Liquid Partition Research Articles

Application of HPLC–DAD after SPE/QuEChERS with ZrO2-based sorbent in d-SPE clean-up step for pesticide analysis in edible oils

In this study, the solid-phase extraction/quick, easy, cheap, effective, rugged and safe (SPE/QuEChERS) technique was adapted to develop a simple sample treatment for multi-residue pesticide analysis of edible oils. The proposed method is based on liquid–liquid partitioning with acetonitrile followed by dispersive solid phase extraction using zirconia-coated silica particles for extract purification. To evaluate the described method, 21 pesticides belonging to different chemical classes were analysed using high performance liquid chromatography with diode-array detection (HPLC–DAD). For validation purposes, recovery studies were performed at 75ngg−1, 125ngg−1, 250ngg−1, 500ngg−1 and 1000ngg−1 levels. Recoveries were over the range of 50–130% for most of the analytes, with relative standard deviations less than 15% being observed. HPLC–DAD provided suitable linearity, precision and accuracy. The validated method was successfully applied to the analysis of edible oil samples selected from the market.

Ethanolic Echinacea purpurea Extracts Contain a Mixture of Cytokine-Suppressive and Cytokine-Inducing Compounds, Including Some That Originate from Endophytic Bacteria.

Echinacea preparations, which are used for the prevention and treatment of upper respiratory infections, account for 10% of the dietary supplement market in the U.S., with sales totaling more than $100 million annually. In an attempt to shed light on Echinacea's mechanism of action, we evaluated the effects of a 75% ethanolic root extract of Echinacea purpurea, prepared in accord with industry methods, on cytokine and chemokine production from RAW 264.7 macrophage-like cells. We found that the extract displayed dual activities; the extract could itself stimulate production of the cytokine TNF-α, and also suppress production of TNF-α in response to stimulation with exogenous LPS. Liquid:liquid partitioning followed by normal-phase flash chromatography resulted in separation of the stimulatory and inhibitory activities into different fractions, confirming the complex nature of this extract. We also studied the role of alkylamides in the suppressive activity of this E. purpurea extract. Our fractionation method concentrated the alkylamides into a single fraction, which suppressed production of TNF-α, CCL3, and CCL5; however fractions that did not contain detectable alkylamides also displayed similar suppressive effects. Alkylamides, therefore, likely contribute to the suppressive activity of the extract but are not solely responsible for that activity. From the fractions without detectable alkylamides, we purified xanthienopyran, a compound not previously known to be a constituent of the Echinacea genus. Xanthienopyran suppressed production of TNF-α suggesting that it may contribute to the suppressive activity of the crude ethanolic extract. Finally, we show that ethanolic extracts prepared from E. purpurea plants grown under sterile conditions and from sterilized seeds, do not contain LPS and do not stimulate macrophage production of TNF-α, supporting the hypothesis that the macrophage-stimulating activity in E. purpurea extracts can originate from endophytic bacteria. Together, our findings indicate that ethanolic E. purpurea extracts contain multiple constituents that differentially regulate cytokine production by macrophages.

Se–Te fractionation by sulfide–silicate melt partitioning: Implications for the composition of mantle-derived magmas and their melting residues

Partitioning of Se and Te has been measured between coexisting sulfide liquid, monosulfide solid solution (MSS) and silicate melt at 0.9–1.5 GPa, 1200–1300 °C, fO2 controlled near the fayalite–magnetite–quartz buffer (FMQ-1.2 to -1.6) and 3–22 wt% FeO in the silicate melt. Both elements are highly compatible in the sulfide phase relative to silicate liquid (Dsulfide phase/silicate liquid > 600), with the identity of the sulfide dictating the sense of Se–Te fractionation. Whereas the measured DTe/DSe is ∼5–9 for sulfide liquid/silicate liquid partitioning, MSS/silicate melt partitioning fractionates Te from Se in the opposite sense, with DTe/DSe of ∼0.5–0.8. At fixed fO2, DSulLiq/SilLiq values for both Se and Te decrease ∼8-fold over the range in silicate melt FeO content investigated. The relative values of DSulLiq/SilLiq for Cu to Se increase with increasing FeO in the silicate melt, such that DCu exceeds DSe only for melts with >11 wt% FeO. Hence the standard belief that DCu>DSe as indicative of sulfide removal should be carefully assessed in the context of the FeO content of the magmas involved.Assuming a chondritic mantle Se/Te, predicted MSS and sulfide liquid compositions are generally in accord with natural mantle sulfides, in terms of their designation as MSS or sulfide liquid, based on independent criteria. However, additional variability is likely due to Te redistribution in accessory platinum group minerals (PGM), or that some sulfides are metasomatic. Calculations show that the Se/Te ratio of silicate melt derived from a sulfide liquid-saturated mantle is significantly higher, and more variable, than for silicate melt in equilibrium with residual MSS; modest sulfide liquid removal at low pressure, however, likely obscures the Se/Te fractionation imposed by the source sulfide phase. Models indicate that the composition of MORB is consistent with melts produced from sulfide-bearing sources with chondritic Se/Te, and source sulfur contents higher than estimates for depleted mantle. The calculated composition of sulfide-saturated melting residues show relatively little deviation in Se/Te if MSS is residual, but a sharp drop in this ratio for sulfide liquid control. Although the data are scattered, a portion of the peridotite array near the primitive mantle composition is consistent with model trends, and suggests control by residual MSS.

