Ethanol-modified subcritical water extraction combined with solid-phase microextraction for determining atrazine in beef kidney

The determination of the levels of pesticides in food products has prompted the development of sensitive and rapid methods of analysis that are solvent-free or utilize solvents that are benign to the environment and laboratory worker. In this study we have developed a novel extraction method that utilizes ethanol-modified subcritical water in combination with solid-phase microextraction (SPME) for the removal of atrazine from beef kidney. In situ sample cleanup was achieved using the technique of matrix solid-phase dispersion. A cross-linked polymer, XAD-7 HP, was utilized as a dispersing material for kidney samples. Subcritical water extractions were performed with a pressurized solvent extraction unit at 100 degrees C and 50 atm. Experimental parameters investigated were the volume of solvent and amount of modifier required for the complete extraction of atrazine and optimization of the extraction time. It was determined that 30% ethanol in water (v/v) is adequate for the complete extraction of atrazine. A Carbowax-divinylbenzene SPME fiber was used to sample the aqueous extracts. Analysis of the fiber contents was by ion-trap GC/MS utilizing the single ion mode. The total time of analysis for a single kidney sample is 90 min. The average percent recoveries from samples spiked to the concentrations of 2 and 0.2 microg/g were 104 and 111, respectively. The average relative standard deviations were 10 and 9, respectively. The method limit of detection for beef kidney spiked with atrazine was found to be 20 ng/g of sample.     

Pressurized fluids for extraction of cedarwood oil from Juniperus virginianna

The extraction of cedarwood oil (CWO) using liquid carbon dioxide (LC-CO(2)) was investigated and compared to supercritical fluid extraction, including the effects of extraction pressure and length of extraction. The chemical composition of the extracts was monitored over the course of the extraction as well. The cumulative yields of CWO from cedarwood chips using 80 L of carbon dioxide varied very little treatment to treatment, with all temperature/pressure combinations yielding between 3.55 and 3.88% CWO, and the cumulative yields were statistically equivalent. The rate of extraction was highest under the supercritical extraction conditions (i.e., 100 degrees C and 6000 psi). Under the liquid CO(2) conditions (i.e., 25 degrees C), the extraction rates did not vary significantly with extraction pressure. However, there were differences in the chemical composition of the collected CWO. Extractions at 100 degrees C gave a much lower ratio of cedrol/cedrene than extractions at 25 degrees C. The highest ratio of cedrol/cedrene was obtained using 25 degrees C and 1500 psi. The use of subcritical water was also investigated for the extraction of CWO as well. Although some CWO was extracted using this method, the temperature/pressure combinations that gave the highest weight percentage yields also gave oils with an off odor while those combinations that gave a higher quality oil had very low yields. It appears that the high temperatures and acidic conditions cause a dehydration of the tertiary alcohol, cedrol, to its hydrocarbon analogue, cedrene, during CO(2) or pressurized water extractions of cedarwood.     

Pressurized fluid extraction for quantitative recovery of chloroacetanilide and nitrogen heterocyclic herbicides in soil

Pressurized fluid extraction (PFE) is a new sample extraction method operated at elevated temperatures and pressures with liquid solvents. The use of PFE was investigated for the extraction of four Hawaiian clayey soils fortified with the selected chloroacetanilide and nitrogen heterocyclic herbicides Alachlor, Bromacil, Hexazinone, Metribuzin, and Tebuthiuron. The effects of operation temperature, pressure, flush volume, and static cycles on PFE performance were studied. Water was the most effective modifier of PFE for quantitative recoveries of the five herbicides in soils. The simple extraction method required pretreatment of the soil with 37.6% water and subsequent two-static-cycle extraction with a total of 32 mL of acetone at 1500 psi and 100 degrees C. Average recoveries of Alachlor, Bromacil, Hexazinone, Metribuzin, and Tebuthiuron ranged from 93 to 103% by the water-assisted PFE, compared with only 68-83% recoveries of the corresponding chemicals when no water was used. The extraction time and total organic solvent consumption were reduced from 18 h and 300 mL by Soxhlet to 22 min or less and 80 mL or less of organic solvent by PFE.     

