scholarly journals Determination of H2S in Crude Oil via a Rapid, Reliable and Sensitive Method

2019 ◽  
Vol 2 (2) ◽  
pp. 37-44 ◽  
Author(s):  
Amir Vahid
Keyword(s):  
Crude Oil ◽  
Dynamic Range ◽  
Liquid Extraction ◽  
Extraction Time ◽  
Dilution Ratio ◽  
Linear Dynamic Range ◽  
Linear Dynamic ◽  
Liquid Liquid Extraction ◽  
Sensitive Method

Determination of hydrogen sulfide, (H2S) in crude oil is very important due to the environmental impacts, industrial problems and legal international limitation of transportation. In the present work, H2S of crude oil is determined by liquid-liquid extraction followed by potentiometric titration. Three factors including dilution ratio of crude oil with toluene, extraction time of H2S into the caustic phase and API of crude oil was investigated via factorial design. The ANOVA results revealed that the dilution ratio, crude type and extraction time have the highest effect of the recovery of H2S from crude oil. The linear dynamic range of the method was from  1 up to 2000 ppm which can be manipulated for lower or higher concentration by further optimization of the above-mentioned parameters. This method is rapid, reliable, operator-independent which make it a useful technique for the field test of crude oil and overcome extreme uncertainty of H2S measurement.

scholarly journals Determination of Nitroimidazoles and Their Metabolites in Swine Tissues by Liquid Chromatography

2003 ◽  
Vol 86 (3) ◽  
pp. 505-509 ◽  
Author(s):  
Jianzhong Shen ◽  
Yue Yhang ◽  
Suxia Zhang ◽  
Shuangyang Ding ◽  
Xinhua Xiang
Keyword(s):  
Chromatographic Method ◽  
Solid Phase ◽  
Liquid Extraction ◽  
Phase Extraction ◽  
Liquid Liquid Extraction ◽  
Liquid Chromatographic Method ◽  
Swine Tissue ◽  
Liquid Chromatographic ◽  
Sensitive Method

Abstract A liquid chromatographic method was developed for determination of metronidazole (MNZ), ronidazole (RNZ), dimetridazole (DMZ), and 2-hydroxymethyl-1-methyl-5-nitroimidazole (DMZOH) in swine tissue. After extraction with ethyl acetate and evaporation, the nitroimidazoles were redissolved in hydrochloric acid. Hexane was used in the liquid–liquid extraction to remove fat. An Oasis® HLB solid-phase extraction was performed after neutralization of the acidic extract. The limits of detection were 1.0–2.0 μg/kg for DMZOH, MNZ, RNZ, and DMZ in muscle and liver. Average recoveries ranged from 80.1 to 83.9% in muscle fortified at 10, 20, and 50 μg/kg; average re-coveries in liver ranged from 78.9 to 82.3%. The procedure provides a simple and sensitive method for monitoring DMZOH, MNZ, RNZ, and DMZ residues in swine tissues.

Determination of doravirine in human plasma using liquid–liquid extraction and HPLC–MS/MS

Bioanalysis ◽  
2019 ◽  
Vol 11 (16) ◽  
pp. 1495-1508
Author(s):  
Rajesh Desai ◽  
Brad Roadcap ◽  
Dina Goykhman ◽  
Eric Woolf
Keyword(s):  
Human Plasma ◽  
Dynamic Range ◽  
Multiple Reaction Monitoring ◽  
Development Program ◽  
Liquid Extraction ◽  
Clinical Development Program ◽  
Liquid Liquid Extraction ◽  
Multiple Reaction Monitoring Mode ◽  
Ionization Mode

Aim: A method to quantitate doravirine (MK-1439) in human plasma has been developed to support human clinical trials designed to evaluate the safety, pharmacokinetics and efficacy of the compound. Methodology & results: The analyte was extracted using liquid–liquid extraction, separated on a reverse phase HPLC column, and detected on an API-4000 mass spectrometer using a Turbo-Ion spray source in positive ionization mode coupled with multiple reaction monitoring mode was used for quantification. The dynamic range for the assay was 0.02–10 ng/ml using 100 μl of human plasma. Conclusion: The assay was found to be sensitive, selective and reproducible and applied to support the doravirine clinical development program.

scholarly journals Sensitive Determination of Indomethacin in Pharmaceuticals and Urine by Sequential Injection Analysis and Optosensing

2010 ◽  
Vol 93 (5) ◽  
pp. 1443-1449 ◽  
Author(s):  
Lucía Molina-García ◽  
M Luisa Fernández-de Córdova ◽  
Antonio Ruiz-Medina
Keyword(s):  
Dynamic Range ◽  
Flow System ◽  
Sample Volume ◽  
Sequential Injection Analysis ◽  
Fluorescent Product ◽  
Sequential Injection ◽  
Linear Dynamic Range ◽  
Linear Dynamic ◽  
Sensitive Determination

