Solid-phase Reactors Research Articles

Determination of Bendiocarb Insecticide by Reverse Flow Injection Analysis Using a Solid-Phase Reactor Containing Micro PbO2, Nano PbO2 and Grafted SiO2 - PbO2 Immobilized

Bendiocarb (BEN) is an acutely toxic carbamate insecticide which used in public places and agriculture, it is also effective against a wide range of nuisance and disease vector insects. A new rapid and sensitive reverse flow injection spectrophotometric procedure coupled with on-line solid-phase reactor is designed in this article for the determination of BEN in its insecticidal formulations and water samples, by using three different solid-phase reactors containing bulk PbO2 (B-SPR), PbO2 nanoparticles (N-SPR) and grafted nanoparticles of SiO2-PbO2 (G-SPR) immobilized on cellulose acetate matrix (CA). This method of oxidative coupling is based on alkaline hydrolysis of the BEN pesticide, and then coupled with N,N dimethyl-p-phenylenediamine sulphate (DMPD) to give a blue color product which measured at λmax 675 nm. It worth to mentioned that under optimal conditions, Beer’s law is obeyed in the range of 1-175 μg mL-1 for B-SPR and 0.25-70 μg mL-1 of BEN for both N-SPR and G-SPR respectively within limit of detection (LOD) of 0.931, 0.234 and 0.210 μg mL-1 for B-SPR N-SPR and G-SPR respectively. The surface methodology of the solid phase was also investigated by using atomic force microscopy.

Determination of Bendiocarb Insecticide by Reverse Flow Injection Analysis Using a Solid-Phase Reactor Containing Micro PbO2, Nano PbO2 and Grafted SiO2 - PbO2 Immobilized

Bendiocarb (BEN) is an acutely toxic carbamate insecticide which used in public places and agriculture, it is also effective against a wide range of nuisance and disease vector insects. A new rapid and sensitive reverse flow injection spectrophotometric procedure coupled with on-line solid-phase reactor is designed in this article for the determination of BEN in its insecticidal formulations and water samples, by using three different solid-phase reactors containing bulk PbO2 (B-SPR), PbO2 nanoparticles (N-SPR) and grafted nanoparticles of SiO2-PbO2 (G-SPR) immobilized on cellulose acetate matrix (CA). This method of oxidative coupling is based on alkaline hydrolysis of the BEN pesticide, and then coupled with N,N dimethyl-p-phenylenediamine sulphate (DMPD) to give a blue color product which measured at λmax 675 nm. It worth to mentioned that under optimal conditions, Beer’s law is obeyed in the range of 1-175 μg mL-1 for B-SPR and 0.25-70 μg mL-1 of BEN for both N-SPR and G-SPR respectively within limit of detection (LOD) of 0.931, 0.234 and 0.210 μg mL-1 for B-SPR N-SPR and G-SPR respectively. The surface methodology of the solid phase was also investigated by using atomic force microscopy.

Treatment of petroleum hydrocarbons contaminated soil by Fenton like oxidation

Experimental tests were carried out in solid phase reactors on a microcosm scale, to removal old petroleum pollution by Fenton like oxidation process. In order to optimize the process, parametric study and statistically designed experiment have been undertaken by considering the amount influence of hydrogen peroxide (H2O2), endogenous and zero-valent iron (Fe) and ethylene diamine tetraacetic acid (EDTA) as chelating agent.The measurement of residual total petroleum hydrocarbons for different H2O2/Fe molar ratios and pH in the vicinity of neutrality highlighted oxidation rates ranging between 29.0 and 39.3%. The Fenton like (FL) oxidation was optimal for H2O2/Fe molar ratio of 15/4. The use EDTA led to result up 72.2% for H2O2/total Fe/EDTA molar ratio of 15/4/4 after 48 h of treatment.The statistical analysis of data by factorial design, has allowed the modeling of Fenton like process performances in the operating domain. It showed that hydrogen peroxide amount, interaction effects of oxidant-catalyst, catalyst-chelating agent, and oxidant-catalyst-chelating agent, were the influential parameters. Moreover, these results suggest that endogenous iron could be used as a source of iron in the presence of the chelating agent to activate FL oxidation. A better accuracy (80.0%) was obtained by statistical analysis for H2O2/endogenous Fe/EDTA molar ratio of 20/1/1.

