Evaluation of solid-phase microextraction with PDMS for air sampling of gaseous organophosphate flame-retardants and plasticizers

As an inexpensive, simple, and low-solvent consuming extraction technique, the suitability of solid-phase microextraction (SPME) with polydimethylsiloxane (PDMS) sorbent was investigated as a quantitative method for sampling gaseous organophosphate triesters in air. These compounds have become ubiquitous in indoor air, because of their widespread use as additive flame retardants/plasticizers in various indoor materials. Results obtained by sampling these compounds at controlled air concentrations using SPME and active sampling on glass fibre filters were compared to evaluate the method. A constant linear airflow of 10 cm s^–1 over the fibres was applied to increase the extraction rate. For extraction of triethyl phosphate with a 100-m PDMS fibre, equilibrium was achieved after 8 h. The limit of detection was determined to be less than 10 pg m^–3. The PDMS–air partition coefficients, K_fs, for the individual organophosphate triesters were determined to be in the range 5–60×10⁶ at room temperature (22–23°C). Air measurements were performed utilising the determined coefficients for quantification. In samples taken from a lecture room four different airborne organophosphate esters were identified, the most abundant of which was tris(chloropropyl) phosphate, at the comparatively high level of 1.1 g m^–3. The results from SPME and active sampling had comparable repeatability (RSD less than 17%), and the determined concentrations were also similar. The results suggest that the investigated compounds were almost entirely associated with the gaseous phase at the time and place sampled.     

Selective determination of organophosphate flame retardants and plasticizers in indoor air by gas chromatography, positive-ion chemical ionization and collision-induced dissociation mass spectrometry

Gas chromatography/ion trap mass spectrometry with in-source ionization and dissociation was used in positive-ion chemical ionization (PICI) mode for the determination of organophosphate triesters in indoor air. These compounds are widely used as additive flame retardants and plasticizers in different types of materials and have become ubiquitous pollutants in indoor environments. When using collision-induced dissociation in PICI mode the fragmentation of the organophosphate triesters can be performed in a more controllable way than in electron ionization (EI) mode. The developed selected-reaction monitoring method provided high selectivity for the investigated compounds. For 8-h air measurements (corresponding to 1.5 m3 of sampled air) the limit of detection of the method was determined to be in the range 0.1-1.4 ng m(-3), which is comparable with nitrogen-phosphorus detection and about 50-fold lower than when using EI in selected-ion monitoring mode. The presented method was applied to samples from three common indoor environments, in which a number of organophosphate triesters were identified and quantified. The dominating compound was found to be tris(2-chloropropyl) phosphate, which occurred at levels up to 0.8 microg m(-3).     

Microwave-assisted extraction of organophosphate flame retardants and plasticizers from indoor dust samples

A procedure for the determination of eight organophosphate flame retardants and plasticizers in dust samples is presented. Microwave-assisted extraction and gas chromatography (GC) with nitrogen-phosphorus detection (NPD) were used for sample preparation and analytes quantification, respectively. Influence of different variables (type and volume of organic solvent, temperature, time, agitation, etc.) on the yield of the extraction step was evaluated. The most important factor was the type of solvent, with the highest efficiencies corresponding to acetone. Under final conditions 10 mL of this solvent were employed. The extraction was carried out at 130 degrees C and satisfactory yields, similar to those obtained with the Soxhlet technique, were achieved. Due to the high content of organic carbon in dust samples, primary acetone extracts had to be subjected to intensive clean-up. Dilution with ultrapure water followed by concentration on a reversed-phase sorbent and further purification using silica, allowed a significant reduction of co-extracted interferences. Application of the developed methodology to indoor dust from private houses showed important concentrations of several organophosphate esters. The highest levels, up to 19 microg/g, corresponded to tris(butoxyethyl) phosphate; moreover, average values of two chlorinated compounds, used as flame retardants and considered as the most concerning species in the group, exceeded the 1 microg/g level.     

