Methanolic Potassium Hydroxide Solution Research Articles

GC–MS/MS method for determining quizalofop ethyl, quizalofop tefuryl, and their metabolites in foods

A gas chromatography–tandem mass spectrometry (GC–MS/MS) method was developed for the quantitative analyses of quizalofop ethyl and quizalofop tefuryl herbicides as well as their metabolites (i.e., quizalofop and its conjugates). This method fulfills the residue definition established by Japan. Following sample reflux in a methanolic potassium hydroxide solution, the residues were converted to 6-chloro-2-methoxyquinoxaline (CMQ) and extracted with hexane. Cleanup was carried out using primary secondary amine and silica gel cartridges prior to GC–MS/MS analysis. The developed method was validated for quizalofop ethyl, quizalofop tefuryl, and quizalofop in six foods at 0.01 mg/kg and at their maximum residue limits set by Japan. A satisfactory analytical performance was achieved (trueness = 80–93%, relative standard deviation = 1–7%, limit of detection = 0.00025 mg/kg for all analytes), and no significant matrix effects were observed for the examined matrices. There were no interfering peaks near the retention time of CMQ, indicating the high selectivity of this method. A satisfactory recovery was also achieved for propaquizafop in soybeans, indicating that the proposed method also complies with the residue definition established by the European Union. This method is suitable for the regulatory analysis of quizalofop ethyl and quizalofop tefuryl residues.

Gas Chromatography–Mass Spectrometric (GC-MS) Determination of Polycyclic Aromatic Hydrocarbons in Smoked Meat and Fish Ingested by Bangladeshi People and Human Health Risk Assessment

This study investigated the human health risk assessment of polycyclic aromatic hydrocarbons (PAHs) (naphthalene, fluorene, phenanthrene, anthracene, pyrene, benzo(a)anthracene, chrycene, and benzo(a)pyrene) from the consumption of smoked fish (Coral, Telapia, Shrimp, and Rupchanda) and smoked meat (Beef Shikh Kabab, Mutton Shikh Kabab, Kashmiri Kabab, and Chicken Grill) highly consumed by Bangladeshi people quantified by gas chromatography-mass spectrometry (GC-MS) technique. The samples were hydrolyzed in methanolic potassium hydroxide solution and treated with cyclohexane for the extraction of the PAHs from the samples and then subjected to GC-MS technique for the analyses of PAHs. Results showed that the minimum and maximum mean concentrations of the aforesaid PAHs were found to be 19.23 and 294.50 µg/kg in smoked meat, and 4.18 and 4.54 µg/kg in smoked fish samples. Of the carcinogenic PAHs, benzo(a)pyrene (BaP) was the most representative in smoked meat samples ranging from 6.68 to 46.90 µg/kg that exceeded the 5.0 µg/kg maximum level for smoked meat and smoked fish set by the European Commission (EC Regulation No 1881/2006).The present data indicate that all of the smoked meat are unsafe for human consumption. Mathematically calculation representing the carcinogenic risk value of targeted compounds was −4 within the acceptable range of 1.0 × 10−6 to 1.0 × 10−4 (USEPA, 1989). The spike recovery of PAHs was ranging from 70.0 to 90.5% that demonstrated the perfect reliability and accuracy of the methodology employed in this study.

Valuation of Citrus reticulata (kinnow) peel for the extraction of lutein using ultrasonication technique

Citrus reticulata (kinnow) peel is a good source of carotenoids which can be extracted using ultrasound-assisted extraction (UAE). The present study was conducted to optimize the process parameters for the extraction of lutein using UAE method with methanolic solution of potassium hydroxide as the extractant to obtain its maximum yield. The obtained extract was used for the determination of lutein yield using high-pressure liquid chromatography (HPLC). The optimized values of process parameters in the current investigation were 6.16 mL/g solvent/solid ratio, 43.14 °C temperature, 32.88% amplitude and time duration of 33.71 min, which resulted in highest lutein yield of 29.70 μg/g. The results of this study showed that UAE system has the ability to replace the conventional techniques for extraction of lutein from citrus peels. Moreover, the extracted lutein from citrus peels can be further used as an antioxidant and colouring agent in various food applications.

