Hyperbranched molecules based on calixarenes

Synthesis of the diamide 2 derived from tris(2-aminoethyl)amine and monocarboxymethylcalix[4]arene provides a starting material useful for the preparation of a variety of hyperbranched molecules. Metal ion binding is one of the potentially useful properties of these new materials.     

Solid-phase microfibers based on modified single-walled carbon nanotubes for extraction of chlorophenols and organochlorine pesticides

Solid-phase microextraction (SPME) based on carboxylated single-walled carbon nanotube fibers was used to extract several chlorophenols (CPs) and organochlorine pesticides (OCPs) from aqueous samples prior to their determination by GC with electron capture detection. The main parameters affecting microextraction (temperature, time, stirring rate and salting-out effect) and the conditions of the thermal desorption in the GC injector were optimized. Compared with commercial SPME fibers, the fiber presented better selectivity and sensitivity. Linear response was found for the concentration range between 2 and 1000 ng L^?1 (20–1000 ng L^?1 for CPs), and the limits of detection were in the range from 0.07 to 4.36 ng L^?1. The repeatability expressed as relative standard deviation ranged from 4.1 % to 8.2 % and the fiber-to-fiber reproducibility for four prepared fibers was between 6.5 % and 10.8 %. The method was successfully applied to the analysis of CPs and OCPs in lake water and waste water samples. Recovery was tested with spiked lake water and waste water samples, with values ranging from 89.7 % to 101.2 % in case of waste water samples.

Controlled drug delivery systems based on calixarenes

Recent advances on calixarene-based drug delivery systems in the form of inclusion complexes, amphiphilic self-assembly nanocarriers including micelles, hydrogels, vesicles and liposomes, and supramolecular nanovalves on mesoporous silicas, were reviewed and discussed.     

Microwave extraction of organochlorine pesticides from soils

The purpose of this work was to develop a rapid, reliable and sensitive method for the extraction of organochlorine pesticides from soils using microwave energy with closed vessel technology. Three oven programs were assayed with two different solvent mixtures in order to achieve adequate experimental conditions for the complete extraction of organochlorine pesticides from the matrix. The method was validated using a certified reference soil material (CRM804-050).     

Mixed liquids for single-drop microextraction of organochlorine pesticides in vegetables

A new approach for the extraction of nine kinds of organochlorine pesticides (OCPs) from vegetable samples coupling single-drop microextraction with gas chromatography-mass spectrometry was presented. Experimental parameters, such as organic solvent, exposure time, agitation and organic drop volume were controlled and optimized. An effective extraction was achieved by suspending a 1.00microL mixed drop of p-xylene and acetone (8:2, v/v) to the tip of a microsyringe immersed in a 2mL donor aqueous solution and stirred at 400rpm. The approach was applied to the determination of OCPs in vegetable samples with a linearity range of 0.05-20ng mL(-1) for alpha-, beta-, gamma-, delta-hexachlorobenzene (BHC) and dicofol, 0.5-20ng mL(-1) for dieldrin and 2,2-bis(4-chlorophenyl)-1,1-dichloroethane (DDD) or 0.5-50ng mL(-1) for 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (DDE) and 2-(2-chlorophenyl)-2 (4-chlorophenyl)-1,1,1-trichloroethane (p,p'-DDT). Correspondingly, the determination limit at an S/N of 3 ranged from 0.05ng mL(-1) for alpha-, beta-, gamma-, delta-BHC to 0.2ng mL(-1) for dicofol, dieldrin or p,p'-DDT. The relative recoveries were from 63.3 to 100%, with repeatability ranging from 8.74 to 18.9% (relative standard deviation, R.S.D.). The single-drop microextraction was proved to be a fast and simple approach for the pre-concentration of organochlorine pesticides in vegetable samples.     

Rapid method for the determination of organochlorine pesticides in milk

This method involved one step solvent extraction of milk with ethyl acetate-acetone-methanol by ultrasonication. The supernatants were further cleaned-up and enriched by solid-phase extraction using octadecyl (C18)-bonded silica cartridges, then assayed by capillary gas-liquid chromatography with electron capture detection. The recoveries of eleven organochlorine pesticides (OCPs) from raw milks were quantitative, ranging from 90-110% at 10 times the limit of detection (LOD). The LOD ranged from 0.5 micrograms/l whole milk for alpha-hexachlorocyclohexane to 2.5 micrograms/l whole milk for 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane. The day-to-day variation of the method was evaluated over 7 days using 3 different pools of spiked cow milks (at the LOD, 5 and 10 times the LOD). The coefficient of variations (C.V.s) were 16 +/- 6, 10 +/- 2 and 9 +/- 3% (mean S.D.), respectively. The method showed no emulsion problems common with conventional non-polar solvent extraction, and the use of solid-phase extraction considerably reduced the sample clean-up process compared with the existing methods. The method also showed that OCPs in milk could be extracted quantitatively without extraction of total fat, and that OCPs spiked into cows milk could be used to construct calibration curves for human milk determinations.     

