Performance Liquid Chromatography Column Research Articles

A comparison of results of determining the hydrocarbon group-type composition of petroleum samples obtained using various test methods of open-column liquid chromatography

The hydrocarbon group-type composition (so-called SARA-composition) is one of the main characteristics of oil, providing an information about its chemical nature and determining the quality of the obtained petroleum products. In world laboratory practice, data on the hydrocarbon group-type composition of petroleum feedstock are widely used to assess its colloidal stability and compatibility with crude oil, reactivity in various conversion processes, predicting physical properties, etc. Traditionally, the hydrocarbon group-type composition is determined in accordance with standard and research chromatographic methods that differ significantly from each other, which often leads to obtaining incomparable analytical results. In this paper, a comparative analysis of the results of determining the hydrocarbon group-type composition obtained in accordance with two test methods within the open-column liquid chromatography method is carried out for various of petroleum samples of Russian origin (commercial oils of different classes and two petroleum products). Using the standard test method ASTM D4124 (method B) and the research test method developed by JSC VNII NP, the content of identical hydrocarbon groups in the maltene part of petroleum samples was determined: saturated hydrocarbons (SH) and paraffinic-naphthenic hydrocarbons (PNH), naphthenic aromatic (NAH) and aromatic hydrocarbons (AH), polar aromatic hydrocarbons (PAH) and resins (R), respectively. It is shown that with an increase the density and viscosity of petroleum samples, the content of less polar groups (SH and PNH) in their composition decreases and the content of more polar groups (PAH and R) obviously increases, and there is no pronounced distribution pattern of the NAH and AH groups. Statistical processing revealed insignificant differences in the results for «heavy and viscous» oils, despite the large error of those obtained according to the research test method. Obtaining comparable results justifies the use of both test methods not only for the analysis of high-boiling petroleum products, but also for the analysis «heavy and viscous» oil samples.

Partial upgrading of heavy oils by catalytic aquathermal visbreaking with dispersed iron oxide catalysts

The impact of water and red mud-like Fe oxide catalysts on aquavisbreaking (AVB) of heavy-oils was studied under various circumstances. Vacuum residue (VR) was employed as a good substitute for low-viscous bitumen grades. The reaction products were separated into SARA fractions using open-column liquid chromatography (OCLC), and boiling point groups were classified using thermogravimetric analysis (TGA). In addition, Fourier-transform infrared (FTIR) spectroscopy was used to study the structural features of VR and its derivatives. It was observed that the thermal visbreaking of VR led to a severe coke formation with asphaltene (ASP) to coke selectivity over 130 %, while the addition of water and Fe catalyst could increase the conversion of ASP to liquid oil products with inhibiting coke formation. Furthermore, the structural properties of spent catalysts recovered after reactions were analyzed using X-ray absorption near edge structure (XANES) and X-ray diffraction (XRD) to identify the active phase, confirming that the Fe precursor is converted to a 20–30 nm Fe2O3 and Fe3O4 during VR AVB. Moreover, the addition of carbon additives to AVB further improved the dispersion of ASP and catalyst particles, contributing to the decrease of the selectivity for ASP conversion to coke by 50 %.

