Analysis Of Determinants Research Articles

EspalomaCharge: Machine Learning-Enabled Ultrafast Partial Charge Assignment.

Atomic partial charges are crucial parameters in molecular dynamics simulation, dictating the electrostatic contributions to intermolecular energies and thereby the potential energy landscape. Traditionally, the assignment of partial charges has relied on surrogates of ab initio semiempirical quantum chemical methods such as AM1-BCC and is expensive for large systems or large numbers of molecules. We propose a hybrid physical/graph neural network-based approximation to the widely popular AM1-BCC charge model that is orders of magnitude faster while maintaining accuracy comparable to differences in AM1-BCC implementations. Our hybrid approach couples a graph neural network to a streamlined charge equilibration approach in order to predict molecule-specific atomic electronegativity and hardness parameters, followed by analytical determination of optimal charge-equilibrated parameters that preserve total molecular charge. This hybrid approach scales linearly with the number of atoms, enabling for the first time the use of fully consistent charge models for small molecules and biopolymers for the construction of next-generation self-consistent biomolecular force fields. Implemented in the free and open source package EspalomaCharge, this approach provides drop-in replacements for both AmberTools antechamber and the Open Force Field Toolkit charging workflows, in addition to stand-alone charge generation interfaces. Source code is available at https://github.com/choderalab/espaloma-charge.

The use of deep eutectic solvent-liquid phase microextraction as green analytical sample treatment for the analysis of drugs in urine

In this paper, a natural deep eutectic solvent (NADES)-based liquid phase microextraction (LPME) of 20 pharmaceuticals from urine, employing liquid chromatography tandem mass spectrometry (LC-MS/MS) for precise quantification, has been developed. The chromatographic gradient was accurately evaluated to ensure the effective separation of tramadol, an opioid receptor agonist, and o-desmethylvenlafaxine, one active metabolite of the antidepressant venlafaxine, both compounds sharing identical molecular mass for the precursor ion (Q1: 264.2 m/z) and fragmentation patterns (Quantifier ion: 58.2 m/z; qualifier ion: 246.0 m/z). NADES consisted of menthol-octanoic acid in a molar ratio of 1:2. Using the appropriate extraction conditions, the developed methodology provided appropriate LOQ values, ranging from 15 to 208 ng L–1, with reasonable RSD values (below 11 %), recoveries ranging from 64 to 120 % and preconcentration factors up to 66.6 folds. Application of the developed method to the analysis of urine samples served to highlight its usefulness. An AGREEprep score of 0.64 was obtained despite the demand for substantial sample volumes and the use of LC-MS/MS for analyte determination.

Chromatographic Methods for the Determination of Glyphosate in Cereals Together with a Discussion of Its Occurrence, Accumulation, Fate, Degradation, and Regulatory Status.

The European Union's recent decision to renew the authorization for the use of glyphosate until 15 December 2033 has stimulated scientific discussion all around the world regarding its toxicity or otherwise for humans. Glyphosate is a chemical of which millions of tons have been used in the last 50 years worldwide to dry out weeds in cultivated fields and greenhouses and on roadsides. Concern has been raised in many areas about its possible presence in the food chain and its consequent adverse effects on health. Both aspects that argue in favor of toxicity and those that instead may indicate limited toxicity of glyphosate are discussed here. The widespread debate that has been generated requires further investigations and field measurements to understand glyphosate's fate once dispersed in the environment and its concentration in the food chain. Hence, there is a need for validated analytical methods that are available to analysts in the field. In the present review, methods for the analytical determination of glyphosate and its main metabolite, AMPA, are discussed, with a specific focus on chromatographic techniques applied to cereal products. The experimental procedures are explained in detail, including the cleanup, derivatization, and instrumental conditions, to give the laboratories involved enough information to proceed with the implementation of this line of analysis. The prevalent chromatographic methods used are LC-MS/MS, GC-MS/SIM, and GC-MS/MS, but sufficient indications are also given to those laboratories that wish to use the better performing high-resolution MS or the simpler HPLC-FLD, HPLC-UV, GC-NPD, and GC-FPD techniques for screening purposes. The concentrations of glyphosate from the literature measured in wheat, corn, barley, rye, oats, soybean, and cereal-based foods are reported, together with its regulatory status in various parts of the world and its accumulation mechanism. As for its accumulation in cereals, the available data show that glyphosate tends to accumulate more in wholemeal flours than in refined ones, that its concentration in the product strictly depends on the treatment period (the closer it is to the time of harvesting, the higher the concentration), and that in cold climates, the herbicide tends to persist in the soil for a long time.