Abstract A selective and sensitive method based on coupling of sequential injection analysis (SIA) and optosensing was developed and applied to the determination of indomethacin in pharmaceutical and urinary samples. After alkaline hydrolysis, the fluorescent product generated from indomethacin is inserted in the flow system, transitorily retained on an active solid support (Sephadex QAE A-25) filling the flowcell, and monitored at 283/371 nm (λex/λem). The system was calibrated for two sample volumes, 100 and 1000 µL. It showed a linear dynamic range of 0.56.5 ng/mL, with an LOD of 0.15 ng/mL and an RSD of 3.9% (n = 10) when the highest sample volume was used. The proposed fluorometric SIA optosensor was applied to the determination of indomethacin in both pharmaceuticals and urine samples, and satisfactory results were obtained.

Thermochemical Determination of Glucose in Serum, Plasma, and Whole Blood without Prior Deproteinization

1975 ◽  
Vol 21 (6) ◽  
pp. 741-745 ◽  
Author(s):  
C David McGlothlin ◽  
Joseph Jordan
Keyword(s):  
Dynamic Range ◽  
Direct Injection ◽  
Sample Pretreatment ◽  
Linear Dynamic Range ◽  
Linear Dynamic ◽  
Dewar Vessel ◽  
Quantitation Method ◽  
Electrical Calibration

Abstract Glucose can be determined by phosphorylatlon in the presence of hexokinase (EC 2.7.1.1) by using Mg2+/ (ATP)2- as the phosphorylating agent. A novel instrumental quantitation method is described, direct injection enthalpimetry, whereby the heat of the enzymatically catalyzed reaction was measured. The reaction was allowed to proceed to virtual completion (99.5+%) in an adiabatic Dewar vessel at 25.00 ± 0.01 °C (range). Samples were sequentially injected into a reaction mixture consisting of hexokinase, ATP, Mg2+, and a tris(hydroxymethyl)aminomethane buffer (pH 8). Single analyses required <2 min for 0-3 g/liter samples. The linear dynamic range was 0.3-10 g/liter, with zero intercept and a precision and accuracy of 2%. Electrical calibration in situ obviated the need for chemical standards, and because protein and color do not interfere, no sample pretreatment was necessary before analysis.

Cobalt Monoxide Nanoparticles Modified Glassy Carbon Electrodes as a Sensor for Determination of Nitrite

2015 ◽  
Vol 1120-1121 ◽  
pp. 291-298
Author(s):  
Guang Jun Huang ◽  
Jin Lei Zhang ◽  
Dan Dan Zhao
Keyword(s):  
Glassy Carbon ◽  
Dynamic Range ◽  
Enhancement Effect ◽  
Linear Dynamic Range ◽  
Modified Glassy Carbon Electrode ◽  
Glassy Carbon Electrodes ◽  
Linear Dynamic ◽  
Electrochemical Mechanism ◽  
Coo Nanoparticles

A new method for the determination of nitrite was established based on cobalt monoxide (CoO) nanoparticles modified glassy carbon electrode (CS-CoO/GCE). In 0.15mol/L pH 4.0 HAc-NaAc, the CS-CoO/GCE showed a remarkable catalytic and enhancement effect on oxidation of the nitrite. A linear dynamic range of 8.0×10-7 to 6.0×10-3 mol/L (R=0.997) with a detection limit of 1.0×10-7 mol/L was obtained. The electrochemical mechanism was been obtained. This method has been used to determine the content of nitrite in real samples.

A New Nanostructure Square Wave Voltammetric Platform for Determination of Tert-butylhydroxyanisole in Food Samples

2019 ◽  
Vol 15 (2) ◽  
pp. 172-176 ◽  
Author(s):  
Fatemeh Karimi ◽  
Majede Bijad ◽  
Mohammad Farsi ◽  
Amir Vahid ◽  
Hesam Asari-Bami ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Food Samples ◽  
Linear Dynamic Range ◽  
Carbon Paste ◽  
Square Wave ◽  
Linear Dynamic ◽  
Electro Oxidation ◽  
Paste Electrode

