Solid phase extraction on sax columns as an alternative for ochratoxin A analysis in maize

A sensitive and reliable method is described for the determination of ochratoxin A (OTA) in maize. An extraction and clean-up procedure was used, with chloroform-phosphoric acid as the extractant, and liquid-liquid partition and anion-exchange chromatography (SAX columns) for the clean-up. Quantification of toxin is achieved by high performance liquid chromatography (HPLC). Recoveries were between 81-94 % at 3-90 ng/g levels. The detection limit was 0.02 ng.     

Influence of extraction solvent (buffer, methanol, acetone) and time on the quantification of indoIe-3-acetic acid in plants

The effect of extraction solvent and time on the measured indole-3-acetic acid (IAA) level was investigated in plant materials having different contents of lAA-conjugates, Tissues from pine ( Pinus sylvestris L.). tobacco ( Nicotiana tabacum L.), and maize ( Zea mays L.) were extracted for 1–9 h with Na-phosphate buffer (pH 7.5). 80% methanol and 70% acetone. IAA was measured by combined gas chromatography-selected ion minitoring-mass spectromctry (GC-SIM-MS) with [¹³C₆]-IAA as an internal standard.
Extraction of maize seedlings with buffer gave a higher estimate of free IAA than did extraction with methanol or acetone, which produced similar values. The increase in free IAA after buffer extraction was paralleled by a stoichiometric decrease in lAA-ester conjugates, indicating that free IAA was formed during buffer extraction by hydrolysis of these conjugates, which are abundant in maize seedlings. The amount of hydrolysis during a 1-h extraction period was estimated to be ca 3% of the total lAA-ester pool. However, in the pine extraxylary tissues and tobacco in-ternodes which lack a significant lAA-ester pool, buffer extraction resulted in the same IAA estimate as extraction with the organic solvents, but produced a cleaner extract. For all the plant materials investigated, a 1-h extraction period was sufficient for equilibrating the internal standard with the endogenous IAA pool.     

蝉虫草样品的分级萃取与化学成分分析

利用索氏萃取技术,依次采用石油醚、乙酸乙酯、丙酮、无水乙醇和甲醇等5种溶剂对蝉虫草纯粉进行分级萃取,运用傅里叶变换红外光谱分析法和气相色谱-质谱联用技术对5级萃取物进行分析鉴定。傅里叶变换红外光谱分析显示萃取物中含有与烯烃类、羧酸类、酯类、醇类和酮类等化合物相关的C-H、C=O、C-O和C=C等官能团。气相色谱-质谱联用技术共鉴定出有机小分子化合物34种,以酯类和脂肪酸类为主,多为碳链长度为15-20的长链脂肪酸及对应的酯,其中十八碳不饱和脂肪酸相对含量高达28.95%;分别存在于两种或以上萃取物中的有机化合物共有11种;仅存于石油醚萃取物中的化合物6种,乙酸乙酯萃取物中3种,丙酮萃取物中2种,无水乙醇萃取物中6种,甲醇萃取物中6种。在一定极性范围内,利用溶剂的极性梯度变化,可实现蝉虫草中活性物质的按极性梯度分离;采用分级萃取技术可有效分离蝉虫草中部分化学成分。鉴定结果充实了蝉虫草中化合物的种类资源,为蝉虫草中活性物质谱图库的完善、构效关系的建立及蝉虫草产品的利用开发提供支撑。     

Experimental determination and modelling of the soil water extraction capacities of crops of maize,sunflower, soya bean,sorghum and wheat