Dissipation Kinetics of Cyazofamid in Water

A reliable and sensitive method has been developed and validated for the determination of cyazofamid in water using reverse phase HPLC (RP-HPLC). The analytical procedure involves fortification of water at two doses, liquid–liquid partition with chloroform, separation on Discovery C-18 column using mobile phase acetonitrile: water (60:40 v/v) and detection at 279 nm. Calibration curves for quantification were linear over the dynamic range of 0.01–10.0 µg mL−1 concentrations with the correlation coefficients (R2) greater than 0.99 and percent relative standard deviation [RSD (%) was 1.72. Degradation pattern indicated correspondence to monophasic first order kinetics in water with half-life values 3.92 and 4.25 days. The degradation rate was almost same at both treatments. The average recoveries of cyazofamid from water fortified at 0.01–5.0 µg mL−1 ranged from 90.4–96.6%. The limit of quantitation and limit of detection of analyte were 0.01 and 0.006 µg mL−1, respectively.

Activity coefficients at infinite dilution and physicochemical properties for organic solutes and water in the ionic liquid 4-(3-hydroxypropyl)-4-methylmorpholinium bis(trifluoromethylsulfonyl)-amide

The activity coefficients at infinite dilution, γ13∞ and (gas+liquid) partition coefficients, KL for 61 solutes: alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, esters, butanal, nitrogen compounds and water in the ionic liquid 4-(3-hydroxy)-4-methylmorpholinium bis(trifluoromethylsulfonyl)-amide were determined by (gas+liquid) chromatography at the temperatures from (298.15 to 368.15)K. The partial molar excess Gibbs free energies ΔG1E,∞, enthalpies ΔH1E,∞ and entropies ΔS1E,∞ at infinite dilution were calculated from the experimental γ13∞ values obtained over the temperature range. The selectivities and capacities at infinite dilution for selected extraction problems (water/butanol, hexane/benzene, heptane/thiophene) were calculated from the γ13∞ and compared to the literature values for other ionic liquids based on bis(trifluoromethylsulfonyl)-amide anion. The values of KL were used to determine the linear free energy relationship (LFER) system constants as a function of temperature. The density and viscosity of the investigated ionic liquid at temperatures from (298.15 to 368.15)K as well as other physicochemical properties: temperature of fusion and glass transition temperature were also measured.

Chemical and biological comparison of raw and vinegar-baked Radix Bupleuri

Ethnopharmacological relevanceRadix Bupleuri (RB) is a commonly used herbal drug in Traditional Chinese Medicine (TCM), and it can be baked with vinegar to afford vinegar-baked Radix Bupleuri (VBRB), which is used in TCM for liver diseases treatment. In this study, the chemical compositions and biological effects between raw and two processed RBs by different vinegars were systematically compared. Materials and methodsThe chemical compositions of raw and two processed RBs were analyzed by 1H NMR spectroscopy coupled with multivariate analysis. Two different extraction procedures were used, including direct extraction and liquid–liquid partition. Then HPLC was applied to determine the changes of saikosaponin contents. In addition, their liver protective effects against CCl4 induced liver injury were also investigated, and the biochemical parameters and histopathology were measured after treatment of mice with raw RB and two processed RBs (5g/kg/day) for 14 days. ResultsMultivariate analysis showed clear differences between the raw and the two processed RBs, and the vinegar-baking process induced elevated contents of ssb1, ssb2, acetic acid, malic acid, citric acid, 5-HMF, and ligustrazine, as well as the decreased contents of ssa, ssd, sucrose, glycine, succinic acid etc. In addition, both raw and processed RBs showed liver protective effects against CCl4 induced liver injury, and the vinegar-baked RBs showed better effects than that of raw RB. ConclusionsThe raw and vinegar-baked RBs differed not only in the chemical compositions but also in the pharmacological effects. And two processed RBs also showed chemical differences, suggesting that the type of vinegar had an important effect on vinegar baking. In order to ensure the therapeutic effect and safety of TCM, the effect of different vinegars on processing of herbal drugs should be further studied.