Supramolecular catalytic systems based on calixarenes and cyclodextrins

A number of supramolecular metal complex catalitic system based on cyclodextrins and calixarenes have been developed. Particular attention has been given to design of new metal complexes with molecular recognition abilities. Data on application catalytic systems based on receptor molecules capable to formation of inclusion “host-guest” complexes in hydroformylation and Wacker-oxidation are given. Influence of different factors on activity, stability, selectivity of metal complex supramolecular catalytic systems is discussed.     

Small-scale method for the determination of selected organochlorine pesticides in soil

A small-scale method was developed for the simultaneous determination of gamma-HCH, heptachlor, aldrin, dicofol, mirex, endosulfan I, endosulfan II and endosulfan sulphate in soil. The extraction and clean-up steps were combined into one step by transferring soil samples to chromatographic columns prepacked with neutral alumina. The pesticides elution was processed with n-hexane : dichloromethane (7 : 3) and the concentrated eluate was analysed using gas-liquid chromatography with electron capture detection. Analyses of the "in vitro" fortified samples with the selected pesticides were performed at three different levels. Mean recoveries for aldrin, gamma-HCH and heptachlor, at levels of 2, 10 and 20 ng/g, ranged from 71 to 87%; for dicofol, at levels of 8, 40 and 80 ng/g, ranged from 97 to 103%; for endosulfan I and II, at levels of 5, 25 and 50 ng/g, ranged from 88 to 96%; for mirex, at levels of 6, 30 and 60 ng/g, ranged from 86 to 110%; and for endosulfan sulphate, at levels of 15, 75 and 150 ng/g, ranged from 93 to 104%. The method can be used for rapid determination of these pesticides in soil.     

Gold nanoparticles based solid‐phase microextraction coatings for determining organochlorine pesticides in aqueous environmental samples

The use of solid‐phase microextraction coatings based on gold nanoparticles was investigated, focusing the attention on the preparation of nanoparticles with nonclassical reduction agents of HAuCl₄ such as gallic acid and H₂O₂, rather than the conventional sodium citrate. All nanoparticles were characterized by diode array spectroscopy, whereas novel nanoparticles prepared with gallic acid and H₂O₂ were also characterized by microscopic techniques. Solid‐phase microextraction coatings were prepared with a layer‐by‐layer approach. Gallic acid permitted the preparation of stable nanoparticles with milder experimental conditions (1 min, room temperature) and provided the most uniform coatings (thickness ∼3 μm). Seven organochlorine pesticides were determined in different environmental waters using gas chromatography with electron capture detection. Despite the low thickness of the coatings, limits of detection of the entire method down to 0.13 μg/L were obtained. A comparison with the commercial polyacrylate in terms of the partition coefficients of the analytes to the coatings gave logarithm of the partition coefficient values two times higher with gallic acid than polyacrylate (although the commercial fiber is 28 times thicker). Interfiber relative standard deviation values ranged from 8.67 to 21.3%. Optimum fibers also presented an adequate lifetime (>100 extractions).     

Preparation of reference material for organochlorine pesticides in a herbal matrix

The development of reference material for four organochlorine pesticides, namely hexachlorobenzene and three isomers of hexachlorocyclohexane (alpha-hexachlorocyclohexane, beta-hexachlorocyclohexane and gamma-hexachlorocyclohexane), in a ginseng root sample is presented. Raw materials (Panax ginseng) were purchased from a local market and confirmed to contain certain levels of incurred organochlorine pesticide residues by a validated gas chromatography-mass selective detection method. A total of more than 300 bottles each containing 25 g of samples were prepared after the materials had been freeze-dried, milled and thoroughly mixed. The homogeneity and stability of samples from randomly selected bottles were verified and the reference values were characterized using a highly precise isotope dilution gas chromatography-mass spectrometry (ID-GCMS) method that was recently developed by our laboratory. The purity of standard organochlorine chemicals was determined against certified reference materials to establish the accuracy of the ID-GCMS analysis. The concentrations (+/- expanded uncertainty) of hexachlorobenzene, alpha-hexachlorocyclohexane, beta-hexachlorocyclohexane and gamma-hexachlorocyclohexane in the reference material were 0.198 +/- 0.015, 0.450 +/- 0.022, 0.213 +/- 0.011 and 0.370 +/- 0.032 mg kg(-1), respectively. A portion (70 bottles) of the samples was also used in a proficiency testing (PT) scheme for assessing the testing capabilities of field laboratories. The consensus mean values of the PT obtained from the 70 participants were on the same order but deviated by -2.7 to -14.1% from those of the assigned reference values. Because of the wide spread of participants' data (relative standard deviation ranging from 44 to 56%), the PT results were not included in the calculation of the assigned values of the reference materials. The materials served as suitable reference materials to ascertain the quality control and validation processes for the determination of organochlorine pesticides in herbal matrices.     