The estimation of soil water reserves is essential for irrigation management. The usual way of calculating these reserves, held between the soil moisture content at field capacity and the classical limit of –1.5 MPa considered as the lower limit of available water, over the rooting depth of the crop, does not correspond with the real behaviour of crops as regards their ability to extract soil water and should be only considered as the apparent available water (AAW). Measurements of moisture profiles made using a neutron probe soil moisture meter from 1970 until 1991 on unirrigated crops at the INRA Agronomy Station at Toulouse-Auzeville, France, on a deep silty clay soil with a high water holding capacity have enabled us to define the water extraction capacities of maize ( Zea mays L.), sunflower (Helianthus annuus L.), sorghum (Sorghum bicolor L. Moench), soya bean (Glycine max L. Merr.), and winter wheat (Triticum aestivum L.). The results show, not only that all the crops can extract soil water from beyond –1.5 MPa in the surface layers to varying degrees and depths, depending on the crop, but also that deeper down, AAW is not fully used, as the moisture profile gradually returns to field capacity. Of the five crops studied, maize extracts the most water from the top 0.5 m, removing 150% of AAW. This amount falls rapidly lower down, reaching nil at 1.6 m. Conversely sunflower extracts less near the surface, but uses all AAW up to 1.2 m, and still extracts 85% of AAW at 1.6 m. Sorghum is somewhat comparable to sunflower, but with a lower use over the entire profile. Soya bean exhibits strong extraction to 1.0 m, and then much less at depth. As to wheat, its extraction capability is quite high near the surface, and then falls steadily with depth where it is still 30% of AAW at 1.6 m. Soil moisture measurements realised on a bare soil during several successive years were used to fix the maximum soil evaporation and to suggest the contribution of crops in soil water depletion from uppermost layers.The water extraction capacities have been modelled and introduced into the model EPICphase, a modified version of the model EPIC, adapted for irrigation management. Four parameters have been introduced to simulate: (1) the rooting pattern of the crop (parameter ), (2) the degree of involvement of deep layers (parameter p), (3) the fraction of AAW beyond which crop transpiration is affected (parameter t) and (4) the intensity of extraction beyond the limit of –1.5 MPa as a function of soil depth (parameter d). Calibrated on the basis of the driest year since 1970 for each crop, the model was then validated under unirrigated conditions, and then tested on irrigated maize plots. Under unirrigated conditions, the simulations correctly reproduced the water extraction by the five crops, both in an extremely dry year and in a wet year. The observed differences between simulations and observations were found mostly at about 0.1 m depth, and were due to lack of precision of moisture measurements with the neutron probe. From 0.2 to 0.6 m the simulations have a tendency to overestimate the extraction. These differences are explained by water fluxes which are especially high in these layers because of the processes of evaporation from the soil and plant transpiration, which are difficult to simulate with precision. Below 0.6 m, a more stable zone where water movements are of minor importance, the simulations are very precise. For irrigated maize, the results show a very good fit between simulation and measurement, indicating that these water extraction capacity figures could be used for irrigation management provided that the rules for exploitation of the water reserves are well established.     

Determination of tobramycin in soil by HPLC with ultrasonic-assisted extraction and solid-phase extraction

Pharmaceuticals residues in the environment have become a growing scientific interest worldwide. In the light of the possible harmful effects of tobramycin, a rapid and sensitive analytical method for determination of tobramycin in soil was developed. The extraction and purification methods, derivatization conditions, and chromatographic conditions in the determination of tobramycin in soil have been fully investigated. Extraction was carried out by a combination of vortex mixer and ultrasonic oscillation using acetone/water as the extraction agent. The extract was concentrated to 1 mL and passed through the C(18) SPE cartridge rinsed with water (3 mL), methanol (3 mL). The derivatization procedure was followed by the reaction of tobramycin with 4-Chloro-3,5-dinitrobenzotrifluoride at 60°C for 10 min in pH 9.0 H(3)BO(3)-Na(2)B(4)O(7) medium. The labeled tobramycin was determined by high performance liquid chromatography at 245 nm. Separation was accomplished within 15 min in gradient elution mode with trifluoroacetic acid in mobile phase as ion-pair reagent. The correlation coefficient for the method was 0.9999 in concentrations ranging from 0.10 to 100.0 μg/g. The limit of detection was 0.02 μg/g for tobramycin in soil at a signal-to-noise ratio of 3. The calculated recoveries of the proposed method were from 78.0 to 91.0% and RSDs were 3.38-9.79% in the application to the quantitative determination of tobramycin in all types of soil. The method will help to establish adequate monitoring of tobramycin residue in soil and make the contribution to environmental behavior evaluation.     

