Silver Nitrate-impregnated Silica Gel Research Articles

Thin-layer chromatography on silver nitrate-impregnated silica gel for analysis of homemade tetrahydrocannabinol mixtures.

Various forms of cannabidiol (CBD)-containing products are sold in Japan. CBD is easily converted to mixtures of ∆9-tetrahydrocannabinol (∆9-THC) and its isomer, ∆8-THC, using household chemicals like diluted hydrochloric acid. This ease of production increases concerns regarding production of homemade THC mixtures. It is difficult to separate ∆9-THC, ∆8-THC, and CBD using thin-layer chromatography (TLC) on conventional silica gel. The selectivity of TLC on silver nitrate-impregnated silica gel (AgNO3-silica gel) differs from that of conventional silica gel. This study thus aimed to evaluate the separation ability of AgNO3-silica gel TLC. To evaluate potential separation ability, standards of five THC isomers (∆9-THC, ∆8-THC, a pair of diastereomers of ∆10-THC, and ∆6a,10a-THC), CBD, CBN, and ∆9-THCA were analyzed by 10% AgNO3-silica gel TLC (developed using toluene, system A) and silica gel TLC [developed using n-hexane/diethyl ether (8:2, v/v), system B]. Then, mock homemade THC mixtures, prepared by heating crystalline CBD in acidic ethanol, were analyzed using systems A and B. System A showed clear separation between the five THC isomers and between ∆9-THC, ∆8-THC, CBD, and their by-products in the mock homemade THC mixture. However, system B did not separate some combinations of THC isomers and gave a single group-like spot to the THC mixture. AgNO3-silica gel TLC shows high separation ability between THC isomers and among ∆9-THC, ∆8-THC, and CBD. It will thus be useful for analyzing homemade THC mixtures.

Isolation of Jatropha curcas Oil Based Linoleic Acid By Using Argentation Column Chromatography

Argentation column chromatography is a method used for separating similar molecules such as fatty acids which have a slightly different in stereochemistry. In this study, silver nitrate-impregnated silica gel was used as the adsorbent to isolate and purify Jatropha curcas oil fatty acids mixtures. The effects of silica gel, silver nitrate, adsorbent quantity and fatty acid quantity on the purity and recovery percentage as well as ratio of linoleic acid to oleic acid were investigated. The results showed that at optimal condition of purification, the purity of linoleic acid increased from 38.4% to 78.7%. In the isolation process, linoleic acid adsorbed most strongly on the AgNO3/SiO2 adsorbent followed by oleic acid due to greater number of double bond and high ability to form polar charge-transfer complexes.

Studying the Physicochemical Properties and Isolation of Unsaturated Fatty Acids from Edible Oils by GC-MS and Argentated Silica Gel Chromatography

The core objective of this study was to investigate the physicochemical characteristics and fatty acid composition of the oils of sunflower, olive, virgin coconut and ginger oils, as well as the separation of their unsaturated fatty acids. The data indicated a significant variation in physicochemical properties (acid, saponification, ester, and iodine values) among oils. Transesterification process was carried out at a molar ratio of 1:7:0.1 of oil: methanol: KOH. Fatty acid methyl esters of oils were analyzed by infrared (IR) and gas chromatography–mass (GC-MS) spectrometry. Twelve fatty acids were identified, where the major fatty acid of olive oil was found to be oleic acid (89%), whereas those of sunflower and ginger oils were linoleic acid (80.9 %) and (79.3 %), respectively. Sunflower and olive oils were fractionated by 25% silver nitrate-impregnated silica gel column chromatography. By this method, linoleic acid methyl ester from sunflower and oleic acid methyl ester from olive oil were isolated with high purity percentages and yields. This study is significant for the development of food and pharmaceutical products.

Rapid Production of trans‐Cyclooctenes in Continuous Flow

AbstractA new method for rapid larger‐scale production of trans‐cyclooctenes (TCOs) in continuous flow was developed: Up to 2.2 g/h of specific TCOs can be produced by using this procedure. This method utilizes the classical photoisomerization of cis‐cyclooctenes (CCOs) for the synthesis of TCOs but substitutes the conventionally used silver nitrate impregnated silica gel column for a liquid−liquid extraction module. In addition, this method provides the possibility of external addition of a substrate to scale up and speed up the production of TCOs because the concentration of the CCO is kept constant. This method was applied for the synthesis of several commonly used TCOs.