Asphaltene Stability of Some Iraqi Dead Crude oils

Asphaltene is one of the fractions of the crude oil which is soluble in aromatics such as benzene or toluene and insoluble in alkane such as n-heptane, n-pentane or petroleum ether (mixture of alkane compounds). Asphaltene precipitation is one of the most common problems that sometimes occurs in both oil recovery and refinery processes as a result of changing in pressure, oil composition, or temperature. Therefore the stability of asphaltene in the crude oil must be studied to show the tendency of it for precipitating asphaltene to prevent it (Asphaltene precipitation and deposition problem) and eliminate the burden of high treatment costs.
 In the present study, saturate, aromatic, resin and asphaltene (SARA) analysis of the six dead crude oil samples from different Iraqi oil fields was conducted by using open column liquid chromatography after separating the asphaltene from them through filtration process. The asphaltene stability of dead crude oil samples was studied depending on changing the composition of them by adding the petroleum ether as an alkane and using colloidal instability index (CII) to determine the tendency of these crude oil samples to precipitate asphaltene depending on the SARA analysis results of these dead crude oils.
 All of dead crude oil samples showed the instability of asphaltene depending on this index and this means that all of them might precipitate asphaltene if the composition of these crude oil samples changed due to existing with the alkane in the live case in wells (Live oil is oil containing gas phase at reservoir conditions) such as injection of gas which has high ratio of alkane or the expanding the gas in the oil when the pressure decreases until reaches bubble point pressure.
 The refractive index of the dead crude oil samples was measured experimentally and calculated by two correlations which were Fan et al. correlation and Chamkalani correlation. The last one showed the best match between the experimental and calculated values of the refractive index of the dead crude oil samples.
 

Abstract 1049: Prognostication of patients with clear cell renal cell carcinomas based on quantification of DNA methylation levels of CpG island methylator phenotype marker genes using anion exchange high performance liquid chromatography

Abstract Background: We have identified CpG island methylator phenotype (CIMP)-positive clear cell renal cell carcinomas (ccRCCs) characterized by accumulation of DNA hypermethylation of CpG islands, tumor aggressiveness and poorer patient outcome. Furthermore, the criteria for prognostication of patients with ccRCCs have been established based on DNA methylation levels of ccRCC-specific CIMP marker genes. Recently, we have developed an anion exchange High Performance Liquid Chromatography (HPLC) column for detection of methylated DNA. To make the prognostication of patients with ccRCCs clinically applicable, the newly developed HPLC column has been applied to DNA methylation analysis of CIMP marker genes. Methods: Genomic DNA extracted from tumorous tissue samples of nephrectomy specimens of 5 patients with CIMP-positive ccRCCs and 5 patients with CIMP-negative ccRCCs was amplified by Polymerase Chain Reaction (PCR) after sodium bisulfite conversion with the EpiTect Bisulfite Kit (QIAGEN). Three-hundred and eighty-four bp-PCR products encompassing the promoter region of the FAM150A gene, a CIMP marker gene, and including 39 CpG sites were subjected to the HPLC column. DNA methylation levels were quantitatively evaluated using 0% and 100% methylated DNA controls (QIAGEN). Results: The analysis time for all samples was within 10 minutes. The retention time difference between 0% and 100% methylated DNA controls was 0.34 min. CIMP-negative ccRCCs were detected as a distinct single peak which had similar retention time with the 0% methylated DNA control, whereas CIMP-positive ccRCCs showed a bimodal peak pattern. Retention time of the later peak of CIMP-positive ccRCCs was similar with the 0% methylated DNA control. On the other hand, an early peak was eluted at various positions depending on its DNA methylation level. Based on the differences of chromatogram patterns, CIMP-positive ccRCCs were completely discriminated from CIMP-negative ccRCCs. DNA methylation levels of the FAM150A gene of each tissue sample calculated from retention time were consistent with those previously evaluated using MassARRAY system (Sequenom). Conclusion: Using newly developed anion exchange HPLC column, tissue specimens of CIMP-positive ccRCCs were readily, quickly and clearly distinguished from those of CIMP-negative ccRCCs, indicating that this HPLC method may be suitable for clinical application of prognostication of patients with ccRCCs based on CIMP diagnosis. Citation Format: Takuya Yotani, Yuriko Yamada, Eri Arai, Ying Tian, Masahiro Gotoh, Motokiyo Komiyama, Hiroyuki Fujimoto, Michiie Sakamoto, Yae Kanai. Prognostication of patients with clear cell renal cell carcinomas based on quantification of DNA methylation levels of CpG island methylator phenotype marker genes using anion exchange high performance liquid chromatography. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1049. doi:10.1158/1538-7445.AM2015-1049