A new approach for the purification of soybean acid extract: Simultaneous production of an isoflavone aglycone-rich fraction and a furfural derivative-rich by-product

Isoflavones are found mostly in legumes, such as soybeans. These compounds have several therapeutic potentials, largely attributed to their aglycone forms. The soybean extraction followed by acid hydrolysis is the usual process for coverting isoflavone glucosides into their bioactive compounds. However, under extreme pH, different compounds, characterized as contaminants or even having important properties, can be obtained. In this context, this paper aimed to produce an isoflavone aglycone-rich fraction (IAF) from a soybean rich cultivar, as well as isolate and identify other compounds formed during the IAF production. The extraction of defatted soybean seeds was performed with ethanol–water (80:20, v/v) in a Soxhlet apparatus, followed by acid hydrolysis with 1.3M HCl, under reflux at 80°C at different times (0–360min). During the hydrolysis procedure, besides the isoflavones, two unknown compounds were produced in high amounts. These compounds were isolated by column chromatography and identified as 5-hydroxymethylfurfural (HMF) and 5-ethoxymethyl-2-furfural (EMF), both isolated for the first time from soybeans. These substances are derived from sugars, classified as furanic derivatives, possibly toxic for medicinal uses, but with significant importance in the biofuel field. In order to produce an IAF intended for a future food or pharmaceuticals use, the soybean acid extract was submitted to liquid–liquid partition, solid phase extraction, and antisolvent precipitation processes, resulting in a fraction with high isoflavone aglycones purity (92%). From this process, the removed impurities originated a furfural derivative- rich solution, which can be an attractive by-product for the biofuel field.

An equation of state for predicting the thermodynamic properties and vapour–liquid partitioning of aqueous Ge(OH)4 in a wide range of water densities

Although germanic acid is an important compound in many engineering and natural aqueous environments, its exact stoichiometry, structure and stability are insufficiently known. To fill this gap, we combined theoretical quantum chemistry simulations of Ge speciation and structure with a recently developed equation of state for aqueous neutral species, applied to available experimental GeO2(s) solubility measurements. Results allow generation of a consistent set of thermodynamic properties of Ge(OH)4(aq) over a large T–P-fluid density range (298–900K, 0.1–300MPa, and 0.01–1.0gcm−3). These properties enable quantitative predictions of Ge transport and its fractionation from similar elements (e.g. Si) in aqueous vapour–liquid and supercritical fluid systems.

New Insight into the Americium/Curium Separation by Solvent Extraction using Diglycolamides

The liquid–liquid extraction process called EXAm was developed by the CEA to allow the recovery of Americium alone from a PUREX raffinate. Americium is extracted from a highly acidic feed solution (HNO3 4–6 M) by a mixture of two extractants: DMDOHEMA and HDEHP. The Am/Cm selectivity is improved using a specific diglycolamide (TEDGA) as a selective aqueous complexing agent which retains preferentially Cm and heavier lanthanides in the aqueous phase. In this study, the impact of the lipophilicity and steric hindrance of several diglycolamides on the Am/Cm selectivity was investigated in order to understand the enhancement brought by TEDGA. For this purpose, liquid–liquid extraction and partitioning experiments were performed under various conditions.