Preparative separation of α- and β-santalenes and (Z)-α- and (Z)-β-santalols using silver nitrate-impregnated silica gel medium pressure liquid chromatography and analysis of sandalwood oil

The major sesquiterpene constituents of East-Indian sandalwood oil (Z)-α- and (Z)-β-santalols have shown to be responsible for most of the biological activities and organoleptic properties of sandalwood oil. The work reported here describes the strategic use of medium pressure liquid chromatography (MPLC) for the separation of both α- and β-santalenes and (Z)-α- and (Z)-β-santalols. Silver nitrate impregnated silica gel was used as the stationary phase in MPLC for quantitative separation of α- and β-santalenes and (Z)-α- and (Z)-β-santalols with mobile phases hexane and dichloromethane, respectively. The purities of α-santalene and (Z)-α-santalol obtained were >96%; however, β-santalene and (Z)-β-santalol were obtained with their respective inseparable epi-isomers. Limits of quantification (LoQ) relative to the FID detector were measured for important sesquiterpene alcohols of heartwood oil of S. album using serial dilutions of the standard stock solutions and demonstrated that the quality of the commercial sandalwood oil can be assessed for the content of individual sesquiterpene alcohols regulated by Australian Standard (AS2112-2003), International Organization for Standardization ISO 3518:2002 (E) and European Union (E. U.).

Enantioselective Trace Analysis of Polychlorinated Biphenyl Enantiomers in Soils by GC-ECD/MS

A simple method for qualitative and quantitative determination of PCB95, 132, 149 and 174 enantiomers in soils and sediments using GC-ECD/MS was proposed. On the promise of good purification efficiency, high recovery and easy operability, H2SO4 washing and a multi-layer column filled with 1 g anhydrous sodium sulfate, 2 g 10% silver nitrate-impregnated silica gel, 4 g 3.3% water-deactivated silica gel and 1.5 g anhydrous sodium sulfate were selected as purification procedures. The chromatographic conditions were optimized to obtain the best enantiomeric separation. Complete baseline separations were achieved for PCB95, 132 and 149, as well as approximate baseline separation was obtained for PCB174. This method was proved to have highly satisfactory accuracy, precision and sensitivity with mean recoveries of target PCB enantiomers in range of 71.42−80.12% and RSD<6%. The detection limits of the method were 11.37−25.36 pg•g−1.

Quantitative and Qualitative Trapping of Arsines Deployed to Assess Loss of Volatile Arsenic from Paddy Soil

Arsenic volatilization in the environment is thought to be an important pathway for transfer from terrestrial pools to the atmosphere. However, this phenomenon is not well characterized due to inherent sampling issues in trapping, quantifying and qualifying these arsine gases; including arsine (AsH(3)), monomethyl arsine (MeAsH(2)), dimethyl arsine (Me(2)AsH) and trimethyl arsine (TMAs). To quantify and qualify arsines in air we developed a novel technique based on silver nitrate impregnated silica gel filled tubes. The method was characterized by measuring the recovery of trapped arsines after elution of this chemo-trap with hot boiling diluted nitric acid. Results from three separate experiments, measured by ICP-MS, showed that the method is reproducible and quantitative. Arsine species recovery ranged from 80.1 to 95.6%, with limit of detection as low as 3.8 ng per chemo-trap tube. Moreover, HPLC-ICP-MS analysis of hot boiling water eluted traps showed that the corresponding oxy ions of the arsines were formed with the As-C bonds of the molecule intact, hence, allowing qualification of trapped arsine species. A microcosm study examining volatile arsenic evolution from field contaminated Bangladeshi paddy soils (24.2 mg/kg arsenic) was used to show the application of silver nitrate chemo-trapping approach. Traps were placed on the inlet and the outlet of microcosms containing the soils that were either (cattle derived) manured or not, or flooded or not, in a factorial design. The headspace was purged with air at a flow rate of 12 mL/min. Results showed that as much as 320 ng of arsenic (0.014% of total soil content) could be emitted in a 3 week period for manured and flooded soils and that TMAs was the dominant species evolved, with lesser quantities of Me(2)AsH. No volatile arsenic evolution was observed for nonmanured treatments, and arsine release from the nonflooded, manured treatment was much less than the flooded treatment.

