Reduced Solvent Consumption Research Articles

Separation of stereoisomers in a simulated moving bed-supercritical fluid chromatography plant

The combination of two techniques, simulated moving bed (SMB) and supercritical fluid chromatography (SFC), leads to an apparatus with unique features. Besides the known advantages of the SMB process, like reduced solvent consumption and its continuity, the use of supercritical carbon dioxide as the mobile phase offers an easy product recovery by depressurizing the supercritical fluid. Details of a SMB-SFC plant are presented for the first time. Due to the large number of process parameters a simulation of the SMB process is necessary to achieve optimal operating conditions. The most important thermodynamic information for a SMB process is the adsorption isotherms. Therefore, isotherms for two phytol isomers are measured and correlated. A fast dynamic model for the simulation of SMB is used to calculate the region of complete separation taking different column configurations and the compressibility of the mobile phase into account.

A solvent extractor system for the rapid extraction of lipids and trace bioactive micronutrients in oilseeds

AbstractA low‐cost laboratory extractor has been designed and constructed that selectively extracts polar and nonpolar components from oilseeds and other matrices. The extractor uses available high‐performance liquid chromatography laboratory equipment for pumping the solvent into the extractor. Pressure, temperature, and valving arrangements are automatically controlled by commercially available components. Advantages of this system include low initial investment, reduced solvent consumption, shorter extraction times, quantitative lipid recovery, use of multiple extraction solvents, and reduction in cost per sample. The method has broader applications that include extraction of trace components from a variety of matrices, for example, the extraction of pesticides from foods and polychlorobiphenyls from soil. Class separation of components from different matrices can be achieved easily by selection of solvents with the appropriate polarity characteristics. Very small samples can be extracted simply by changing cell size or by adding an inert material to the cell to fill the void volume. Analyte collection can be accomplished by collecting in a test tube with an appropriate solvent, or on a solid‐phase material. Optimization of extraction times, number of extractions, matrices, and solvent used is described. Neutral lipids were extracted from peanut meal in 70 min by the rapid extraction method compared to 1440 min required to extract the comparable amount of neutral lipids from a similar sample by the Soxhlet extraction method.

Accelerated solvent extraction of paclitaxel and related compounds from the bark of taxus cuspidata

Accelerated solvent extraction (ASE) of paclitaxel and related compounds from Taxus cuspidata (Japanese yew) bark has been investigated under various conditions. In ASE, pressure is applied to the sample extraction cell to maintain the heated solvent in a liquid state during the extraction. This method is able to shorten the extraction time and to increase the recovery of target compounds. In this study, ASE of paclitaxel, baccatin III, and 10-deacetylbaccatin III produced amounts of these compounds that were higher than those from ordinary solvent extraction at room temperature. The conditions providing the highest recovery of paclitaxel were as follows: solvent, MeOH-H2O (90:10); temperature, 150 degrees C; and pressure, 10.13 MPa (0.128% w/w recovery based on oven-dried sample powder). ASE does not require chlorinated solvents and can reduce solvent consumption because of its strong dissolving power. Moreover, with water alone, the recovery of paclitaxel and related compounds using ASE is much higher than with other extraction methods.

The determination of polychlorinated biphenyls in municipal sewage sludges using microwave-assisted extraction and gas chromatography-mass spectrometry

The presence of organic micropollutants [such as poly(chlorobiphenyls)] in municipal sewage sludges is a major problem on account of risks associated with the agricultural valorisation of the sludges. In France, since January 1998, maximum values for trace organic pollutants are imposed [0.8 mg kg–1 dry matter for the sum of seven poly(chlorobiphenyls)]. The aim of this study was to develop a reliable, accurate and fast analytical procedure (extraction, clean-up, quantification) in order to determine polychlorinated biphenyls in municipal sewage sludges. Such pollutants could be efficiently extracted from dried sewage sludge samples using microwave-assisted extraction. This technique affords several advantages as compared to the classical Soxhlet extraction, mainly rapidity and reduction in solvent consumption. Extractions (10 min under 30 W with 30 ml hexane–acetone 1:1) were conducted in the presence of copper to avoid sulfur interferences in the extracts. The latter were further concentrated and purified onto disposable silica cartridges. After final concentration and addition of the internal standard, they were analysed by gas chromatography coupled to mass spectrometry (in the selected ion monitoring mode). Two types of sludges (from Acheres and Valenton sewage treatment plants near Paris, France) were analysed, whose polychlorobiphenyl concentrations differed largely (Acheres sludge being the most contaminated). The microwave extraction compared favourably with the classical Soxhlet extraction. In addition, the sludge concentrations found with our experimental procedure were close to the analyses made by another laboratory, even though some discrepancy was noted.