Toxic Microcystis novacekii T20-3 from Phakalane Ponds, Botswana: PCR Amplifications of Microcystin Synthetase (mcy) Genes, Extraction and LCESI- MS Identification of Microcystins

Treated water effluent from Phakalane waste water secondary maturation ponds in Gaborone City (Botswana) enters the Limpopo River via Notwane River. Effluent samples from these ponds were collected and investigated using molecular and analytical methods to determine presence of mcy genes and microcystins (MCs), respectively. It was observed that, potentially toxic algal blooms were present in this effluent and therefore algal toxins. Using Polymerase Chain Reaction (PCR) method; cyanobacterial 16S-rRNA and mcyA, -B, -C, -D, -E and -G genes were amplified and PCR products separated by gel electrophoresis and visualized after ethidium bromide staining. DNA sequence for mcyA gene was obtained using PCR products from a newly designed primer pair for the amplification of mcyA gene. BLAST results of the obtained DNA sequence were evaluated and aligned to NCBI database for species identification. The alignment gave the highest similarity (100%) in nucleotide sequence that was aligned to the DNA sequence of a toxigenic M. novacekii T20-3 based on the published data. Microcystin-RR, -YR, -LR and -WR were chromatographed, identified and quantified from M. novacekii T20-3 cell extracts using LC-ESI-MS technique after liquid-partitioning (LP) and solid-phase extraction (SPE) steps complementing PCR findings. Higher quantities of MC-RR, -LR and YR: 53.620 ± 0.063, 12.114 ± 0.024 and 5.280 ± 0.035 μg/g DW were observed, respectively.

Development of a test system for high level liquid waste partitioning

The partitioning and transmutation strategy has increasingly attracted interest for the safe treatment and disposal of high level liquid waste, in which the partitioning of high level liquid waste is one of the critical technical issues. An improved total partitioning process, including a tri-alkylphosphine oxide process for the removal of actinides, a crown ether strontium extraction process for the removal of strontium, and a calixcrown ether cesium extraction process for the removal of cesium, has been developed to treat Chinese high level liquid waste. A test system containing 72-stage 10-mm-diam annular centrifugal contactors, a remote sampling system, a rotor speed acquisition-monitoring system, a feeding system, and a video camera-surveillance system was successfully developed to carry out the hot test for verifying the improved total partitioning process. The test system has been successfully used in a 160 hour hot test using genuine high level liquid waste. During the hot test, the test system was stable, which demonstrated it was reliable for the hot test of the high level liquid waste partitioning.

ISOLASI DAN IDENTIFIKASI KOMPONEN KIMIA EKSTRAK N-HEKSAN DAUN PALA (Myristica fragrans)

Nutmeg plant is a multi-purpose plant because each part can be utilized in the industry. Nutmeg leaves contain essential oils and phenolic compounds. Essential oils are used as traditional medicine ingredients and as raw material for the manufacture of cosmetics, soaps, perfumes and others. This study aimed to isolate and identify the chemical components in the leaves of nutmeg (Myristica fragrans). Have done isolation and Identification of chemical components of the methanol extract of leaves pala ( Myristica fragrans .) of 500 grams to determine the class of chemical components caontained in the leaf pala ( Myristica fragrans .). The methanol extract which obtained by maseartion method 9,45 grams continued by solid liquid partition with n-hexane 4,61 grams extract. N-hexan extract isolated by column chromatography method obtained 37 bottles vials. Fraction D of the merger based on the appearance of spotting the chromatograms isolated by preparative thin-layer chromatography method, obtained 3 band. D.1 fractions isolated by TLC obtained a stain. In fractions spotting D.1 is obtained by testing a single two-dimentional TLC ang the elution system of multi eluen. Interpretation UV-Visible spectra data showed maximum absorption at a wavelength 0f 2 73 nm and showed infrared fungtional group (OH) on the wave number (3 927.78 cm -1 , 3828.59 cm -1 , 3743.30 cm -1 , 3387.93 cm -1 ), group (CH) on the wave number ( 2925.93 cm -1 , 2859.02 cm -1 , 2364.17 cm -1 ), alken group (C = C) aromatik on the wave number ( 1642.54 cm -1 , 1565.88 cm -1 , 1516.65 cm -1 , 1458.92 cm -1 , 1114.33 cm -1 ), benzene group on the wave number ( 698.24 cm -1 ). Single spots obtained gave a positive reaction to spotting visualizer class of flavonoids. Key words : Nutmeg , Isolation, Essential Oils.

Activity Coefficients at Infinite Dilution and Physicochemical Properties for Organic Solutes and Water in the Ionic Liquid 1-Ethyl-3-methylimidazolium trifluorotris(perfluoroethyl)phosphate.