A Th2-type immune response and low-grade systemic inflammatory reaction as potential immunotoxic effects in intensive agriculture farmers exposed to pesticides

Pesticides are chemicals widely used in agriculture to keep crops healthy and prevent them from being destroyed by pests, thus contributing to a sustainable food and feed production. However, long-term exposure to these compounds may be harmful to human health as they can affect the function of various organs systems, including the immune system. There is growing evidence that pesticides may increase the risk of developing immune-based diseases and inflammation. This study assessed whether greenhouse farmers occupationally exposed to pesticides presented alterations in immunoregulatory proteins, used as surrogate biomarkers of immune function. The study population consisted of 175 greenhouse workers occupationally exposed to pesticides and 91 non-exposed controls. Serum levels of 27 cytokines, chemokines and growth factors were measured using a magnetic bead-based immunoassay in a subpopulation of 111 greenhouse workers and 79 non-exposed controls. Since analytical determinations were performed in two periods of the same crop season with different use of pesticides (period of high and low pesticide exposure), linear mixed models for repeated measures were used to optimize statistical inference. The increase in IL-13, IL-4 and IL-6 observed in greenhouse workers compared to controls, and in the period of high exposure to pesticides relative to that of low exposure, suggest an altered Th1/Th2 balance towards the Th2 response. This finding points to a type-2 inflammation commonly presented as allergic inflammation, which has often been reported in farm-workers and in which pesticide exposure is considered a risk factor. Furthermore, the increase in IL-1β and VEGF, mediators of inflammation and angiogenesis, may suggest a low-grade systemic inflammation that might underlie chronic pathological conditions linked to pesticide exposure.

Analytical determination of a quasi-stationary electromagnetic field created by magnetic moments and eddy currents in conducting half-space

Aim. Study of the distribution of a three-dimensional alternating quasi-stationary electromagnetic field at the surface of conducting half-space with strong skin-effect, the source of which is an arbitrarily oriented magnetic moment. Methodology. The expressions for non-uniform electromagnetic field with strong skin effect are used for the analysis, which is based on the found exact analytical solution of the general three-dimensional problem and the use of expansion into asymptotic series with respect to a small parameter that is proportional to the ratio of the field penetration depth to the distance between the sources of the external field and the surface of body. Specific expressions at the surface are completely determined by the known field of external sources. In this work, the external magnetic moment field is used. Results. For strong skin effect, expressions for the electric and magnetic field strength are obtained separately for the components of the magnetic moment oriented perpendicularly and parallel to the flat surface between the dielectric and conducting areas. The features of the electromagnetic field distribution are analyzed depending on the value of introduced small parameter. The results are presented for the module and phase shift of the field strength with respect to the phase of the external field source. Originality. The expressions found for the electromagnetic field appear to be more general than the use of closed contours with alternating current, since they extend types of external field sources and allow the use of the superposition method instead of integration over the entire contour. Practical value. The found specific analytical expressions of the electromagnetic field at the surface for the external field of magnetic moments significantly simplify the solution of the problems, since they do not require additional solution of the field equations. References 20, figures 8.

МОДЕЛЮВАННЯ РОБОЧОГО ПРОЦЕСУ СТРУМИННОГО НАСОСА ПРИ ЙОГО АСИМЕТРИЧНОМУ ОБЕРТАННІ В СВЕРДЛОВИНІ

The structure of the equations of the pressure-flow characteristics of the high-pressure jet pump is supplemented with a component that determines the additional pressure caused by the influence of eddy currents during the asymmetric rotation of the ejection system around the axis of the well. On the basis of the joint solution of the Bernoulli equations, the preservation of the integrity of the moving medium, the momentum and moment of movement of the mixed flows, a relationship was obtained for the analytical determination of the additional dynamic pressure created by the rotation of an eccentrically placed jet pump in the well. In the process of researching the resulting equation, the extreme nature of the growth of the pressure-flow and energy characteristics of the overbite ejection system was established. The increase in pressure and efficiency caused by the asymmetric rotation of the over-chisel ejection system is inversely proportional to the value of the main geometric parameter of the jet pump.

