scholarly journals Optimization of conditions for esterification of thiodiacetic acid in urine using mathematical planning for biological monitoring

2021 ◽  
Vol 100 (8) ◽  
pp. 869-874
Author(s):  
Olga M. Zhurba ◽  
Anton N. Alekseenko ◽  
Salim F. Shayakhmetov
Keyword(s):  
Sample Preparation ◽  
Reaction Temperature ◽  
Conversion Rate ◽  
Dimethyl Ester ◽  
Degree Of Conversion ◽  
Process Time ◽  
Mass Chromatogram ◽  
Mathematical Planning ◽  
The Impact

Introduction. To assess the impact of the toxicants vinyl chloride (VC) and 1,2-dichloroethane (DCE) on humans, personalized biomonitoring of thiodiacetic acid (TDAA) is of most significant importance. Determination of TDAA in urine was carried out using the method of gas chromatography-mass spectrometry GC-MS. Materials and methods. Sample preparation consists of the analyte’s esterification in a biological matrix with methyl alcohol (with 10% boron trifluoride), extraction of the derivative by liquid extraction with ethyl acetate. We used an Agilent 7890A gas chromatograph with an HP-5MS capillary column and a mass-selective detector. TDAA was identified in the form of a dimethyl ester on a mass chromatogram according to the retention time and the ratio of the intensities of the registered ions. Results. To determine the rational parameters of the sample preparation process for the determination of TDAA in urine studies were carried out under the method of planning the experiment, which makes it possible to obtain the most accurate mathematical description of the processes. Optimization of the conditions for esterification of TDAA was carried out using mathematical planning, varying the temperature, process time, and the nature of the catalyst (BF3 or H2SO4). The scheduling matrix included eight experiments; the degree of conversion of TDAA served as an optimization parameter. Interpretation of the model showed that temperature makes more contribution to the formation of the degree of conversion than the processing time. The nature of the catalyst does not affect the degree of conversion. Conclusion. A mathematical model developed for optimizing the conditions for sample preparation of the biomarker of exposure to VC (TDAA) in urine, showed the contribution of three factors (reaction temperature, reaction time, catalyst nature) to the conversion rate, of which the reaction temperature makes the greatest contribution to the choice of optimal esterification conditions. The nature of the catalyst (BF3 or H2SO4) does not affect the conversion rate.

scholarly journals Optimization of conditions for the sample preparation using mathematical planning for determination of 1-hydroxypyrene in urine using method of gas chromatography-mass spectrometry

2020 ◽  
Vol 99 (10) ◽  
pp. 1153-1158
Author(s):  
A. N. Alekseenko ◽  
O. M. Zhurba ◽  
A. V. Merinov ◽  
S. F. Shayakhmetov
Keyword(s):  
Mass Spectrometry ◽  
Gas Chromatography ◽  
Sample Preparation ◽  
Biological Monitoring ◽  
Magnesium Sulfate ◽  
Liquid Extraction ◽  
Extraction Time ◽  
Gas Chromatography Mass Spectrometry ◽  
Mathematical Planning

Introduction. Biological monitoring of 1-hydroxypyrene is the most widely used method for evaluating the effects of PAHs on humans. The determination of 1-hydroxypyrene in urine is performed using gas chromatography-mass spectrometry (GC-MS). Material and methods. Sample preparation consists of extracting the analyte from the biological matrix by 2-fold liquid extraction with hexane, evaporation the extract to the dry residue in the nitrogen current, and re-dissolution of the dry residue in the silylating agent BSTFA. We used gas chromatograph Agilent 7890A with an HP-5MS capillary column and a mass-selective detector. 1-hydroxypyrene was identified as trimethyl silane on a mass chromatogram based on the retention time and intensity ratio of the registered ions. Results. Optimization of the conditions for liquid extraction of 1-hydroxypyrene was performed using mathematical planning, varying the mass of magnesium sulfate, the extraction time, and the extraction multiplicity. The planning matrix included eight experiments, and the degree extraction of 1-hydroxypyrene was used as an optimization parameter. Interpretation of the model showed the multiplicity of extraction to contribute more to the formation of the degree of extraction than the mass of magnesium sulfate and the extraction time. Discussion. The proposed method foк the sample preparation, based on the extraction of 1-hydroxypyrene by 2-fold liquid extraction with hexane for 2 min with the addition of 0.5 g of magnesium sulfate to the biological sample, allowed reaching the detection limit of 0.1 ng/ml. The evaluation of metrological characteristics showed RSD of the reproducibility to do not exceed 6.4%, the systematic error is not significant, and the accuracy index in the form of a total error is not higher than 15%. Levels of 1-hydroxypyrene in the urine of aluminum production workers are 53 - 414 times higher than in the control group. Conclusion. The choice of optimal conditions for liquid extraction of 1-hydroxypyrene by mathematical planning allowed developing a method for the determination this analyte in urine by GC-MS for biological monitoring.

