Sensitive Detection of Heregulin-α from Biological Samples Using a Disposable Stochastic Sensor Based on Plasma Deposition of GNPs–AgPs’ Nanofilms on Silk

A composite material comprised of graphene nanoplatelet and silver particles (GNPs–AgPs) was used for the deposition of GNPs–AgPs’ nanofilms with cold plasma on silk. α-Cyclodextrin was used as a modifier of the active surface of the disposable sensor. The disposable stochastic sensor was used in screening tests for the assay of heregulin-α in whole blood and tissue samples. The disposable stochastic sensor showed a low limit of determination (4.10 fg mL−1) and can be used with high sensitivity on a wide concentration range (4.10 fg mL−1–0.04 µg mL−1). The screening method was validated against ELISA when good correlations (confirmed also by the t-test) were obtained.

Detection of Carrageenan in Meat Products Using Lectin Histochemistry

Carrageenan is a polysaccharide that is widely used in the food industry. Due to its water holding capacity, there is a higher risk of adulteration for economic reasons related to it. A verifiable method for detecting carrageenan is still missing in the food inspection sector. The detection of carrageenan in meat products is not well described. Our study describes lectin histochemistry as a novel approach for carrageenan detection. Within this study, the detection of carrageenan in meat products by lectin histochemistry is validated. Lectins of Arachis hypogaea (PNA) and Bandeiraea simlicifolia (BSA), specific for galactose units of carrageenan, were used. The samples included model meat products (ground chicken-meat products) and meat products from retail markets (chicken and pork hams, sausages, salami, and dried sausages). The limit of determination (LoD) of this method was set at 0.01 g kg−1. The method sensitivity for lectin PNA reached 1, and, for lectin BSA, it reached 0.96. Method specificity for lectin PNA was 1, and, for lectin BSA, it was 1.33. Cross-reactivity with other hydrocolloids tested was not confirmed. The results confirm that lectin histochemistry is suitable for detecting carrageenan in meat products.

Rhodamine B - as New Chromophore for the Determination of Melatonin in Biological, Food, and Pharmaceutical Samples

Aim and Objective: Melatonin is an essential biomarker for sleep-related disorders. Reliable methods of analysis are needed for melatonin. Therefore, a new chromophore (Rhodamine B) was proposed for the assay of melatonin; this method succeeded to enlarge the working concentration range and to decrease the limit of determination comparing with the method that just used the native fluorescence of melatonin. Materials and Methods: Rhodamine B was proposed as a new chromophore for the assay of melatonin in biological, food, and pharmaceutical samples. Fluorescence was used for the determination of melatonin. Results: The results obtained using Rhodamine B were compared with those obtained by the native fluorescence of melatonin. Using the new chromophore, melatonin was determined in the concentration range between 0.01 and 50 pmol L-1, with the detection limit of 2.4 fmol L-1. The recovery of melatonin was higher than 98.00% with a relative standard deviation of less than 0.10%, when the method was applied for the assay of melatonin in samples such as breast milk, whole blood, milk powder, and pharmaceutical formulations. Conclusion: Utilization of Rhodamine B enlarged the linear concentration range for the assay of melatonin and decreased the detection limit, making possible the assay of melatonin in a variety of samples such as pharmaceuticals, food, and biological samples.

Conductive Metal-Organic Frameworks for Amperometric Sensing of Paracetamol

An electrochemical sensor for paracetamol is executed by using conductive MOF (NiCu-CAT), which is synthesized by 2, 3, 6, 7, 10, 11-hexahydroxytriphenylene (HHTP) ligand. The utility of this 2D NiCu-CAT is measured by the detection of paracetamol, p-stacking within the MOF layers is essential to achieve high electrical conductivity, redox activity, and catalytic activity. In particular, NiCu-CAT demonstrated detection Limit of determination near 5μM for paracetamol through a wide concentration range (5–190 μM). The NiCu-CAT/GCE exhibits excellent reproducibility, stability, and interference for paracetamol.