New data of activity coefficients at infinite dilution, γ 13∞, for 65 different solutes including alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, aldehydes, esters and water in the ionic liquid 1-ethyl-3-methylimidazolium trifluorotris(perfluoroethyl)phosphate, were determined using inverse gas chromatography within the temperature range from 318.15 to 368.15 K. This is a continuation of our study of ionic liquids based on this anion. The results are compared with the other trifluorotris(perfluoroethyl)phosphate ionic liquids. The γ 13∞ values were used to calculate thermodynamic functions such as partial molar excess Gibbs energies Delta G_{1}^{{{text{E,}}infty }} , enthalpies Delta H_{1}^{{{text{E,}}infty }} and entropies Delta S_{1}^{{{text{E,}}infty }} as well as gas–liquid partition coefficients of the solutes, K L. These values were used to determine the linear free energy relationship (LFER) system constants as a function of temperature. The selectivities at infinite dilution needed for some extraction problems were calculated and compared with literature data of ionic liquids based on the trifluorotris(perfluoroethyl)phosphate anion and the 1-ethyl-3-methylimidazolium cation. Additionally, the density and viscosity of the investigated ionic liquid at temperatures from 298.15 to 348.15 K were measured.Electronic supplementary materialThe online version of this article (doi:10.1007/s10953-014-0274-0) contains supplementary material, which is available to authorized users.

In vitro anti-proliferative activity on colon cancer cell line (HT-29) of Thai medicinal plants selected from Thai/Lanna medicinal plant recipe database “MANOSROI III”

Ethnopharmacological relevanceThai/Lanna region has its own folklore wisdoms including the traditional medicinal plant recipes. Thai/Lanna medicinal plant recipe database “MANOSROI III” has been developed by Prof. Dr. Jiradej Manosroi. It consists of over 200,000 recipes for all diseases including cancer. To investigate the anti-proliferative and apoptotic activities on human colon cancer cell line (HT-29) as well as the cancer cell selectivity of the methanolic extracts (MEs) and fractions of the 23 selected plants from the “MANOSROI III” database. Materials and methodsThe 23 selected plants were extracted with methanol under reflux and evaluated for their anti-proliferative activity by sulforhodamine B assay. The 5 plants (Gloriosa superba, Caesalpinia sappan, Fibraurea tinctoria, Ventilago denticulata and Psophocarpus tetragonolobus) with potent anti-proliferative activity were fractionated by liquid–liquid partition to give 4 fractions including each hexane (HF), methanol–water (MF), n-butanol (BF) and water (WF) fractions. They were tested for anti-proliferative activity and cancer cell selectivity. The ME and fractions of G. superba which showed potent anti-proliferative activity were further examined for morphological changes and apoptotic activities by acridine orange (AO)/ethidium bromide (EB) staining. ResultsThe ME of G. superba root showed active with the highest anti-proliferative activity at 9.17 and 1.58 folds of cisplatin and doxorubicin, respectively. After liquid–liquid partition, HF of V. denticulata, MFs of F. tinctoria, V. denticulata and BF of P. tetragonolobus showed higher anti-proliferative activities than their MEs. The MF of G. superba indicated the highest anti-proliferative activity at 7.73 and 1.34 folds of cisplatin and doxorubicin, respectively, but only 0.86 fold of its ME. The ME and HF, MF and BF of G. superba and MF of F. tinctoria demonstrated high cancer cell selectivity. At 50µg/ml, ME, HF, MF and BF of G. superba demonstrated higher apoptotic activities than the two standard drugs. ConclusionsThis present study has not only confirmed the traditional use of the Thai/Lanna medicinal plant recipes for cancer treatments, but also the potential of the selected plant, G. superba for the further development as a modern anti-cancer drug.

K-targeted metabolomic analysis extends chemical subtraction to DESIGNER extracts: selective depletion of extracts of hops (Humulus lupulus).