Assessment of sensitivity of the efficiency of regional tax spending towards investment attractiveness of the types of economic activity carried out by the residents of advanced development territory

2020 ◽  
pp. 98-110
Author(s):  
Evgeniya Mikhailovna Popova ◽  
Guzel Mukhtarovna Guseinova ◽  
Sergei Borisovich Milov
Keyword(s):  
Economic Activity ◽  
Socioeconomic Development ◽  
Federal District ◽  
Tax Incentives ◽  
Capital Investments ◽  
The Subject ◽  
Investment Process ◽  
The Impact ◽  
Advanced Development

The deficit of subnational budgets and deceleration capital investments in multiple Russian regions increase the relevance of research aimed at improvement of tax incentivizing practice of the regional investment process. The studies focused on determination of the impact of socioeconomic and institutional factors upon the efficiency of investment tax expenses obtained wide circulation within the foreign scientific literature. The subject of this article is the assessment of sensitivity of the efficiency of regional tax expanses towards investment attractiveness of the types of economic activity carried out by the residents of territories of advanced socioeconomic development, created in the subjects of Far Easter Federal District. The scientific novelty and practical values of this research consists in substantiation of the reasonableness of assessment of investment attractiveness of the types of economic activity that are stimulated by tax incentives. Methodology for assessing investment attractiveness is proposed and tested. The conclusion is made that in case of low investment attractiveness of the type of economic activity, which was planned to support by tax incentives, it is required to conduct and additional analysis to avoid unjustified tax expanses.

TEM Sample Prep Tool Matching—DualBeam FIB Cut Look and Measure Monitoring for Process Control and Development in a 300 mm IC Fab

2016 ◽  
Author(s):  
Jangbae Jeon
Keyword(s):  
Process Control ◽  
Sample Preparation ◽  
Continuous Improvement ◽  
Process Time ◽  
Operational Monitoring ◽  
Thickness Control ◽  
Running Time ◽  
End Products ◽  
Novel Method

Abstract This work presents a novel method of continuous improvement for faster, better and cheaper TEM sample preparation using Cut Look and Measure (CLM). The improvement of the process is executed by operational monitoring of daily beam conditions, end products, bulk thickness control, recipe usage and tool running time. This process produces a consequent decrease in rework rate and process time. In addition, it also increases throughput with better quality TEM samples.

Method development for the determination of textural properties of sugar beet roots

2019 ◽  
pp. 392-400 ◽  
Author(s):  
Gunnar Kleuker ◽  
Christa M. Hoffmann
Keyword(s):  
Sugar Beet ◽  
Compression Test ◽  
Storage Period ◽  
Textural Properties ◽  
Small Sample ◽  
Root Tip ◽  
Flexural Test ◽  
Sample Distribution ◽  
The Impact

The harvest of sugar beet leads to root tip breakage and surface damage through mechanical impacts, which increase storage losses. For the determination of textural properties of sugar beet roots with a texture analyzer a reliable method description is missing. This study aimed to evaluate the impact of washing, soil tare, storage period from washing until measurement, sample distribution and number of roots on puncture and compression measurements. For this purpose, in 2017 comprehensive tests were conducted with sugar beet roots grown in a greenhouse. In a second step these tests were carried out with different Beta varieties from a field trial, and in addition, a flexural test was included. Results show that the storage period after washing and the sample distribution had an influence on the puncture and compression strength. It is suggested to wash the roots by hand before the measurement and to determine the strength no later than 48 h after washing. For reliable and comparable results a radial distribution of measurement points around the widest circumference of the root is recommended for the puncture test. The sample position of the compression test had an influence on the compressive strength and therefore, needs to be clearly defined. For the puncture and the compression test it was possible to achieve stable results with a small sample size, but with increasing heterogeneity of the plant stand a higher number of roots is required. The flexural test showed a high variability and is, therefore, not recommended for the analysis of sugar beet textural properties.

Development and Validation of an LC-MS/MS Method for Simultaneous Determination of Canagliflozin and Metformin HCl in Rat Plasma and its Application

2020 ◽  
Vol 16 (6) ◽  
pp. 752-762
Author(s):  
Vivek Nalawade ◽  
Vaibhav A. Dixit ◽  
Amisha Vora ◽  
Himashu Zade
Keyword(s):  
Internal Standard ◽  
Rat Plasma ◽  
Precipitation Method ◽  
Herbal Extracts ◽  
One Step ◽  
Precision And Accuracy ◽  
Development And Validation ◽  
The Impact ◽  
Metformin Hcl

Background: Food and herbal extracts rich in Quercetin (QRT) are often self-medicated by diabetics and can potentially alter the pharmacokinetics (PK) of Metformin HCl (MET) and Canagliflozin (CNG) leading to food or herb-drug interactions and reduced therapeutic efficacy. However, the impact of these flavonoids on the pharmacokinetic behaviour of MET and CNG is mostly unknown. Methods: A simple one-step protein precipitation method was developed for the determination of MET and CNG from rat plasma. The mobile phase chosen was MeOH 65% and 35% water containing 0.1% formic acid at a flow rate of 1mL/min. Results: The retention time of MET, internal standard (Valsartan) and CNG was 1.83, 6.2 and 8.2 min, respectively. The method was found to be linear in the range of 200 - 8000 ng/mL for CNG and 100 = 4000 ng/ml for MET. Precision and accuracy of the method were below 20% at LLOQ and below 15% for LQC, MQC, and HQC. Conclusion: The method was successfully applied for the determination of PK of MET and CNG by using 100 μL of rat plasma. QRT co-administration affects the PK parameters of MET and CNG. This alteration in PK parameters might be of significant use for clinicians and patients.

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