scholarly journals Analysis of bilirubin and bilirubin mono- and di-conjugates. Determination of their relative amounts in biological samples

1980 ◽  
Vol 185 (1) ◽  
pp. 115-128 ◽  
Author(s):  
N Blanckaert
Keyword(s):  
Biological Samples ◽  
Methyl Esters ◽  
Dimethyl Ester ◽  
Crystalline Form ◽  
Reaction Products ◽  
Reaction Conditions ◽  
Normal Rat ◽  
Novel Method ◽  
Rat Bile

1. A novel method for determination of the relative amounts of unconjugated bilirubin and sugar mono- and di-conjugates of bilirubin in biological samples, including serum, is described and illustrated by its application to the analysis of bilinoids in rat bile. 2. The method is based on specific conversion of the carbohydrate conjugates of bilirubin into the corresponding mono- or di-methyl esters by base-catalysed transesterification in methanol. Under the selected reaction conditions, unconjugated biliru-in remains intact and no dipyrrole exchange in the bilinoids is detectable; transesterification of bilirubin mono- or di-glucuronide is virtually complete (approx. 99%), and sponification is negligible (less than 1%); recovery of the pigments is approx. 95%. 3. The reaction products bilirubin and its methyl esters are separated by t.l.c. and determined spectrophotometrically; the two isomeric bilirubin-IX alpha monomethyl esters are separated and therefore can be determined individually. 4. Reference bilirubin mono- and di-methyl esters have been synthesized and characterized, and the two isomers of bilirubin-IX alpha monomethyl ester and bilirubin dimethyl ester were obtained individually, in crystalline form. 5. With this new method, virtually all bilinoids (over 99%) in normal rat bile have been found to be conjugated, with diconjugates (71%) predominating. A significantly increased proportion of monoconjugates is present in bile collected from heterozygous Gunn rats or from normal rats that were refused with large amounts of bilirubin.

Spectrophotometric Determination of Isoniazid in Pharmaceutical Sample by Silicomolybdenum Blue

2014 ◽  
Vol 1033-1034 ◽  
pp. 548-551
Author(s):  
Xin Rong Wen ◽  
Chang Qing Tu
Keyword(s):  
Linear Regression ◽  
Linear Relationship ◽  
Spectrophotometric Determination ◽  
Linear Correlation ◽  
Effect Factors ◽  
Reaction Conditions ◽  
Pharmaceutical Sample ◽  
Novel Method ◽  
Maximum Absorption Wavelength

A novel method for the spectrophotometric determination of isoniazid by silicomoly- bdenum blue has been established.The various effect factors on the spectrophotometric determination of isoniazid by silicomolybdenum blue were investigated in detail.The results showed that under certain reaction conditions,silicomolybdenum yellow could be reduced to silicomolybdenum blue by isoniazid, and the content of isoniazid was determinated indirectly through determinating the absorbance of the silicomolybdenum blue. The maximum absorption wavelength of chromogenic system is 740 nm, good linear relationship is obtained between the absorbance and the concentration of isoniazid in the range of 1.968～27.55 μg/mL,and the equation of the linear regression is A=0.0247+61.824ρ (μg/mL) with a linear correlation coefficient is 0.9995.This proposed method has been successfully applied to determinate of isoniazid in isoniazid tablets, and the results agree well with those obtained by pharmacopoeial method.

scholarly journals Indirect Spectrophotometric Methods for the Determination of Tadalafil

2015 ◽  
Vol 1 (2) ◽  
pp. 11 ◽  
Author(s):  
Safwan Mohammad Fraihat
Keyword(s):  
Oxidation Reaction ◽  
Indigo Carmine ◽  
Pharmaceutical Preparations ◽  
Pharmaceutical Formulations ◽  
Blue Dye ◽  
Reaction Products ◽  
Reaction Conditions ◽  
Factors Affecting ◽  
Spectrophotometric Methods

Two spectrophotometric methods were developed for the determination Tadalafil in pharmaceutical preparations. The methods are based on the oxidation reaction with known excess amount of Ce(IV) and estimation of the unreacted amount using Indigo carmine dye (Method A) and in Methylene blue dye  (Method B). the factors affecting the reaction conditions were studied and the absorbance of absorbance of the oxidation reaction products were monitored at 610 and 600 nm for methods A and B respectively. Beer's law is obeyed in the concentration ranges 11 to 50 and 10 to 55 ppm, the limits of detection and quantification are reported. The proposed method was applied to the determination of the drug in pharmaceutical formulations and the results demonstrated that the method is equally accurate, precise and reproducible as the official methods. The validity of method was established by recovery studies with satisfactory results.