Background: Antioxidants are one of the important additives in food samples due to their role in protecting human cells against the effects of free radicals. The analysis of antioxidants is essential due to the role of antioxidants in improving body health. Objective: A square wave voltammetric sensor was fabricated for the determination of tert-butylhydroxyanisole (TBHA) based on the application of CdO/SWCNTs and 1-methyl-3-butylimidazolium chloride as mediators for the modification of carbon paste electrode (MBCl/CdO/SWCNTs/CPE). The MBCl/CdO/SWCNTs/CPE improved the sensitivity of TBHA ~ 6.7 times and showed a linear dynamic range 0.07-600 µM with detection limit 0.02 µA for the analysis of TBHA. The pH investigation confirmed that electro-oxidation of TBHA occurred by exchanging two electrons and two protons. In addition, the MBCl/CdO/SWCNTs/CPE was used for determination of TBHA in food samples.

scholarly journals First Report for Determination of d-Penicillamine in the Presence of Tryptophan Using a 2-Chlorobenzoyl Ferrocene/Ag-Supported ZnO Nanoplate–Modified Carbon Paste Electrode

2018 ◽  
Vol 101 (1) ◽  
pp. 208-215 ◽  
Author(s):  
Hadi Beitollahi ◽  
Abbas Gholami ◽  
Mohammad Reza Ganjali
Keyword(s):  
Carbon Paste Electrode ◽  
High Selectivity ◽  
Dynamic Range ◽  
Modified Carbon Paste Electrode ◽  
Linear Dynamic Range ◽  
Carbon Paste ◽  
Linear Dynamic ◽  
Wide Linear Dynamic Range ◽  
Paste Electrode

Abstract In this work, a carbon paste electrode modified with Ag-ZnO nanoplates and 2-chlorobenzoyl ferrocene was prepared and applied for the determination of d-penicillamine in the presence of tryptophan. The morphologies of Ag-ZnO nanoplates were examined by scanning electron microscopy. It was found that under an optimum condition (pH 7.0), the oxidation of d-penicillamine at the surface of such an electrode occurs at a potential about 165 mV less positive than that of an unmodified carbon paste electrode. The diffusion coefficient (D = 7.6 × 10−6 cm2/s) and the electron transfer coefficient (α = 0.54) for d-penicillamine oxidation were also determined. The proposed method exhibited a wide linear dynamic range of 0.03–250.0 µM, with an LOD (S/N = 3) of 0.015 µM. Moreover, the modified electrode exhibited good reproducibility and high selectivity, demonstrating its feasibility for the analytical purpose. Lastly, this new sensor was used for the determination of d-penicillamine and tryptophan in real samples.

Pentafluorobenzylation Derivatization for Determination of Chlorinated Herbicide Acids

1987 ◽  
Vol 70 (5) ◽  
pp. 889-891
Author(s):  
Donald F Gurka ◽  
Fred L Shore ◽  
Shu-Teh Pan
Keyword(s):  
Gas Chromatography ◽  
Dynamic Range ◽  
Methyl Esters ◽  
Detection Limits ◽  
Relative Importance ◽  
Linear Dynamic Range ◽  
Linear Dynamic ◽  
Dynamic Concentration ◽  
Better Than

Abstract Pentafluorobenzyl and methyl esterification methods for several common herbicide acids have been evaluated and compared. Gas chromatography,' electron capture instrumental detection limits for 2 of 7 pentafluorobenzyl esters were better than the corresponding methyl esters, and comparable for the other S herbicide esters. The linear dynamic concentration range was generally wider for the methyl esters. Gas chromatography of some pentafluorobenzyl derivatives was complicated by coelution of certain derivatives with each other and with byproducts of the derivatization reaction. The ruggednessoptimized pentafluorobenzylation procedure was subjected to linear dynamic range and detection limit studies. The choice between methyl or pentafluorobenzyl esters is contingent on the relative importance of detection limits and linear dynamic range

Gas-chromatographic determination of ethylene glycol in serum.

1982 ◽  
Vol 28 (1) ◽  
pp. 75-78 ◽  
Author(s):  
W H Porter ◽  
A Auansakul
Keyword(s):  
Ethylene Glycol ◽  
Dynamic Range ◽  
Limit Of Detection ◽  
Chromatographic Determination ◽  
Good Precision ◽  
Linear Dynamic Range ◽  
Linear Dynamic ◽  
Analytical Recovery ◽  
Chromatographic Procedure

Abstract We describe a new gas-chromatographic procedure for ethylene glycol in serum, determined as the cyclic phenylboronate ester. The method is rapid, requires only 100 microL of serum, and either an OV-1 or an OV-17 column is used. The linear dynamic range extends to at least 5000 mg/L, with a lower limit of detection of 10 mg/L. Analytical recovery of ethylene glycol from serum averaged 97% (95-101%) over the concentration range of 250-5000 mg/L. The method demonstrates good precision, with CVs less than 2.5%, over the concentration range 500-2000 mg/L.

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