Chemotrapping-atomic fluorescence spectrometric method as a field method for volatile arsenic in natural gas

Volatile arsenic compounds in natural gas, existing in the form of trimethylarsine (TMAs), have been determined using gas cryo-trapping gas chromatography coupled to inductively coupled plasma-mass spectrometry (CT-GC-ICP-MS). The results from a number of different gas wells revealed a huge concentration spread ranging from below the detection limit of 0.2 up to 1800 microg/m(3) TMAs (as As) in the gas. Due to the toxicity and corrosive nature of these arsines, they need near real time monitoring via a method that can easily be implemented on site, i.e. during gas exploitation. Here, we introduce a novel method which utilises silver nitrate impregnated silica gel tubes for quantitative chemotrapping of trimethylarsine (TMAs) from a natural gas matrix. Subsequent elution with hot nitric acid followed by online photo-oxidation hydride generation atomic fluorescence spectrometry (HG-AFS) is used for the determination of TMAs gas standards in nitrogen and natural gas samples, respectively. The chemotrapping method was validated using CT-GC-ICP-MS as a reference method. The recovery of arsenic from nitrogen or natural gas matrix ranged from 85 to 113% for a range of 20 to 2000 ng As. Trapping efficiency was >98%, from the methods LOD of 20 ng to 4.8 microg (absolute amount As) with sample sizes of 0.02 and 2 L gas. Method performance was established by comparing the results obtained for eight natural gas samples containing between 1 and 140 microg As/m(3) with those achieved by the reference method (CT-GC-ICP-MS).

The synthetic organic chemist's companion

Preface. Acknowledgments. 1. Searching the Literature. 1.1. Commercial availability. 1.2. Literature preparations. 2. Reagents. 2.1. Short path distillation. 2.2. Ampules. 2.3. Reagent solutions. 2.4. Titration. 2.5. Reagent storage. 2.6. Subtle reagent variations. 2.7. Dangerous reagents. 2.8. Reagent properties. 3. Gases. 3.1. Lecture bottles. 3.2. Tanks or cylinders. 3.3. Gas safety. 4. Reactions on a Small Scale - 1-25 mmol. 4.1. Reaction flasks. 4.2. Stirring. 4.3. Glass joints. 4.4. Inert atmosphere. 4.5. Apparatus for addition. 4.6. Condensers. 4.7. Other equipment and considerations. 5. Temperature Control. 5.1. Heating. 5.2. Cooling. 6. Solvents. 6.1. Selection. 6.2. Purity. 6.3. Degassing. 6.4. Ammonia. 7. The Research Notebook. 8. Conducting the Reaction Itself. 8.1. Reagents supplied as dispersions. 8.2. Azeotropic drying. 8.3. Stoichiometry. 8.4. Syringe and inert atmosphere techniques. 8.5. General procedure for transfer of materials by syringe. 8.6. Addition. 8.7. Special techniques. 8.7.1.Water removal. 8.7.2.Reactions above atmospheric pressure. 8.7.3.Reagent gases. 8.7.4.Ultrasonication. 8.8 Quenching . 8.9. Specialized reagents. 8.9.1. Diazomethane. 8.9.2. Lithium aluminum hydride. 8.9.3.Hydrogen peroxide. 8.10. Reaction time vs. purification time. 9. Following the Reaction. 9.1. Thin layer chromatography (TLC). 9.1.1. Cutting glass TLC plates. 9.1.2. Spotting TLC plates. 9.1.3. Eluting TLC plates. 9.1.4. Visualizing TLC plates. 9.2. Gas chromatography (GC). 9.3. High pressure liquid chromatography (HPLC). 9.4. NMR spectroscopy. 10. Working Up Reactions. 10.1. Solvent extracation. 10.2. Drying organic solutions. 10.3. Specialized work-ups. 10.3.1. Reactions producing triphenylphosphine oxide. 10.3.2. Reactions involving boron compounds. 10.3.3. Reactions involving copper salts. 10.3.4. Reactions involving aluminum reagents. 10.3.5. Reactions involving tin reagents. 11. Evaporation. 12. Vacuum Systems. 12.1. Vacuum sources. 12.2. Vacuum manifolds. 12.3. Vacuum gauges. 13. Purification of Products. 13.1. Distillation. 13.2. Silica gel chromatography. 13.3. Flash column chromatography. 13.4. Gradients. 13.5. Special absorbents. 13.5.1. Triethylamine-treated silica gel. 13.5.2. Oxalic acid-coated silica gel. 13.5.3. Silver nitrate-impregnated silica gel. 13.5.4. Other sorbents. 13.6. Preparative gas chromatography. 14. Methods for Structure Elucidation. 14.1. Nuclear magnetic resonance spectroscopy. 14.2. Infrared spectroscopy (IR). 14.3. Ultravilolet spectroscopy (UV). 14.4. Combustion analysis. 14.5. Mass spectrometry. 14.6. Crystallography. 15. Cleaning Up After the Reaction. 16. Specific Examples. 16.1. The experimental. 16.2. The Org. Syn. Prep. 16.3. Comparison. 17. Strategies for Reaction Organization. Appendices. 1. NMR spectral data of common contaminants of organic reaction products. 2. Synthetic solvent selection chart. 3. Recipes for TLC stains. 4. Mixotropic series. 5. Stuck joints. 6. Acidities of organic functional groups. 7. Acidities of organic functional groups in DMSO. 8. Web resources for synthetic chemistry.