Determination of polychlorinated biphenyls in sediments, using sonication extraction and capillary column gas chromatography-electron capture detection with internal standard calibration

A sonication technique is presented for the extraction of polychlorinated biphenyls (PCBs) from sediments. In addition, a quantitation scheme is described which allows peak-specific and, in many cases, congener-specific determination of PCBs. PCBs are quantitated by capillary column gas chromatography-electron capture detection, with internal standard calibration. Results utilizing sonication extraction were compared with those obtained by Soxhlet and steam distillation extractions of 3 U.S. Environmental Protection Agency (EPA) quality control sediment samples and 3 lake sediments known to be contaminated with PCBs. Environmental lake sediments were extracted wet, with no drying prior to extraction. Recoveries by each technique varied depending on the sediment sample being extracted and degree of chlorination of PCB congeners. With proper selection of extraction solvent, the sonication technique can recover amounts of PCBs equivalent to and sometimes greater than recoveries by the Soxhlet or steam distillation techniques. A 24-h quiescent period in the extraction solvent between 2 sonications improved extraction efficiency for 2 freeze-dried sediments but did not affect results obtained for 3 environmentally contaminated sediments that were extracted without drying. Replacement of Soxhlet extraction with the sonication technique results in reduced sample preparation time, decreased volumes of solvents and sample, and substitution of common laboratory glassware in place of fragile, expensive Soxhlet glassware. Sonication extraction can also improve precision compared with Soxhlet extraction.     

Improved extraction of atrazine and metolachlor in field soil samples

A method was developed for extraction of weathered residues of atrazine and metolachlor from field soils; soils had last been treated with commercial formulations of the herbicides 8-15 months prior to sample collection. Maximum yields were obtained by batch extraction at 75 degrees C for 2-16 h with methanol-water (80 + 20) in a sealed vial. Hydrolysis or other decomposition reactions were minor or negligible, depending on the extraction time. This method is an improvement over published methods that are validated by spike recoveries; the proposed method gives 1.7-1.8 times higher yields compared to shaking for 2 h at room temperature, and 1.3-1.8 times higher yields compared to Soxhiet extraction. The reproducibility of the method was better than 12%. The results underscore the impact of nonequilibrium sorption of organic compounds on analytical methodology and emphasize the need to validate extraction methods with field samples.     

Fate and Transport of Nursery-Box-Applied Tricyclazole and Imidacloprid in Paddy Fields

The fate and transport of tricyclazole and imidacloprid in paddy plots after nursery-box application was monitored. Water and surface soil samples were collected over a period of 35 days. Rates of dissipation from paddy waters and soils were also measured. Dissipation of the two pesticides from paddy water can be described by first-order kinetics. In the soil, only the dissipation of imidacloprid fitted to the simple first-order kinetics, whereas tricyclazole concentrations fluctuated until the end of the monitoring period. Mean half-life (DT₅₀) values for tricyclazole were 11.8 and 305 days, respectively, in paddy water and surface soil. The corresponding values of imidacloprid were 2.0 and 12.5 days, respectively, in water and in surface soil. Less than 0.9% of tricyclazole and 0.1% of imidacloprid were lost through runoff during the monitoring period even under 6.3 cm of rainfall. The pesticide formulation seemed to affect the environmental fate of these pesticides when these results were compared to those of other studies.     

Subcritical water extraction of antioxidant compounds from rosemary plants

Subcritical water extraction at several temperatures ranging from 25 to 200 degrees C has been studied to selectively extract antioxidant compounds from rosemary leaves. An exhaustive characterization of the fractions obtained using subcritical water at different temperatures has been carried out by LC-MS, and the antioxidant activities of the extracts have been measured by a free radical method (DPPH). Results indicate high selectivity of the subcritical water toward the most active compounds of rosemary such as carnosol, rosmanol, carnosic acid, methyl carnosate, and some flavonoids such as cirsimaritin and genkwanin. The antioxidant activity of the fractions obtained by extraction at different water temperatures was very high, with values around 11.3 microg/mL, comparable to those achieved by SFE of rosemary leaves. A study of the effect of the temperature on the extraction efficiency of the most typical rosemary antioxidant compounds has been performed.     