One-pot synthesis and antimicrobial activity of new 4,6-disubstituted-3,4-dihydropyrimidine-2(1H)-thiones

A series of 3,4-dihydropyrimidine-2(1 H )-thiones (3a-i) were synthesized in moderate yields via a one-pot reaction of 3-acetyl-2,5-diclorothiophene (1), aryl aldehydes (2a-i) and thiourea in methanolic solution of potassium hydroxide under reflux conditions. All newly synthesized compounds were characterized by extensive NMR analysis, including 1 D NMR experiments ( 1 H and 13 C) and 2D NMR experiments (COSY, HMBC and HSQC), as well as ESI-MS and HRESI-MS data. The antimicrobial activity of all new compounds (3a-f) was tested against bacteria and fungi. Thione derivative (3c) only showed activity against Staphylococcus aureus , Bacillus subtilis and Aspergillus niger .

Interspecies and seasonal differences of retinol in dairy ruminant´s milk

Milk is an essential source of macronutrients and among lipophilic vitamins is significant source of retinol. The contribution of milk to the reference daily intake for retinol varies from 11% to 16%, worldwide. The most consumed dairy products are fresh, dehydrated and condensed milk in which the amonuts of retinol are not modified to those of in whole milk. Retinol is essential to ensure a good functionality of the immune system and plays a critical role in vision, reproduction, cell differentiation as well as growth and development and is found only in animal tissues. The aim of our study was to evaluate the interspecies differences in the retinol concentration of whole raw bovine, caprine and ovine milk and to observe seasonal variation of retinol in bulk tank milk samples. Samples of raw milk were colleceted on different farms in the Czech Republic between 2013 and 2014. Retinol was measured by ultra high performance liquid chromatography with UV detection (325 nm) in isocratic mode after alkaline saponification with methanolic potassium hydroxide solution and liquid-liquid extraction into non polar organic solvent of whole raw milk. To avoid vitamin losses or degradation during the procedure, antioxidants were added to the sample extraction media. Our results indicate significant interspecies differences between bovine and ovine milk and caprine and ovine milk. Concentration of retinol is very similar in bovine and caprine milk 0.96 ±0.11 mg/L, 0.94 ±0.25 mg/L, respectively. The mean concentration in sheep´s milk is 1.75 ±0.24 mg/L. The seasonal variation of retinol in raw bovine milk was detected as high significant, with the highest concentration during winter. These results contribute to the nutrition evaluation of milk in the Czech Republic and indicate, that the sheep´s milk is the best source of retinol among the milks of ruminants kept in the Czech Republic, however it is not used in its fluid form for human consumption.

Synthesis, urease inhibition, antioxidant and antibacterial studies of some 4-amino-5-aryl-3H-1,2,4-triazole-3-thiones and their 3,6-disubstituted 1,2,4-triazolo[3,4-b]1,3,4-thiadiazole derivatives

A new series of 4-amino-5-aryl-3H-1,2,4-triazole-3-thiones, bearing various methoxybenzyl- and methoxyphenethyl groups, was synthesized by refluxing potassium hydrazinecarbodithioate salts in dilute aqueous solution of hydrazine hydrate. These salts were formed by the reaction of acid hydrazides and carbon disulfide in methanolic potassium hydroxide solution at 0-5 °C. 4-Amino-5-aryl-3H-1,2,4-triazole-3-thiones were condensed with different substituted aromatic acids to yield 3,6-disubstituted-1,2,4-triazolo[3,4-b]1,3,4-thiadiazoles. The structures of the synthesized compounds were characterized by infrared (IR), 1H and 13C nuclear magnetic resonance (NMR), elemental analysis and mass spectrometric (MS) studies. All the synthesized compounds were screened for their urease inhibition, antioxidant and antibacterial activities. Some compounds showed excellent urease inhibition activity, more than the standard drug. Others exhibited potent antioxidant activity. All the compounds showed significant antibacterial activities as compared to the standard drug.

Analysis of Methylmercury Concentration in the Blood of Koreans by Using Cold Vapor Atomic Fluorescence Spectrophotometry

BackgroundMethylmercury is an organic form of mercury that is highly toxic to humans. Here, we present and establish a novel method to detect methylmercury concentrations in the blood of Koreans.MethodsMethylmercury concentration was analyzed with an automated methylmercury analytic system (MERX, Brooks Rand Co., USA) using cold vapor atomic fluorescence spectrophotometry (CVAFS). A variety of biological materials were digested in methanolic potassium hydroxide solution. The analysis method was validated by examination of certified reference material (955c, National Institute of Standard and Technology, USA). We randomly selected 30 Korean adults (age 20 yr or older) to analyze total blood mercury and methylmercury concentrations.ResultsThe detection limit and methylmercury recovery rate using this method were 0.1 pg/L and, 99.19% (range: 89.33-104.89%), respectively. The mean blood concentration of methylmercury was 4.54±2.15 µg/L (N=30). The mean proportion of methylmercury to the total mercury concentration was 78.27% (range: 41.37-98.80%).ConclusionsThis study is the first report to analyze blood methylmercury concentration using CVAFS in Korea. We expect that this method will contribute to the evaluation of mercury exposure and the assessment of the toxicological impact of mercury in future studies.