Investigation into the determination of trimethylarsine in natural gas and its partitioning into gas and condensate phases using (cryotrapping)/gas chromatography coupled to inductively coupled plasma mass spectrometry and liquid/solid sorption techniques

Speciation of trialkylated arsenic compunds in natural gas, pressurized and stable condensate samples from the same gas well was performed using (Cryotrapping) Gas Chromatography-Inductively Coupled Plasma Mass Spectrometry. The major species in all phases investigated was found to be trimethylarsine with a highest concentration of 17.8 ng/L (As) in the gas phase and 33.2 μg/L (As) in the stable condensate phase. The highest amount of trimethylarsine (121 μg/L (As)) was found in the pressurized condensate, along with trace amounts of non-identified higher alkylated arsines. Volatile arsenic species in natural gas and its related products cause concern with regards to environment, safety, occupational health and gas processing. Therefore, interest lies in a fast and simple field method for the determination of volatile arsenicals. Here, we use simple liquid and solid sorption techniques, namely absorption in silver nitrate solution and adsorption on silver nitrate impregnated silica gel tubes followed by total arsenic determination as a promising tool for field monitoring of volatile arsenicals in natural gas and gas condensates. Preliminary results obtained for the sorption-based methods show that around 70% of the arsenic is determined with these methods in comparison to volatile arsenic determination using GC-ICP-MS. Furthermore, an inter-laboratory- and inter-method comparison was performed using silver nitrate impregnated silica tubes on 14 different gas samples with concentrations varying from below 1 to 1000 μg As/m 3 natural gas. The results obtained from the two laboratories differ in a range of 10 to 60%, but agree within the order of magnitude, which is satisfactory for our purposes.

LXR-mediated activation of macrophage stearoyl-CoA desaturase generates unsaturated fatty acids that destabilize ABCA1

Abnormal HDL metabolism among patients with diabetes and insulin resistance may contribute to their increased risk of atherosclerosis. ATP binding cassette transporter A1 (ABCA1) mediates the transport of cholesterol and phospholipids from cells to HDL apolipoproteins and thus modulates HDL levels and atherogenesis. Because fatty acids are increased in diabetes, we examined their effects on ABCA1 activity in cultured macrophages. cAMP analogs and ligands for the liver X receptor/retinoid X receptor (LXR/RXR) system can induce Abca1 transcription in murine macrophages. When induced by cAMP, unsaturated but not saturated long-chain fatty acids inhibit apolipoprotein-mediated lipid efflux by destabilizing ABCA1 protein. Here, we show that the saturated fatty acids palmitate and stearate also destabilize ABCA1 when Abca1 is induced by LXR/RXR ligands instead of cAMP. This was associated with increased palmitate and stearate desaturation by stearoyl-CoA desaturase (SCD), another gene product induced by LXR/RXR ligands. The SCD inhibitors conjugated linoleic acid and troglitazone nearly abolished ABCA1 destabilization by palmitate and stearate but not by linoleate. These results suggest that LXR/RXR ligands generate ABCA1-destabilizing monounsaturated fatty acids from their saturated precursors by activating SCD. Thus, with cholesterol-loaded macrophages exposed to saturated fatty acids, activated LXR/RXR may counteract the enhanced ABCA1 transcription by reducing the ABCA1 protein content.