Efficiency of methanol:Water solutions for metribuzin extraction from selected soils

Abstract

Extraction efficiency for metribuzin [4‐amino‐6‐(1,1‐dimethyl‐ethy 1)‐3‐(methylthio)‐l,2,4‐triazin‐5(4H)‐one] from soil was evaluated using four solutions of methanol:water at ratios of 1:1, 7:3, 4:1, and 1:0 v/v. Two concentrations of metribuzin (O.216 and 2.44 ug/ g soil, unlabeled and ^I4C‐metribuzin, respectively) were added to surface and subsurface samples of a Dundee silt loam soil. Although the differences in extraction efficiencies were slight due to differences in methanol:water ratios, the metribuzin recovery varied with soil depth. Less metribuzin was recovered from surface soil extracted with 1:1 and 1:0 methanol:water solutions when compared to 7:3 and 4:1 solutions (80 and 81% vs 89 and 88% recoveries, respectively). About equal quantities, 81 to 85%, were recovered from the subsurface soil. Three extraction shaking times (0.5 h followed by another 0.5 h; 4 h:4 h; and 24 h:24 h) were also evaluated using the 4:1 extractant. No recovery differences were observed between the 0.5 h and 4 h shaking times. However, significantly higher recoveries occurred in both the surface and subsurface soil with 24 h shaking. The efficiency of this method was also determined on Eustis loamy sand, Sharkey clay, and Dorovan muck soils of diverse physical and chemical properties. The 4:1 extracting solution consistently yielded among the highest metribuzin recovery (74 to 97%) from the four soil types, and two soil depths of a Dundee soil.     

Investigation of the Effect of Mesh Size on the Effectiveness of Hotplate Aqua Regia Extractions

Aqua regia extractions with subsequent inductively coupled plasma determinations are a very common method of elemental analysis of soils and sediments. Before extraction, the material must be dried and sieved. Small variations in this early step can have a significant impact on the later outcomes, especially for unassisted (for example, without ultrasonic or microwave) extraction procedures. Therefore the impact of mesh size on the sieving process was investigated. A mesh size of 2.0 mm or greater yielded unacceptably high variations between the subsamples and a very poor recovery rate when compared to a 0.063-mm sieve. A mesh size of 0.3 mm resulted in the best outcomes, losing nearly no material in the fine sediment samples and about a tenth in the coarse samples. The precision was high for the 0.3-mm samples as well, only negligibly surpassed by the 0.1-mm samples for some materials.     

New alternative method of benzo[a]pyrene extractionfrom soils and its approbation in soil under technogenic pressure

Purpose

The optimization of benzo[a]pyrene extraction conditions by subcritical water extraction method from soils is the purpose of the research. The optimal conditions for benzo[a]pyrene recovery are 30-min extraction by water in a special steel cartridge at 250 °C and 100 atm.

Materials and methods

Studies were conducted on the soils of monitoring plots subjected to Novocherkassk Power Station emissions. Monitoring plots were established at different distances from the Novocherkassk Power Station (NPS; 1.0–20.0 km).

Results and discussion

It was shown that the use of water in subcritical state as a solvent for benzo[a]pyrene extraction from soil allows to avoid large volumes of organic solvents and to decrease the time of sample preparation. It is shown that the maximum benzo[a]pyrene maintenance was observed in soils of the monitoring plots located most close (to 5 km) to a pollution source in the area of the prevailing direction of a wind rose. Dynamics of pollutant accumulation in soils depend on number of Novocherkassk state district power station emissions.

Conclusions

The method of benzo[a]pyrene subcritical water extraction from soil was developed and approbated during long-term monitoring researches of technogenic polluted territories. The optimum conditions for benzo[a]pyrene extraction from soil have been determined: the soil is treating by subcritical water at 250 °C and 100 atm of pressure for 30 min. Trends in the accumulation of benzo[a]pyrene in soil zones of the thermal power plant influence have been researched over a 5-year period of monitoring observations by subcritical water extraction method. Benzo[a]pyrene accumulation in soils depends on the technogenic emissions to the atmosphere from Novocherkassk power station and on the soil physical and chemical properties.