Organophosphate esters by GC–MS: An optimized method for aquatic risk assessment

Organophosphate esters used as flame retardants and plasticizers are ubiquitous contaminants in surface waters. Many studies indicate that these compounds are neurotoxicants, endocrine disruptors, and may affect reproduction and development of aquatic organisms. Thus, analytical methods that allow accurate quantification of these contaminants at environmentally relevant concentrations are desirable for risk assessment studies. In this study, a method based on solid phase extraction and gas chromatography coupled to mass spectrometry was developed for determination of organophosphate esters in river water extracts. Multivariate optimization was used to determine the best conditions for injection of larger volumes of sample in a Programmable Temperature Vaporization inlet. Furthermore, the matrix effect on the instrumental response was evaluated and compensated by association of extraction‐blank‐matched calibration and isotopically labeled focus standards. The method quantification limits ranged from 0.009 to 0.11 µg/L, staying below the predicted non‐effect concentration for the aquatic compartment for all analytes, which is a requisite for using in risk assessment studies. The method was applied to freshwater samples collected in rivers from the Sao Paulo State, Brazil, and eight out of the ten target organophosphate esters were quantified, being tris(2‐chloroisopropyl) phosphate and tris(phenyl) phosphate the most frequently detected compounds.     

Yolk‐Shell Porous Microspheres of Calcium Phosphate Prepared by Using Calcium L‐Lactate and Adenosine 5′‐Triphosphate Disodium Salt: Application in Protein/Drug Delivery

A facile and environmentally friendly approach has been developed to prepare yolk‐shell porous microspheres of calcium phosphate by using calcium L ‐lactate pentahydrate (CL) as the calcium source and adenosine 5′‐triphosphate disodium salt (ATP) as the phosphate source through the microwave‐assisted hydrothermal method. The effects of the concentration of CL, the microwave hydrothermal temperature, and the time on the morphology and crystal phase of the product are investigated. The possible formation mechanism of yolk‐shell porous microspheres of calcium phosphate is proposed. Hemoglobin from bovine red cells (Hb) and ibuprofen (IBU) are used to explore the application potential of yolk‐shell porous microspheres of calcium phosphate in protein/drug loading and delivery. The experimental results indicate that the as‐prepared yolk‐shell porous microspheres of calcium phosphate have relatively high protein/drug loading capacity, sustained protein/drug release, favorable pH‐responsive release behavior, and a high biocompatibility in the cytotoxicity test. Therefore, the yolk‐shell porous microspheres of calcium phosphate have promising applications in various biomedical fields such as protein/drug delivery.     

Development of a silica monolith modified with Fe3O4 nano‐particles in centrifugal spin column format for the extraction of phosphorylated compounds

In this study, citrate‐stabilised iron oxide nano‐particles (～16 nm) have been immobilised on commercial silica monolithic centrifugal spin columns (MonoSpin) for the extraction of phosphorylated compounds. Two alternative strategies were adopted involving either direct electrostatic attachment to an aminated MonoSpin (single‐layer method) in the first instance, or the use of a layer‐by‐layer method with poly(diallyldimethylammonium) chloride. Field‐emission scanning electron spectroscopy and energy‐dispersive X‐ray spectroscopy was used for confirming notably higher coverage of nano‐particles using the layer‐by‐layer method (2.49 ± 0.53 wt%) compared with the single‐layer method (0.43 ± 0.30 wt%). The modified monolith was used for the selective separation/extraction of adenosine monophosphate, adenosine diphosphate and adenosine triphosphate with elution using a phosphate buffer. A reversed‐phase liquid chromatographic assay was used for confirming that adenosine, as a non‐phosphorylated control was not retained on the modified MonoSpin devices, whereas recovery of 80% for adenosine monophosphate, 86% for adenosine diphosphate and 82% for adenosine triphosphate was achieved.     

Influence of the properties of modified dextran hydrogel polymer network on the kinetics of the release of prospidin antitumor agent

The influence exerted by the conditions of the synthesis of dextran phosphate hydrogels in the orthophosphoric acid–urea system on their functional composition and swellability in water was studied. The main parameters of the polymer network, namely, the mean molecular mass of segments between cross-linking points, the pore size, and the cross-linking density, were determined. Samples of prospidin immobilized on dextran phosphate hydrogels were prepared, and the kinetics of the cytostatic release into phosphate buffer solution (pH 7.4) was studied in relation to the functional composition and parameters of the polymer network of the support. The prospidin release from dextran phosphate hydrogels is due both to diffusion processes and to breakdown of the polymer network of the hydrogel.     

Analytical methodology for organophosphorus pesticides used in Canada

An overview of analytical methodology for the determination of organophosphate pesticides residues in foods is presented. Sample extraction is carried out with acetone followed by a dichloromethane-hexane partition. The organic extract is purified by automated gel permeation chromatography and analysed by capillary gas chromatography with flame photometric or thermionic detection. Confirmation can be carried out by a variety of chemical derivatization techniques including hydrolysis followed by reaction of the phosphate or phenol moiety, direct alkylation or trifluoracetylation. Thin-layer chromatography with enzyme inhibition detection can be used as a rapid screening technique or to confirm results obtained by gas chromatography. Liquid chromatography has not been used much for the determination of organophosphorus compounds in foods.     

