Nonpolarizing Interference Research Articles

Development of Paraquat Pesticide Determination Methodology in Urine Samples by UHPLC-MS/MS

In technical-scientific development, mankind has developed different ways of managing pests, diseases and weeds, increasing agricultural production impacting social, economic and environmental aspects. As major grains producer (such as corn, soybeans and beans), the Brazilian State, through the Brazilian agencies as Institute for the Environment and Renewable Natural Resources (IBAMA), the National Health Surveillance Agency (ANVISA), and the Ministry of Agriculture, Livestock and Supply (MAPA) authorize and regulate the use of different pesticides, including Paraquat, to improve and guarantee the production. However, the direct contact and long-term exposure to these substances offer environmental and occupational risks, impacting negatively on the workers, population of neighbor cultures, and environmental health. Considering the potential damages, it is of utmost importance to develop effective analytical methodologies for the biomonitoring and assessment of the level of exposure of farmers and ranchers in direct contact with pesticides. Thus, this work proposed to develop a sensitive and selective analytical method, using the ultra-high efficiency liquid chromatography technique, coupled to mass spectrometry seeking a fast and simple sample preparation for the Paraquat quantification in urine samples. To achieve this, two sample preparations were compared in terms of speed and practicality. The first method (A) used C18 silica as adsorbent to remove the non-polar interferences. The second preparation (B) consisted in direct sample dilution in acetonitrile. Both methodologies used centrifugation under refrigeration to precipitate suspended artifacts. The linearity of the Paraquat detection by the analytical methodology, developed in a HILIC column, was evaluated between 10 to 70 µg L-¹ (r²=0.9911; y=19427x+479868), enabling the matrix evaluation after applying the best sample preparation. The method developed was simple, fast, which makes it useful and efficient for toxicology laboratories routine to monitor the exposure levels of farmers dealing with Paraquat daily.

Enhanced separation and analysis of low abundant soy proteins by dual washing extraction process

Soybean seeds provide a rich source of proteins, fats, carbohydrates, and micronutrients. Extraction and analysis of low abundant soybean seed proteins are challenging because of its complex seed composition. For characterizing various proteins, it is paramount to remove the other interfering components, primarily oils, and carbohydrates. In the present study, we used a sequential dual washing process initially with hexane to remove oil and non-polar interferences, followed by 80% ethanol washing to remove about 60% of the total soluble sugars. The extracted soluble sugars were quantified using a newly developed and validated high-performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD). This newly developed combined washings process significantly enhanced the separation of both low molecular weight and low abundant proteins using 1D (one dimensional)- and 2D (two dimensional) gel electrophoresis. The separated proteins were trypsinized and analyzed by using Bruker amazon speed ion trap mass spectrometer equipped with an ESI source. This combined washing process allowed the identification of 18 additional low abundant soy proteins as compared to the simple hexane washed samples. This purification process will allow researchers to identify and investigate the role of low molecular weight and low abundant proteins as it relates to plant functions, nutrition, and health.

Design of Structures of Neutral Nonpolarizing Interference Systems Placed between Media with the Same Refraction Indices

The design of neutral nonpolarizing interference systems formed on the face of one of the two prisms that are components of an optical element in the form of a cube is considered. An analysis is carried out of the spectral characteristics of the energy reflection coefficient of the developed structures.

Проектирование конструкций нейтральных неполяризующих интерференционных систем, размещенных между средами с одинаковыми показателями преломления

The design of nonpolarizing interference systems formed inside a cube is considered. The spectral characteristics of the energy reflection coefficient of the developed structures are analyzed.

Nonpolarizing Interference Systems Containing Metallic Layers

The structure of nonpolarizing interference systems incorporating the layers manufactured from metallic materials is considered. The method of searching for the structures of metal-dielectric interference systems providing a small deviation between the spectral characteristics of the energy reflection (transmission) coefficient for s- and р-polarizations is presented. The structures developed on the basis of the presented method have a rather simple structure, which makes them easy to implement. The analysis of the spectral characteristics of the obtained structures has demonstrated that the difference between the integral refl-ection coefficients for s- and p-polarizations within the considered spectral region (460–580 nm) is less than 1%.

Stability analysis of a nonpolarizing interference system to a varying angle of incidence of radiation during operation

In this work, the influence of deviations of the angle of incidence of radiation on the spectral characteristics of the reflectance of a nonpolarizing interference system is analyzed. A technique is presented for determining the deviation of the reflection coefficient of the interference system considered here from the calculated value in the presence of a deviation of the angle of incidence of radiation. A stability assessment of the coating structure under consideration with varying angles of incidence of radiation is carried out.