Reducing and Oxidizing Columns in the Flow Injection Determination of Nitrazepam in Pharmaceutical Formulations

Two flow injection analysis (FIA) systems for determining nitrazepam (NZP) in pharmaceutical formulations using two kinds of solid-phase reactors were developed. The first system involved on-line oxidation of the reagent using a mini column containing PbO2 immobilized on cellulose acetate, while the second one involved on-line reduction of drug using a mini-Jones reductor. Both methods are based on spectrophotometric method involving oxidative coupling reaction to phenothiazine with reduced NZP in the presence of a suitable oxidizing agent to form a green color product measured at 615 or 589 nm for the two methods, respectively. The calibration graphs were linear over the range 0.5 to 45 and 10 to 250 μg/mL with a relative standard deviation less than 3.6% (n = 32) and 2.4% (n = 35) for the two methods. Solid-phase reactors can be applied for the determination of NZP in a FIA with high sensitivity and significant advantages over conventional procedures.

Bioremediation of petroleum-contaminated soil enhanced by aged refuse

In this study, the effect of aged refuse on biodegradation of total petroleum hydrocarbons (TPH), microbial counts, soil ecotoxicity, dehydrogenase activity and microbial community compositions were investigated in solid phase reactors during a 30-week period. The results demonstrate that the removal efficiency of TPH was significantly higher in the soil supplemented with aged refuse than in the soil without aged refuse. After 30 weeks, the removal efficiencies of TPH in soils were 29.3%, 82.1%, 63.7% and 90.2% in the cases of natural attenuation, nutrient addition (with NH4NO3 and K2HPO4), supplement with 20% (w/w, dry weight basis) of aged refuse and the combination of nutrient and aged refuse. Nutrient plus aged refuse made the TPH concentration decrease to below the threshold level of commercial use required for Chinese soil quality for TPH (<3000 mg/kg) in 30 weeks. It was also found that dehydrogenase activity, bacterial counts and degrader abundance in the soil were remarkably enhanced by the addition of aged refuse (20%,w/w). Total organic carbon analysis demonstrates that large amounts of hydrocarbon intermediates occurred in the soil after bioremediation.

The impact of DO and salinity on microbial community in poly(butylene succinate) denitrification reactors for recirculating aquaculture system wastewater treatment

The interactions between environmental factors and bacterial community shift in solid-phase denitrification are crucial for optimum operation of a reactor and to achieve maximum treatment efficiency. In this study, Illumina high-throughput sequencing was applied to reveal the effects of different operational conditions on bacterial community distribution of three continuous operated poly(butylene succinate) biological denitrification reactors used for recirculating aquaculture system (RAS) wastewater treatment. The results indicated that salinity decreased OTU numbers and diversity while dissolved oxygen (DO) had no obvious influence on OTU numbers. Significant microbial community composition differences were observed among and between three denitrification reactors under varied operation conditions. This result was also demonstrated by cluster analysis (CA) and detrended correspondence analysis (DCA). Hierarchical clustering and redundancy analysis (RDA) was performed to test the relationship between environmental factors and bacterial community compositions and result indicated that salinity, DO and hydraulic retention time (HRT) were the three key factors in microbial community formation. Besides, Simplicispira was detected under all operational conditions, which worth drawing more attention for nitrate removal. Moreover, the abundance of nosZ gene and 16S rRNA were analyzed by real-time PCR, which suggested that salinity decreased the proportion of denitrifiers among whole bacterial community while DO had little influence on marine reactors. This study provides an overview of microbial community shift dynamics in solid-phase denitrification reactors when operation parameters changed and proved the feasibility to apply interval aeration for denitrification process based on microbial level, which may shed light on improving the performance of RAS treatment units.