Optimization of the GC method for routine analysis of the fatty acid profile in several food samples

The fatty acids profile of food samples was determined by gas chromatography (GC). The fat was extracted from different food samples using Soxhlet technique. Extracted triglycerides were converted to corresponding methyl esters using methanolic solution of potassium hydroxide (trans-esterification). GC method for the analysis of obtained methyl esters was optimized on two different cyanopropyl capillary columns. Good resolution of all fatty acids commonly found in foodstuffs was achieved. After optimization, the method was validated and the results for linearity, precision, limit of quantitation (LOQ), limit of detection (LOD), robustness and stability were presented. The method has been applied to the quantitative determination of the fatty acid content in different food samples: edible oil, dairy products rich with omega-3 fatty acids, different food supplements, baby food, etc.

Determination of methylmercury in fish and seafood using optimized digestion and derivatization followed by gas chromatography with atomic emission detection

Mercury is an environmental contaminant that appears in different chemical forms. Organic forms of mercury, such as methylmercury, can occur in marine organisms like fish and shellfish and are far more toxic than the inorganic form. It is therefore vital to have refined analytical methods for the different mercuric species in order to evaluate the potential risk for seafood consumers. The aim of our investigations was to develop a simple, robust and valid method for differentiation of the mercury species in marine organisms. Different alkaline and acidic digestion procedures were evaluated. The best performing methodology consisted of digestion of 0.5 g sample in methanolic potassium hydroxide solution. After derivatization with sodium tetraethylborate and extraction of the ethylated mercury species using n-hexane, a quantitative determination of the extract using gas chromatography, combined with atomic emission detection, was possible. The procedure was shown to be selective and sensitive with a limit of detection of 6.1 μg/kg for methylmercury. The average recovery for the full procedure was 91 ± 19%. A preliminary survey of seafoods confirmed the previous observation that the proportion of methylmercury in the total mercury can vary widely, up to a complete occurrence as methylmercury.

Synthesis and antimycobacterial activity of novel 4-[5-(substituted phenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol derivatives

In the present investigation, 4-hydroxy-3-methylacetophenone, on condensation with appropriate aldehydes in methanolic potassium hydroxide solution, yielded the corresponding chalcones (CI-XI). These corresponding chalcones were reacted with phenyl hydrazide in glacial acetic acid, which led to the formation of novel 4-[5-(substituted phenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol derivatives. All newly synthesized compounds were evaluated for their antimycobacterial activities against isoniazid-resistant Mycobacterium tuberculosis using agar dilution. 4-[5-(4-Fluoro phenyl)-1-phenyl-4,5-dihydro-1H-3-pyrazolyl]-2-methylphenol showed good antimycobacterial activity, with a minimum inhibitory concentration of 0.62 μg/ml.

Development and Validation of a Spectrophotometric Method for the Determination of Macrolide Antibiotics by Using 2,4-Dinitrophenylhydrazine

A simple, novel, sensitive, and specific spectrophotometric method was developed and validated for the determination of azithromycin (AZ), clarithromycin (CLA), and roxithromycin (ROX) in bulk powders and their dosage forms. The proposed method was based on the interaction of any of the cited drugs with 2,4-dinitrophenylhydrazine in the presence of an acid catalyst, followed by treatment with a methanolic solution of potassium hydroxide; an intensely colored chromogen was formed that was measured in dimethylformamide, as the diluting solvent, at 542-545, 523-526, and 539-542 nm for AZ, CLA, and ROX, respectively. All variables affecting the development of the measured chromogens were studied and optimized. Beer's law was obeyed in the concentration ranges of 5-40, 5-35, and 5-35 microg/mL for AZ, CLA, and ROX, respectively, with good correlation coefficients (0.9991-0.9999). The limits of detection for this method ranged from 0.77 to 1.47 microg/mL, and the relative standard deviations were 1.24-1.8%. The proposed method was applied successfully to the determination of the 3 drugs in pure bulk form, tablets, and suspensions without interference from commonly encountered additives. The results compared favorably with those of a previously reported method. The mechanism of the reaction was also studied.