Noncompetitive Determination of Small Analytes by Sandwich-Type Lateral Flow Assay Based on an Aptamer Kissing Complex.

Here, we present the proof-of-concept of a lateral flow assay (LFA) that is capable of detecting small-molecule targets in a noncompetitive manner by deploying a sandwich-type format based on the aptamer kissing complex (AKC) strategy. A fluorescently labeled hairpin aptamer served as the signaling agent, while a specific RNA hairpin grafted onto the strip served as the capture element. The hairpin aptamer switched from an unfolded to a folded form in the presence of the target, resulting in kissing interactions between the loops of the reporter and the capture agents. This design triggered a target-dependent fluorescent signal at the test line. The AKC-based LFA was developed for the detection of adenosine, achieving a detection limit in the micromolar range. The assay revealed the presence of the same analyte in urine. The method also proved effective with another small molecule (theophylline). We believe that the AKC-based LFA approach could overcome many of the shortcomings associated with conventional signal-off methods and competitive processes.

РАСЧЕТ КОНТАКТНОГО ТЕРМИЧЕСКОГО СОПРОТИВЛЕНИЯ

An approach to determining the contact thermal resistance of two-layer materials and the results of comparing the analytical determination of thermal resistance with experimental data are considered. The necessity of taking into account the contact thermal resistance in the design of heat exchangers is shown

In Situ Use of Mining Substrates for Wetland Construction: Results of a Pilot Experiment.

This paper evaluates an experimental wetland as part of a pilot soil reclamation project in a mining area. The wetland was constructed using materials of mining origin from the area; most reactive materials of acid pH were stabilised using limestone filler. The study selected macrophytes that are tolerant to potentially toxic elements (PTEs) and resistant to salinity, namely Phragmites australis, Juncus effusus, and Iris pseudacorus. These macrophytes were then placed in pots containing substrates composed of different mixtures of topsoil, peat, and mining waste (black or yellow sand). A thorough analysis of the physicochemical and mineralogical characteristics of the materials included studies of PTE mobilisation. This study emphasises the significance of the rhizosphere in directing the transfer of PTEs to the plant and the correlation between the substrate and the development of plant defence mechanisms, such as the formation of Fe-plates. Scanning electron microscopy was used to highlight these aspects and validate the results of the analytical determinations. These wetlands can be proposed as a phytoremediation strategy for areas affected by mining and maritime influence. They are easy to construct and remain stable, providing important ecosystem services such as the natural attenuation of acid mine drainage, support for vegetation development and fauna, and a clean ecosystem.

Alterations of Photosynthetic and Oxidative Processes Influenced by the Presence of Different Zinc and Cadmium Concentrations in Maize Seedlings: Transition from Essential to Toxic Functions.

The study examined the impact of varying the concentrations of zinc (Zn) on plant responses, particularly on photosynthetic and oxidative metabolic processes. This investigation aimed to distinguish between the beneficial and harmful effects of Zn on plants, highlighting significant nutrient supply concerns. The investigation methods were centered around non-invasive methods, such as biophoton emission (delayed fluorescence-DF, ultra-weak bioluminescence-UWLE), fluorescence induction (Fv/Fm) measurements, chlorophyll content estimation (SPAD) and vegetation index (NDVI) determination. Furthermore, the analytical determination of lipid oxidation (MDA level) and antioxidant capacity (FRAP) as well as gene expression studies of the antioxidative enzymes glutathione reductase (GR), glutathione S-transferase (GST) and lipoxygenase (LOX) for essential Zn and nonessential cadmium (Cd) were also carried out in order to clarify toxic symptoms through different Zn investigation approaches. It was possible to identify a metabolic enhancement from 1000 µM; however, stress symptoms from the 2000 µM Zn treatment were noted for both the investigated photosynthetic and oxidative processes. The outcomes of this research contribute to the improvement of Zn mineral-supplementation technology, which is essential for maize growth, and the optimization of agricultural practices.

Bond analysis in meta- and para-substituted thiophenols: overlap descriptors, local mode analysis, and QTAIM.

