Good Extraction Yield Research Articles

Rapid assays of clozapine and its metabolites in dried blood spots by liquid chromatography and microextraction by packed sorbent procedure

A novel analytical approach has been developed for the determination of clozapine and its metabolites in dried blood spots on filter paper, using a chromatographic method coupled with a microextraction by packed sorbent procedure. The analytes were separated on a RP-C18 column using a mobile phase composed of 20% methanol, 16% acetonitrile and 64% aqueous phosphate buffer. Coulometric detection was used, setting the guard cell at +0.050 V, the first analytical cell at −0.200 V and the second analytical cell at +0.500 V. Clozapine and its metabolites were extracted from dried blood spots with phosphate buffer and, then, a microextraction by packed sorbent procedure for the sample clean-up was implemented obtaining good extraction yields. The calibration curve was linear over the 2.5–1000 ng mL −1 blood concentration ranges for all the analytes. The method validation gave satisfactory results in terms of sensitivity, precision, selectivity and accuracy. The analytical method was successfully applied to dried blood spots from several psychiatric patients for therapeutic drug monitoring purpose.

Analysis of cocaine and two metabolites in dried blood spots by liquid chromatography with fluorescence detection: A novel test for cocaine and alcohol intake

An original HPLC method coupled to spectrofluorimetric detection is presented for the simultaneous analysis in dried blood spots (DBS) of cocaine and two important metabolites, namely benzoylecgonine (its main metabolite) and cocaethylene (the active metabolite formed in the presence of ethanol). The chromatographic analysis was carried out on a C8 column, using a mobile phase containing phosphate buffer (pH 3.0) – acetonitrile (85:15, v/v). Native analyte fluorescence was monitored at 315 nm while exciting at 230 nm. A fast and feasible sample pre-treatment was implemented by solvent extraction, obtaining good extraction yields (>91%) and satisfactory precision values (RSD < 4.8%). The method was successfully applied to DBS samples collected from some cocaine users, both with and without concomitant ethanol intake. The results were in good agreement with those obtained from plasma samples subjected to an original solid-phase extraction procedure on C8 cartridges. The method has demonstrated to be suitable for the monitoring of cocaine/ethanol use by means of DBS or plasma testing. Assays are in progress to apply this method on the street, for the control of subjects suspected of driving under the influence of psychotropic substances.

Quantification of free and total bisphenol A and bisphenol B in human urine by dispersive liquid–liquid microextraction (DLLME) and heart-cutting multidimensional gas chromatography–mass spectrometry (MD–GC/MS)

A novel method combining dispersive liquid–liquid microextraction (DLLME) and heart-cutting multidimensional gas chromatography coupled to mass spectrometry was developed for the determination of free and total bisphenol A (BPA) and bisphenol B (BPB) in human urine samples. The DLLME procedure combines extraction, derivatization and concentration of the analytes into one step. Several important variables influencing the extraction efficiency and selectivity such as nature and volume of extractive and dispersive solvents as well as the amount of acetylating reagent were investigated. The temperature and time to hydrolyze BPA and BPB conjugates with a β-glucuronidase and sulfatase enzyme preparation were also studied. Under the optimized conditions good efficiency extraction (71–93%) and acceptable total DLLME yields (56–77%) were obtained for both analytes. Matrix-matched calibration curves were linear with correlation coefficients higher than 0.996 in the range level 0.1–5 μg/l, and the relative standard deviations (%RSD) were lower than 20% ( n = 6). The limits of detection were 0.03 and 0.05 μg/l for BPA and BPB, respectively. The applicability of the proposed method for determining urinary free and total BPA and BPB was assessed by analyzing the human urine of a group of 20 volunteers. Free BPA was detected in 45% of the sample whereas total BPA was detected in 85% of the samples at concentrations ranging between 0.39 and 4.99 μg/l. BPB was detected in conjugated form in two samples.