Potential of microemulsion electrokinetic chromatography for the separation of priority endocrine disrupting compounds

This work examines the potential of microemulsion electrokinetic chromatography for the separation of several priority endocrine disrupting compounds (EDCs). The optimised microemulsion system comprised 25 mM phosphate buffer pH 2, 80 mM octane, 900 mM butanol, 200 mM sodium dodecyl sulphate and was further modified with 20% propanol. The use of a low pH buffer resulted in the suppression of electroosmotic flow within the capillary. Reversal of the conventional electrode polarity resulted in faster migration of hydrophobic compounds. Test analytes included the octylphenol, nonylphenol and nonylphenol diethoxylate, which are breakdown products of the alkylphenolic detergents. The synthetic oestrogens diethylstilbestrol and ethynyloestradiol were also included in the separation along with the plastic monomer bisphenol-A. Test analytes were selected due to their reported presence in environmental samples namely industrial and domestic wastewater treatment effluents and sludges. Using the optimised method a separation of six EDCs was achieved within 15 min. The optimised method was then applied to the analysis of a spiked wastewater influent sample with UV detection of all six compounds at 214 nm.     

Effect of organophosphate antioxidant on the thermo-oxidative degradation of a mineral oil

This study shows the synthesis, characterization, and evaluation of the effect of organophosphate antioxidant on the thermo-oxidative degradation of a mineral oil. The organophosphate was synthesized by nucleophilic substitution (S_N2) of hydrogenated cardanol. For this study, were employed thermogravimetry, derivative thermogravimetry, differential scanning calorimetry, and differential thermal analysis techniques. The results showed that organophosphate contributed for thermo-oxidative stability of mineral oil (initial decomposition temperature (IDT) mineral oil: 91.28 °C < IDT mineral oil + organophosphate (1%): 156.42 °C). The organophosphate obtained shows significant thermal stability when compared with other compound of the same class (diphenyl phosphate).     

Paraoxon and parathion hydrolysis by aqueous molybdenocene dichloride (Cp2MoCl2): first reported pesticide hydrolysis by an organometallic complex

We report the first case of an organometallic complex that effectively hydrolyzes the organophosphate pesticides parathion and paraoxon. The complex is the water-soluble compound bis(eta 5-cyclopentadienyl)molybdenum(IV) dichloride (1), which hydrolyzes parathion to produce ethanol and deethyl parathion in a biphasic reaction in D2O. Rate accelerations were 130 and 10(5) at pH 7 and 3, respectively. Paraoxon is readily hydrolyzed by 1 to yield p-nitrophenol and diethyl phosphate with rate accelerations of 2300 and 27 at pH 7 and 3, respectively. Kinetic data for paraoxon hydrolysis by 1 are consistent with a process that involves intermolecular (delta S++ = -49 +/- 10 eu) hydroxide attack on the phosphate triester in which the aquated 1 serves as a coordinated Lewis acid that activates the organophosphate. Interestingly parathion hydrolysis by 1 occurs via nucleophilic attack at the alpha-carbon of the phosphorothioate pesticide that involves C-O bond cleavage. These parathion results represent one of the few cases of this type of unusual hydrolytic chemistry and the first case of an organometallic complex that accelerates organophosphate pesticide hydrolysis.     

Efficient Solid‐Phase Synthesis of pppRNA by Using Product‐Specific Labeling

A novel solid‐phase synthesis and purification strategy for 5′‐triphosphate oligonucleotides by using lipophilic tagging of the triphosphate moiety is reported. This is based on triphosphate synthesis with 5′‐O‐cyclotriphosphate intermediates, whereby a lipophilic tag, such as decylamine, is introduced during the ring‐opening reaction to give a linear gamma‐phosphate‐tagged species. This method enables the highly efficient synthesis of 5′‐triphosphorylated RNA derivatives and their gamma‐phosphate‐substituted analogues and will especially facilitate the advancement of therapeutic approaches that make use of 5′‐triphosphate oligonucleotides as potent activators of the cytosolic immune sensor RIG‐I.     