Improved extraction of PCR-quality community DNA from digesta and fecal samples

Several DNA extraction methods have been reported for use with digesta or fecal samples, but problems are often encountered in terms of relatively low DNA yields and/or recovering DNA free of inhibitory substances. Here we report a modified method to extract PCR-quality microbial community DNA from these types of samples, which employs bead beating in the presence of high concentrations of sodium dodecyl sulfate (SDS), salt, and EDTA, and with subsequent DNA purification by QIAamp columns [referred to as repeated bead beating plus column (RBB + C) method]. The RBB + C method resulted in a 1.5- to 6-fold increase in DNA yield when compared to three other widely used methods. The community DNA prepared with the RBB + C method was also free of inhibitory substances and resulted in improved denaturing gradient gel electrophoresis (DGGE) profiles, which is indicative of a more complete lysis and representation of microbial diversity present in such samples.     

Comparison of quenching and extraction methodologies for metabolome analysis of Lactobacillus plantarum

Background

A reliable quenching and metabolite extraction method has been developed for Lactobacillus plantarum. The energy charge value was used as a critical indicator for fixation of metabolism.

Results

Four different aqueous quenching solutions, all containing 60% of methanol, were compared for their efficiency. Only the solutions containing either 70 mM HEPES or 0.85% (w/v) ammonium carbonate (pH 5.5) caused less than 10% cell leakage and the energy charge of the quenched cells was high, indicating rapid inactivation of the metabolism. The efficiency of extraction of intracellular metabolites from cell cultures depends on the extraction methods, and is expected to vary between micro-organisms. For L. plantarum, we have compared five different extraction methodologies based on (i) cold methanol, (ii) perchloric acid, (iii) boiling ethanol, (iv) chloroform/methanol (1:1) and (v) chloroform/water (1:1). Quantification of representative intracellular metabolites showed that the best extraction efficiencies were achieved with cold methanol, boiling ethanol and perchloric acid.

Conclusion

The ammonium carbonate solution was selected as the most suitable quenching buffer for metabolomics studies in L. plantarum because (i) leakage is minimal, (ii) the energy charge indicates good fixation of metabolism, and (iii) all components are easily removed during freeze-drying. A modified procedure based on cold methanol extraction combined good extractability with mild extraction conditions and high enzymatic inactivation. These features make the combination of these quenching and extraction protocols very suitable for metabolomics studies with L. plantarum.     

HPLC determination of fumonisin mycotoxins in maize: a comparative study of naphthalene-2,3-dicarboxaldehyde and o-phthaldialdehyde derivatization reagents for fluorescence and diode array detection