Comparison of GC and HPLC Methods for Quantitative Analysis of Tinuvin 622 After Saponification in Polyethylene

This study describes the sample preparation and two chromatographic techniques for determination of Tinuvin 622 in polyethylene. The first part of the two methods consisting of dissolving the polyethylene in boiling xylene is followed by addition of a methanolic solution of potassium hydroxide. The polymeric light stabilizer, Tinuvin 622, is thereby saponified to 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (diol). Addition of the methanolic solution of the saponification reagent simultaneously precipitates the polyethylene matrix. Then the diol is quantified using either gas chromatography (GC) or high performance liquid chromatography (HPLC). For GC, a Macherey Nagel Optima-17 capillary column (30 m×0.25 mm ID, film thickness 0.25 µm) is used. Nitrogen is used as carrier gas and make-up gas. The detection system is a flame ionization detector. For HPLC, an octadecyl silane (ODS) column (30 cm×4 mm, particle size 5 µm) and a mobile phase methanol: water mixture (3:97, v/v) are used. Detection of analyte is carried out at 215 nm. Both methods can be used to determine Tinuvin 622 in polyethylene in the concentration range of 0.02–1%, which represents the usual application concentration.

Spectrophotometric and fluorimetric determination of diazepam, bromazepam and clonazepam in pharmaceutical and urine samples

New spectrophotometric and fluorimetric methods have been developed to determine diazepam, bromazepam and clonazepam (1,4-benzodiazepines) in pure forms, pharmaceutical preparations and biological fluid. The new methods are based on measuring absorption or emission spectra in methanolic potassium hydroxide solution. Fluorimetric methods have proved selective with low detection limits, whereas photometric methods showed relatively high detection limits. Successive applications of developed methods for drugs determination in pharmaceutical preparations and urine samples were performed. Photometric methods gave linear calibration graphs in the ranges of 2.85–28.5, 0.316–3.16, and 0.316–3.16 μg ml −1 with detection limits of 1.27, 0.08 and 0.13 μg ml −1 for diazepam, bromazepam and clonazepam, respectively. Corresponding average errors of 2.60, 5.26 and 3.93 and relative standard deviations (R.S.D.s) of 2.79, 2.12 and 2.83, respectively, were obtained. Fluorimetric methods gave linear calibration graphs in the ranges of 0.03–0.34, 0.03–0.32 and 0.03–0.38 μg ml −1 with detection limits of 7.13, 5.67 and 16.47 ng ml −1 for diazepam, bromazepam and clonazepam, respectively. Corresponding average errors of 0.29, 4.33 and 5.42 and R.S.D.s of 1.27, 1.96 and 1.14 were obtained, respectively. Statistical Students t-test and F-test have been used and satisfactory results were obtained.

2-(3-Acylselenoureido)benzonitriles and 2-(3-Acylselenoureido)thiophene-3-carbonitriles. Preparation, Structure Elucidation, Cyclization and Retrocyclization Reactions

Synthesis of 2-(3-acylselenoureido)benzonitriles and 2-(3-acylselenoureido)thiophene- 3-carbonitriles 5a-5f by addition of 2-aminonitriles 4a-4c to benzoyl- or 2,2-dimethyl- propanoylisoselenocyanate and their cycloaddition reactions are described. Structures of compounds 5a-5f were supported by CIMS, FTIR, 1H, 13C, 77Se and 15N NMR spectra. The parameters of 15N and 77Se nuclei were obtained from inverse 1H-X 2D HMBC and GSQMBC correlation experiments at natural abundance. Structure of compound 5b was confirmed by X-ray analysis. The geometry of 5b was optimized by ab initio RHF/DZVP quantum chemistry calculation. A very good correlation between the calculation and experimental data was found. The geometry of 5e was optimized by ab initio DFT/VWN/DZVP quantum chemistry calculation. It was found that title compounds 5a-5f do not undergo isomerization to acylisoselenoureas, in contrast to analogous ester derivatives. Fused 6-imino-6H-1,3- selenazinium salts (chlorides 6a-6f, hydrogensulfates 7a-7f and tetrafluoroborates 8a-8f) were prepared by an acid cyclization of 5a-5f. It was found that neutralization of 6a-6f, 7a-7f and 8a-8f led to their retrocyclization to 5a-5f. Selenoureas 5a-5f with equimolar amounts of methanolic potassium hydroxide afforded potassium salts 9a-9f. Only the salts 9b, 9c, 9e and 9f of the thiophene series were isolated. Their heating in methanol solution led to deacylation of isoselenoureas 10b and 10c. The in situ prepared compounds 9a and 9d cyclized and deacylated to 4-aminoquinazoline-2-selenole 11a under the same conditions. The compounds 5a-5f and 10a-10c cyclized to fused 4-aminopyrimidine-2-selenols 11a, 11b and 4-aminopyrimidine-2-selenone 12c by boiling in methanolic potassium hydroxide solution.