Recent Advances in Heterogeneous Catalytic Systems Containing Metal Ions for Phosphate Ester Hydrolysis

Organophosphates are a class of organic compounds that are important for living organisms, forming the building blocks for DNA, RNA, and some essential cofactors. Furthermore, non-natural organophosphates are widely used in industrial applications, including as pesticides; in laundry detergents; and, unfortunately, as chemical weapons agents. In some cases, the natural degradation of organophosphates can take thousands of years; this longevity creates problems associated with handling and the storage of waste generated by such phosphate esters, in particular. Efforts to develop new catalysts for the cleavage of phosphate esters have progressed in recent decades, mainly in the area of homogeneous catalysis. In contrast, the development of heterogeneous catalysts for the hydrolysis of organophosphates has not been as prominent. Herein, examples of heterogeneous systems are described and the importance of the development of heterogeneous catalysts applicable to organophosphate hydrolysis is highlighted, shedding light on recent advances related to different solid matrices that have been employed.     

Aluminum phosphinate and phosphates of salen ligands

A new dealkylation reaction between organophosphate esters and Salen aluminum bromide compounds has been used to prepare three new aluminum salen compounds salen((t)Bu)AlOP(O)Ph2 (1) (salen = N,N'-ethylenebis(3,5-di-tert-butylsalicylideneimine)), [(MeOH)Alsalen((t)Bu)[OMePO2(O)]Alsalen((t)Bu)[OMePO2(O)]Alsalen((t)Bu)]Br (2), and [salpen((t)Bu)AlO]2[(BuO)2PO]2 (3) (salpen = N,N'-propylenebis(3,5-di-tert-butylsalicylideneimine)). Compounds 1.MeOH, 2, and 3 were characterized by single-crystal X-ray diffraction. Compound 1 is the first example of a monomeric aluminum Schiff base phosphinate. Compound 2 is a cationic Salen aluminum phosphate, and compound 3 contains an aluminophosphate ring. This work is the first example of the intentional use of an aluminum-based dealkylation reaction to form new compounds.     

Synthesis of 8-vinyladenosine 5′-di- and 5′-triphosphate: evaluation of the diphosphate compound on ribonucleotide reductase

The synthesis of 5′-di- and 5′-triphosphate of 8-vinyladenosine to be tested on ribonucleotide reductases requires the modification of known methods. The phosphate group was introduced by treatment with an in situ generated chlorophosphite. Protection of the 2′,3′ diol with acetyl groups suppressed depurination during acid removal of the phosphotriester protecting groups. The di- and triphosphate compounds were obtained by treatment of the activated adenylic acid with phosphate or pyrophosphate anions followed by removal of the acetate protecting groups. Preliminary studies were conducted on Escherichia coli ribonucleotide reductase and have shown that the diphosphate compound is efficiently reduced.     

Synthesis of methylene- and difluoromethylenephosphonate analogues of uridine-4-phosphate and 3-deazauridine-4-phosphate

Cytidine triphosphate synthetase (CTPS) catalyzes the formation of cytidine triphosphate from glutamine, uridine-5'-triphosphate (UTP), and adenosine-5'-triphosphate. Inhibitors of CTPS are of interest because of their potential as therapeutic agents. One approach to potent enzyme inhibitors is to use analogues of high energy intermediates formed during the reaction. The CTPS reaction proceeds via the high energy intermediate UTP-4-phosphate (UTP-4-P). Four novel analogues of uridine-4-phosphate (U-4-P) and 3-deazauridine-4-phosphate (3-deazaU-4-P) were synthesized in which the labile phosphate ester oxygen was replaced with a methylene and difluoromethylene group. The methylene analogue of U-4-P, compound 1, was prepared by a reaction of the sodium salt of tert-butyl diethylphosphonoacetate with protected, 4-O-activated uridine followed by acetate deprotection and decarboxylation. It was found that this compound undergoes relatively facile dephosphonylation presumably via a metaphosphate intermediate. The difluoromethylene derivative, compound 2, was prepared by electrophilic fluorination of protected 1. This compound was stable and did not undergo dephosphonylation. Synthesis of the methylene analogue of 3-deazaU-4-P, compound 3, was achieved by ribosylation of protected 4-(phosphonomethyl)-2-hydroxypyridine. Electrophilic fluorination was also employed in the preparation of protected 4-(phosphonodifluoromethyl)-2-hydroxypyridine which was used as the key building block in the synthesis of difluoro derivative 4. These compounds represent the first examples of a nucleoside in which the base has been chemically modified with a methylene or difluormethylenephosphonate group.     

