The separation of glycerides by liquid-liquid column partition chromatography

A liquid-liquid partition chromatography method was developed to separate triglycerides. The solvent was a two phase mixture of acetone, heptane, and water supported on silane treated celite. A study was made of the best means for equilibrating the solvents and support, packing the column, and introducing the sample. The effect of various operating variables such as flow rate, sample size, column length, and solvent compositions was studied using trilaurin and trimyristin as model glycerides. Under the best conditions achieved, it was calculated that glycerides differing by two carbon atoms or one double bond would not separate completely, but glycerides differing by two double bonds or four carbon atoms would be separated. Cocoa butter, a relatively simple triglyceride, was fractionated, and the fatty acid composition of each fraction was determined by gas chromatography. The glyceride composition was calculated and compared with theoretical compositions. The results indicate that useful glyceride separation can be obtained with this system. Probably even more useful separations could be obtained if a more sensitive device were used to detect the triglycerides in the effluent. This would allow the use of solvent compositions which give larger retention volumes and more plate efficiency. Journal Paper No. J-4517 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa, Project No. 1517. Presented at the AOCS meeting in Toronto, Canada, 1962. Based on a thesis presented by B. C. Black in partial fulfillment of the requirements for a master’s degree.     

Separation and purification of aflatoxins B1, B2, G1 and G2, and comparison of semi-synthetic aflatoxins B2 and G2 with naturally-occurring aflatoxins B2 and G2

A method is described for the isolation of highly purified aflatoxins B₁, B₂, G₁ and G₂ from extracts ofAspergillus flavus. The four aflatoxins, isolated from background impurities by rapid passage of the extracts through an acid alumina column, are separated from each other by chromatography on a silica gel column. Aflatoxins B₂ and G₂ are prepared by hydrogenation of the mixture of aflatoxins B₁, B₂, G₁ and G₂ and then separated by elution from a silica gel column with chloroform containing 0.7% ethanol. A comparison of semi-synthetic aflatoxins B₂ and G₂ with naturally-occurring aflatoxins B₂ and G₂ shows no significant difference in physical properties. Presented at the AOCS-AACC Meeting, Washington, D.C. April, 1968.     

An improved separation of aflatoxins

Crude aflatoxin from a chloroform extract ofAspergillus flavus cultures on rice was precipitated with Skelly Solve B and chromatographed on 100–200 mesh silica gel columns, using ethyl acetate as eluant. On this column there was no separation of aflatoxins from each other, but most of the brown, oily material was removed. The next step in the purification was chromatography on 100–200 mesh silica gel columns with chloroform and 5% methanol/chloroform as eluants. A large part of the B₁ was purified, but B₂, G₁ and G₂ did not separate, and M₁ had a brown oil that prevented crystallization. The M₁ was purified by chromatography on Sephadex LH-20 with chloroform; the brown material was retained while the M₁ passed through. The separation of aflatoxin B₂, G₁, and G₂ was achieved by column chromatography on Silica Gel H for TLC. In addition, aspertoxin was separated and identified. The purity and identity of the compounds were established by 100 MHz NMR. Presented at the AOCS-AACC Joint Meeting, 1968, Washington, D.C. W. Utiliz. Res. Dev. Div., ARS, USDA.     

Size-dependent separation of graphene oxide by deformation of packed-gel in a chromatographic column

ABSTRACT

A deformable gel-packed chromatographic column was used to separate as-synthesized graphite oxide with different sizes. The synthesized gel (56 µm) was deformed by pressure of the fluid flow and the gaps in the gels showed a range of sizes. A suspension of graphene oxide (0.1 g/L, 10 mL) was injected, and graphene oxide in the elution had a size at 0.56 μm and 0.14 μm, whereas in half upper and bottom domain of the gel layer graphene oxide had a size at 33 µm and 2.9 µm, respectively, demonstrating that graphene oxide suspension was separated by size through gel layer.     

Ultramicro fatty acid analysis of polar lipids: Gas-liquid chromatography after column and thin-layer chromatographic separation

A procedure is described for the analysis of the fatty acid composition of polar lipid classes in the nanogram range. The lipids are first fractionated by column chromatography followed by further separation into pure lipid classes by thin-layer chromatography. Lipid spots scraped from the thin-layer plates are esterified directly (i.e., without prior elution) with 6% sulfuric acid in methanol. The methyl esters are then analyzed by gasliquid chromatography with a hydrogen flame ionization detector. Samples of 200 nanograms or less give accurate results with helium as carrier gas, oxygen rather than air to support combustion, careful adjustment of the recorder and general attention to optimum electrical connections, dissociation of the column oven from the recorder and electrometer, and careful preconditioning of columns. Under proper conditions the base line is stable and a 10% of full scale deflection of the recorder can be obtained from 1 nanogram of a methyl ester, allowing highly precise analyses of fatty acid composition from the amount of lipid obtainable from one spot on a thin-layer chromatogram. Control studies demonstrated that extraneous peaks did not arise from the procedure or from the sphingosine and dihydrosphingosine of sphingolipids. The thin-layer chromatographic procedure did not influence the fatty acid composition of a pure sample of glucocerebroside isolated by column chromatography and the method was applied to lecithin and sphingomyelin or normal and pathological human brain specimens.     