Synthesis and analysis of symmetrical and nonsymmetrical disaturated/monounsaturated triacylglycerols.

Symmetrical disaturated triacylglycerols of the structure SUS, where S is stearic acid (18:0) and U is an unsaturated fatty acid, either oleic (O; 9cis-18:1), linoleic (L; 9cis,12cis-18:2), or linolenic (Ln; 9cis,12cis,15cis-18:3), are important components providing functionality to interesterified fat blends and structurally modified oils. Nonsymmetrical triacylglycerols of the structure SSU can significantly change melting point and solid fat content profiles. To characterize the physical properties of pure and symmetrical and nonsymmetrical triacylglycerol mixtures, the same reaction sequence has been used to prepare multigram quantities of triacylglycerols SUS and SSU. Tristearin was converted to a mixture of mono-, di-, and triacylglycerols, and the 1,3- and 1,2-diacylglycerol fraction was isolated by silica column chromatography. The 1,3-diacylglycerols were removed by crystallization from acetone and esterified with the appropriate fatty acid to form the symmetrical triacylglycerols with >99% SUS structure. The more difficult to obtain 1,2-diacylglycerols were prepared by esterification of the enriched 1,2-diacylglycerol fraction (80-86% 1,2-diacylglycerols) remaining after removal of much of the 1,3-isomer by crystallization, but silver resin or silver nitrate impregnated silica gel chromatography was required to isolate the nonsymmetrical triacylglycerols. SSL and SSLn were prepared in purities of >98% by this procedure, but not SSO. Silver ion HPLC was found to be as accurate as, and more rapid than, lipolysis/gas chromatography for the determination of the isomeric purities of the synthesized triacylglycerols.

Variability of fatty acid components of marine and freshwater gastropod species from the littoral zone of the Red Sea, Mediterranean Sea, and Sea of Galilee

Eight marine gastropod species from the littoral zone of the Red and Mediterranean Seas, and four freshwater gastropods from the Sea of Galilee were analysed for their fatty acid composition using TLC (silver nitrate impregnated silica gel) and gas chromatography–mass spectrometry (GC/MS). The major fatty acid components in all twelve samples were polyunsaturated fatty acids (PUFA). The total lipids of the Sea of Galilee species contained considerably more 22:6n-3 (from 10.33% to 12.63%) and 20:5n-3 (up to 2.67%) than those from marine species. The differences among the PUFA in these species appear to be due mainly to different environmental conditions, dietary habits and geographical spreading.

Alkadienes and alkenes, sex pheromone components of the almond seed wasp Eurytoma amygdali.

Whole body extracts of virgin Eurytoma amygdali females were attractive to males in laboratory bioassays. Extracts of various body parts of the female wasp elicited different responses to males, with the thorax extract being the most active. Preparative fractionation of the crude hydrocarbon extract on a silver nitrate impregnated silica gel column (alkanes, alkenes, and alkadienes) revealed that the highest male response was elicited by alkadienes and the lowest by alkenes, with the alkane fraction being inactive. The identification of alkenes and alkadienes was based on gas chromatographic, mass spectrometric, and gas-phase infrared data. Laboratory bioassays suggested that the two alkadienes, (Z,Z)-6,9-tricosadiene [(Z,Z)-6,9-C23:2], and (Z,Z)-6,9-pentacosadiene [(Z,Z)-6,9-C25:2], and to a lesser extent alkenes, identified in the female extract of E. amygdali were male attractants.