Preparation and characterization of an aptamer‐functionalized solid‐phase microextraction fiber and its application in the selective monitoring of adenosine phosphates with liquid chromatography and tandem mass spectrometry

An aptamer with adenosine triphosphate as a ligand was immobilized onto the surface of a porous‐polymer‐coated fiber to obtain an aptamer‐functionalized porous‐polymer‐coated solid‐phase microextraction fiber. The fiber was observed with a crosslinked and porous morphological surface structure. It shows specific selectivity to adenosine triphosphate with a selectivity coefficient of 22.1 compared to the scrambled oligonucleotide functionalized fiber, and the selectivity factors over other analogues and reference compounds were from 6.1 to 77.5. When the fiber‐based solid‐phase microextraction was coupled with liquid chromatography and tandem mass spectrometry, detection limits of 2.7, 29, and 34 μg/L were achieved for adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate, respectively. The spiking recoveries of 77.6–91.9% were achieved for trace adenosine phosphates in human serum sample. Furthermore, the fibers showed high stability and good reusability and could be used over 50 times for the real serum sample pretreatment without remarkable performance reduction.     

The influence of electrolyte concentration on nanofractures fabricated in a 3D-printed microfluidic device by controlled dielectric breakdown

A three-dimensional-printed microfluidic device made of a thermoplastic material was used to study the creation of molecular filters by controlled dielectric breakdown. The device was made from acrylonitrile butadiene styrene by a fused deposition modeling three-dimensional printer and consisted of two V-shaped sample compartments separated by 750 µm of extruded plastic gap. Nanofractures were formed in the thin piece of acrylonitrile butadiene styrene by controlled dielectric breakdown by application voltage of 15–20 kV with the voltage terminated when reaching a defined current threshold. Variation of the size of the nanofractures was achieved by both variation of the current threshold and by variation of the ionic strength of the electrolyte used for breakdown. Electrophoretic transport of two proteins, R-phycoerythrin (RPE; <10 nm in size) and fluorescamine-labeled BSA (f-BSA; 2–4 nm), was used to monitor the size and transport properties of the nanofractures. Using 1 mM phosphate buffer, both RPE and f-BSA passed through the nanofractures when the current threshold was set to 25 µA. However, when the threshold was lowered to 10 µA or lower, RPE was restricted from moving through the nanofractures. When we increased the electrolyte concentration during breakdown from 1 to 10 mM phosphate buffer, BSA passed but RPE was blocked when the threshold was equal to, or lower than, 25 µA. This demonstrates that nanofracture size (pore area) is directly related to the breakdown current threshold but inversely related to the concentration of the electrolyte used for the breakdown process.     

Synthesis of 4-{{[(Isopropyloxy)methylphosphoryloxy]imino}methyl}-1-methylpyridinium Iodide and Its Characterisation

Oximes are used in the therapy of organophosphate poisoning. They form an interaction product with the organophosphate which is claimed to be more toxic than the organophosphate itself. We have synthesized one of these compounds which would be formed by the reaction of pyridine-4-carbaldehyde oxime methiodide with sarin (GB). Thus, reaction of oxime 1 with sarin chloridate ( 2 ), yielded 4-{{[(isopropyloxy)methylphosphoryloxy]-imino}methyl}-1-methylpyridinium iodide ( 4 ) which was characterized by NMR spectroscopy and X-ray crystallography.     

Membrane‐permeable Triphosphate Prodrugs of Nucleoside Analogues

The metabolic conversion of nucleoside analogues into their triphosphates often proceeds insufficiently. Rate‐limitations can be at the mono‐, but also at the di‐ and triphosphorylation steps. We developed a nucleoside triphosphate (NTP) delivery system (TriPPPro‐approach). In this approach, NTPs are masked by two bioreversible units at the γ‐phosphate. Using a procedure involving H‐phosphonate chemistry, a series of derivatives bearing approved, as well as potentially antivirally active, nucleoside analogues was synthesized. The enzyme‐triggered delivery of NTPs was demonstrated by pig liver esterase, in human T‐lymphocyte cell extracts and by a polymerase chain reaction using a prodrug of thymidine triphosphate. The TriPPPro‐compounds of some HIV‐inactive nucleoside analogues showed marked anti‐HIV activity. For cellular uptake studies, a fluorescent TriPPPro‐compound was prepared that delivered the triphosphorylated metabolite to intact CEM cells.