Thin layer chromatographic analysis of possible aflatoxins within grain dusts

The National Institute for Occupational Safety and Health is interested in assessing the hazards to grain workers associated with respirable grain dusts of all types. One of these hazards could involve the occurrence of mycotoxin producing fungi either upon or within grains. Aflatoxins, types of mycotoxins produced by bothAspergillus flavus andA. parasiticus, are hepatocarcinogens, mutagens, teratogens and toxins. Here, we report an attempt to determine whether settled and/or airborne dusts from barley, corn, flax, oats and Durum as well as spring wheats contain aflatoxins. These dusts were collected at port grain terminals in the Superior-Duluth regions of the United States. The dusts were extracted with and chromatographed upon thin layer plates in a variety of solvents which have been approved for the separation of aflatoxins. Two acceptable aflatoxin B₁ confirmatory tests were employed to verify suspected aflatoxin B₁ within the extracts. Each dust contained a chloroform-soluble, blue fluorescent compound(s) which possessed an Rf similar to that of aflatoxin B₁ upon chromatography of chloroform extracts in chloroform/95% methanol. Methylene chloride/H₂O) extracted a blue fluorescent compound(s) from each dust, and the compound(s) possessed Rf intermediate between those of aflatoxin B₁ and B₂ upon chromatography in acetone/methylene chloride. The methylene chloride/H₂O extracted compounds failed to turn yellow upon spraying with 25% sulphuric acid in methanol and subsequent viewing with an ultraviolet source. Our results confirm those of Sorenson et al., who reported that aflatoxins were absent from airborne grain dusts collected from the Superior-Duluth areas of the United States in the fall of 1977. In conclusion, we stress the need for extracting, detecting, and identifying aflatoxins by a variety of analytical procedures including thin layer and high performance liquid chromatography and “approved” confirmatory tests.     

Kinetic study of acid-catalyzed conversion of aflatoxins B1 and G1 to B2a and G2a

Adjusting dilute aqueous solutions of aflatoxins B₁ and G₁ to pH 1, 2 and 3, and heating over a range of 40–100 C resulted in the conversion of B₁ to B_2a and G₁ to G_2a as major products. Both B_2a and G_2a were identified by co-thin layer chromatography with authentic B_2a and G_2a and M₁ on silica gel plates developed in two different solvents. The rate of disappearance of B₁ or G₁ at given temperature and at constant pH was found to be first order with respect to each aflatoxin. At given temperature the conversion is strongly pH dependent, a 10-fold increase in H⁺ ion (1 pH unit) producing about a 9-fold increase in the reaction rate, indicating first order dependent of the rate on H⁺ ion concentration. S. Market. Nutr. Res. Div., ARS, USDA.     

A new benzene-ethanol-water solvent system for TLC separation of aflatoxins

Gas liquid chromatography was used to determine the composition of the benzene-ethanol-water (BEW) solvent system frequently used in the separation of aflatoxins by thin layer chromatography. Investigation of a rapid procedure for preparing and using this solvent system led to the discovery of a new BEW solvent system with advantages for the routine determination of aflatoxins in roasted nut products, which consists of benzene-ethanol-water 40:6:3 for the trough solution and 4:27:20 for the bottom solution.     

Paper chromatographic separation of aliphatic lactones

Summary Paper chromatographic procedures are described, whereby a homologous series of n-aliphatic gamma lactones from butyrolactone through dodecalactone can be resolved as hydroxamic acid derivatives. Similar resolutions can be obtained with a series of n-aliphatic delta lactones from nonalactone through dodecalactone. Procedures also are described, whereby lactones in the presence of ester or glyceride material can be identified using a modified hydroxylamine reagent. Analyses of commercial synthetic peach extracts demonstrate the practical use of these procedures. Authorized for publication on November 2, 1956, as paper No. 2,100 in the Journal Series of the Pennsylvania Agricultural Experiment Station.     

Cell and surfactant separation by column flotation

The separation of rehydrated Saccharomyces cerevisiae and an alkyl polyglycoside surfactant by column flotation was studied as a function of wash water flow and cation concentration. Separation of cells and surfactant was measured under steady-state conditions. Surfactant recovery in the foam concentrate was in the range of 86–95%. Yeast cells were enriched in the foam concentration by a factor of up to 11, but the recovery only reached 55%. The use of wash water was very effective for removing the cells from the foam, giving a good separation between the cells and the surfactant. Addition of chloride salts of Na, K, Ca, and Mg at concentrations in the range of 0.05-0.1 mol/L increased both the enrichment and the recovery of yeast in the foam. The most effective salt levels for cell flotation, less than 0.1 mol/L, were in the same range of concentration as the minimum electrophoretic mobility of the cells.     