Analysis of soy isoflavone plasma levels using HPLC with coulometric detection in postmenopausal women

A reliable chromatographic method for the determination of soy isoflavones (genistein, daidzein and glycitein) using a coulometric detection has been developed and applied to analyse plasma of postmenopausal women. The chromatographic separation was performed on a C18 reversed phase column with a mobile phase composed of acetonitrile–phosphate buffer mixture. Coulometric detection was carried out at +0.500 V. A careful and rapid solid phase extraction procedure on hydrophilic/lipophilic cartridges was chosen for plasma sample purification with and without hydrolysis obtaining good extraction yield values for all the analytes (>90.0%). The enzymatic hydrolysis step was necessary for the determination of the total amount of soy isoflavones. The limit of quantitation was 0.5 ng mL −1 for genistein and 0.25 ng mL −1 for daidzein and glycitein. The method was found to be precise and accurate. Thus, the proposed method is suitable for the analysis of soy isoflavones (free and total amounts) in plasma of postmenopausal women under treatment with the SoymenGN ® dietary supplement.

Analysis of risperidone and its metabolite in plasma and saliva by LC with coulometric detection and a novel MEPS procedure

A new analytical method, based on the use of liquid chromatography with coulometric detection, has been developed and applied to quantify risperidone and its main active metabolite 9-hydroxyrisperidone in human plasma and saliva. The analytes were separated on a reversed phase C18 column, using a mobile phase composed of acetonitrile (26%) and a pH 6.5 phosphate buffer (74%). Pipamperone was used as the internal standard. A high sensitivity coulometric detection analytical cell containing two flow-through working electrodes was used: electrode 1 was set at +0.500V and electrode 2 at +0.700V. The detector response was linear over a plasma and saliva concentration range of 0.5-50.0ngmL(-1) for risperidone and 0.5-100.0ngmL(-1) for 9-hydroxyrisperidone. The limit of quantitation and the limit of detection for risperidone and 9-hydroxyrisperidone were 0.5ngmL(-1) and 0.17ngmL(-1), respectively. A novel clean-up procedure of biological samples was developed using the microextraction by packed sorbent technique, which gave good extraction yield for both the analytes, with absolute recovery values higher than 90.1%. The intra-day and the inter-day precision results, expressed by relative standard deviation values, were lower than 5.8%. Accuracy and selectivity assays were also satisfactory. The validated method has been successfully applied to the analysis of risperidone and 9-hydroxyrisperidone in plasma and saliva of psychiatric patients undergoing therapy with risperidone.

Determination of orphenadrine plasma levels using HPLC with diode array detection and a novel solid-phase extraction procedure in psychiatric patients

Orphenadrine is an antimuscarinic agent mainly used for the treatment of parkinsonism and to alleviate the neuroleptic syndrome induced by antipsychotic drugs. A new, rapid analytical method, based on liquid chromatography with diode array detection (DAD), has been developed and applied to the determination of orphenadrine in plasma of schizophrenic patients for therapeutic drug monitoring and toxicological purposes. The chromatographic separation was performed on a pentafluorophenyl reversed phase column with a mobile phase composed of acetonitrile–phosphate buffer mixture. DAD detection was carried out at 220 nm. A careful and rapid solid-phase extraction procedure on cyanopropyl cartridges was chosen for plasma sample purification and pre-concentration obtaining good extraction yield values for the analyte (>96.0%). The assays showed a linear response for orphenadrine (30–1000 ng mL −1). The method is also precise and selective. Thus, the method developed seems to be suitable for routine analysis of orphenadrine in psychiatric patients. Moreover, it was applied to plasma samples from a psychotic patient who had tried to poison himself with 1000 mg of orphenadrine and was undergoing polypharmacy.

Leaching of pyrolusite using molasses alcohol wastewater as a reductant

Extraction of manganese from a pyrolusite ore was investigated using molasses alcohol wastewater as a reducing agent in dilute sulfuric acid medium. The effects of molasses alcohol wastewater dosage, concentration of sulfuric acid, leaching temperature and reaction time were studied. High manganese recovery, coupled with relatively low Fe and Al extraction yields, was obtained with this leaching process. The optimal leaching conditions were obtained using 1.9 mol/L H 2SO 4 and 2.0 mL/g ratio of molasses alcohol wastewater to pyrolusite for 120 min at 90 °C. These conditions resulted in leaching yields of 93% for Mn, with relatively low recoveries of 37% for Fe and 25% for Al. These results demonstrate that molasses alcohol wastewater is a low cost resource, containing renewable and non-hazardous reducing agents (when compared to other available reagents) that can be used for manganese leaching under mild acidic conditions. In short, the method provides a good extraction yield while making an economically productive use of molasses alcohol wastewater.