This study introduces a flexible and compound targeted approach to Deplete and Enrich Select Ingredients to Generate Normalized Extract Resources, generating DESIGNER extracts, by means of chemical subtraction or augmentation of metabolites. Targeting metabolites based on their liquid–liquid partition coefficients (K values), K targeting uses countercurrent separation methodology to remove single or multiple compounds from a chemically complex mixture, according to the following equation: DESIGNER extract = total extract ± target compound(s). Expanding the scope of the recently reported depletion of extracts by immunoaffinity or solid phase liquid chromatography, the present approach allows a more flexible, single- or multi-targeted removal of constituents from complex extracts such as botanicals. Chemical subtraction enables both chemical and biological characterization, including detection of synergism/antagonism by both the subtracted targets and the remaining metabolite mixture, as well as definition of the residual complexity of all fractions. The feasibility of the DESIGNER concept is shown by K-targeted subtraction of four bioactive prenylated phenols, isoxanthohumol (1), 8-prenylnaringenin (2), 6-prenylnaringenin (3), and xanthohumol (4), from a standardized hops (Humulus lupulus L.) extract using specific solvent systems. Conversely, adding K-targeted isolates allows enrichment of the original extract and hence provides an augmented DESIGNER material. Multiple countercurrent separation steps were used to purify each of the four compounds, and four DESIGNER extracts with varying depletions were prepared. The DESIGNER approach innovates the characterization of chemically complex extracts through integration of enabling technologies such as countercurrent separation, K-by-bioactivity, the residual complexity concepts, as well as quantitative analysis by 1H NMR, LC-MS, and HiFSA-based NMR fingerprinting.

Prediction of gas-to-ionic liquid partition coefficient of organic solutes dissolved in 1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate using QSPR approaches

The present work represents a quantitative structure–property relationship (QSPR) study for predicting the gas-to-ionic liquid partition coefficients (log K) of organic solutes dissolved in 1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate based on replacement method (RM) and support vector machine (SVM). The variable selection technique of replacement method (RM) was employed to select the most favorable subset of descriptors from the more than 1000 theoretical descriptors calculated using the Dragon package. The six descriptors selected were used as inputs of SVM to predict the gas-to-ionic liquid partition coefficient of a set of 92 aliphatic and aromatic solutes dissolved in 1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate. Results of our computations demonstrate that SVM can be used as a substitute powerful modeling tool for QSPR studies. The log K values calculated by SVM were in good agreement with the experimental data, and the performances of the SVM models were superior to RM one.

Screening of polychlorinated biphenyls in insulating oil using a microfluidic based pretreatment and immunoassay

Polychlorinated biphenyls (PCBs) are persistent organic pollutants in insulating oil of a large number of transformers. A rapid and economical analytical method to detect PCB contamination is still required. To address this issue, we propose here the first microfluidic screening method for PCB contamination in insulating oil. The insulating oil was pretreated using a multilayer capillary column and a microfluidic liquid–liquid partitioning. PCBs in the pretreated oil were measured using a microfluidic kinetic exclusion assay. In order to detect PCBs with high sensitivity, conditions of the microfluidic kinetic exclusion assay were optimized. Measurements were rapidly completed (within 43min). The measurement range was estimated to be 0.26–3.3mg/kg defined as the relative absorbance from 20% to 80%. The screening performance (false positive and false negative rates) was tested on fifty real oil samples; results about these tests were discussed in detail, especially suitable cutoff by comparing with the data analyzed using high-resolution-gas-chromatography/high-resolution-mass-spectrometry. Finally, the screening performance was confirmed using our proposed stochastic screening model. A cutoff of 0.3 to judge as positive is suitable considering the risk of the PCB release into the environment.

Novel equilibrium headspace gas chromatographic technique for the measurement of noncovalent association and partition of n-alkylbenzenes in water/n-dodecane and water/1-octanol systems at low phase ratio without phase separation