Immobilization of Distinctly Capped CdTe Quantum Dots onto Porous Aminated Solid Supports

Immobilization of quantum dots (QDs) onto solid supports could improve their applicability in the development of sensing platforms and solid-phase reactors by allowing the implementation of reusable surfaces and the execution of repetitive procedures. As the reactivity of QDs relies mostly on their surface chemistry, immobilization could also limit the disruption of solution stability that could prevent stable measurements. Herein, distinct strategies to immobilize QDs onto porous aminated supports, such as physical adsorption and the establishment of chemical linking, were evaluated. This work explores the influence of QD capping and size, concentration, pH, and contact time between the support and the QDs. Maximum QD retention was obtained for physical adsorption assays. Freundlich and Langmuir isotherms were used to analyze the equilibrium data. Gibbs free energy, enthalpy, and entropy were calculated and the stability of immobilized QDs was confirmed.

FLOW INJECTION DETERMINATION OF SALBUTAMOL USING A SOLID-PHASE REACTOR CONTAINING LEAD (IV) DIOXIDE IMMOBILIZED

A simple, sensitive and fast continuous flow injection system with spectrophotometric detection was proposed for the determination of salbutamol sulphate (SAL) in pharmaceutical formulations using a solid-phase reactor containing PbO2 immobilized in a polymeric matrix. The method was based on oxidation of the reagent (N, N-dimethyl-p-phenelynediamine) with PbO2 producing dimethylbenzoquinone diimine, which is then coupled with SAL in alkaline medium. The blue colored product was monitored at 640 nm. The calibration graph was linear over the range 0.5 to 60 µg mL -1 with a relative standard deviation less than 3.8% (n=33) and sample throughput 60 samples per hour. Solid-phase reactors can be applied to the determination of SAL in a flow injection system with high sensitivity and significant advantages over conventional procedures. Keyword: Reverse-flow injection, Salbutamol sulphate, spectrophotometric.

ChemInform Abstract: The Case for the Use of Unrefined Natural Reagents in Analytical Chemistry: A Green Chemical Perspective

AbstractReview: 86 refs.

Online Hyphenation of Multimodal Microsolid Phase Extraction Involving Renewable Molecularly Imprinted and Reversed-Phase Sorbents to Liquid Chromatography for Automatic Multiresidue Assays

Molecular imprinted polymers (MIP) have recently drawn much attention as highly selective solid-phase materials for handling and isolation of organic pollutants in complex matrices. Because of the impaired retention capacity for target species as compared with reversed-phase materials and irreversible sorption of interfering compounds by nonspecific interactions, the implementation of MIP-based solid-phase reactors as permanent components in automatic flow-systems has not received widespread acceptance as of yet. To tackle this limitation, a dynamic microscale solid phase extraction (microSPE) method capitalizing on the principle of programmable flow and bead injection analysis is herein proposed as a front end to liquid chromatography for multiresidue assays. It involves in-line renewable tandem-SPE microcolumns composed of molecularly imprinted polymers and copolymeric N-vinylpyrrolidone/divinylbenzene beads integrated within the flow network for multimodal extraction. Chlorotriazine herbicides (namely, atrazine, simazine, propazine) and principal degradation products thereof (namely, deisopropylatrazine and deethylatrazine) were selected as model analytes. The effect of several parameters, including the dimensions and chemical composition of the sorptive microcolumns, the sample loading flow rate, the type and volume of eluent, the interface with liquid chromatography (LC), and the disposable nature of the column on the analytical performance were investigated in detail. The assembled flow setup features appropriate removal of interfering organic species via solvent switch with toluene, the circumvention of analyte band-broadening in LC by in-line merging of the eluate with a water stream, and the transfer of the overall analyte-containing eluate into the LC. For 10-mL sample percolation, limits of detection (S/N = 3) of 0.02-0.04 ng mL(-1), limits of quantification (S/N = 10) of 0.07-0.12 ng mL(-1), absolute recovery percentages >79%, precision within 1.4-5.5%, and enrichment factors of 46-49 were obtained for the suite of assayed herbicides. The multimodal microSPE method with renewable beads was applied to the multiresidue determination of the target herbicides in crude soil extracts and untreated environmental waters at concentration levels below those endorsed by the current EU Water Framework Directives following appropriate sample preconcentration and/or cleanup.