This study delves into the chemical nuances of thiophenols and their derivatives through a comprehensive computational analysis, moving beyond traditional energetic perspectives such as bond dissociation enthalpy and S-H dissociation dynamics. By employing the overlap model along with its topological descriptors (OP/TOP), quantum theory of atoms in molecules (QTAIM), and local vibrational mode (LVM) theories, the research provides a deeper understanding of the S-H and C-S bonding scenarios in substituted thiophenols. The investigation follows the electron-donating capacity of S-H substituent variation with the nature and positioning of other ring substituents. Energy profile analyses indicate distinct stability differences in the cis and trans conformations of meta- and para-PhSH systems, influenced by the electron-donating strength of these substituents. The study also uncovers significant variations in S-H bond distances and descriptor values, particularly in para-substituted PhSH, reflecting the influence of electron-donating or withdrawing substituents. In contrast, alterations at the meta-position show minimal effects on C-S bond descriptors, while para-substitutions markedly influence C-S bond characteristics, demonstrating a clear correlation with the electron-donating or withdrawing capabilities of the substituents. This research sheds light on the intricate bond dynamics in aromatic systems with diverse substituents, highlighting the complex interaction between electronic effects and molecular conformation. The study employs the B97X-D/Def2TZVP level of theory for molecular geometries, ensuring accurate characterization of structures as true minima via analytical harmonic frequency determination. The electronic properties of S-H and C-S bonds in variously substituted thiophenols were analyzed using OP/TOP, QTAIM, and LVM methodologies. Computational processes, including conformational scans, geometry optimizations, and vibrational frequency calculations, were conducted using Gaussian 09, with ultra-fine integration grids and tight convergence criteria for the SCF procedure. Bond descriptors were computed utilizing ChemBOS, Multiwfn, and LModeA software, providing a robust and detailed examination of bond properties.

Response surface experimental design for simultaneous chromatographic determination of two antiviral agents “Favipiravir and Remdesivir” in pharmaceuticals and spiked plasma samples

AbstractThe antiviral agents, Favipiravir (FAV) and Remdesivir (REM), were introduced in the last few years alone or as combination regimen for successful management of the rapidly spreading CORONA virus pandemic. A newly developed rapid and sensitive high performance liquid chromatographic method (HPLC) has been developed for the simultaneous determination of their mixture. Firstly, one factor at a time optimization (OFAT) has been applied. Afterwards, quality by design approach (QbD) has been utilized using Box Behnken experimental design (BBD) for the development of an experimental design of four independent and nine dependent variables for much better refining of the optimized parameters. The established model has given an optimum resolution at; acetonitrile percentage of 52.66, mobile phase of pH 2.91, percentage of triethylamine of 0.15 and 1.30 mL/min flow rate. The proposed method has been validated according to the USP 31 NF 26 guidelines. Good linearity ranges have been obtained from 5.00 up to 50.00 μg/mL for FAV and from 2.00 up to 60.00 μg/mL for FAV and REM, respectively. Excellent relative standard deviation values (not more than 1.40) were obtained upon investigation of accuracy, precision and robustness. The developed method has succeeded in analysis of investigated drugs in their pharmaceutical formulations and spiked plasma samples with good recoveries of 99.00 and up to 106.00%. The proposed method is considered eligible for the quality control laboratories as well as in‐vivo determinations of both analytes.

Analytical determination of enthalpy, heat capacity and Gibbs free energy for nitrogen and iodine

The analytical solutions for the modified shifted Morse potential model have been obtained for some molecules. Despite the importance of this potential in molecular systems, this model hasn’t gained extensive attention. This research delves into predicting thermodynamic functions, specifically examining molar enthalpy, molar heat capacity, and molar Gibbs free energy for nitrogen and iodine molecules using this modified shifted Morse potential. The predicted result aligned with the experimental data, with iodine exhibiting a closer match.