     

Improved GC/MS method for quantitation of n-alkanes in plant and fecal material

A gas chromatography-mass spectrometry (GC/MS) method for the quantitation of n-alkanes (carbon backbones ranging from 21 to 36 carbon atoms) in forage and fecal samples has been developed. Automated solid-liquid extraction using elevated temperature and pressure minimized extraction time to 30 min per sample as compared to more than 24 h for traditional GC-flame ionization detection methods that use saponification and liquid-liquid extraction. Extraction solvent requirements were also minimized to 10 mL per sample. Under optimal conditions, complete method recoveries, including extraction efficiency, were greater than 91%. The linear dynamic range was 5 to 100 nmol injected onto the column, with a limit of quantitation of 5 nmol. Intra-assay coefficients of variation for the analysis of annual ryegrass (Lolium rigidum), subterranean clover (Trifolium subterranean), and bovine feces ranged from 0.1%-12.9%, where lower concentrations of n-alkane produced a higher degree of imprecision. The reported GC/MS method permits simple, rapid, and precise quantitation of n-alkanes in plant and fecal material and reduces reagent and labor requirements.     

Simultaneous determination of ethidimuron, methabenzthiazuron, and their two major degradation products in soil

An analytical method has been developed for the quantification of two herbicides (ethidimuron and methabenzthiazuron) and their two main soil derivatives. This method involves fluidized-bed extraction (FBE) prior to cleanup and analysis by reverse-phase liquid chromatography with UV detection at 282 nm. FBE conditions were established to provide efficient extraction without degradation of the four analytes. (14)C-labeled compounds were used for the optimization of extraction and purification steps and for the determination of related efficiencies. Extraction was optimal using a fexIKA extractor operating at 110 degrees C for three cycles (total time = 95 min) with 75 g of soil and 150 mL of a 60:40 v/v acetone/water mixture. Extracts were further purified on a 500 mg silica SPE cartridge. Separation was performed on a C18 Purosphere column (250 mm x 4 mm i.d.), at 0.8 mL min(-1) and 30 degrees C with an elution gradient made up of phosphoric acid aqueous solution (pH 2.2) and acetonitrile. Calibration curves were found to be linear in the 0.5-50 mg L(-1) concentration range. Besides freshly spiked soil samples, method validation included the analysis of samples with aged residues. Recovery values, determined from spiked samples, were close to 100%. Limits of detection ranged between 2 and 3 microg kg(-1) of dry soil and limits of quantification between 8 and 10 microg kg(-1) of dry soil. An attempt to improve these performances by using fluorescence detection following postcolumn derivatization by orthophthalaldehyde-mercaptoethanol reagent was unsuccessful.     

Design and optimization of a semicontinuous hot-cold extraction of polyphenols from grape pomace

Grape pomace contains appreciable amounts of polyphenolic compounds such as anthocyanins and procyanidins which can be recovered for use as food supplements. The extraction of these polyphenols from the pomace is usually accomplished at slightly elevated temperatures, frequently employing hydroethanolic solvents. Due to governmental regulations and the cost involved in using ethanol as a solvent, as well as the loss in polyphenolics due to thermal degradation, improved extraction techniques are required. In this study, a semicontinuous extraction apparatus employing only water was developed to maximize the recovery of anthocyanins and procyanidins from red grape pomace (Vitis vinifera). Water is preheated prior to its entry to the extraction cell containing the grape pomace sample, where it is allowed to then flow continuously through the unheated extraction vessel prior to its collection at ambient conditions. Extraction variables that impacted the polyphenolic recovery included pomace moisture content (crude or dried), sample mass, water flow rate, and extraction temperature. A response surface method was used to analyze the results from the extraction, and the optimal conditions were found to be 140 °C and 9 mL/min water flow rate. These conditions can produce an extract containing 130 mg/100 g DW of anthocyanins and 2077 mg/100 g DW of procyanidins. Higher yields of polyphenolics were observed using crude (wet) rather than dried pomace, hence avoiding the need to dry the pomace prior to extraction. The described semicontinuous extraction method using only water as the extraction solvent under subcritical conditions allowed the efficient extraction of polyphenols from red grape pomace without the attendant loss of polyphenolic content due to having to heat the extraction vessel prior to commencement of extraction.     