Validation of the framycetin sulfate determination technique by HPLC in a Framidex medicinal preparation

A method for determination of framycetin sulfate in a Framidex preparation (eye and ear drops) by HPLC-UV (λ = 365 nm) using 2, 4-dinitrofluorobenzene as a derivatizing agent has been developed The characteristics of analytical methods determined for the purpose of their validation and relevant criteria for the validity of validated methods with the goal of the quality control of drugs (pharmaceutical substances and drugs) are presented. According to the results of an intralaboratory experiment on the validation assessment of the method by the parameters of the specificity, limit of determination (LOD), linearity, precision and laboratory accuracy, it is shown that the LOD decreases by an order of magnitude, the correlation coefficient is not less than 0.99 correctness (average value — 97.5 – 102.5%; variation coefficient — not more than 2.0%; the confidence range should include 100% of values), convergence (variation coefficient — not more than 1.5%), intermediate precision (variation coefficient — not more than 1.5%). It is shown that the obtained values of metrological characteristics do not exceed the validation criteria and the developed method matches all the well-known requirements of GMP (Good Manufacturing Practice).

Method Of Polarographic Determination Of Platyphylline In A Form Of N-Oxide And Its Validation In Solution For Injection

A new approach was studied for determination of alkaloid Platyphylline in a form of N-oxide by reduction current on the dropping mercury electrode. The optimal conditions were selected for chemical transformation (using of potassium peroxymonosulfate) of Platyphylline into N-oxide and with following product reduction on the electrode. On this basis, the methods of determination of Platyphylline in the solution for injections and in tablets were developed. New methods of indication are characterized by very simple sample preparation, wide linear range, low limit of determination (2.1∙10-6 mol∙L–1), sufficient accuracy and selectivity. These methods were checked while analysing one-component solution for injections and combined drug – tablets. The obtained results of analysis were compared to those indicated in the certificate of analysis issued by testing laboratories of the State Service of Ukraine on Medicines and Drugs Control. Defined metrics vary from 97.17 to 102.02 %. The method of determination Platyphylline in the solution for injections «Platyphylline-Zdorovye» is validated (the criterion linearity, accuracy as well as precision). The validation evaluation results have proved the correctness and reliability of the developed method. The main feature of the proposed method for the determination of Platyphylline using N-oxide as an analytical form is the ability to determine directly the metabolite of Platyhylline. Consequently, the work can be adapted for the determination of N-oxide Platyphylline in plant materials.

HYGIENIC EVALUATION OF INSECTICIDES CONTENT DYNAMICS IN PLANTS AFTER APPLICATION ON SOYA CROPS

Relevance. Taking into account the widespread application of plant protection products in soybean cultivation, there is a need for research aimed at hygienic evaluation of the potential danger of soybean crop contamination after pesticide and in particular insecticides application. Objective of the study is a hygienic evaluation of insecticides content dynamics in plants after application on soya crops. Materials and methods. Materials – active ingredients of the studied insecticidal preparations, soya plants (verdurous mass, beans and seeds). Full-scale in-field hygienic experiment, high-performance liquid chromatography, gas-liquid chromatography, statistical methods were used in the study. Results. The highest concentration of active substances was determined in green plants, if processing had been performed at an early stage of plant formation (acetamipride – 0.63 mg/kg, fenproximate – 0.41 mg/kg, thiamethoxam – 0.21 mg/kg). In the case of twice repeated applications, the largest amount of pesticides was determined in beans and seeds (alpha-cypermethrin – 0.51 mg/kg, chlorpyrifos, tebufenpyrad – 0.35 mg/kg). As the culture ripened and the formation of beans and seeds took place, the content of active substances gradually decreased and after 20-25 days residues were found at or below the limit of determination for the corresponding methods. Conclusions. The redidues of alpha-cypermethrin, bifenthrin, chlorpyrifos cypermethrin, tebufenpyrad, phenpyroximate, acetamiprid, thiamethoxam in plants, beans and soybean seeds gradually decreased and did not exceed established hygienic standards by the harvesting period in field studies. It is proved that if to follow the established hygienic and agrotechnical regulations for its application, the studied insecticides dissipate or decompose in crop plants during one vegetative season and do not pose a potential risk to the health of consumers.