Transformation of Sulfur Compounds in the Hydrotreatment of Supercritical Fluid Extraction Subfractions of Saudi Arabia Atmospheric Residua

Atmospheric residue from Saudi Arabia (SZAR) was subjected to supercritical fluid extraction fractionation (SFEF) experiments. Four extractable subfractions (SFEF 1–4) and an unextractable end-cut were obtained. SFEF 1–4 were subjected to a hydrotreating (HDT) test in a mini-tubular reactor packed with commercial hydrodemetallization (HDM) and hydrodesulfurization (HDS) catalysts in order to determine the structural composition transformation of sulfur-containing compounds. Experiments were undertaken at a temperature of 360 °C, a hydrogen pressure of 14.7 MPa, a liquid hour space velocity (LHSV) of 0.25 h–1, and a H2/feed ratio of 650:1 (m3/m3). The SFEF subfractions and their products were subjected to analysis of their sulfur and nitrogen contents, using an ANTEK 7000S analyzer, and their saturates, aromatics, resins, and asphaltenes (SARA) compositions were analyzed using open column liquid chromatography. The detailed molecular composition of sulfur heteroatom species was determined by methylation, f...

Molecular Characterization of Polar Heteroatom Species in Venezuela Orinoco Petroleum Vacuum Residue and Its Supercritical Fluid Extraction Subfractions

A Venezuela Orinoco petroleum vacuum residue (VR) was subjected to supercritical fluid extraction fractionation (SFEF) and separated into 13 extractable fractions and an unextractable end-cut. Detailed molecular composition of polar heteroatom species in the SFEF subfractions were determined by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The SFEF subfractions were also subjected to high-temperature gas chromatography (GC) for their simulated distillation analysis, gel permeation chromatography (GPC) for their molecular distributions, and open column liquid chromatography for their saturates, aromatics, resins, and asphaltenes (SARA) compositions. In ESI FT-ICR analysis, the mass spectra showed that the mass range and maximum peak of the SFEF subfraction increased as the SFEF subfraction became heavier. Multifunctional group compounds, such as N1S1, N1S2, N1O1, and N2, show high relative abundance in heavier subfractions. The double bond equivalence (DBE) values and carbon numbers of all class species increased steadily as the SFEF subfraction became heavier. This indicated that the molecules in various SFEF subfractions are separated by their aromaticity and molecular weight. The SFEF end-cut could not be thoroughly characterized by ESI because of its low intensity, while basic species detected by positive-ion ESI were suppressed by a strong response of metal porphyrin species. Results from GPC and SARA compositional analysis show that the end-cut enriches most of the asphaltene in feedstock and has the highest apparent molecular size.

PURIFICATION AND CARBOHYDRATE ANALYSIS OF RECOMBINANT HUMAN ERYTHROPOIETIN EXPRESSED IN YEAST SYSTEM Pichia pastoris

For clinical purposes, pure protein and identification of carbohydrate structure from recombinant erythropoietin are needed. Purification was done by Immobilized Metal Affinity Chromatography (IMAC) column charged with Ni2+ (His-Trap affinity chromatography) and continued with gel filtration chromatography column to get purer protein. The carbohydrate group which is oligosaccharide from the resulting pure protein then can be recognized by using N- and O-glycosidase. Pure oligosaccharide was hydrolyzed to produce various monosaccharide through incubation with 4 N HCl in 100 oC temperature for 6 hours and the result was applied on High Performance Liquid Chromatography (HPLC) column to learn the composition of its monosaccharide. Keywords: EPO, gel filtration chromatography, His-Trap affinity chromatography, monosaccharide

