and 14.57(25)) and Zn²⁺ (6.84(16), 13.05(29) and 18.74(43)) at 25 °C are estimated using SQUAD(84) nonlinear regression of the mole-ratio spectrophotometric data. The computational strategy is presented with goodness-of-fit tests and various regression diagnostics capable of proving the reliability of the chemical model proposed.     

Synthesis of a novel tricyclic 1,6,7,8-tetrahydro-2H-cyclopenta[b]furo[3,2-d]pyridine derivative,the 5-aza analog of ramelteon

The 5-aza analog of ramelteon 3, a novel tricyclic 1,6,7,8-tetrahydro-2H-cyclopenta[b]furo[3,2-d]pyridine derivative, was synthesized by hetero-Diels–Alder reaction and chemoselective Dieckmann condensation.