Optimization of the Reaction Conditions for the Synthesis of Dihydrobenzofuran Neolignans

2020 ◽  
Author(s):  
Herbert Dias ◽  
Matheus Rodrigues ◽  
Antônio Eduardo Crotti
Keyword(s):  
Reaction Time ◽  
Oxidative Coupling ◽  
Methyl Esters ◽  
Dimethyl Ester ◽  
Intermediate Species ◽  
Radical Intermediate ◽  
Reaction Conditions ◽  
Experimental Conditions ◽  
Methyl Ferulate ◽  
Optimized Conditions

We have optimized the experimental conditions for the silver(I)-promoted oxidative coupling of methyl <i>p</i>-coumarate (<b>I</b>) and methyl ferulate (<b>II</b>), which is the most frequently used methodology to synthesize the bioactive dihydrobenzofuran neolignans <b>1</b> ((±)-<i>trans</i>-dehydrodicoumarate dimethyl ester) and <b>2</b> ((±)-<i>trans</i>-dehydrodiferulate dimethyl ester). Most of the tested conditions affected the conversion (i.e., the consumption of <b>I</b> and <b>II</b>) and the selectivity (i.e., the percentage of <b>I</b> and <b>II</b> that was converted into <b>1</b> and <b>2</b>, respectively), so the optimized conditions were the conditions that afforded the best balance between conversion and selectivity. Silver(I) oxide (0.5 eq) is the most efficient oxidant agent amongst the silver(I) reagents that were tested to convert methyl esters <b>I </b>and <b>II </b>into compounds <b>1</b> and <b>2</b>, respectively. Acetonitrile, which has not yet been reported as a solvent for this reaction, provided the best balance between conversion and selectivity, besides being “greener” than other solvents that are more often employed (e.g., dichloromethane and benzene). Under the optimized conditions, the reaction time decreased from 20 h to 4 h without significantly impacting the conversion and selectivity. However, the relation between the results obtained by adding a radical initiator (AIBN) or a radical inhibitor (isoquinoline) and the previously reported involvement of radical intermediate species in the silver(I)-promoted oxidative coupling of <b>I</b> and <b>II</b> is not clear and deserves further investigation.

Optimization of the Reaction Conditions for the Synthesis of Dihydrobenzofuran Neolignans

2020 ◽  
Author(s):  
Herbert Dias ◽  
Matheus Rodrigues ◽  
Antônio Eduardo Crotti
Keyword(s):  
Reaction Time ◽  
Oxidative Coupling ◽  
Methyl Esters ◽  
Dimethyl Ester ◽  
Intermediate Species ◽  
Radical Intermediate ◽  
Reaction Conditions ◽  
Experimental Conditions ◽  
Methyl Ferulate ◽  
Optimized Conditions

We have optimized the experimental conditions for the silver(I)-promoted oxidative coupling of methyl <i>p</i>-coumarate (<b>I</b>) and methyl ferulate (<b>II</b>), which is the most frequently used methodology to synthesize the bioactive dihydrobenzofuran neolignans <b>1</b> ((±)-<i>trans</i>-dehydrodicoumarate dimethyl ester) and <b>2</b> ((±)-<i>trans</i>-dehydrodiferulate dimethyl ester). Most of the tested conditions affected the conversion (i.e., the consumption of <b>I</b> and <b>II</b>) and the selectivity (i.e., the percentage of <b>I</b> and <b>II</b> that was converted into <b>1</b> and <b>2</b>, respectively), so the optimized conditions were the conditions that afforded the best balance between conversion and selectivity. Silver(I) oxide (0.5 eq) is the most efficient oxidant agent amongst the silver(I) reagents that were tested to convert methyl esters <b>I </b>and <b>II </b>into compounds <b>1</b> and <b>2</b>, respectively. Acetonitrile, which has not yet been reported as a solvent for this reaction, provided the best balance between conversion and selectivity, besides being “greener” than other solvents that are more often employed (e.g., dichloromethane and benzene). Under the optimized conditions, the reaction time decreased from 20 h to 4 h without significantly impacting the conversion and selectivity. However, the relation between the results obtained by adding a radical initiator (AIBN) or a radical inhibitor (isoquinoline) and the previously reported involvement of radical intermediate species in the silver(I)-promoted oxidative coupling of <b>I</b> and <b>II</b> is not clear and deserves further investigation.