Tracking Neutral Nitrogen Compounds in Subfractions of Crude Oil Obtained by Liquid Chromatography Separation Using Negative-Ion Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Neutral nitrogen compounds have been used as molecular markers for tracking secondary oil migration in geochemistry. However, the distribution of neutral nitrogen compounds in the separation process is not well-characterized because the conventional analytical technique, such as gas chromatography−mass spectrometry (GC−MS), is non-selective for neutral nitrogen and not capable of detecting non-volatile high-molecular-weight compounds. In this paper, a crude oil was subjected to the traditional two-step open-column liquid chromatography (LC) technique to prepare subfractions, which were characterized for their molecular composition of neutral nitrogen compounds by negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). The results showed that the two-step LC technique produced a low yield of carbazole in the neutral nitrogen fraction. The neutral nitrogen fraction was enriched with low-molecular-weight neutral nitrogen compounds. Most N1 class speci...

Phytochemical and biological activities of Crataegus sinaica growing in Egypt

Objective To evaluate the cardiac activity and hepatoprotection of Crataegus sinaica ( C. sinaica ). Methods All the isolated compounds were isolated by open-column liquid chromatography (CC) using sephadex LH-20 as stationary phase. Elution of the column was performed with EtOH or MeOH. The phytochemical investigation of the young stem of C. sinaica for the first time together with the leaves and flowers lead to the isolation and identification of quercetin, hyperoside, vitexin-2″-O-rhamnoside, epicatechin, procyanidin B2 and procyanidins C1. Results Rats treated with the low and high dose of C. sinaica leaves with flowers extract showed 15% and 17% reduction in the heart rate, and reduction in the ST-segment by 107% and 57%; respectively. The T-amplitude was decreased by 59% of the high dose extract. On the other hand, the young stems and leaves with flowers extracts of C. sinaica on primary culture of rat hepatocytes monolayer indicated a hepatoprotection for the total extract, ethyl acetate, butanol, and chloroform fractions at 100 μg/mL, 75 μg/mL, 50 μg/mL, and 25μg/mL; respectively. Conclusions The results of these chemical and biological studies suggest the use of C. sinaica growing in Egypt as a preventive drug against cardiovascular and hepatic diseases. The chemical studies suggest the use of woody young stems as a newly investigated bioactive organ. The extraction of unsaturated fatty acids from the seeds of the plant would serve as a good health and nutritive product.

Toxicity of Solanum xanthocarpum fruit extract against Alternaria brassicae, causal agent of Alternaria blight of Indian mustard (Brassica juncea)

Fruit extract of Solanum xanthocarpum was evaluated for its toxicity against Alternaria brassicae, the causal agent of Alternaria blight of Indian mustard [Brassica juncea (L.) Czern. & Coss]. The mass obtained after vacuum drying of the crude methanolic extract was utilised for further sequential fractionation using n-hexane, ethyl acetate, n-butanol and methanol. Among the crude and different fractions tested, methanolic fraction was most effective with a minimum inhibitory concentration (MIC) of 62.5 μg/ml. The methanolic fraction was further fractionated using open column liquid chromatography into five subfractions (I–V) to identify the antifungal bioactive compounds. Among the five subfractions (SFs) tested SF IV was most effective at inhibiting A. brassicae conidial germination and thereby inhibited lesion development of Alternaria blight at a concentration of 15.625 μg/ml or higher. Furthermore, bioautography of SF IV with Alternaria alternata and diagnosis with Dragendorff reagent indicated that SF IV contains a mixture of bioactive alkaloids, namely a1 (Rf = 0.12) and a2 (Rf = 0.22). The potential of using S. xanthocarpum as a resource for the development of biofungicides is discussed.