Automated Method for Cleanup and Determination of Benomyl and Thiabendazole in Table-Ready Foods

An automated solid-phase extraction (SPE) cleanup with on-line liquid chromatographic (LC) analysis was developed to determine residues of benomyl (as carbendazim) and thiabendazole in table-ready food items from the U.S. Food and Drug Administration Total Diet Study (TDS). A strong-cation-exchange cleanup of an acetone extract replaces the methylene chloride solvent partitioning steps in the procedure described in the Pesticide Analytical Manual (PAM). LC analysis is accomplished with a C8 analytical column and tandem fluorescence and UV detection. Recoveries of both analytes from 32 representative TDS foods fortified at 0.05 and 0.5 microgram/g were determined. Method precision was evaluated with triplicate recovery assays on 11 foods fortified at both levels. Accuracy was tested further by assaying 47 foods for incurred residues in parallel with the validated PAM procedure for comparison, and good agreement was found. The automated SPE method reduces solvent consumption, analysis time, and labor.

Determination of Phenylurea Herbicide Residues in Vegetables by Liquid Chromatography after Gel Permeation Chromatographyand Florisil Cartridge Cleanup

A liquid chromatographic method for quantitative determination of 9 phenylurea herbicide residues (metoxuron, metobromuron, monolinuron, chlortoluron, isoproturon, diuron, linuron, chloroxuron, and neburon) in potatoes, carrots, and mixed vegetables is described. Samples are extracted with acetone, partitioned with ethyl acetate-cyclohexane (50 + 50, v/v) and cleaned up by gel permeation chromatography with ethyl acetate-cyclohexane (50 + 50, v/v) as eluant. A small column (1 cm id) packed with Biobeads SX3 resin is used to reduce solvent consumption and analytical time. After solid-phase extraction on a Florisil cartridge, herbicide residues are successfully separated on a C18 column by gradient elution and determined by UV detection at 242 nm. Average recoveries of 9 compounds from different samples range from 70 to 98% at 0.010 and 0.100 mg/kg fortification levels. Quantitation limits are 0.010 mg/kg.

Solid-Phase Microextraction and Headspace Solid-Phase Microextraction for the Determination of Polychlorinated Biphenyls in Water Samples

A solid-phase microextraction (SPME) method has been developed for the quantification of polychlorinated biphenyls (PCBs) in water samples. Parameters such as sampling time, volume of water, volume of headspace, temperature, addition of salts, and agitation of the sample were studied. Because the time for reaching equilibrium between phases takes several hours or days, depending on the experimental conditions, it was necessary to work in nonequilibrium conditions to keep the sample analysis to a reasonable time. The possibility of sampling the headspace over the water sample (HSSPME), instead of immersing the fiber into the water (SPME), was also investigated, and despite the low partition of PCB into the headspace, HSSPME offered higher sensitivity than SPME at 100 °C. The adsorption kinetics for SPME at room temperature, SPME at 100 °C, and HSSPME at 100 °C were investigated and compared. The proposed HSSPME method exhibits excellent linearity and sensitivity. The detection limit was in the sub-ng/L level. This method has been applied to a real industrial harbor water and compared with liquid-liquid extraction. Both techniques offered similar results, but HSSPME was much more sensitive and considerably faster, by eliminating all the manual process intensive sample workup, and reduces solvent consumption entirely. The only drawback was that matrix effects were observed, but with the addition of deuterated surrogates to the sample or the use of a standard addition calibration, accurate quantification can be achieved.

Development of a supercritical fluid extraction method for the determination of temazepam in whole blood.