scholarly journals GC-MS Discrimination of Citrulline from Ornithine and Homocitrulline from Lysine by Chemical Derivatization: Evidence of Formation of N5-Carboxy-ornithine and N6-Carboxy-lysine

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2301
Author(s):  
Svetlana Baskal ◽  
Alexander Bollenbach ◽  
Dimitrios Tsikas
Keyword(s):  
Amino Acids ◽  
Biological Samples ◽  
Methyl Esters ◽  
Gas Chromatography Mass Spectrometry ◽  
Reaction Products ◽  
Internal Standards ◽  
In Situ Preparation ◽  
Synthetic Amino Acids ◽  
Carboxylic Groups

Derivatization of amino acids by 2 M HCl/CH3OH (60 min, 80 °C) followed by derivatization of the intermediate methyl esters with pentafluoropropionic anhydride (PFPA) in ethyl acetate (30 min, 65 °C) is a useful two-step derivatization procedure (procedure A) for their quantitative measurement in biological samples by gas chromatography-mass spectrometry (GC-MS) as methyl ester pentafluoropropionic (PFP) derivatives, (Me)m-(PFP)n. This procedure allows in situ preparation of trideutero-methyl esters PFP derivatives, (d3Me)m-(PFP)n, from synthetic amino acids and 2 M HCl/CD3OD for use as internal standards. However, procedure A converts citrulline (Cit) to ornithine (Orn) and homocitrulline (hCit) to lysine (Lys) due to the instability of their carbamide groups under the acidic conditions of the esterification step. In the present study, we investigated whether reversing the order of the two-step derivatization may allow discrimination and simultaneous analysis of these amino acids. Pentafluoropropionylation (30 min, 65 °C) and subsequent methyl esterification (30 min, 80 °C), i.e., procedure B, of Cit resulted in the formation of six open and cyclic reaction products. The most abundant product is likely to be N5-Carboxy-Orn. The second most abundant product was confirmed to be Orn. The most abundant reaction product of hCit was confirmed to be Lys, with the minor reaction product likely being N6-Carboxy-Lys. Mechanisms are proposed for the formation of the reaction products of Cit and hCit via procedure B. It is assumed that at the first derivatization step, amino acids form (N,O)-PFP derivatives including mixed anhydrides. At the second derivatization step, the Cit-(PFP)4 and hCit-(PFP)4 are esterified on their C1-Carboxylic groups and on their activated Nureido groups. Procedure B also allows in situ preparation of (d3Me)m-(PFP)n from synthetic amino acids for use as internal standards. It is demonstrated that the derivatization procedure B enables discrimination between Cit and Orn, and between hCit and Lys. The utility of procedure B to measure simultaneously these amino acids in biological samples such as plasma and urine remains to be demonstrated. Further work is required to optimize the derivatization conditions of procedure B for biological amino acids.

scholarly journals Development of Dispersive Liquid-Liquid Microextraction method combined with UV spectrophotometry for the Determination of Malathion Pesticide

2018 ◽  
Vol 28 (2) ◽  
pp. 93
Author(s):  
Wijdan Shakir Khayoon
Keyword(s):  
Limit Of Detection ◽  
Binary Solution ◽  
Calibration Graph ◽  
Uv Spectrophotometry ◽  
Reaction Conditions ◽  
Extraction Solvent ◽  
Salt Addition ◽  
Novel Method ◽  
Dispersive Liquid Liquid Microextraction

A simple and novel method was developed by combination of dispersive liquid-liquid microex-traction with UV spectrophotometry for the preconcentartion and determination of trace amount of malathion. The presented method is based on using a small volume of ethylenechloride as the extraction solvent was dissolved in ethanol as the dispersive solvent, then the binary solution was rapidly injected by a syringe into the water sample containing malathion. The important parame-ters, such the type and volume of extraction solvent and disperser solvent, the effect of extraction time and rate, the effect of salt addition and reaction conditions were studied. At the optimum conditions, the calibration graph was linear in the range of 2-100 ng mL-1 of malathion with a limit of detection of 0.8 ng L-1. In addition, the enrichment factor was 30. The developed method was successfully applied for the determination of malathion pesticide in water samples