Antifungal activity of Agave americana leaf extract against Alternaria brassicae, causal agent of Alternaria blight of Indian mustard (Brassica juncea)

Leaf extract of Agave americana was evaluated for antifungal activity against Alternaria brassicae, the causal agent of Alternaria blight of Indian mustard [Brassica juncea (L.) Czern. & Coss]. Methanolic leaf extract (crude extract) of A. americana showed antifungal activity against A. brassicae. The green mass obtained by vacuum drying of the crude extract was used for further sequential fractionation using ethyl acetate, n-butanol and methanol. Among the three fractions, the methanolic fraction showed the strongest antifungal activity by its inhibition of conidial germination of A. brassicae. The methanolic fraction of A. americana leaves was fractionated further using open column liquid chromatography into six sub-fractions (I – VI). Among the six sub-fractions tested, sub-fraction II showed a strong inhibitory effect on conidial germination of A. brassicae and thereby inhibited lesion development of Alternaria blight of Indian mustard at a concentration of 40 µg/ml or higher. Qualitative separation of molecules present in sub-fraction II by thin layer chromatography followed by diagnosis with Libermann – Burchard reagent indicated that sub-fraction II contained a mixture of saponins. The potential of using A. americana for the management of fungal pathogens of crop plants is discussed.

Graft copolymerization of N-isopropylacrylamide with 3-(methacryloxy)propyl trimethoxysilane on ultrafine silica and its application in chromatography separation

Thermosensitive core-shell particles were synthesized through graft copolymerization of N-isopropylacrylamide with [ 3-(methacryloxy) propyl]trimethoxysilane (MPT) coupled on the surface of ultrafine silica beads. The copolymerization was carried out using polyvinyl alcohol as a surfactant, water and cyclohexanol as mixed solvent, and 2,2′-azobis(isobutyronitrile) as an initiator. The effect of surfactant concentration and the composition of the mixed solvent on the graft rate were investigated. The structure of modified silica was confirmed by infrared spectra. Differential scanning calorimetry (DSC) has revealed the thermosensitivity of the particles. The thermosensitive particles were used as packing materials of high performance liquid chromatography (HPLC) columns for separating naphthalene derivatives. Satisfactory separation was obtained by controlling the temperature of the column. In contrast, the packing material of silica-MPT has no such separation efficiency due to the lack of thermosensitivity. The effect of the composition of the mobile phase on the separating efficiency was also investigated. The temperature-controlled separation was effective only when the water content was higher than 90% (v/v) in the water-methanol mobile phase. The mechanism for the temperature-controlled separation is attributed to a polarity change of poly(N-isopropylacrylamide) which undergoes volume phase transition on the silica surface as the temperature increases.

Influence of Alternative Liquid Chromatography Techniques on the Chemical Complexity and Bioactivity of Isolated Proanthocyanidin Mixtures

Extracts rich in proanthocyanidins, which are implicated in multiple human health benefits, were comparatively separated using alternative separation methods [vacuum or open column liquid chromatography], separation matrices [Toyopearl, Sephadex, or silica gel], and degrees of subfractionation [8 or 12 subfraction series], to evaluate the influence of separation technique on the resolution of the chemical composition and the biological activity of separated proanthocyanidin mixtures in individual subfractions. Bioactivity was assessed using a DNA human topoisomerase II bioassay and structural composition by acid thiolysis (average degree of polymerization, DP) and HPLC-ESI/MS. The amount of parent fraction needed to inhibit 50% of topoisomerase II was 3.38 ng/mL with an average DP of 25.5. A 2(3) factorial analysis revealed that the vacuum and open column strategies for separation, when individually considered, did not yield significantly different results in terms of mass recovery, DP, or bioactivity; however, interactions with other factors such as matrix or subfraction series resulted in distinctive shifts in fraction profiles and biological activity. In general, Sephadex as a matrix permitted elution and separation of discrete, polymerized subfractions with potent inhibition against human topoisomerase II. Sephadex vacuum chromatography, Toyopearl open column chromatography, and Toyopearl vacuum chromatography separation techniques eluted highly polymerized proanthocyanidin mixtures, but the inhibitory bioactivity was attenuated as compared to the parent fraction, whereas Sephadex open column chromatography eluted highly polymerized subfraction mixtures that retained bioactive potential.