A supercritical fluid extraction (SFE) procedure for the analysis of temazepam from whole blood was developed. Quantitative recoveries were obtained by high-performance liquid chromatography using prazepam as an internal standard and carefully monitoring the extraction temperature and pressure. The results were found to compare well with those obtained by solid-phase extraction techniques, but they also had the advantages of reduced solvent consumption and minimal sample handling. The application of this method to authentic forensic blood specimens showed the SFE method to be useful as an alternative procedure for the extraction of temazepam in the toxicology laboratory.

Evaluation of procedures for solid-phase extraction of [125I]-methodone from serum on to discs and cartridges

Biological samples must be purified before chromatography to eliminate interfering compounds. Discs have recently been developed to enhance the performance of solid-phase extraction (SPE) and reduce solvent consumption. This type of support is available in all the bonded-phases typically found in conventional packed SPE devices. The process for solid-phase extraction of [125I]-methadone from water and serum (i.e. retention and losses of [125I]-methadone during sample loading, washing, elution, etc.) has been studied to determine the behaviour of this compound on several extracting supports. For serum solutions we observed significant matrix effects on discs because of their low capacity. This resulted in loss of [125I]-methadone during the loading step because the contact time between the analyte and the functional groups of the support was too short. Although mixed-mode discs, which have both hydrophobic and cation-exchange extraction mechanisms, do not perform as well as conventional cartridges, they can, nevertheless, be used before liquid chromatographic analysis because of their several mechanical and economical advantages in comparison with cartridges.

Staining Paraffin Embedded Sections of Scald of Barley before Paraffin Removal

Staining of paraffin embedded sections with periodic acid-Schiff reagent and fast green before paraffin removal resulted in differentiation of barley seed and leaf tissue from fungal structures of Rhynchosporium secalis. Crystal violet, toluidine blue O and aniline blue also successfully stained fungal structures of R. secalis in barley leaf tissues. Staining of embedded sections before paraffin removal allows simple processing of a series of sections, saves time and reduces solvent consumption.

Supercritical fluid extraction of meat lipids: An alternative approach to the identification of irradiated meats

AbstractIonizing radiation is currently under study as an alternative method for extending the shelf life of meats and meat products. Accordingly, methods are needed to determine if a meat or meat product has been exposed to ionizing radiation. In this study, a method is described for the isolation and analysis of volatile hydrocarbons formed in meat lipids after exposure to ionizing radiation. The method is based on supercritical fluid extraction of the hydrocarbons from meat lipids and subsequent identification and quantitation of individual hydrocarbons by gas chromatography (GC) with a mass selection detector (MSD). Supercritical carbon dioxide at 175 bar and 40°C extracted the hydrocarbon fraction from total meat lipids within 20 min. The presence of radiolytic hydrocarbons, as determined by GC/MSD, was then correlated to the degree of irradiation of the meat from 0 to 10 kGy. Besides being faster, this method has the advantage of reduced solvent consumption when compared to current methods for determining if a meat or meat product has been irradiated.

Optimization of a chromatographic method for the gram-scale preparative fractionation of soybean phospholipids

To enable the study of the functional properties of pure soybean phospholipids, a chromatographic method was developed for the preparative fractionation of soybean lecithin. A coarse and irregularly shaped silica gel was used as the stationary phase, whereas the mobile phase consisted of three mixtures of hexane, 2-propanol and water of increasing polarity. These solvents were included in a step gradient, formed by an isocratic pump connected to a solvent changer. To reduce solvent consumption, the procedure was optimised using a method development column. The solvent program and the sample load were shown to affect mainly the purity and recovery of phosphatidylinositol.