Determination of selected phenothiazines in human plasma by solid-phase extraction and liquid chromatography with coulometric detection

A new analytical method, based on liquid chromatography with coulometric detection, has been developed and applied to the determination of selected phenothiazines (chlorpromazine, promazine, fluphenazine and levomepromazine) in human plasma. The drugs were separated on a Discovery pentafluorophenylpropyl column, using a mobile phase composed of acetonitrile (32%) and a pH 1.9 phosphate buffer (68%). Promethazine was used as the internal standard. Detection was carried out at an oxidation potential of +0.500 V. A novel clean-up procedure was developed by means of solid-phase extraction, using cyanopropyl cartridges, which gave good extraction yield for all the analytes, with absolute recovery values higher than 91.0%. The detector response was linear over a plasma concentration range of 0.5–250.0 ng mL −1 for chlorpromazine, promazine and levomepromazine and of 0.2–4.0 ng mL −1 for fluphenazine. Precision results, expressed by the intra-day and the inter-day relative standard deviation values, were good, being lower than 3.9%. Accuracy data were satisfactory as well. The method has been successfully applied to the analysis of drug plasma levels of psychiatric patients undergoing therapy with selected phenothiazines.

Validation of a pressurized solvent extraction and GC–NCI–MS method for the low level determination of 40 polybrominated diphenyl ethers in mothers’ milk

This study reports an efficient method for the determination of 40 PBDEs from mono- to hepta-brominated in human milk. Pressurized liquid extraction (PLE) was optimized to recover PBDEs in a quantitative way using 1 g of freeze dried milk. Due to the great amount of coextracted compounds, the clean-up step was optimized using alumina SPE disposable cartridges of 2 and 5 g. Whereas 2 g alumina SPE failed in providing good extraction yields, all PBDEs were satisfactorily recovered using 5 g alumina SPE cartridges. Detection was performed with gas chromatography coupled to mass spectrometry with negative chemical ionization and method detection limits ranged from 0.01 to 0.05 μg kg −1 wet weight (ww) with a good intra and inter-day variation (coefficient of variation lower than 13.4%). This method was validated by participating in an interlaboratory exercise from Quasimeme (United Kingdom), where a standard solution containing seven congeners and a certified unspiked mothers’ milk were analyzed. In the standard mixture, levels between 96.915 and 570.172 μg l −1 were quantified, whereas in certified mothers’ milk, BDEs 47, 99, 100 and 154 were detected at levels from 0.010 and 0.061 μg kg −1 ww, with an error <30%. The applicability of the method was tested experimentally in five mothers’ milk samples, where only BDE 47 was detected at a maximum concentration of 10.45 μg kg −1 lipid weight (lw). PLE succeeded in extracting all PBDEs from the sample with good reproducibility although the clean-up step had to be severely performed to eliminate sample interferences such as milk lipids and proteins.

Selective solid-phase extraction of a triterpene acid from a plant extract by molecularly imprinted polymer

A molecularly imprinted polymer (MIP) has been prepared by a thermal polymerisation method using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linking agent, chloroform as porogenic solvent and an oleanane triterpene compound (18-β-glycyrrhetinic acid) as imprinted molecule (template). Equilibrium ligand binding experiments were done to assess the performance of the MIP relative to non-imprinted polymer (NIP). After optimisation of SPE protocol (CHCl 3 as washing solvent and MeOH as elution solvent), successful imprinting was confirmed by comparison of the recoveries between NIP (5%) and MIP (97%) cartridges. The binding capacity of the MIP for 18-β-glycyrrhetinic acid was determined to be 0.94 mg g −1. Four structurally related oleanane triterpenes (18-α-glycyrrhetinic acid, oleanolic acid, echinocystic acid, erythrodiol) were selected to assess the MIP selectivity. Experimental data illustrated the influence of functional groups on the triterpene skeleton. The MIP was applied to the solid-phase extraction of triterpenoids from a plant extract prior HPLC analysis. However, CHCl 3 was replaced by ACN during the washing step in order to suppress non-specific interactions due to polar matrix components. A selective extraction of 18-β-glycyrrhetinic acid from hydrolyzed extract of liquorice roots was achieved with a good extraction yield (98%).