Deformation of layered soil

One of the consequences of the aggression of the russian federation in Ukraine is a change in the properties of the surface layers of some regions of the soil. Construction of structures in such areas must be carried out considering the above. In order to create prerequisites for taking into account the artificially created layering of the soil, an algorithm for analytical determination of the stress-strain state of a two-layered soil was developed in a linear setting within the limits of plane deformation. Layers are considered as linear elastic bodies of limited dimensions in the plan. The algorithm is based on the Ery stress function with arbitrary coefficients, on the dependence of the indicators of the stress-strain state of the soil layers on it and on the mechanical indicators of the material of the layers, the thickness of the artificially formed surface layer. The algorithm provides for the formulation of the load conditions by the normally distributed force of part of the soil surface, the conditions of the interaction of the layers, and the unlimited thickness of the main soil layer.The listed conditions and features of the layers constitute a system of linear algebraic equations. The solution of the system of levels provides an opportunity to determine the coefficients of the stress function and, accordingly, to determine the indicators of the stress-strain state of the two-layer soil support. The generalization of the results, carried out by planning the experiment for the selected limits of possible realizations of the mechanical properties of the soil layers, allows for determining the deflections of the surfaces of the layers depending on individual factors.The following is established. The characteristics of the dependences of the deflections of the layer surfaces on other parameters are similar. Maximum deflections decrease with increasing surface layer thickness. Deflections of the interaction surface of the soil layers are linearly dependent on the Poisson ratio of the main soil layer and decrease as the ratio increases. The results obtained within the limits of the linear formulation can be considered sufficiently reliable because they are obtained analytically and generalized by the methods of the linear theory of elasticity and the method of planning the experiment.

3D Printable Multifunctional Electrochemical Nano‐Doped Biofilament

AbstractFused deposition modeling (FDM) represents a state‐of‐the‐art 3D printing technology that holds great promise in the field of electrochemistry as a fast, in‐house, and digital fabrication method of sustainable sensors. Despite the progress in FDM, existing practical 3D printed sensors still require post‐printing treatment to improve their operational features, either through (electro)chemical surface activation or surface modification with external functional materials. Herein, a novel lab‐made conductive biofilament with integrated two different types of metallic nanoparticles (NPs) for the 3D printing of ready‐to‐use and multiplexed electrochemical sensors is introduced. The filament is composed of biodegradable polylactic acid as a base, polyethylene glycol dimethyl ether as a plasticizer, carbon black as a conductive filler, and nanopowder oxides of bismuth and copper as integrated functional precursor materials. The as‐printed sensors serve as multifunctional transducers for the direct and sensitive determinations of several analytes, by exploiting the different properties of the two co‐existing NPs. Particularly, heavy metals (such as lead, and cadmium) are voltammetrically quantified by amalgamation with BiNPs electrogenerated from Bi2O3, while biomarkers (such as glucose, and uric acid) are determined in enzymatic‐free modes. Determination of glucose takes advantage of the electrocatalytic properties of CuO, while uric acid is directly oxidized at the sensor.

Antifouling coatings for electrochemical sensors

Electrochemical sensors are extremely promising for the analysis of a number of organic and inorganic compounds both in biological fluids and natural waters during environmental monitoring due to easing operation, ease of miniaturization, low cost, low limits of analyte determination and the possibility of modifying electrodes with a wide range of organic and inorganic compounds and nanomaterials. One of the main problems limiting the use of electrochemical sensors is electrode fouling. The main way to solve this problem is antifouling coatings. Depending on the application, various additional requirements are imposed on the antifouling coatings, such as, for example, biocompatibility or mechanical strength. In this review, various types of antifouling coatings for sensors are considered, the main areas of application of certain coatings are indicated. The main emphasis is placed on non-biocidal coatings, as the most promising ones.

A simple, sensitive, and selective colorimetric chemosensor for sequential determination of dual analytes, Ce3+, H2PO4−, and its applications in the logic gate construction and the system of keypad lock

AbstractSodium (E)‐3‐hydroxy‐4‐((2‐hydroxynaphthalen‐1‐yl)diazenyl)naphthalene‐1‐sulfonate (Calcon, CAL), is employed for the first time as a reversible colorimetric chemosensor to detect and measure Ce3+ and H2PO4− sequentially in the aqueous medium. The detection process has two steps. The interaction of CAL and Ce3+ in the first step with a noticeable color shift from purple to blue. Further, the reaction between CAL‐Ce3+ and H2PO4− shows a clear color return from blue back to initial purple similar to that for CAL. The UV–visible examination of this color return reveals that H2PO4− removes Ce3+ and restores CAL content. The results showed that CAL and CAL‐Ce3+ had a strong binding affinity and adequate detection limits for the Ce3+ and H2PO4−, respectively. For Ce3+, the linear range and detection limit are 1.20 × 10−6‐1.02 × 10−4 and 2.0 × 10−7molL−1, while for H2PO4−, they are 2.0 × 10−7‐8.7 × 10−6 and 3.0 × 10−8 molL−1. Finally, we measured these two ions in real samples using this methodology. Furthermore, the examination of the suggested receptor's logical behavior revealed that it can operate as a colorimetric chemosensor of the INHIBIT type, receiving chemical inputs and producing a UV–visible absorbance signal as the output. If Ce3+ and H2PO4− inputs are added in proper order, the receptor may also function as a molecular “keypad lock.”