Very long chain polyunsaturated fatty acids in crustacea of the order Bathynellacea

Abstract Total lipids of three crustacean species, Bathynella natans , B. baicalensis and Baicalobathynella magna from Lake Baikal and the caves of Central Europe were analyzed for very long chain polyunsaturated fatty acids (VLCPUFA) using TLC (silver nitrate impregnated silica gel) and gas chromatography–mass spectrometry (GC–MS). The VLCPUFA in the total lipids were mainly n-6 and n-3 PUFA, i.e. 24 : 3n6, 24 : 3n3, 24 : 5n3, 26 : 3n6, 26:5n6 and 28 : 7n6. The major VLCPUFA components in all three samples were 24 : 3n6 (0.4–0.5% of total fatty acids) and 24 : 3n3 (∼1%), but 26 : 5n6 (0.08%) was also prominent in the species from Lake Baikal. The total lipids of the Lake Baikal species contained considerably more 26 : 5n6 and 28 : 7n6 than those from caves. The differences among the VLCPUFA in these species appear to be due mainly to different environmental conditions, dietary habits and geographical spreading.

Chemical Constituents of the Lichen Cladina macaronesica

Column chromatography of the acetone extract of the lichen Cladina macaronesica (Sephadex LH-20, silica gel and silver nitrate-im pregnated silica gel) afforded eight triterpenes identified by chemical and spectral m eans. α-Amyrenone, lupenone, taraxerol, taraxerone and /so-arborinol acetate were isolated for the first time from lichens and (-)-usnic acid and five mononuclear phenolic compounds were also obtained, four for the first time as natural products. The possible transformation of perlatolic acid into these phenolic compounds is briefly outlined.

A high-performance liquid chromatographic procedure for the determination of disaturated phosphatidylcholine in human plasma

Plasma disaturated phosphatidylcholine (DSPC) concentration has been implicated as a risk factor for atherosclerosis. However, suitable methods for the estimation of these compounds in plasma are not available. In this paper, a method for the estimation of DSPC using argentation thin-layer chromatography and high-performance liquid chromatography is described. It is quantitative for the measurement of individual and total DSPC species and is not dependent on fatty acid chain length. The method employs hydrolysis of total plasma phosphatidyl choline by phospholipase C, followed by benzoylation of the diacylglycerols. The benzoates are then fractionated on silver nitrate-impregnated silica gel thin-layer chromatography plates, and the disaturated species separated and quantitated by high-performance liquid chromatography. The method is sensitive and reproducible and allows many samples to be done at once. With this method, the amounts of DSPC were found to be significantly higher in a group of normolipidemic diabetic subjects, compared to agematched controls.

9-Deoxy drimane sesquiterpenes from Canella winterana

The stem bark of Canella winterana collected in Florida yielded three new drimane sesquiterpenes. Their structures were elucidated from their spectral data as: 9-deoxymuzigadial, 9-deoxyisomuzigadial and 3β-acetoxypolygodial. The first two compounds, which are double bond isomers, could only be separated from each other on silver nitrate-impregnated silica gel.

Sesquiterpene Hydrocarbons from the Seed Oil of Iris tectorum Maxim.

Sesquiterpene hydrocarbons from the seed oil of Iris tectorum M. were investigated. Fractionation of the hexane extract of the seeds by column chromatography on activated alumina and steam distillation gave monoterpene-free hydrocarbons which showed approximately thirty peaks by capillary gas chromatography. A combination of techniques including a silver nitrate addition procedure, rectification and silver nitrate-impregnated silica gel column chromatography was used to separate the sesquiterpenes.Twenty-four compounds could be identified on the basis of spectral data (IR, NMR, GC, GC-MS) and chemical transformations. The main components were germacrene D (45%), alloaromadendrene (12%), δ-, γ-cadinene (13%), and β-caryophyllene (7%). These sesquiterpenes in Iridaceae plants were characterized for the first time in the present research.

Studies on the constituents of Orchidaceous plants. II. Isolation, structures, and stereochemistry of cyclonervilol, cyclohomonervilol, and dihydrocycloeucalenol C-24 epimers, new triterpenes from Nervilia purpurea Schlechter.

Five new triterpenes, 24 (R/α)-and 24 (S/β)-dihydrocycloeucalenol, dihydrocyclonervilol, cyclonervilol, and cyclohomonervilol, were isolated along with cycloeucalenol and cyclofuntumienol from the triterpene fraction of Nervilia purpurea by the combination of chromatography on silver nitrate-impregnated silica gel and reversed-phase high-performance liquid chromatography (HPLC). The structures 4a, 5a, 7a, 2a, and 10a are proposed for these compounds, respectively.