The case for the use of unrefined natural reagents in analytical chemistry—A green chemical perspective

An important part of the Green Chemistry philosophy is the need to develop and adopt green analytical techniques and procedures. These include the reduction of reagent and solvent usage, the minimization of solid, liquid and gaseous materials produced by analytical processes, the replacement of reagents and solvents of high occupational or environmental toxicity with much more innocuous materials, and the reduction of energy use in analytical processes. One aspect that has received little attention in this context is the use of unrefined natural reagents derived from plant and animal tissues or microbial cells. Crude plant extracts may contain chemical compounds that enable their use as indicators in acid–base or redox titrations, or as chromogenic or fluorogenic agents. Enzymes extracted from plants may be used directly in soluble form, or incorporated in biosensors or solid phase reactors, for analytical measurements, or as a means of removing interferences or performing speciation studies. The use of natural reagents in conjunction with a flow injection system can confer a number of advantages. The enhanced kinetic control that flow analysis offers may assist in avoiding undesirable side reactions that would otherwise occur using unpurified reagents. The lifetime of natural reagents may be prolonged when used in a flow analysis system because their exposure to light or air can be controlled. Any changes in response that do occur may be readily corrected by regular standard checking and recalibration. This article reviews the use of natural reagents with an emphasis on flow-based analytical systems, and makes the case for further research in this latent area of green analytical chemistry.

A Comparative Study of AgX (X = Cl−, Br−, I− and N3−) Solid-Phase Reactors for Flow-Injection Determination of Cyanide in Electroplating Wastewater

In this study, a rapid flow injection-flame atomic absorption spectrometry for cyanide detection was developed. Different AgX (where X is Cl(-), Br(-), I(-) and N(3)(-)) solid-phase reagents (SPR) were tested for indirect determination of cyanide. In a single-line FIA system, the cyanide was allowed to react with AgX SPR, which in turn changed Ag ions in AgX to silver cyanide complexes in a sodium hydroxide carrier stream. The eluent containing the analyte as silver cyanide complexes was measured by FAAS. The calibration curve was linear up to 30 mg l(-1) with a detection limit of 0.05 mg l(-1) for cyanides. The sampling rate and the relative standard deviation were <1.09% and >200 h(-1), respectively. The method was applied to the determination of cyanide in electroplating wastewater.

Bioremediation of Diethylhexyl Phthalate Contaminated Soil: A Feasibility Study in Slurry- and Solid-Phase Reactors

The aim of the research was to verify the possibility of applying bioremediation as a treatment strategy on a poly(vinyl chloride) (PVC) manufacturing site in the north of Italy contaminated by diethylhexyl phthalate (DEHP) at a concentration of 5.51 mg/g of dry soil. Biodegradation kinetic experiments with DEHP contaminated soil samples were performed in both slurry- and solid-phase systems. The slurry-phase results showed that the cultural conditions, such as N and P concentrations and the addition of a selected DEHP degrading strain, increased the natural DEHP degradation rate. On the basis of these data, experiments to simulate bioventing on contaminated soil columns were performed. The DEHP concentration reached 0.63 mg/g of dry soil in 76 days (89% of degradation). A kinetic equation was developed to fit the experimental data and to predict the concentration of contaminant after treatment. The data obtained are encouraging for a future in situ application of the bioventing technology.