Monolithic capillary microextraction on-line combined with ICP-MS for determining Ni, Cu and Cd in biological samples

2016 ◽  
Vol 8 (23) ◽  
pp. 4680-4688 ◽  
Author(s):  
Feiya Suo ◽  
Beibei Chen ◽  
Man He ◽  
Bin Hu
Keyword(s):  
Biological Samples ◽  
Amino Group ◽  
Capillary Microextraction ◽  
Icp Ms ◽  
On Line ◽  
Novel Method

A novel method of amino group modified monolithic capillary microextraction on-line combined with ICP-MS was developed for the determination of Ni, Cu, Cd in biological samples.

scholarly journals Simple Sensitive Spectrophotometric Determination of Vanadium in Biological and Environmental Samples

2006 ◽  
Vol 3 (4) ◽  
pp. 286-297 ◽  
Author(s):  
B. Krishna Priya ◽  
P. Subrahmanyam ◽  
J. Dilip Kumar ◽  
P. Chiranjeevi
Keyword(s):  
Biological Samples ◽  
Wave Length ◽  
Coupling Reaction ◽  
Basic Medium ◽  
Reaction Conditions ◽  
Highly Sensitive ◽  
Biological And Environmental Samples ◽  
Environmental And Biological Samples ◽  
Optimum Reaction

Novel, rapid, highly sensitive and selective spectrophotometric method for the determination of traces of vanadium (V) in environmental and biological samples, pharmaceutical and steel samples was studied. The method is based on oxidation of 2,4- dinitro phenyl hydrazine(2,4-DNPH) by vanadium (V) followed by coupling reaction withN-(1-naphthalene-1-yl)ethane-1,2-diamine-dihydrochloride (NEDA) in acidic medium to give red colored derivative or on oxidation of 4-Amino Pyridine by vanadium (V) followed by coupling reaction with NEDA in basic medium to give pink colored derivative. The red colored derivative having an λmax495 nm which is stable for 8 days and the pink colored derivative with 525 nm is stable for more than 7 days at 350C. Beer's law is obeyed for vanadium (V) in the concentration range of 0.02 - 3.5 μg mL–1(red derivative) and 0.03 – 4.5 μg mL–1(pink derivative) at the wave length of maximum absorption. The optimum reaction conditions and other analytical parameters were investigated to enhance the sensitivity of the present method. The detailed study of various interferences made the method more selective. The proposed method was successfully applied to the analysis of vanadium in natural water samples, plant material, soil samples, synthetic mixtures, pharmaceutical samples and biological samples. The results obtained were agreed with the reported methods at the 95 % confidence level. The performance of proposed method was evaluated in terms of Student'st-test and Variance ratiof-test which indicates the significance of proposed method over reported method.

scholarly journals Effective Degradation of Cellulose by Microwave Irradiation in Alkaline Solution

2021 ◽  
Author(s):  
Lama Jabareen ◽  
Moorthy Maruthapandi ◽  
Arumugam Saravanan ◽  
Aharon Gedanken
Keyword(s):  
Lignocellulosic Biomass ◽  
Crystalline Cellulose ◽  
Reaction Products ◽  
Reaction Conditions ◽  
One Pot ◽  
Platform Chemicals ◽  
Subsequent Step ◽  
Novel Method ◽  
Main Component ◽  
C Nmr

Abstract The utilization of lignocellulosic biomass is effective to produce chemicals and fuels, which are of importance for the establishment of a sustainable society. The conversion of cellulose, which is the main component of the lignocellulosic biomass, into significant chemicals that can be further converted to different chemicals or fuels in the subsequent step, under gentle conditions is a promising route. Organic acids such as acetic acid, glycolic acid and formic acid are significant chemicals are examples of such products. A novel method to producing important platform chemicals from Micro-crystalline cellulose was developed. Micro-crystalline cellulose was degraded as a result of an oxidation with potassium chlorate by microwave radiation, in a one-pot procedure, efficient reaction conditions such as short reaction time and full conversion of the cellulose were identified. The reaction products have been analyzed by 1H, 13C NMR, XPS, TGA and XRD.

Sign in / Sign up

Export Citation Format

Share Document