Analysis of Leukotrienes, Lipoxins, and Monooxygenated Metabolites of Arachidonic Acid by Reversed-Phase High-Pressure Liquid Chromatography

Arachidonic acid can be converted to a large number of metabolites by various lipoxygenases, cyclooxygenase, and other enzymes. Because of the complex profiles of products formed by many types of cells, high-pressure liquid chromatography (HPLC) has proved to be an invaluable technique for their purification and analysis. In the present study we have developed improved methods for the analysis of complex mixtures of eicosanoids by HPLC using binary gradients containing trifluoroacetic acid (TFA), which allows considerable manipulation of the retention times of the cysteine-containing leukotrienes (LTs) LTC4, LTD4, and LTE4 relative to those of other eicosanoids. With a gradient between 0.003 and 0.005% TFA and a 4.6-mm-i.d. column of Spherisorb ODS-2, cysteinyl-LTs are very well resolved from one another and are separated as a group with retention times longer than those of all other major eicosanoids. These conditions can be used for the analysis of prostaglandin B2 (PGB2), LTB4, monohydroxyeicosatetraenoic acids (HETEs), and cysteinyl-LTs in only 30 min. Slightly longer analysis times must be used for the separation of more polar eicosanoids such as hydroxy metabolites of LTB4 and lipoxins. We have also developed methods for the analysis of eicosanoids using a midbore (3.2 mm i.d.) column containing Spherisorb ODS-2, which improves sensitivity and reduces solvent consumption. In this case higher concentrations (0.04 to 0.05%) of TFA have been used, resulting in retention times for cysteinyl-LTs between those of the cyclooxygenase product 12-hydroxy-5,8,10-heptadecatrienoic acid and the HETEs. This approach permits analysis of PGB2, LTB4, HETEs, and cysteinyl-LTs in only 20 min. Samples which also contain hydroxy-LTB4 and lipoxins can be analyzed in 40 min. The above techniques are highly reproducible and give baselines which are free of interfering peaks.

Use of Supercritical Fluid Extraction for Sample Preparation of Sustained‐Release Felodipine Tablets

Supercritical fluid extraction (SFE) was shown to be an accurate and precise alternative to liquid extraction for sample preparation of sustained‐release felodipine tablets (5 mg potency) while realizing an 80% reduction in solvent consumption. Extractions of felodipine spiked on an inert support were used to evaluate the solubility of felodipine in CO2as well as analyte trapping after SFE. Even though the pure drug was found to be soluble in pure CO2, extractions of felodipine from the tablet matrix required moderate modifier concentrations [8.7% (v/v) methanol in CO2] in order to overcome strong matrix‐drug interactions. Sequential static/dynamic extraction steps were also required to quantitatively recover the drug from the tablet matrix, indicating that the drug extraction was diffusion‐limited. Average recoveries (n= 5) for the optimized SFE method were determined to be 4.93 mg felodipine/tablet (98.6% claim) with an RSD of 1.2% versus those for the liquid extraction procedure (n= 5, 4.98 mg/tablet, 99.6% claim, 2.4% RSD). Similar levels of drug degradation (0.12% expressed as felodipine) were also obtained with both the traditional liquid extraction and with the SFE method.

Purification, par dissolution selective, de dechets d'objets usages broyes en polyethyleneterephtalate, pollues notamment par du polychlorure de vinyle

PVC is a common pollution of crushed PET refuse. In order to purify PET waste, we have researched solvent systems efficient with PVC, as inert as possible with PET and showing a minimum of defects. Active solvents may react specifically on both polar and non-polar parts of the polymers. This research is mainly based on solubility parameters systematics. Experiments are carried in a batch stirred vessel in order to determine the effect of temperature and solvent nature on the yield and the rate of dissolution. With bottle-PVC, molecular weight and macromolecular orientation are found to play an important role. In order to measure the efficiency of by-products elimination, a standard procedure is set and checked on a common industrial mixture containing 93% PET, 6% PVC and 1% polyolefin. In the case of total PVC dissolution, the purification depends mainly on spin drying quality. Several solvent systems may be convenient: tetrahydrofuran dissolves well and quickly the bottle-PVC; methylethylketone is quite inert with PET; amyl acetate-xylene mixtures may leach polyolefin too. A flowsheet is designed in order to maintain PVC pollution around some parts per 10,000 level or less with a reduced solvent consumption.