Small-scale method for the determination of selected organochlorine pesticides in soil

A small-scale method was developed for the simultaneous determination of -HCH, heptachlor, aldrin, dicofol, mirex, endosulfan I, endosulfan II and endosulfan sulphate in soil. The extraction and clean-up steps were combined into one step by transferring soil samples to chromatographic columns prepacked with neutral alumina. The pesticides elution was processed with n-hexane : dichloromethane (7:3) and the concentrated eluate was analysed using gas-liquid chromatography with electron capture detection. Analyses of the in vitro fortified samples with the selected pesticides were performed at three different levels. Mean recoveries for aldrin, -HCH and heptachlor, at levels of 2, 10 and 20 ng/g, ranged from 71 to 87%; for dicofol, at levels of 8, 40 and 80 ng/g, ranged from 97 to 103%; for endosulfan I and II, at levels of 5, 25 and 50 ng/g, ranged from 88 to 96%; for mirex, at levels of 6, 30 and 60 ng/g, ranged from 86 to 110%; and for endosulfan sulphate, at levels of 15, 75 and 150 ng/g, ranged from 93 to 104%. The method can be used for rapid determination of these pesticides in soil.     

Ultrasonic solvent extraction of organochlorine pesticides from soil

Ultrasonic solvent extraction of the organochlorine pesticides (OCP) including α-, β-, γ- and Δ-hexachlorocyclohexane (HCH), heptachlor, aldrin, o,p′-DDE, dieldrin, p,p′-DDE, p,p′-DDT, methoxychlor, mirex from soil is reported. The extraction procedure was optimized with regard to the solvent type, amount of solvent, duration of sonication and number of extraction steps. Determination of pesticides was carried out by gas chromatography (GC) equipped with electron capture detection (ECD). Twice ultrasonic extraction using 25 mL of a mixture of petroleum ether and acetone (1/1 v/v) for 20 min of sonication showed satisfactory extraction efficiency. Recoveries of pesticides from fortified soil samples are over 88% for three different fortification levels between 15 and 200 μg kg⁻¹, and relative standard deviations of the recoveries are generally below 6%. Real soil samples were analyzed for OCP residues by optimized ultrasonic solvent extraction and shake-flask as well as soxhlet extraction technique. Investigated all extraction methods showed comparable extraction efficiencies. Optimized ultrasonic solvent extraction is the most rapid procedure because the use of time in ultrasonic extraction was considerably reduced compared to shake-flask and soxhlet extraction.     

Simplified method for the determination of organochlorine pesticides in honey.

A method is described for the detection and quantitative determination of organochlorine pesticides in honey. After extraction with hexane, the pesticides were cleaned-up by adsorption chromatography on a Florisil Sep-Pak cartridge and eluted with 15% diethyl ether in hexane. The detection of organochlorine pesticides was performed by capillary gas chromatography with electron-capture detection. The quantification limit obtained for different pesticides ranged from 0.56 to 2.78 micrograms kg-1 and recoveries from fortified honey samples averaged 89.6%.     

Virus-sized DNA nanoparticles for gene delivery based on micelles of cationic calixarenes

Macrocyclic amphiphilic molecules based on calix[4]arenes are highly attractive for controlled supramolecular assembly of DNA into small nanoparticles, since they present a unique conical architecture and can bear multiple charged groups. In the present work, we synthesized new amphiphilic calixarenes bearing cationic groups at the upper rim and alkyl chains at the lower rim. Their self-assembly in aqueous solution was characterized by fluorescent probes, fluorescence correlation spectroscopy, dynamic light scattering, gel electrophoresis and atomic force microscopy. We found that calixarenes bearing long alkyl chains (octyl) self-assemble into micelles of 6 nm diameter at low critical micellar concentration and present the unique ability to condense DNA into small nanoparticles of about 50 nm diameter. In contrast, the short-chain (propyl) analogues that cannot form micelles at low concentrations failed to condense DNA, giving large polydisperse DNA complexes. Thus, formation of small DNA nanoparticles is hierarchical, requiring assembly of calixarenes into micellar building blocks that further co-assemble with DNA into small virus-sized particles. The latter showed much better gene transfection efficiency in cell cultures relative to the large DNA complexes with the short-chain analogues, which indicates that gene delivery of calixarene/DNA complexes depends strongly on their structure. Moreover, all cationic calixarenes studied showed low cytotoxicity. Thus, this work presents a two-step hierarchical assembly of small DNA nanoparticles for gene delivery based on amphiphilic cone-shaped cationic calixarenes.     