Multisensors based on electrolyte-gated organic field-effect transistors (EGOFETs) with aptamers as recognition elements: current state of research

The review gives a systematic account of published data devoted to multisensor technologies for manufacturing effective miniature devices capable of simultaneous accurate determination of several analytes and/or characteristics of biological fluids. The use of electrolyte-gated field-effect transistors as a biosensing platform is considered in detail. The devices based on these transistors demonstrate record-low limits of detection and are easy for mass production. The use of electrolyte-gated field-effect transistors in combination with aptamers capable of specifically binding to various analytes forms the grounds for innovations in early medical diagnosis (label-free biomarker detection). The most successful examples of multisensor devices using these transistors are presented, and the prospects of using aptamers as a recognition element in these devices are demonstrated.<br>Bibliography — 154 references.

On-site preparation of sandwich plasmonic coupled SERS tape toward pesticide residue determination on food surface.

Asandwich plasmonic coupled surface enhanced Raman spectroscopy (SERS) tape is proposedprepared by peeling the chemical printed silver nanocorals (AgNCs) from Cu sheet with adhesive tape, which can sample targets from food surface and sandwich them between substrates and Cu sheet for SERS detection. The solid-to-solid transformation method for fabricating SERS tapes can effectively avoid the weakening of tape stickiness during the preparation process. The sandwich plasmonic coupled structure of AgNC substrate, targets, and Cu sheet display excellent SERS activity (EF = 1.62 × 107) for sensitive determination of analytes. In addition, due to the high heat conductivity of Cu sheet, the thermal effect of laser irradiation during SERS detection cannot damage the AgNC tapes, which ensures the reproducibility of subsequent quantification. The sandwich plasmonic coupled SERS tape is demonstrated to quantify malachite green (MG) and methyl parathion (MP) with good linear coefficients (> 0.98) by two typical calibration plots under different concentration ranges. The limit of detection (LOD) of the method is 0.17 ng/cm2 and 0.48 μg/cm2 (S/N = 3) for MG and MP. This method can realize the quantitative determination of MP and MG on the surface of fruits and fish scale with recoveries of 93-113%. The satisfactory detection results demonstrate the proposed sandwich plasmonic coupled AgNC tape can be successfully applied toSERS-based point-of-care testing (POCT) for pesticide residue determination, which will provide a new path for designing and constructing SERS tapes.

Development of a dispersive liquid-liquid microextraction method for the evaluation of maternal-fetal exposure to cocaine employing human umbilical cord tissue.

Illicit drug use is a serious and complex public health problem, not only due to the severity of the health damage but also to the social implications, such as marginalization and drug trafficking. Currently, cocaine (COC) is among the most abused drugs worldwide with about 22 million users. Drug abuse has also been found in women during the pregnancy period, which has shed light on a new group for epidemiology. The diagnosis of COC use in these cases usually depends largely on the mother's reports, which in several cases omit or deny consumption. Therefore, considering physical-chemical methods of sample preparation and exposure biomarkers, the development of analytic toxicological methods can help to confirm drug use during pregnancy. Thus, the objective of the present work was to develop an analytical method based on dispersive liquid-liquid microextraction for the determination of COC analytes, using umbilical cord tissue as an alternative biological matrix, and detection by gas chromatography coupled to mass spectrometry. Therefore, after optimization, the dispersive liquid-liquid microextraction method was fully validated for quantification of COC, benzoylecgonine, cocaethylene, ecgonine, ecgonine methyl ester and norcocaine. The limits of detection were between 15 and 25 ng/g, the limits of quantification were 30 ng/g for ecgonine and 25 ng/g for the other analytes. Linearity ranged from the limits of quantification to 1,000 ng/g. Coefficients of variation for intra-assay precision were <18.5%, inter-assay was <8.75% and bias was <16.4% for all controls. The developed method was applied in 10 suspected positive samples, based on the mother's report and maternal urine screening and confirmation. COC, benzoylecgonine, ecgonine and ecgonine methyl ester were quantified in four umbilical cords with concentrations that ranged from 39.6 to 420.5 ng/g.