Reducing Solvent Consumption in Automated Gel Permeation Chromatographic Cleanup for Pesticide Residue Analysis: A Modified GPC AutoPrep 1002

Abstract Modifications to the gel permeation chromatographic apparatus recommended in AOAC method 984.21 for multiresidue analysis of organochlorine pesticides in animal fat are described. By using 1.0 mL sample loops and a 1.0 cm id column, organic solvent usage was reduced by 85%. Organochlorine pesticides were collected in a 14 mL fraction. Mean recoveries using the modified apparatus for aldrin, α-BHC, lindane, dieldrin, p,p′-DDD, p,p′-DDE, p,p′-DDT, heptachlor, heptachlor epoxide, methoxychlor, and mirex from beef fat fortified at 0.10-2.75 μg/g were in the 91.4-108% range, with CV of 3.3-10.0%.

Rapid quantitative analysis of a gibberellin-sterol inhibitor using high-performance liquid chromatographic cartridge columns

A rapid, sensitive, and economical chemical analysis of the triazole, gibberellin-inhibitor, paclobutrazol (PP333, [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4 triazol-1-yl) pentan-3-ol]) was sought, featuring high-performance liquid chromatography (HPLC) as the final quantitation step. Three C18-reverse phase columns (conventional, 250×4.6 mm; cartridge type, 125×4.6 mm; and minicolumn, 33×4.6 mm) were evaluated for their performance in HPLC separation and quantitation of PP333 applied to soil and plant foliage. The 125-mm Whatman Partisil 5 ODS-3 cartridge column was superior to the standard 250-mm DuPont Zorbax ODS unit, and provided enhanced resolution and reduced solvent consumption, analysis time, and cost. A Perkin-Elmer Pecosphere 3×3C-C18 cartridge system was also superior to the 125-mm column with respect to these parameters. Although this minicolumn necessitated an additional purification step prior to HPLC analysis, its exceptionally fast analysis time and recovery period coupled with a high degree of sensitivity rendered it the most superior unit. This HPLC technology provided an efficient means of assaying for PP333 in large-scale experiments dealing with the chemical's absorption, translocation, and physiological response.

Supercritical fluid chromatography and microbore liquid chromatography for drug analysis.

Supercritical fluid and microbore liquid chromatography offer potential applications for drug analysis. In supercritical fluid chromatography (SFC), the mobile phase is a gas (e.g., carbon dioxide) maintained at its supercritical state--that is, above its critical temperature and pressure, above which it cannot be liquefied even with further increases in applied pressure. The SFC mobile phase has low viscosity, approximating that of a gas, and high diffusivity, between those of a gas and a liquid. These properties yield favorable column efficiency, between that of capillary gas chromatography (GC) and liquid chromatography (LC). SFC analysis may be performed by either packed or open tubular capillary columns and with GC and LC detectors. SFC, interfaced with mass spectrometry, may become a viable alternative to GC/MS for drug identification in clinical and forensic toxicology. Advantages of microbore liquid chromatography include enhanced mass sensitivity, reduced solvent consumption, and others. Microbore columns (internal diameters 1 to 2 mm) may be packed with 3-, 5-, or 10-micron particles. Potential applications include micro-sample analysis (5-200 microL) for neonatal and pediatric drug monitoring, and drug confirmation analysis for toxicology.

Centrifugal Cleaning—A New Technology for Cleaning Printed Circuit Boards and Hybrid Circuits

Cleaning or defluxing of populated printed circuit boards has become a very difficult problem as component stand‐off clearances have become smaller, line spacings tighter, and solvents limited because of the CFC/ozone issue. This paper discusses the new technology of Centrifugal cleaning where ACCEL Energy™ is harnessed inside an enclosed chamber to provide significant cleaning benefits. Among these benefits are: superior washing, effective rinsing, superior drying, reduced solvent consumption by orders of magnitude, small footprint, and compatibility with H2O, saponifiers, chlorocarbons, fluorocarbons and terpenes.

Simultaneous determination of flurazepam and five metabolites in serum by high-performance liquid chromatography and its application to pharmacokinetic studies in rats

A reversed-phase high-performance liquid chromatographic method is described which allows the quantification of flurazepam and five of its metabolites with a single, isocratic determination. In addition, it has the advantage of possessing a low detection limit and high precision. A 2 mm I.D. column was used to minimize sample size (50 μl), increase sensitivity and reduce solvent consumption. The method was used to demonstrate that N-1-desalkylflurazepam, the major metabolite, has a short half-life in the rat in contrast to its prolonged life in humans.