Fumonisins are mycotoxins produced by various species of Fusarium and occur naturally in contaminated maize and maize-based foods. Ingestion of fumonisins has considerable health implications for humans and animals. Since fumonisins lack a useful chromophore or fluorophore, their determination in maize is routinely achieved via HPLC with fluorescence detection (FLD) after precolumn derivatization. This study optimized naphthalene-2,3-dicarboxaldehyde (NDA) derivatization of fumonisins in naturally contaminated maize following strong anion exchange (SAX) solid phase extraction (SPE) clean-up and utilizing diode array detection (DAD) as a practical alternative simultaneously to FLD. The limit of detection (LOD) for fumonisin B(1) (FB(1)), fumonisin B(2) (FB(2)) and fumonisin B(3) (FB(3)) with FLD was 0.11 ng, 0.50 ng and 0.27 ng, respectively, and with DAD it was 13.8 ng, 12.5 ng and 6.6 ng, respectively injected on column. The coefficient of variation (CV, n = 6) for FB(1), FB(2) and FB(3) in a naturally contaminated samples obtained with FLD was 2.6%, 1.8% and 5.3%, respectively, compared to 6.0%, 3.4% and 9.5%, respectively, obtained with DAD. Subsequently the optimized NDA derivatization was compared to the widely used o-phthaldialdehyde (OPA) derivatization agent as well as alternative sample clean-up with immunoaffinity column (IAC) by analyzing naturally contaminated maize samples (n = 15) ranging in total fumonisin (TFB = FB(1)+FB(2)+FB(3)) levels from 106 to 6000 μg/kg. After immunoaffinity column clean-up of extracted samples, the recoveries of spiked maize samples for NDA-FLD of FB(1), FB(2) and FB(3) were 62%, 94% and 64%, respectively. NDA proved to be an effective derivatization reagent of fumonisin in naturally contaminated maize samples following IAC clean-up, except for DAD at TFB levels below 1000 μg/kg. In contrast NDA derivatization following SAX clean-up produced results comparable to OPA only for levels below 1000 μg/kg. Aside from the difference in detection limits, FLD and DAD produced comparable results irrespective of the clean-up method or the derivatization agent.     

Solvent effects on focused microwave assisted extraction of polyphenolic acids from Eucommia ulmodies

An open microwave-assisted extraction system was used to extract gallic acid, protocatechuic acid, chlorogenic acid and caffeic acid from Eucommia ulmodies. The effect of extraction variables, especially solvent, on the recoveries of these polyphenolic compounds was investigated using factorial design. As extracting solvent for these compounds, methanol produced a higher recovery than pure water. For straight chain alcohol solvents, the lower the carbon number, the higher the recoveries of the polyphenolic acids. The optimal ratio of methanol:water:glacial acetic acid in the solvent mixture used in microwave-assisted extraction was 2:8:0.3 (v/v) and this solvent could be directly used as the mobile phase in HPLC separation without additional intermittent treatment as reported in literature. The extraction under the condition of 50% microwave power and 30 s irradiation at a solvent:sample ratio of 10 (mL/g) was found to be the most advantageous. The repeatability test of extraction and chromatographic analysis was satisfactory for the analysis of these polyphenolic compounds.     

Direct extraction of DNA from soils for studies in microbial ecology

Molecular analyses for the study of soil microbial communities often depend on the extraction of DNA directly from soils. These extractions are by no means trivial, being complicated by humic substances that are inhibitory to PCR and restriction enzymes or being too highly colored for blot hybridization protocols. Many different published protocols exist, but none have been found to be suitable enough to be generally accepted as a standard. Most direct extraction protocols start with relatively harsh cell breakage steps such as bead-beating and freeze-thaw cycles, followed by the addition of detergents and high salt buffers and/or enzymic digestion with lysozyme and proteases. After typical organic extraction and alcohol precipitation, further purification is usually needed to remove inhibitory substances from the extract. The purification steps include size-exclusion chromatography, ion-exchange chromatography, silica gel spin columns, and cesium chloride gradients, among others. A direct DNA extraction protocol is described that has been shown to be effective in a wide variety of soil types. This protocol is experimentally compared to several published protocols.     

Reusability of immunoaffinity columns for determination of fumonisins in maize

Eighteen maize samples were assayed for fumonisin B1 (FB1) and B2 content by immunoaffinity column coupled with high performance liquid chromatography (HPLC). The FumoniTest columns were used once for the isolation of fumonisins (single-use column method). In the second part of the assay the columns were regenerated. After elution with methanol, PBS solution was left on the column for one day at room temperature to regenerate the columns (regenerated column method). The efficiency of columns regenerated twice was tested by determining FB, recovery and the reproducibility of the determinations. The recovery rate of FB1 proved to be 82% by the single-use column method (RSD: 5.7%) and 82.6% (RSD: 5.6 %) by the regenerated column method; 500-8,000 ng FB1 loaded onto the columns did not affect column performances. Nearly identical values were obtained when the FB1 content of fumonisin-containing maize samples was determined by both methods. The results indicate that the FumoniTest columns can be regenerated by the method applied at least twice without decrease in column performance. The fumonisin affinity, capacity and specificity of the regenerated columns were not changed. Thus, columns regenerated in this way can be used for determining the fumonisin content of maize samples at least three times.     