Selective pressurized liquid extraction for multi-residue analysis of organochlorine pesticides in soil

A selective pressurized liquid extraction (SPLE) procedure capable of performing simultaneous extraction and clean-up has been demonstrated for multi-residue analysis of organochlorine pesticides (OCPs) in soil. The final method was performed at 100 degrees C for 3 x 10 min using acetone/n-heptane (1:1, v/v). Florisil was placed inside the extraction cell downstream the sample to remove interfering compounds. Extraction of two soil samples by SPLE gave a recovery which was over 80% for beta-endosulfan, endosulfan sulfate, p,p'-DDT and p,p'-DDE compared to PLE with off-line clean-up. The same trend was observed when applying the SPLE method to a certified reference soil sample (CRM 811-050) containing 13 OCPs, where the SPLE method gave 80-90% recovery vis-à-vis the PLE method with off-line clean-up. Feasibility of the SPLE method was further demonstrated by applying it to five real soil samples collected in Ethiopia.     

Oligodentate glycoconjugates based on calixarenes: methods for the synthesis and biological activity

The review considers principal methods for the preparation of conjugates of carbohydrates with calixarenes and resorcinarenes. The data on the biological activity of glycoconjugates are discussed taking their interaction with the carbohydrate-binding proteins, lectins as an example.     

Maternal body burden of organochlorine pesticides and dioxins.

To investigate the body burden of organochlorine pesticides and dioxins in Japanese women, 125 milk samples were collected from 41 mothers in 1994, 42 in 1995, and 42 in 1996. Of the 125 samples, 82 were from primipara mothers (first delivery) and 43 were from multipara mothers (second or later delivery). By using capillary gas chromatography with electron capture detection, beta-HCH and p,p'-DDE were detected as the major chlorine pesticides in human milk. Average levels of beta-HCH and p,p'-DDE were 475 and 368 ng/g lipid, respectively, in primipara breast milk, 314 and 259 ng/g lipid in multipara breast milk, and 420 and 330 ng/g lipid in total breast milk. Dieldrin, heptachor epoxide, oxychlordane, trans-chlordane, and cis-chlordane were detected at lower average levels of 3, 4, 34, 41, and 5 ng/g lipid, respectively. By using high-resolution gas chromatography with mass spectrometric detection, dioxins were detected in all samples. Average levels of total polychlorinated dibenzo-p-dioxin (PCDD), total polychlorinated dibenzofuran (PCDF), total PCDD + PCDF, total coplanar polychlorinatedbiphenyl (CoPCB), and total dioxin were 10.0, 7.8, 17.7, 9.9, and 27.5 TEQ (toxic equivalent) pg/g lipid, respectively, in primipara breast milk; 7.0, 5.8, 12.8, 7.3, and 20.1 TEQ pg/g lipid in multipara breast milk; and 8.9, 7.1, 16.1, 8.9, and 25.0 TEQ pg/g lipid in total breast milk. In primipara breast milk, significant correlations were found among levels of beta-HCH, p,p'-DDE, total PCDD-TEQ, total PCDF-TEQ, total CoPCB-TEQ, and total TEQ except for less correlation between p,p'-DDE and total PCDF-TEQ. Levels of these analytes also significantly increased depending on mother's age, except for total Co-PCB-TEQ. For the correlation with food habit, the only positive correlation was between total PCDF-TEQs and fish intake.     

Development of liquid phase microextraction based on manual shaking and ultrasound-assisted emulsification method for analysis of organochlorine pesticides in aqueous samples

A novel method using sample preparation method, "ultrasound-assisted emulsification microextraction" (USAEME) with manual shaking, coupled with gas chromatography using and an electron capture detector (GC-ECD) was developed for the analysis of organochlorine pesticides (OCPs) in aqueous samples. The apparatus is simple and easy to operate. After manual shaking for 10s, ultrasound was used to accelerate emulsification of the organic solvent (1-decanol) in aqueous solution. Only 10 μL of the low-toxicity extraction solvent is used in this method; no dispersive solvent is required and the total extraction time is ～4 min. Manual shaking before ultrasound-assisted emulsification enhances the extraction efficiency by >100%. The effects of horizontal and vertical orientation as well as the location of the sample within the ultrasonic bath were studied. After centrifugation, we used an improved solvent collection system (ISCS) to reduce the amount of extraction solvent required. A 1 μL sample of the extract was injected into the GC column. Under optimum conditions, the linear range of the method is 5-2500 ngL(-1) for most of the OCPs, and the limit of detection of the method ranged from 0.6 to 2.9 ngL(-1).The relative recoveries ranged from 75 to 107% for sea water and from 70 to 99% for field fresh water. The method, which provides good enrichment factors, low LODs and minimization of the consumption of organic solvent, provides a rapid, simple and environment-friendly procedure for determining OCPs in aqueous samples.