Simultaneous determination of the antipsychotic drugs levomepromazine and clozapine and their main metabolites in human plasma by a HPLC-UV method with solid-phase extraction

A HPLC method with UV detection has been developed for the simultaneous determination of levomepromazine, clozapine and their main metabolites: N-desmethyl-levomepromazine, levomepromazine sulphoxide, O-desmethyl-levomepromazine, N-desmethylclozapine and clozapine N-oxide. The analytes were separated on a C8 reversed-phase column using a mobile phase composed of acetonitrile and a pH 2.0, 34 mM phosphate buffer containing 0.3% triethylamine (29:71, v/v). Loxapine was used as the internal standard. A reliable biological sample pre-treatment procedure by means of solid-phase extraction on C1 cartridges was implemented, which allows to obtain good extraction yields (>91%) for all analytes and appropriate sample purification from endogenous interference. The method was validated in terms of extraction yield, precision and accuracy. These assays gave RSD% values for precision always lower than 4.9% and mean accuracy values higher than 92%. The method is suitable for the therapeutic drug monitoring (TDM) of patients undergoing polypharmacy with levomepromazine and clozapine.

Alternative Sample Preparation Techniques in Gas Chromatographic-Mass Spectrometric Analysis of Urinary Androgenic Steroids

The following study describes the gas chromatography-mass spectrometry (GC-MS) based screening and confirmation analysis of urinary androgenic steroids. Four commercially available solid-phase extraction (SPE) cartridges, Serdolit PAD-1, Sep-pak <TEX>$C_{18}$</TEX>, amino-propyl, and Oasis HLB, and three different extractive organic solvents, diethyl ether, methyl tert-butyl ether (MTBE), and n-pentane, were tested for sample preparation. Overall, Oasis HLB combined with MTBE extraction provided the highest recoveries in 39 of 46 total androgenic steroids examined and it showed a good extraction yield (>82.1%) for polar steroids, such as metabolites of fluoxymesterone, oxandrolone, and stanozolol, which gave a poor recovery in both n-pentane (9.2-64.3%) and diethyl ether (22.2-73.6%) extractions. All SPE sorbents tested showed potential, because they were efficient in extraction for most or selective steroids. When applied to positive urine samples based on the results obtained, the present method allowed selective and sensitive analysis for detection of urinary androgenic steroids. The experiments showed that the high-resolution MS method is clearly more efficient than the low-resolution MS technique for the detection of many urinary steroids. However, comprehensive sample clean-up procedures also might be needed especially in confirmation analysis to increase detectability.

Formulation of stable detoxifying w/o/w reactive multiple emulsions: in vitro evaluation

Over the last decade, acute drug intoxications have been known to be a serious threat to the public health field. Nevertheless, only a few means of imperfect detoxication treatments have, unfortunately, been applied to date. This paper presents water-in-oil-in-water (w/o/w) reactive multiple emulsions (ME) as an efficient method of in vitro detoxication against Nivaquine, a drug widely accused of being used in suicide attempts. The detoxication efficiency of these emulsions is attributed to the use of an adequate extractant-trapping agent couple giving a good extraction yield. Interestingly, some prepared emulsions showed a Nivaquine extraction yield of about 85%. A series of studies was conducted to recognize the effect of the preparation protocol, the emulsion ingredients, especially the extractant-trapping agent couple, and the experimental conditions on the extraction output. The extraction yield increases with the concentration of the extractant and with the alcalinization of the extraction medium. Globally, these reactive multiple emulsions have shown to be stable and highly detoxifying against Nivaquine taken as a toxic molecule model. Moreover, the process of Nivaquine extraction by the extractant in the oily phase and its trapping in the internal aqueous phase has been elucidated and validated.