缩醛磷脂提取和制备的实验研究

通过将新鲜猪心切块、绞碎,制成组织匀浆后,再经一系列过程包括总脂的提取、从总脂提取物中制取磷脂酰乙醇胺、碱水解进一步纯化缩醛磷脂酰乙醇胺以及对获得的缩醛磷脂酰乙醇胺制剂鉴定其纯度。通过Ｉｏｄｉｎｅ ｄｉｓａｐｐｅａｒａｎｃｅ法测出缩醛磷脂酰乙醇胺制剂中的含量为１５．３５ｍｍｏｌ／Ｌ,通过Ｂａｒｔｅｌｌ法测出缩醛磷脂酰乙醇胺制剂中无机磷含量为１６．１０ｍｍｏｌ／Ｌ。因此,获得缩醛磷脂酰乙醇胺制剂的纯     

烟草废料中绿原酸的提取工艺研究

讨论了从烟草废料中提取绿原酸的优势和甲醇、乙醇、丙酮、水等不同溶剂经超声波辅助提取绿原酸的效果：研究结果表明,用体积分数40％的甲醇得到的浸提液中,绿原酸质量浓度为2．11mg／mL,比以水为溶剂时高出近50％.不同浓度的甲醇溶液中,体积分数50％的甲醇提取绿原酸的浓度最高。对树脂的吸附动力学分析表明,大孔树脂CN-101对烟草浸提液中绿原酸的吸附遵循Freundlich等温方程,吸附和解析分离所得的绿原酸收率为87．6％.在超声辅助条件下,利用甲醇等有机溶剂提取烟草中的绿原酸,进而用大孔树脂进行吸附分离的方法可行。     

Influence of water stress on endogenous hormone contents and cell damage of maize seedlings

Phytohormones play critical roles In regulating plant responses to stress. We Investigated the effects of water stress Induced by adding 12% (w/v) polyethylene glycol to the root medium on the levels of abscisic acid (ABA), indole-3-acid (IAA), zeatin (ZT), and gibberellin3 (GA3) in maize leaves. The results suggested that water stress had significant effects on the four hormone levels. There was a transient increase in the IAA content during the initial stage of adaptation to water stress in maize leaves, but it dropped sharply thereafter in response to water stress. ABA content increased dramatically in maize leaves after 24 h of exposure to water stress, and then the high levels of ABA were maintained to the end, The contents Of ZT and GA3 rapidly declined in maize leaves subjected to water stress. The effects of water stress on chlorophyll content, electrolyte leakage and malondialdehyde levels in maize leaves were also studied. The variation of cell damage was negatively correlated with ZT and GA3 levels in maize leaves under water stress. Thus, we explored the roles of ZT and GA3 on the growth of maize seedlings under water stress by exogenous application. It is possible that both ZT and GA3 were effective in protecting maize seedlings from water stress, which would be of great importance for the improvement of drought tolerance in maize by genetic manipulation.     

Recovery process of lactic acid using two distillation columns

Lactic acid is of interest as the raw materials of polylactide that is a biodegradable polymer. For an effective purification of lactic acid, batch distillation with the simultaneous reactions was used. Two Oldershaw columns and reboilers were used for fractionation of methanol and reactions. Esterification reaction of lactic acid with methanol produced methyl lactate and water. The products of the esterification reaction, methyl lactate and water were transported to the reboiler of the hydrolysis part. In hydrolysis part, reaction of methyl lactate and water reproduced lactic acid and methanol. Methanol produced in the hydrolysis part and unreacted methanol in the esterification part were separated by distillation and recycled to the reboiler of the esterification part so that the esterification reaction would be stimulated. Thus, pure lactic acid solution remained in the reboiler of the hydrolysis part. The effect of the number of stages in column on the recovery yield was also investigated. In the operation with columns the recovery yield of lactic acid was improved. It is due to the fact that the columns improved the fractionation of components and stimulated the reactions in two parts.     