色谱分析中毛细管技术的进发

在分析组份复杂的混合物时，毛细管柱色谱法比传统的填充柱色谱法具有分离能力高、分析速度快等优点，因此近年发展迅速。文中介绍了毛细管柱的特点和制造方法以及该技术的最新进展和应用。     

The rapid separation of aflatoxins on silica gel coated glass cylinders

A chromatographic method is described for the separation of aflatoxins on silica gel coated glass cylinders prepared with a chloroformacetone slurry. This can be done in 35–40 min compared with more than 2 hr for thin layer chromatography (TLC). This method is more rapid, economical and its sensitivity is comparable to TLC. University of Georgia College of Agriculture Experiment Stations, Journal Series Paper Number 643, College Station, Athens, Ga.     

二氯丙醇的萃取分离

采用萃取法分离出氯丙烯氯醇化反应得到的溶液中的二氯丙醇,并对萃取工艺进行优化:选择磷酸三辛酯为萃取剂,萃取剂与二氯丙醇溶液的质量比为0.6∶1,萃取剂分成5份萃取5次,萃取率达到99.8%。萃取得到的油层与质量分数为10%的NaOH溶液在负压下进行皂化反应,皂化收率可以达到93%以上。萃取剂和萃余水可以循环使用。     

Extraction chromatographic method of preconcentration and separation of lead (II) with high molecular mass liquid cation exchanger

A selective method has been developed for the extraction chromatographic separation of lead (II) with Versatic 911 (liquid cation exchanger) coated on silanised silica gel. Lead (II) has been extracted from 0.1 M acetate buffer at the range of pH 4.5-6.5. The effects of pH, flow-rate, stripping agents on extraction and elution have been investigated. Exchange capacity of the prepared exchanger at different temperatures with respect to lead (II) has been determined. The extraction equilibrium constant (K_ex) and different standard thermodynamic parameters have also been calculated by temperature variation method. The effect of pH on R_f values in ion exchange paper chromatography has been investigated. In order to investigate the sorption isotherm, two equilibrium models, the Freundlich and Langmuir isotherms, were analyzed. Lead (II) has been separated from synthetic binary and multi-component mixtures containing various metal ions associated with it in ores and alloy samples. The method effectively permits sequential separation of lead (II) from synthetic quaternary mixture containing its congeners Cu (II), Sn (II), Hg (II) and Cu (II), Cd (II), Bi (III) of the same analytical group. The method was found effective for removal and recovery of lead (II) from industrial waste and standard alloy samples following its preconcentration on the column. A plausible mechanism for the extraction of lead (II) has been suggested.     

隔壁式空分精馏塔应用性能研究

为了降低空气低温分离过程的设备投资和能耗,在分析空分体系的热力学性质及流程特点的基础上,提出了一种新型的隔壁式空分精馏塔流程。应用Aspen Plus模拟软件,对空气分离的传统流程和隔壁塔流程进行了模拟对比,考察了隔壁式空分精馏塔各结构参数与操作参数对其年总成本的影响,并分析比较了空分传统流程和隔壁式空分精馏塔流程的热力学效率。结果表明,隔壁式空分精馏塔的建模合理可行,通过年总成本优化得到了该隔壁塔的最优结构参数与操作参数,分别为:液氧流量为3 kmol/h,气相分配比(体积比)为0.05,精馏段理论板数为33,侧线精馏段理论板数为30,公共提馏段理论板数为22。与传统空分流程相比,隔壁式空分精馏塔流程的有效能损失降低并且在热力学效率方面高出4.7%。     

Development of bubble column for foam separation

The foam separation of metal in model wastewater is performed by using two different bubble columns in a continuous operation mode. The equipment and operation conditions are changed, and the foam flow rate and metal concentration in foam flow are measured. The foam flow ratio (the ratio of foam flow rate to the inlet one) increases with increasing gas velocity, with decreasing liquid velocity, with decreasing foam layer height and with decreasing metal concentration in model wastewater. Metal enrichment (the ratio of metal concentration in foam flow to that in inlet flow) shows the reverse tendencies. When a draft tube is inserted in the bubbling layer, the foam flow rate decreases. The enrichment is strongly governed by the foam flow ratio. Since the foam flow ratio is adjusted by means of the equipment and operation conditions, the metal concentration in foam flow is controlled to be a desired value. This paper was presented at The 5th International Symposium on Separation Technology-Korea and Japan held at Seoul between August 19 and 21, 1999.