A novel equilibrium headspace gas chromatographic (eHSGC) method was developed to study the basis of liquid–liquid partitioning (LLP) as set of two reactions and the solute mass balance. The equations describe the system completely with minimum assumptions. The theory was tested for n-dodecane/water and 1-octanol/water systems with n-alkylbenzenes (benzene, B, toluene, T, ethtylbenzene, EB, n-propylbenzene, PB, and n-butylbenzene, BB) as solutes at infinite dilution (ca. 10−7 mf), without solute concentration, without calibration, and most importantly, without phase separation at low phase ratio (0.001). The only requirements are the accurate measurement of relative peak areas and the phase ratio. Three fundamental parameters- the critical phase ratio (cpr), monomer solute-organic solvent association constant (KSB), and monomer solute-organic pseudo-phase association constant (KSpB) were obtained experimentally. Other parameters such as the molar and mole fraction partition coefficients (KSW, Kx), and the intra-organic phase infinite dilution activity coefficients (γ∞s) of solutes were also calculated to characterize the LLP process. The noncovalent association constants, KSW and KSpB are reported here for the first time. The results show that the cpr is indicative of the solubility of lipophilic 1-octanol while significantly different for completely nonpolar n-dodecane due to strong solute-organic solvent (SB) association i.e., larger KSB. The partition coefficients (KSW and Kx) are shown to be a specific case of KSpB equilibrium. These values are in fair agreement with literature values. The existence of a water rich pseudo-phase in a water continuous mixed immiscible solvent is reflected in the relative values of ΔG°CH2= −(674 to 988) J/mol CH2 compared to the literature ΔG°CH2= −(1674 to 3349) J/mol CH2 for LLP into neat phases. The mutual influence of phases is clearly demonstrated by similarity of γ∞s (B-BB=0.25–8.38) for 1-octanol and γ∞s (B-BB=0.55–12) for n-dodecane.

Development of a modified QUick, Easy, CHeap, Effective, Rugged and Safe method for the determination of multi-class antimicrobials in vegetables by liquid chromatography tandem mass spectrometry

A modified quick, easy, cheap, efficient, rugged and safe (QuEChERS) method coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed for rapid determination of 26 veterinary antimicrobials in vegetables. Samples were extracted by single-phase extraction with acetonitrile-methanol (85:15, v/v) and citric buffer solution, followed by liquid–liquid partitioning with the addition of anhydrous magnesium sulfate and sodium chloride. A dispersive solid-phase extraction with primary secondary amine was applied for cleanup. Concentration and solvent exchange was performed prior to LC-MS/MS analysis. All matrix-matched calibration curves were linear with correlation coefficients (r) over 0.99. Recoveries for all the analytes spiked at 0.5 (1 or 1.5), 5 and 50ng/mL were in the range of 60.0–98.0%, except for sulfaquinoxaline, sulfaclozine and doxycycline, with relative standard deviations below 25% for the low concentration level, 20% for the medium and 15% for the high. The decision limits and the detection capabilities of the analytes ranged from 0.005 to 0.5μg/kg and from 0.02 to 1.5μg/kg, respectively. The method was developed and validated in accordance with romaine lettuce matrix, and higher recovery rates were obtained from the other five kinds of vegetables including white radish, Chinese cabbage, cucumber, string bean and green pepper. Matrix effects of different vegetables were evaluated and signal suppression effect was observed for the majority of 26 analytes. Finally, the method was applied to the analysis of real samples collected from the agricultural areas in the vicinity of local pig farms, and the phenomenon of vegetables contaminated by antimicrobials residues is provoking.

Carbon isotope effects of methane transport through Anahuac Shale — A core gas study

Compositional data and stable isotope ratios are critical datasets for the study of hydrocarbon generation, expulsion, and migration. These geochemical parameters are also important for studies of leakage detection for geological carbon sequestration. Diffusion, gas–liquid partitioning and adsorption, the three most crucial processes to affect gas transport through shale and other low-permeability formations, are known to cause stable isotope fractionation. A considerable number of studies have been conducted on stable isotope fractionation associated with diffusion and gas–liquid partitioning. However, significantly fewer data are reported in the literature that specifically addresses adsorption carbon isotope effects. Moreover, adsorption isotope effects are rarely verified or seldom demonstrated in geologic systems. In this study, a shale core taken from the Anahuac Formation in Texas Gulf Coast, which overlies several Frio reservoirs, was analyzed for composition and stable isotope ratios of the residual gas. These geochemical parameters are used to identify gas migration and associate transport mechanisms in the caprock formation. Gas samples extracted from the core contain alkane gas components (C1–C5) and show a systematic variation in carbon isotope ratios of methane along depth. An analytical model is proposed to interpret the observed carbon isotope trend on the basis of coupled processes of diffusion and adsorption. At a ratio of retardation of 0.99 between 12CH4 and 13CH4 (with 12CH4 having a preferential bonding with the clay mineral) and a diffusion time of 1.5Ma, the modeled curve fits well with observed upward increasing δ13CCH4 values. This study demonstrates the isotope effect of adsorption in a natural system and its importance in quantifying gas-migration rate and distance in low-permeability systems.