Microdetermination of diosgenin from fenugreek (Trigonella foenum-graecum) seeds

Sulfuric acid hydrolysis of steroidal glycosides of Amber fenugreek was studied by capillary gas chromatographic analysis of diosgenin [(25R)-spirost-5-en-3-ol] and isomeric spirostadiene artifacts from 100 mg samples of seed material. Following extraction with 80% ethanol, highest recoveries of diosgenin occurred when hydrolyses were conducted in sulfuric acid, prepared at 1 molar (M) concentration in water containing 60-80% 2-propanol. Compared to a previous method with aqueous hydrochloric acid, the selected conditions of hydrolysis at 100 degrees C for 2 h with sulfuric acid in 70% 2-propanol reduced diene formation but did not completely eliminate these artifacts. Extraction of steroidal saponins with various alcohol/water mixtures prior to sulfuric acid hydrolysis gave similar recoveries of diosgenin. Application of the quantitative method to experimental samples of Amber, Quatro, and ZT-5 fenugreek, using 10 mg subsamples of crushed seed that had been defatted with petroleum ether and dried at 60 degrees C, gave diosgenin levels of 0.55, 0.42, and 0.75%, respectively. Levels of smilagenin and sarsasapogenin were very low in hydrolyzed seed extracts from ZT-5, a Canadian breeder line of fenugreek.     

Extraction of polycyclic aromatic hydrocarbons from spiked soil

A homogenization method was evaluated for extracting polycyclic aromatic hydrocarbons (PAHs) from soils. Fifteen PAHs were spiked and recovered from 2 soils at concentrations ranging from 1 to 1000 micrograms/g, using the homogenization method and a Soxhlet extraction method. Each extraction method performed well in removing the 15 PAHs from both soils over a broad range of concentrations. In general, Soxhlet extraction yielded slightly but significantly (P less than 0.05) higher recoveries than did the homogenization method. The homogenization method, however, was easy to use, and the extraction step turnaround time was less than 15 min/sample. The method should be suitable for other applications requiring the extraction of hydrophobic organic compounds from soils.     

土壤样品中多环芳烃分析方法研究进展

概述了国内外土壤样品中多环芳烃(PAHs)测定方法的研究状况,其中提取方法包括加速溶剂萃取方法、固相微萃取方法、超临界流体萃取方法、亚临界水萃取方法和流化床提取方法等,测定方法有HPLC法、GC法和免疫分析法等。重点介绍了PAHs的提取过程,同时总结了各种方法的优缺点。     

Simplified extraction of ginsenosides from American ginseng (Panax quinquefolius L.) for high-performance liquid chromatography-ultraviolet analysis

Four methods were tested for extraction and recovery of six major ginsenosides (Rb1, Rb2, Rc, Rd, Re, and Rg1) found in roots of American ginseng (Panax quinquefolius): method A, sonication in 100% methanol (MeOH) at room temperature (rt); method B, sonication in 70% aqueous MeOH at rt; method C, water extraction (90 degrees C) with gentle agitation; and method D, refluxing (60 degrees C) in 100% MeOH. After 0.5-1 h, the samples were filtered and analyzed by high-performance liquid chromatography (HPLC)-UV. A second extraction by methods C and D was done, but 85-90% of ginsenosides were obtained during the first extraction. Lyophilization of extracts did not influence ginsenoside recovery. Method D resulted in the highest significant recoveries of all ginsenosides, except Rg1. Method C was the next most effective method, while method A resulted in the lowest ginsenoside recoveries. Method B led to similar recoveries as method C. All methods used one filtration step, omitted time-consuming cleanup, but maintained clear peak resolution by HPLC, and can be used for quantitative screening of ginsenosides from roots and commercial ginseng preparations.     

Determination of 2-methylisoborneol and geosmin produced by Streptomyces sp. and Anabaena PCC7120