Search for designs of nonpolarizing interference systems

This research looks into methods for searching of designs of nonpolarizing interference systems, which provide a small discrepancy between spectral characteristics of the energy reflection/transmission coefficient for s- and p- polarizations. The layer thickness of these systems is a multiple of a quarter wavelength. Depending on the method used, the number of film-forming materials can vary from two to four. Analysis of spectral characteristics shows that in the spectral range of interest the discrepancy between the integral characteristics for s- and p-polarizations is less than 2%.

Неполяризующие интерференционные системы, содержащие металлические слои

The structure of nonpolarizing interference systems containing metallic layers is considered. The technique of searching metal-dielectric interference systems, providing a small discrepancy between the spectral characteristics reflection (transmission) for s- and p- polarizations, is presented. The constructions developed on the basis of the presented method have a rather simple structure that ensures the ease of their implementation. Analysis of the spectral characteristics showed that in the spectral range (460–580) nm, the difference between the integral reflection coefficients for s- and p- polarizations does not exceed 1%.

Analysis of the stability of a non-polarizing interference system to a change in the angle of incidence of radiation in operation

Analysis of the stability of a non-polarizing interference system to a change in the angle of incidence of radiation in operation

Determination of Paraquat and Diquat in Potato by Liquid Chromatography/Tandem Mass Spectrometer

A high-throughput liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed for the determination of paraquat and diquat in potatoes using a reversed-phase with weak anion-exchange and cation-exchange mixed-mode Acclaim™ Trinity Q1 column. Five grams of sample was shaken with fifteen milliliters of 1:1 MeOH: 0.1 N HCl for 10 min at room temperature and heated for 15 min at 80°C. After centrifugation, the supernatant was passed through an Oasis HLB SPE to retain suspended particulates and non-polar interferences. The sample was directly injected and analyzed for 10 min by LC-MS/MS with no sample concentration. Two multiple reaction monitoring (MRM) channels were monitored in the method for each target compound to achieve true positive identification. Two internal standards corresponding to each analyte were used to counter matrix suppression effect. Linearity of the detector response with a minimum coefficient of determination (r2) of more than 0.997 was demonstrated in the range from 2 to 250 ng/mL for each analyte using matrix-matched standard. The average recovery for all analytes at 10, 25, 100, and 500 ng/g (n$=$5) are between 87-106% with a relative standard deviation of less than 12%.https://doi.org/10.21423/jrs-v05n01p001 (DOI assigned 4/17/2019)

Direct determination of glyphosate, glufosinate, and AMPA in soybean and corn by liquid chromatography/tandem mass spectrometry.

Glyphosate, glufosinate, and aminomethylphosphonic acid (AMPA) are amphoteric, low mass, high water soluble, and do not have chromophore. They are very difficult to be retained on a reversed phase HPLC and detected by UV or fluorescence detectors. A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method was developed to determine these analytes in soybean and corn using a reversed phase with weak anion-exchange and cation-exchange mixed-mode Acclaim™ Trinity™ Q1 column. The sample was shaken with water containing ethylenediaminetetraacetic acid disodium salt (Na2EDTA) and acetic acid for 10min to precipitate protein and extract the analytes into the solution. The supernatant was passed thru an Oasis HLB SPE to retain suspended particulates and non-polar interferences. The sample was directly injected and analyzed in 6min by LC-MS/MS with no sample concentration or derivatization steps. Three isotopically labeled internal standards corresponding to each analyte were used to counter matrix suppression effect. Linearity of the detector response with a minimum coefficient of determination (R (2)) of more than 0.995 was demonstrated in the range of 10 to 1000ng/mL for each analyte. Accuracy (recovery %) and precision (relative standard deviation or RSD %) were evaluated at the fortification levels of 0.1, 0.5, and 2μg/g in seven replicates in both soybean and corn samples.