Uptake and Dissipation of Carbofuran and Its Metabolite in Chinese Kale and Brinjal Cultivated Under Humid Tropic Climate

Carbofuran is an insecticide with a broad spectrum of activity and is relatively cheap. It is banned in many countries in the world; however, it remains widely used in Asia, Australia, and South America. Carbofuran is commonly used in vegetable farming in Malaysia and it is a legally registered pesticide. This study reports the uptake and dissipation of carbofuran and 3-ketocarbofuran in Chinese kale and brinjal under humid tropic field conditions. The residue profile in plants demonstrated an increase to a maximum, followed by a consistent reduction to a level below the limit of determination (<0.01 mg/kg) over the experimental period. The maximum residue concentration was attained on Day 3 for kale (1.16 mg/kg fresh weight) and Day 7 for brinjal (0.06 mg/kg fresh weight) after carbofuran application. In order to comply with the maximum residue level (MRL) of 0.01 mg/kg, the preharvest interval for kale and brinjal were suggested at 23 and 28 days, respectively. The preharvest interval indicates that carbofuran is not recommended for Chinese kale but it is acceptable for brinjal. The average half-life of carbofuran in soil is 1.24 days, shorter than the literature values reported based on temperate condition, indicating accelerated dissipation under tropical climate. The estimated half-life of carbofuran in leaves was shorter than that in fruits with kale leaves reported at 2.54 days whilst brinjal leaves and fruits recorded at 3.22 and 10.33 days, respectively.

Method Validation for Analysis of Aroclor 1260 in Transformer Oil using Gas Chromatography – Electron Capture Detection

Since early 1980’s, the production and usage of Polychlorinated biphenyls (PCBs) have been banned throughout the world due to its carcinogenicity to humans and animals. However, due to the large half-lives of PCBs, large amounts of stocks are still available in storage. This study presents the validation data of the method developed for analysis of Aroclor 1260 in transformer oils in order to determine the concentrations for systematic disposal and destruction.The transformer oil samples were prepared according to the ASTM D 4059 with few modifications. PCBs in transformer oils were extracted with iso-octane followed by deactivated florisil cleanup and detection by GC – ECD using HP 5 GC column (30 m x 0.32 mm x 0.25 μm). The study was performed under matrix matched condition to eliminate the matrix effect that was found to be significant. The method was found linear over a wide working range from 2.5 ppm – 100 ppm with a regression coefficient of 0.994 and a lower limit of determination of 2.5ppm. Method showed satisfactory repeatability with relative standard deviation below 7% over the entire working range. Accuracy of the method was assured using spike recoveries at 5 ppm, 10 ppm and 50 ppm with 85%, 105% and 93% respectively. The selectivity of Aroclor 1260 was confirmed against Aroclor 1254 and Aroclor 1242 considering uniquely identified non – overlapping chromatographic peaks. Based on the performance characteristics, this method can be suggested as an accurate and precise methodology to analyze Aroclor 1260 present in transformer oil.

Preparation and Electrochemical Properties of Multi-Walled Carbon Nanotube/Dextran/Nano-Gold Composites

Multi-walled carbon nanotube (MWCNT)/dextran/nano-gold composite was prepared by chemical solution reaction. The average diameter of gold nanoparticles was around 15 nm. MWCNT/dextran/nano-gold composites were uniformly dispersed in aqueous solution as electrode materials. MWCNT/dextran/nano-gold composites exhibited excellent electrochemical property in [Fe(CN)6]3– /4– solution. Experimental results showed that the MWCNT/dextran/nano-gold composites with 50% MWCNTs presented obvious redox peak and low impedance and had good electrochemical response to Cu2+. The redox peak currents were linear while the concentration of copper ions ranged from 1× 10–2 to 1 × 10–4 M. The relationship between oxidation peak currents I (A) and Cu2+ concentration C (M) was: ipk (A) = 2.6207 × 10–6 + 43.91572 × 10–4 × C (M), and the limit of determination (LOD) of Cu2+ was 0.63 × 10–6 M, and linear coefficient was 0.9923.