Laboratory evaluation of ensiled mixtures of alkali-treated cattle excreta and whole-crop maize

Faeces or manure (faeces + urine + straw bedding) from beef cattle given maize silage diets were ensiled with whole-crop maize (27% dry matter), after treatment with NaOH at 0, 7.5 or 15 g per 100 g excreta DM, so that excreta DM comprised 25, 50 or 100% of the total DM, in a factorial design. A control treatment consisted of maize forage ensiled alone. The ensiled products were analysed for the content of fermentation acids, pH, nitrogenous compounds, structural carbohydrates, starch, water-soluble carbohydrates, ash, sodium and digestibility in vitro. Mixtures which contained 25% excreta DM were well preserved with relatively low values for pH, butyric acid and ammonia-N, and a high proportion of fermentation acids as lactic acid. Mixtures which contained 50% excreta DM were generally poorly preserved. Addition of NaOH to excreta prior to ensiling was reflected in a decrease in the content of neutral detergent fibre and increased digestibility of organic matter in vitro in the ensiled products. Mixtures of 25% excreta treated with 15 g NaOH/100 g excreta DM gave values for digestibility in vitro similar to that of the maize ensiled alone.     

Influence of the extraction solvent on antioxidant activity of Althaea officinalis L. root extracts

Althaea officinalis (Malvaceae) is a well-known plant that is widely distributed throughout the world. Aqueous and hydroalcoholic extracts from A. officinalis root are used mainly because of their antitussive and expectorant activity. It is well known that these activities are based on the polysaccharide composition, but little is known about the possible antioxidant activity of root extract. The present study evaluated antioxidant activity of root extracts prepared with different extraction solvents applying ABTS^·+ (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), hypochlorous acid scavenging assay and iron-induced lipid peroxidation. The results showed that the extract prepared with water as extraction solvent did not possess antioxidant activity, whereas the extracts obtained using ethanol:water as extraction agent showed well pronounced antioxidant activity. In particular, the extracts obtained at low concentration of ethanol in the mixed solvent (50:50 and 70:30, v/v) showed higher scavenging activity for ABTS^·+ radicals and hypochlorite ions than the extract obtained with the higher ethanol concentration (90:10, v/v). These results correlated very well with phenolic and flavonoid content of the extracts. The extracts did not show cytotoxic effect on human BV-173 leukemic cells but may have immunomodulating effects due to their antioxidant properties.     

Discriminative determination of alkyl methylphosphonates and methylphosphonate in blood plasma and urine by gas chromatography-mass spectrometry after tert.-butyldimethylsilylation