Solid Phase Treatment of an Aged Soil Contaminated by Polycyclic Aromatic Hydrocarbons

Laboratory scale tests were carried out in order to evaluate the removal efficiency of polyaromatic hydrocarbons (PAHs) during the different biological treatments of a Manufacturing Gas Plant site aged soil, heavily contaminated by high molecular weight compounds. Biodegradation studies were carried out at nearly 25°C in solid phase reactors. Three tests were performed, over a period of 100 days for each test. In the first test (P1-bioaugmentated), soil was mixed with wood chips and urea at the start of the treatment and after six weeks from the beginning of the test was also periodically inoculated (at 42, 54, 69, 82, and 96 days) with selected consortia of autochthonous PAH-degrading bacteria. The second test (P2-biostimulated) was performed similarly to the previous one, but without any inoculations. In the third test (P3-control) only soil was introduced. All systems were aerated daily and humidified at the occurrence. PAH concentration, total cultivable heterotrophs, PAH-degrading bacteria, mycetes, pH, ATP concentration, and enzymatic activities were monitored every two weeks during the treatments. Tests showed that nearly 50% of light (three rings) PAHs, 35% of benzo-PAHs and 40% of the total PAHs could be removed in the reactor P2 following 100 days of treatment. Lower removal efficiency could be observed for light PAHs (28%) in the inoculated reactor (P1) at the end of the treatment; comparable abatements were obtained for benzo- and total PAHs. In the reactor P3 (control), the concentration of all polyaromatic hydrocarbons was nearly always constant, suggesting that the physical losses were negligible during the solid phase treatments. Therefore the C to N ratio balance resulted to be the key factor in promoting the biodegradation process of all PAHs.

Solid-phase iodine as an oxidant in flow injection analysis: determination of ascorbic acid in pharmaceuticals and foods by background correction

A flow injection analysis (FIA)-background correction method comprising two solid-phase reactors and spectrophotometry for determination of ascorbic acid (AsA) is proposed. A polyethylene mini-column filled with solid iodine (30% m/m suspended on silica gel beads), reactor 1, and other column filled only with silica gel, reactor 2, which are then incorporated in a flow system so that solid iodine reagent in reactor 1 is affected as the sample passes through the column. The sample blank is produced by the oxidation of the AsA by iodine to form dehydroascorbic acid, insensitive to ultraviolet at 267 nm. AsA in samples is determined after injected in reactor 2; the difference in two analytical signal observed is related to amount of AsA. The linear range of the system is up to 50 μg ml −1 with a detection limit of 0.08 μg ml −1, R.S.D. of better than 1.0% and sampling frequency of 110 sample h −1. The method is successfully applied to the determination of AsA in pharmaceuticals and foods.

Kinetic control of reagent dissolution for the flow injection determination of iron at trace levels.

A novel methodology for the determination of iron at the ppb level by spectrophotometric flow injection analysis is described. The method is based on the control of the flow dissolution of the colorimetric reagent 1,10-phenanthroline. This is achieved by means of the minimization of the area of contact between the carrier and the solid reagent, thus allowing the use of the fairly soluble organic compound without affecting the reactor lifetime. The reagent is melted inside an acrylic column (3.0 x 0.5 cm id) in such a way that a hollow space is left in the center after cooling. This new design improves some aspects of the performance of the classical solid-phase reactors as no problems related to the increase in the backpressure of the system are evidenced. Furthermore, the total reagent loading of the column is increased as no inert support is needed. A comparison between the performance of this novel methodology and that of the conventional packed reactor was performed and several advantages were observed: the use of higher flow rates, an increase in the reactor lifetime and a decrease in reagent consumption. A mathematical model to fit the concentration profiles of the dissolved reagent as a function of the residence time of the sample within the column is presented. The application of this strategy to the determination of Fe(II) improves the figures of merit in comparison to those obtained with a single-line homogeneous system: the limit of detection is 2 microg Fe L(-1) (3s) and the sensitivity is similar to that of the batch procedure. Results obtained for the determination of iron in natural waters are also presented.