Quantification of endogenous brassinosteroids in sub-gram plant tissues by in-line matrix solid-phase dispersion–tandem solid phase extraction coupled with high performance liquid chromatography–tandem mass spectrometry

A matrix solid-phase dispersion (MSPD)–tandem mixed mode anion exchange (MAX)–mixed mode cation exchange (MCX) solid phase extraction-high performance liquid chromatography coupled with tandem mass spectrometry (HPLC–MS/MS) method was developed for quantification of six endogenous brassinosteroids (BRs) (24-epibrassinolide, 24-epicastasterone, 6-deoxo-24-epicastasterone, dolichosterone, teasterone and typhasterol) in rice plant tissues. Non-polar interferences were removed effectively by C8 dispersant used in MSPD, while the following tandem MAX–MCX process facilitated the elimination of polar and ionizable compounds. The weak reversed-phase retention feature of MAX–MCX leaded to good compatibility of the elution solvents in the in-line coupled MSPD–MAX–MCX system. This system was optimized for extraction and purification of BRs in plant samples. The effects of the type of solid phase, the elution solvent, the extraction temperature and the clean-up material were studied. Before HPLC separation, BRs purified were derivatized by m-aminophenylboronic acid to enhance the sensitivity of MS/MS to BRs. Compared with traditional liquid–liquid extraction and solid phase extraction (LLE–SPE), the proposed MSPD–MAX–MCX method showed higher extraction efficiency, lower matrix effect, and advantages of easy manipulation and time-saving. The in-line MSPD–MAX–MCX coupled with HPLC–MS/MS method provided a linear response over two orders of magnitude of BRs concentration with correlation coefficients above 0.9982, limits of detection between 0.008 and 0.04ngmL−1, relative standard deviations (RSDs) below 29.4%, and recoveries above 77.8%. The proposed method has been successfully applied to analysis of endogenous BRs in rice plant at booting stage and maturity stage.

Determination of trace acrylamide in starchy foodstuffs by HPLC using a novel mixed-mode functionalized calixarene sorbent for solid-phase extraction cleanup.

In this paper, a rapid and effective HPLC method, using tetraazacalix[2]arene[2]triazine-modified silica gel (NCSi) as solid-phase extraction (SPE) sorbent, was developed for the purification and determination of trace acrylamide in starchy foodstuffs. The main influence factors of SPE including amount of NCSi sorbent, sample flow rate, and volume and composition of washing solution were investigated and evaluated in the sample pretreatment step. The optimized purification effect was achieved at the sample flow rate of 3 mL/min with 100 mg of NCSi and 2 mL of washing solution (water, 100%). The HPLC separation was carried out on a C18 column (250×4.6 mm i.d., 5 μm) with a mobile phase of methanol/water (10:90, v/v). The linear range of the calibration curve was 4-4000 ng/mL with s correlation coefficient of >0.9999. The intraday and interday RSDs (n=5) of peak areas of acrylamide were 0.22 and 0.90% and the intraday and interday RSDs (n=5) of retention times were 0.50 and 1.63%, respectively. In addition, overall recoveries through the extraction and NCSi-SPE purification ranged from 73.13 to 98%. Compared with the commercial SPE sorbents, NCSi featured excellent selectivity to retain polar and nonpolar interferences in the sample matrices. The improved method was simple, rapid, accurate, and promising for the determination of trace acrylamide in starchy foods with a complex matrix.

Development of an Analytical Scheme for the Determination of Pyrethroid Pesticides in Composite Diet Samples

Analysis of an individual's total daily food intake may be used to determine aggregate dietary ingestion of given compounds. However, the resulting composite sample represents a complex mixture, and measurement of such can often prove to be difficult. In this work, an analytical scheme was developed for the determination of 12 select pyrethroid pesticides in dietary samples. In the first phase of the study, several cleanup steps were investigated for their effectiveness in removing interferences in samples with a range of fat content (1-10%). Food samples were homogenized in the laboratory, and preparatory techniques were evaluated through recoveries from fortified samples. The selected final procedure consisted of a lyophilization step prior to sample extraction. A sequential 2-fold cleanup procedure of the extract included diatomaceous earth for removal of lipid components followed with a combination of deactivated alumina and C(18) for the simultaneous removal of polar and nonpolar interferences. Recoveries from fortified composite diet samples (10 microg kg(-1)) ranged from 50.2 to 147%. In the second phase of this work, three instrumental techniques [gas chromatography-microelectron capture detection (GC-microECD), GC-quadrupole mass spectrometry (GC-quadrupole-MS), and GC-ion trap-MS/MS] were compared for greatest sensitivity. GC-quadrupole-MS operated in selective ion monitoring (SIM) mode proved to be most sensitive, yielding method detection limits of approximately 1 microg kg(-1). The developed extraction/instrumental scheme was applied to samples collected in an exposure measurement field study. The samples were fortified and analyte recoveries were acceptable (75.9-125%); however, compounds coextracted from the food matrix prevented quantitation of four of the pyrethroid analytes in two of the samples considered.