Improved back extraction of papain from AOT reverse micelles using alcohols and a counter-ionic surfactant

The extraction of papain (MW 23 kDa, p I 9.6) from water was studied using reverse micelles containing sodium bis(2-ethylhexyl)sulfosuccinate (AOT). Forward extraction of papain was carried out in the pH range of 4.0–6.5 and a maximum extraction of 65–70% was observed at pH 6.3. Papain extracted into the micelles could be back extracted to only 30% into a conventional aqueous phase (high pH and high KCl concentrations). In order to improve the back extraction of papain, 8–10 vol% alcohols were added because it was known that alcohols have an effect on the micelle–micelle interactions. However, this way resulted in the loss of papain activity inspite of good back extraction yields (80–90%). The back extraction of papain encapsulated in AOT reverse micelles was then carried out by adding a counter-ionic surfactant tri- n-octylmethyl-ammonium chloride (TOMAC). This technique resulted in faster back extraction compared to conventional method. Around 80–90% of activity recovery was obtained after back extraction. The improved backward transfer was likely caused by electrostatic interaction between the oppositely charged surfactant molecules, which led to the collapse of reverse micelles.

Characterization via liquid chromatography coupled to diode array detector and tandem mass spectrometry of supercritical fluid antioxidant extracts of Spirulina platensis microalga

Spirulina platensis microalga has been extracted on a pilot scale plant using supercritical fluid extraction (SFE) under various extraction conditions. The extraction yield and the antioxidant activity of the extracts were evaluated in order to select those extracts with both the highest antioxidant capacity and a good extraction yield. These extracts were characterized using LC coupled to diode array detection (DAD) and LC coupled to mass spectrometry (MS) with two different interfaces, atmospheric pressure chemical ionization (APCI) and electrospray (ESI) which allowed us to perform tandem MS by using an ion trap analyzer. The best extraction conditions were as follows: CO2 with 10% of modifier (ethanol) as extraction solvent, 55 degrees C (extraction temperature) and 220 bar (extraction pressure). Fractionation was achieved by cascade depressurization providing two extracts with different activity and chemical composition. Several compounds have been identified in the extracts, corresponding to different carotenoids previously identified in Spirulina platensis microalga along with chlorophyll a and some degradation products. Also, the structure of some phenolic compounds could be tentatively identified. The antioxidant activity of the extracts could be attributed to some of the above mentioned compounds.

Isolation and characterization of naphthenic acids from Athabasca oil sands tailings pond water.

A laboratory bench procedure was developed to efficiently extract naphthenic acids from bulk volumes of Athabasca oil sands tailings pond water (TPW) for use in mammalian oral toxicity testing. This solvent-based procedure involved low solvent losses and a good extraction yield with low levels of impurities. Importantly, labour-intensive centrifugation of source water to remove solids was avoided, allowing processing of much larger volumes of water compared with previous protocols. Naphthenic acids, present at an estimated concentration of 81 mg/l, were procured from 515.5 l of TPW at an overall extraction efficiency of approximately 85%. By using distillation to recover and recycle solvent, a high solvent:water ratio was maintained while actual solvent consumption was limited to 70 ml per liter of water processed. Electrospray ionization mass spectrometry suggested a highly heterogeneous naphthenic acid mixture that exhibited nearly identical proportions of monocyclic, polycyclic, and acyclic acids with molecular weights primarily between 220 and 360. Biphenyls, naphthalenes, and phenanthrene/anthracene were the most prominent impurities detected, but their levels were low (< or = 13 microg/l) even in a concentrated solution of the naphthenic acids (8549 mg/l). Naphthenic acids stored at 4 degrees C at this concentration were stable, exhibiting no significant change in concentration over a 10-month period. This bulk isolation procedure should be useful to others needing to process large volumes of tailings or other source water for the purpose of procuring moderate amounts of naphthenic acids.

Extraction of lemongrass essential oil with dense carbon dioxide

Lemongrass ( Cymbopogon citratus) essential oil was extracted with dense carbon dioxide at 23–50 °C and 85–120 bar. The composition of samples collected during the first and the last hours of the extraction experiments was analyzed by gas chromatography–mass spectrometry, and coextraction of cuticular waxes was observed. Liquid carbon dioxide extracts had a larger quantity of coextracted waxes than the supercritical extracts. The process condition of 120 bar and 40 °C was considered ideal for the extraction of lemongrass essential oil, as a good-quality product was obtained together with a good extraction rate and yield.