Solid-phase reactors in sequential injection analysis. Determination of manganese (II) in tap water and effluent streams using a solid-phase lead(IV) dioxide reactor in a sequential injection system.

The determination of manganese(II) in tap water and effluent streams, using a solid-phase reactor incorporated into a sequential injection system was investigated. Mn2+-ions in samples injected into a carrier stream, were oxidised by solid lead(IV) dioxide suspended on silica gel beads to form MnO4- -ions which were detected spectrophotometrically at 526 nm. The linear range of the system is from 1 to 7 mg L(-1) with a detection limit of 0.62 mg L(-1). The proposed system is suitable for the determination of manganese(II) in tap and effluent streams at a rate of approximately 50 samples per hour with a relative standard deviation of better than 3%. Statistical comparison between the proposed sequential injection system and a standard ICP method revealed that there is no significant difference between the two methods at the 95% confidence level for effluent streams and at 99.9% for tap water.

Dual analyte flow injection fluorescence immunoassays using thiophilic gel reactors and synchronous scanning detection.

Heterogeneous fluorescence immunoassays have been automated using flow injection manifolds incorporating thiophilic gel solid phase reactors to separate antibody-bound and unbound analyte molecules. Antibody elution is achieved by changes in ionic strength, thus allowing the use of pH sensitive fluorescent labels. This facilitates the development of dual analyte systems, in which two competitive immunoassays with separate labels are monitored in parallel. Detection of the fluorophores by high speed synchronous fluorescence scanning while the flow is briefly stopped utilises either one synchronous interval which detects both fluorophores, or two separate scans at different wavelength intervals, one for each fluorophore. Simultaneous analyses of serum albumin and transferrin exemplify these novel approaches. Spectroscopic interferences are very small, analyte recoveries are close to 100%, with a relative standard deviation of 5-6% and a sampling rate of 20 h-1.

Use of calcium peroxide to provide oxygen for contaminant biodegradation in a saturated soil

Laboratory studies were conducted in solid-phase reactors on a silty loam contaminated with bis-(2-ethylhexyl) phthalate (BEHP) to determine the conditions under which calcium peroxide (CaO 2) would promote the aerobic bioremediation of water-saturated soil. Closed 500 ml solid-phase reactors were operated to determine whether CaO 2 stimulated the biodegradation of BEHP in saturated soil. Ex situ bioremediation conditions were then simulated by mixing water-saturated soil for 6 h before placing the soil in three vented, 2 l solid-phase reactors for 50 days. Biodegradation of BEHP was quantified using four different measurements of microbial activity: (1) oxygen concentrations in the reactor gas; (2) bacterial colony-forming units (CFU); (3) fungal CFU; and (4) 2-( p-iodophenyl)-3-( p-nitrophenyl)-5-phenyl tetrazolium chloride dehydrogenase activity (INT-DHA). CaO 2 released molecular O 2, which retarded dewatering but substantially enhanced BEHP biodegradation. After 20 days, BEHP in the amended reactor was reduced from 20.3 to roughly 5 g kg −1 vs. 15 g kg −1 in the reactor without CaO 2. Bacterial growth was favored over fungal growth at elevated moisture and BEHP levels.

Determination of cyanide by a flow injection analysis-atomic absorption spectrometric method.

A new flow injection analysis (FIA) procedure is proposed for the indirect atomic absorption spectrometric determination of cyanide. The FIA manifold is based on the insertion of the sample into a distilled water carrier, then the sample flows through a solid-phase reactor filled with silver iodide entrapped in polymeric resin beads. The calibration graph is linear over the range 0.2-6.0 mg l-1 of cyanide (correlation coefficient 0.9974), the detection limit is 0.1 mg l-1, the sample throughput is 193 h-1 and the RSD is 0.8%. The method is simple, quick and more selective than other published FIA procedures. The reproducibility obtained by using different solid-phase reactors and solutions is in the range 2.2-3.1% (RSD). The method was applied to the determination of cyanide in commercial samples such as pharmaceutical formulations and industrial electrolytic baths.