Antioxidant Activities of Compounds Isolated from Fermented Broth of Zygosaccharomyces Rouxii

Previously, a sugar-tolerant strain of Zygosaccharomyces rouxii that had moderate antioxidant activity was isolated. In this investigation four active substances were isolated and their antioxidant activity was determined with different methods. The yeast strain (MAFF 237555) was cultured in yeast extract-malt extract (YM) medium, and the fermented broth was extracted with ethyl acetate. Dried solid extract was separated into neutral and acidic fractions. The neutral fraction was fractionated on a silica-gel column and purified on a Sephadex LH-20 column. The acidic fraction was recrystallized from acetone. The mother liquor was fractionated on two successive silica gel columns, followed by purification on a Sephadex column. The combined active aliquots were further purified on ODS and Phenyl high performance liquid chromatography (HPLC) columns, successively. The chemical structures of isolated substances were analyzed by electron ionization mass spectrometry (EIMS) and nuclear magnetic resonance (NMR) spectroscopy and were identified as tyrosol, succinic acid, vanillic acid and para-hydroxy benzoic acid. Using available commercial compounds, we determined the antioxidant activity of isolated substances with seven assay methods was determined and compared to natural and synthetic standard compounds. It was observed that the activity of each substance varied with the assay mode. No single substance could be identified as an all-round highly active antioxidant, which was also true with the standard compounds. The diverse activities suggested that Z. rouxii could be used as a source of wide-spectrum natural antioxidant.

Procyanidins from Adansonia digitata.

The 80% methanol of the pericarp of the fruits of Adansonia digitata. L. (Bombaceae) was found to contain proanthocyanidins as major compounds, vi.z., (-)-epicatechin, epicatechin-(4 → β.8)-epicatechin B2, epicatechin-(4 → β.6)-epicatechin B5, epicatechin-(2β. → O → 7, 4β. → 8)-epicatechin A2, and epicatechin-(4 → β.8)-epicatechin-(4 → β.8)-epicatechin C1. All the isolated compounds were isolated by open-column liquid chromatography (CC) using Sephadex-LH 20 as stationary phase. Elution of the column was performed with EtOH. The structures of these compounds were elucidated by means of TLC, ESI-MS, and 1D and 2D NMR spectroscopy.

Two‐Stage Fractionation of a Mixture of 10 Pesticides by TLC and HPLC

Relationships between R F values and mobile‐phase composition have been determined for 10 pesticides in normal‐phase (NP) systems, which have enabled choosing optimum systems for preliminary fractionation of the multicomponent mixture of pesticides by zonal micropreparative thin‐layer chromatography (TLC). The 10‐component mixture was applied from the edge of the silica layer and developed with ethyl acetate–diisopropyl ether (10∶90, v/v). The zones were detected in UV light at λ = 254 nm. The separated eight simpler fractions were applied to an octadecyl silica layer wettable with water (TLC, RP‐18W) and rechromatographed. The separated eight simpler fractions were also applied to a cyanopropyl‐bonded silica layer and developed with (NP) and reverse‐phase (RP) systems. The plates were scanned and videoscanned, furnishing real pictures of the plates showing complete separation of the fractions on the RP‐18W plate with the RP and NP systems on cyanopropyl silica layer. The simpler fractions were also separated on a cyanopropyl and octadecyl silica high performance liquid chromatography (HPLC) columns. Preparative separation of the complex mixture by TLC on silica (non‐aqueous eluent, NP system), combined with TLC or/and HPLC (aqueous eluent, RP system) or HPLC (NP system), gives a good perspective of full separation of the simpler fractions in the second stage, by using the two methods with the possibility of full quantitative TLC and HPLC analysis.