Supercritical fluid extraction of polychlorinated biphenyls and pesticides from soil: Comparison with other extraction methods

A comparison is made of supercritical fluid extraction (SFE) with two other techniques widely used for the extraction of polychlorinated biphenyls (PCBs) and organochlorine pesticides in soil. Extraction conditions for the SFE of PCBs and pesticides were first determined. An experimental approach was set up to determine the influence of different extraction parameters such as pressure, extraction time, static and dynamic extraction, restrictor type and collection solvent for off-line SFE. The use of carbon dioxide at 50°C and 20 MPa, 10 min static followed by 20 min dynamic extraction with collection in iso-octane were been found to be the optimum conditions. Two types of soil, with a low and high content of organic carbon, respectively, spiked with 16 PCBs and organochlorine pesticides with a wide range of volatility and polarity at a level of 5 ng/g dry matter, were used as test materials. Conventional solvent extraction gives a good extraction yield for soil with a low content of organic carbon, but for peat soil the recoveries decrease dramatically to 30% for DDE, DDT and PCB 138 and 153. The recoveries with Soxhlet extraction are god, but an extra clean-up step before analysis is necessary. SFE gives good extraction yields for PCBs and organochlorine pesticides, varying between 85 and 105% with a reproducibility of 5% for each component for both types of soil. SFE is a fast, clean and reproducible method for the extraction of PCBs and organochlorine pesticides from these two soil matrices.

ALKYLATION REACTIONS ON ASSAM COAL USING ALKENES AND ALCOHOLS IN LIQUID PARAFFIN IN THE ABSENCE OF EXTERNAL CATALYST UNDER ATMOSPHERIC PRESSURE CONDITIONS AIDED BY THE DISINTEGRATION OF COAL

ABSTRACT Alkylation reactions were performed on Assam coal using long carbon chain alkenes and alcohols respectively (from C6 to C16) in liquid paraffin. Ertractability of the coal was found to increase with increase in the carbon chain length of alkenes or alcohols, with increase in the concentration of alkylating agents, and with increase in the reaction time. Cetene and cetanol were found to give good extraction yields. More than 50% of the coal was rendered eztractable through these reactions. The use of A1C13 as a catalyst in the reaction helped in the reactions using cetene or dodecanol in liquid paraffin. Up to 56% of the Assam coal was rendered extractable through alkylation reaction using dodecanol in liquid paraffin. Pretreatment of coal with anthracene oil was found to enhance the ertractability of coal through alkylation reaction uaing dodecene in liquid paraffin.

An investivation of the extraction, refining and composition of oil from winged bean (Psophocarpus tetragonolobus[L.] D.C.)

Eleven winged bean accessions from Thailand were analyzed. Oil content ranged between 15 and 18%. Oleic and linoleic acids were the major fatty acids (62.5–64.5%) together with behenic (12.6–14.4%) and lignoceric acid (2.4–2.8%). Linolenic acid level was low and traces of 15-, 17- and 21-carbon acids (saturated and unsaturated) were found. No parinaric acid was detected. Campesterol, stigmasterol and β-sitosterol were the principal components of the unsaponifiable fraction. The extracted oil had a very low free fatty acid (FFA) content but was not completely liquid below 35 C. The refining of crude winged bean oil is reported. Oil produced by expeller had a strong, beany aroma but a negligible level of gums and a low level of FFA. Degumming and neutralizing were unnecessary; bleaching produced an attractive colored oil free from beany aroma. Crude solvent-extracted oils from whole and decorticated winged beans had appreciable contents of gums and higher FFA contents than expeller-produced oil. Laboratory refining demonstrated the strong interference on bleaching exerted by gums and FFA. Conventional refining by degumming, neutralizing, bleaching and deodorizing, and by physical refining produced high-quality oils having a good color, low FFA level and no taste or smell. The solid/liquid ratio of refined winged bean oil as a function of temperature was found to be unusual. Oil was extracted from whole and decorticated winged beans in a pilot solvent extraction plant designed to simulate a Rotocei. Winged bean flakes were not as mechanically strong as those from soybean but good oil extraction yields were obtained and a meal was produced having an oil content of less than 1% at 10% moisture. Whole winged beans were expelled in a small expeller (throughput 16.8 kg/hr). Cake was produced with a residual oil content of 3.3–5% in a single pass through the expeller.