A method for determining two nerve gas hydrolysis products, alkyl (ethyl, isopropyl and pinacolyl) methylphosphonates (RMPAs) and methylphosphonate (MPA), separately, in human plasma and urine samples was developed, using two different deproteinization procedures. In the first method, the plasma sample was deproteinized by adding a fourfold volume of acetonitrile, followed by passing the supernatant through a Bond Elut strong anion-exchange (SAX) cartridge [fluoride (F(-)) form]. After washing the cartridge with water and methanol, the RMPAs were eluted with a 3% (v/v) solution of methanolic ammonia, and analyzed by gas chromatography-mass spectrometry (GC-MS) after tert.-butyldimethylsilyl (TBDMS) derivatization. The detection yields of TBDMS derivatives of RMPAs were in the range of 69 to 99%, in contrast to the poor yields obtained when only acetonitrile deproteinization pretreatment was used (yield: 13-26%). The yield of the TBDMS derivative of MPA was very low (8%), however. In a the second method, a plasma sample was deproteinized by adding a half volume of 10% (w/v) trichloroacetic acid (TCA), and the resulting supernatant was extracted with diethyl ether to remove TCA, the aqueous fraction was then passed through a Bond Elut SAX cartridge. After washing the cartridge with 0.5% (v/v) methanolic ammonia, MPA was eluted with 3% (v/v) methanolic ammonia. The detection yield of the TBDMS derivative of MPA was nearly quantitative. A pretreatment method using SAX solid-phase extraction was also developed for the cleanup of a urine sample, in which the sample was directly applied to a Bond Elut SAX cartridge, followed by elution of the RMPAs and MPA with 3% (v/v) methanolic ammonia, which were then derivatized and analyzed by GC-MS. The detection yields of TBDMS derivatives of RMPAs and MPA were in the range of 61 to 97%.     

Silene vulgaris subsp. macrocarpa leaves and roots from Morocco: assessment of the efficiency of different extraction techniques and solvents on their antioxidant capacity,brine shrimp toxicity and phenolic characterization

Abstract

This study was undertaken to investigate the effect of various solvents and techniques on the extractability of antioxidant compounds, particularly phenolics, from leaves and roots of Silene vulgaris subsp. macrocarpa grown wild in Morocco. Maceration and hot extraction with methanol or water and Soxhlet ethanol extraction were utilized. Aimed at establishing the potential safety of the extracts, Artemia salina lethality bioassay was performed. All the extracts were found to be non-toxic, except for the leaf Soxhlet ethanol. The antioxidant potential of the extracts was evaluated in vitro by DPPH, reducing power, and ferrous ions chelating activity assays. The leaf extracts displayed noticeable radical scavenging and chelating activities, and maceration with methanol (Mac-MeOH) resulted the most suitable extraction method for an effective recovery of antioxidants; further, the root Mac-MeOH extract demonstrated good chelating properties (IC₅₀ = 335.49?±?0.70?µg/mL). Thus, leaf and root Mac-MeOH extracts were subjected to phytochemical investigations. The total phenolic, flavonoid and condensed tannin content was determined spectrophotometrically. Thirteen polyphenolic compounds were positively identified, by HPLC-PDA-ESI-MS, in the leaf extract for the first time, with p-coumaric acid derivatives being the most abundant ones (81%), whereas only catechin and procyanidin B1 were found in the root extract.     

Retention and mobility of atmospheric particle-associated organic pollutant PCDD/Fs and PAHs in maize leaves

The fate of polychlorinated dibenzo- p -dioxins and dibenzofurans and polycyclic aromatic hydrocarbons deposited to maize leaves under ambient conditions was investigated, with focus on those compounds that are primarily associated with particles in the atmosphere. Leaf samples collected from mature maize plants over an 8-wk period were subjected to four extraction procedures: (1) rinsing with distilled water; (2) shaking in aqueous EDTA solution; (3) immersion in chloroform/methanol; (4) soxhlet extraction with toluene. Of the compounds deposited primarily in association with particles, > 20% of the total leaf contamination was present in the first two aqueous extracts, indicating that only a small portion of these substances was subject to ready erosion from the leaf surfaces. Some 50–60% of the chemical was present in the third extract, while 20–40% was found in the final extract. The chemical in the final extract was no longer associated with particles, since these had been removed with the first three extractions. This chemical must have desorbed from the particles with which it was originally deposited, and migrated through the epicuticular waxes. Model calculations indicated that 15–35% of the chemical in the third extract had also desorbed from the particles, and there was evidence that polychlorinated dibenzo- p -dioxins and dibenzofurans desorb more readily than polycyclic aromatic hydrocarbons. It is concluded that desorption of chemical from particles and subsequent transport through the cuticle is an important process determining plant accumulation of organic contaminants associated with atmospheric particles.