Isolation of some PUFA from edible oils by argentated silica gel chromatography

Four edible oils, linseed, borage and sunflower seed oils, and the liver oil of shortfin mako ( Isurus oxyrinchus ), have been fractionated by open column liquid chromatography, using partially argentated silica gel as stationary phase, looking for purify polyunsaturated fatty acids (PUFA). By this method, linoleic (LA, 18:2n6),α-linolenic (ALA, 18:3n3), γ-linolenic (GLA, 18:3n6), stearidonic (SDA, 18:4n3), eicosapentaenoic (EPA, 20:5n3) and docosahexaenoic (DHA, 22:6n3) fatty acid esters have been isolated from these oils with high purity percentages and yields.

Bronopol as an Ingredient of a New Test Mixture for Evaluation of HPLC Columns

Different tests, including analytes or mixtures characterized by specific properties, can be used for the evaluation of chromatographic columns. High performance liquid chromatographic (HPLC) columns with chemically modified surfaces, purchased from different producers, were tested in our studies. Characteristic chromatographic parameters, such as: number of plate theoretical (N T ), reduced plate height (h), the retention factor (k), resolution (R S ), and asymmetry factor (f AS ) were determined. Bronopol (2‐bromo‐2‐nitrpropane‐1,3‐diol) was suggested for column evaluation, especially as regards the homogeneity of adsorbent surface coverage by chemically bonded phase and spacing of residual silanols. This analyte was used separately, and in a mixture consisting of other analytes (uracil, acetophenone, benzene, toluene) with different physicochemical properties.

SAMPLE PREPARATION FOR EFFECTIVE DETERMINATION OF POLYCHLORINATED DIBENZODIOXINS FROM LEACHATES

Four pretreatment methods, including LLE-HPLC, LLE- DMSO, SPE-HPLC and SPE-DMSO are compared for the effective determination of polychlorinated dibenzodioxins (PCDDs) from a leachate sample. For the LLE-HPLC method, liquid–liquid extraction (LLE) with dichloromethane is used for the initial extraction of the analytes from leachate. For the elimination of interferences coextracted from leachate, acid treatment, followed by high performance liquid chromatographic (HPLC) column clean-up, is performed. For the LLE-DMSO method, LLE, acid treatment and extraction with dimethyl sulfoxide (DMSO) are accomplished, consecutively. For the SPE-HPLC method, solid-phase extraction of disk-type with toluene–ethanol mixture (3:7, v/v), acid treatment, and HPLC column clean-up are performed, consecutively. For the SPE-DMSO method, SPE with DMSO and acid treatment are performed, consecutively. After each of these methods, column clean-ups including multilayer silica gel and alumina are performed, sequentially. The final extract is analyzed by HPLC-UV. For SPE, a toluene–ethanol mixture, conventional solvent is used for the extraction of PCDDs from SPE of disk-type. However, the use of DMSO with a selective interaction with aromatic compounds shows higher efficiencies when considering time, solvent usage, and removal of interferences.

Dehydrothalebanin: a source of resistance from Glycosmis pentaphylla against the citrus root weevil Diaprepes abbreviatus.

Roots of a citrus relative, Glycosmis pentaphylla (orangeberry), were shown to inhibit the growth and survival of larvae of the citrus root weevil Diaprepes abbreviatus. Roots of G. pentaphyllaincorporated into the diet of D. abbreviatus increasingly inhibited the growth of neonate larvae with increased concentration of roots, while roots from citrus rootstocks produced little inhibition. The diet-incorporation assay was used to guide fractionation of an active acetone extract of G.pentaphylla roots. Three major fractions from silica open-column liquid chromatography were active, and these were purified using semipreparative normal-phase HPLC. A single active HPLC subfraction was isolated from each of the three liquid chromatography fractions, and two active compounds were isolated and identified by GC-MSD. GC-MSD and NMR identified one compound as the amide dehydrothalebanin B, and the other was identified by GC-MSD as dieldrin, a chlorinated hydrocarbon insecticide whose origin in our samples is uncertain.