Chemical and 1H NMR spectroscopic investigations of stereoisomeric Tc(V) DMSA complexes

Stereoisomeric Tc(V) complexes derived from meso and racemic 2,3-dimercaptosuccinic acid dimethylester have been identified by 1H NMR spectroscopy and some of them have been isolated. In methanolic amine or potassium hydroxide solution, complexes of the meso ligand racemize to give the complex compounds of the racemic 2,3-dimercaptosuccinic acid dimethylester. In methanolic potassium hydroxide solution, Tc(V) complexes of racemic 2,3-dimercaptosuccinic acid are formed by ester hydrolysis.

Synthesis of some 5H‐benzo[a]phenoxazin‐5‐one derivatives

AbstractThe substituted 6‐bromo and 6‐chloro‐5H‐benzo[a]phenoxazin‐5‐ones, prepared by condensation of substituted 2‐aminophenols with 2,3‐dibromo or 2,3‐dichloro‐1,4‐naphthoquinone in methanolic potassium hydroxide solution, have been dehalogenated to substituted 5H‐benzo[a]phenoxazin‐5‐ones in the presence of sodium hydrosulfite dissolved in aqueous pyridine under nitrogen atmosphere.

Assay method for urokinase activity by capillary-tube isotachophoresis using a synthetic substrate

Urokinae activity was determined by capillary-tube isotachophoresis using N- a-acetyl- l-lysine methyl ester as a synthetic substrate. The resulting N- a-acetyl- l-lysine was separated and detected isotachophoretically using methanolic potassium hydroxide solution adjusted to pH 5.32 by adding a-ketoglutaric acid as a leading electrolyte and methanolic betaine hydrochloride solution as a terminating electrolyte. The enzymatic reaction was stopped by addition of tannic acid and the resulting supernatant solution was injected into an isotachophoretic analyser. Linearity was observed at urokinase activities in the range 1–30 I.U. The urokinase activities in commercial products determined by the method were in good agreement with those determined by Walton's modified plate method. The coefficient of variation of the method was less than 3.4%.

Reaktionen von β‐Chlorvinylaldehyden. IV [1]. Synthesen von 2‐Formylmethylen‐2H‐1‐benzopyranen und Benzopyrylocyaninfarbstoffen aus β‐Chlorvinylaldehyden

Reactions of β‐Chlorovinylaldehydes. IV. Syntheses of 2‐Formylmethylene‐2H‐1‐benzopyranes and Benzopyrylocyaninedyes from β‐Chlorovinylaldehydesα‐Alkyl‐β‐chlorocrotonaldehydes react with salicylaldehyde in methanolic solution of potassium hydroxide forming 2‐formyl‐methylene‐2H‐1‐benzopyranes 1. The corresponding benzopyryliumsalts 2 which are easily available from 1 and strong acids, exist in the enolic form. They react at room temperature in alcoholic solution with elimination of ethyl formiate, yielding dark blue compounds which were identified as 2,2′‐benzopyrylotrimethincyanindyes 3. The structure of 3 has been elucidated by means of 1H‐n.m.r.‐spectra.

Free and bound lipids of Neurospora crassa

Extraction of light and dark grown cells of Neurospora crassa with chloroform-methanol gave a free lipid extract in which the relative amounts and compositions of sterols, fatty acid and carotenoid fractions were determined. Further extraction of the cells with methanolic potassium hydroxide solution liberated a bound lipid fraction from the cells. The levels of the bound lipid fraction were much lower than those of the free lipids but analysis showed that the composition was similar to that of the free lipids.

Confirmation of pesticide residue identity: part IX. Organophosphorus pesticides.

This paper describes a confirmation procedure for residue levels of dyfonate, dichlorofenthion and cyanox. After extraction and quantitation by flame photometric detector (FPD)-gas liquid chromatography (GLC), the organophosphorus pesticides are hydrolyzed in a 10% methanolic-potassium hydroxide solution. The phenolic hydrolysis products are then extracted from this solution and reacted with pentafluorobenzyl bromide to produce the pentafluorobenzyl (PFB) ether derivatives. These PFB ethers are subsequently cleaned-up and fractionated on a silica gel micro-column and analyzed by electron capture (EC)- GLC.