A new sample preparation and enrichment technique, headspace liquid-phase microextraction (HS-LPME) linked to gas chromatography-mass spectrometry (GC-MS), was developed for the determination of the off-flavor odorants, 2-methylisoborneol and geosmin, produced by Streptomyces sp. and Anabaena PCC7120. Some of the factors that influence the extraction efficiency of HS-LPME, such as the type of extraction solvent, ionic strength of sample solution, and sample agitation rate, were studied and optimized by a single factor test. Other factors, including extraction temperature, extraction time, microdrop volume, and headspace volume were optimized by orthogonal array design. Extraction of 2-methylisoborneol and geosmin was conducted by exposing 2.5 microL of 1-hexanol for 9 min at 50 degrees C in the headspace of a 20 mL vial with a 10 mL of sample solution saturated by NaCl and stirred at 800 rpm. The developed protocol demonstrated good repeatability (relative standard deviations (RSDs) < 5%), wide linear ranges (10-5000 ng/L, r2 > 0.999), and low limits of detection (LODs) for 2-methylisoborneol and geosmin (0.05 ng/L for both analytes). Subsequently, the method was successfully applied to extract the analytes in bacterial cultures with high recoveries (from 94% to 98%). Compared with headspace solid-phase microextraction (HS-SPME), HS-LPME demonstrates better linearity, precision, and recovery. Importantly, the sensitivity is about 1 order of magnitude higher than that of most HS-SPME. The results showed that HS-LPME coupled with GC-MS is a simple, convenient, rapid, sensitive, and effective method for the qualitative and quantitative analysis of 2-methylisoborneol and geosmin.     

Hydrolysis of ginger bagasse starch in subcritical water and carbon dioxide

Ginger bagasse from supercritical extraction was hydrolyzed using subcritical water and CO(2) to produce reducing sugars and other low molecular mass substances. Response surface methodology was used to find the best hydrolysis conditions; the degree of hydrolysis and the yield were the two response variables selected for maximization. The kinetic studies of the hydrolysis were performed at 150 bar and temperatures of 176, 188, and 200 degrees C. The higher degree of hydrolysis (97.1% after 15 min of reaction) and higher reducing sugars yield (18.1% after 11 min of reaction) were established for the higher process temperature (200 degrees C). Different mixtures of oligosaccharides with different molecular mass distributions were obtained, depending on the temperature and on the reaction time. The ginger bagasse hydrolysis was treated as a heterogeneous reaction with a first-order global chemical kinetic, in relation to the starch concentration, which resulted in an activation energy of 180.2 kJ/mol and a preexponential factor of 5.79 x 10(17)/s.     

Interlaboratory comparison of extraction efficiency of pesticides from surface and laboratory water using solid-phase extraction disks

A continuation of an earlier interlaboratory comparison was conducted (1) to assess solid-phase extraction (SPE) using Empore disks to extract atrazine, bromacil, metolachlor, and chlorpyrifos from various water sources accompanied by different sample shipping and quantitative techniques and (2) to compare quantitative results of individual laboratories with results of one common laboratory. Three replicates of a composite surface water (SW) sample were fortified with the analytes along with three replicates of deionized water (DW). A nonfortified DW sample and a nonfortified SW sample were also extracted. All samples were extracted using Empore C(18) disks. After extraction, part of the samples were eluted and analyzed in-house. Duplicate samples were evaporated in a 2-mL vial, shipped dry to a central laboratory (SDC), redissolved, and analyzed. Overall, samples analyzed in-house had higher recoveries than SDC samples. Laboratory x analysis type and laboratory x water source interactions were significant for all four compounds. Seven laboratories participated in this interlaboratory comparison program. No differences in atrazine recoveries were observed from in-house samples analyzed by laboratories A, B, D, and G compared with the recovery of SDC samples. In-house atrazine recoveries from laboratories C and F were higher when compared with recovery from SDC samples. However, laboratory E had lower recoveries from in-house samples compared with SDC samples. For each laboratory, lower recoveries were observed for chlorpyrifos from the SDC samples compared with samples analyzed in-house. Bromacil recovery was <65% at two of the seven laboratories in the study. Bromacil recoveries for the remaining laboratories were >75%. Three laboratories showed no differences in metolachlor recovery; two laboratories had higher recoveries for samples analyzed in-house, and two other laboratories showed higher metolachlor recovery for SDC samples. Laboratory G had a higher recovery in SW for all four compounds compared with DW. Other laboratories that had significant differences in pesticide recovery between the two water sources showed higher recovery in DW than in the SW regardless of the compound. In comparison to earlier work, recovery of these compounds using SPE disks as a temporary storage matrix may be more effective than shipping dried samples in a vial. Problems with analytes such as chlorpyrifos are unavoidable, and it should not be assumed that an extraction procedure using SPE disks will be adequate for all compounds and transferrable across all chromatographic conditions.