Solid phase extraction of penicillins from milk by using sacrificial silica beads as a support for a molecular imprint

We have prepared molecularly imprinted beads with molecular recognition capability for target molecules containing the penicillanic acid substructure. They were prepared by (a) grafting mesoporous silica beads with 6-aminopenicillanic acid as the mimic template, (b) filling the pores with a polymerized mixture of methacrylic acid and trimethylolpropane trimethacrylate, and (c) removing the silica support with ammonium fluoride. The resulting imprinted beads showed good molecular recognition capability for various penicillanic species, while antibiotics such as cephalosporins or chloramphenicol were poorly recognized. The imprinted beads were used to extract penicillin V, nafcillin, oxacillin, cloxacillin and dicloxacillin from skimmed and deproteinized milk in the concentration range of 5–100 μg·L⁻¹. The extracts were then analyzed by micellar electrokinetic chromatography by applying reverse polarity staking as an in-capillary preconcentration step, and this resulted in a fast and affordable method within the MRL levels, characterized by minimal pretreatment steps and recoveries of 64–90 %.

Penicillanic acid-imprinted beads prepared in preformed porous silica by an imprinting &; etching approach show selectivity towards β-lactams antibiotics. Molecularly imprinted solid phase extraction/micellar electrokinetic chromatography coupled with in-capillary preconcentration resulted in a fast and affordable method for penicillins in milk at MRL levels.

     

Solid phase extraction of food contaminants using molecular imprinted polymers

Food contamination from natural or anthropogenic sources poses severe risks to human health. It is now largely accepted that continuous exposure to low doses of toxic chemicals can be related to several chronic diseases, including some type of cancer and serious hormonal dysfunctions.Contemporary analytical methods have the sensitivity required for contamination detection and quantification, but direct application of these methods on food samples can be rarely performed. In fact, the matrix introduces severe disturbances, and analysis can be performed only after some clean-up and preconcentration steps. Current sample pre-treatment methods, mostly based on the solid phase extraction technique, are very fast and inexpensive but show a lack of selectivity, while methods based on immunoaffinity extraction are very selective but expensive and not suitable for harsh environments. Thus, inexpensive, rapid and selective clean-up methods, relaying on “intelligent” materials are needed. Recent years have seen a significant increase of the “molecularly imprinted solid phase extraction” (MISPE) technique in the food contaminant analysis. In fact, this technique seems to be particularly suitable for extractive applications where analyte selectivity in the presence of very complex and structured matrices represents the main problem. In this review, several applications of MISPE in food contamination analysis will be discussed, with particular emphasis on the extraction of pesticides, drugs residua, mycotoxins and environmental contaminants.     

Solid phase extraction of petroleum carboxylic acids using a functionalized alumina as stationary phase

Petroleum essentially consists of a mixture of organic compounds, mainly containing carbon and hydrogen, and, in minor quantities, compounds with nitrogen, sulphur, and oxygen. Some of these compounds, such as naphthenic acids, can cause corrosion in pipes and equipment used in processing plants. Considering that the methods of separation or clean up the target compounds in low concentrations and in complex matrix use large amounts of solvents or stationary phases, is necessary to study new methodologies that consume smaller amounts of solvent and stationary phases to identify the acid components present in complex matrix, such as crude oil samples. The proposed study aimed to recover acid compounds using the solid phase extraction method, employing different types of commercial stationary ion exchange phases (SAX and NH(2)) and new phase alumina functionalized with 1,4-bis(n-propyl)diazoniabicyclo[2.2.2]octane chloride silsesquioxane (Dab-Al(2)O(3)), synthesized in this work. Carboxylic acids were used as standard mixture in the solid phase extraction for further calculation of recovery yield. Then, the real sample (petroleum) was fractionated into saturates, aromatics, resins, and asphaltenes, and the resin fraction of petroleum (B1) was eluted through stationary ion exchange phases. The stationary phase synthesized in this work showed an efficiency of ion exchange comparable to that of the commercial stationary phases.     

Solid phase extraction of lactic acid from fermentation broth by anion-exchangeable silica confined ionic liquids

Three anion-exchangeable, silica-confined ionic liquids were synthesized for solid phase extraction of lactic acid from fermentation broth, followed by high-performance liquid chromatography coupled to ultraviolet detection. By comparing the adsorption isotherms of lactic acid on different silica-confined ionic liquids, interactions between the lactic acid and sorbents were investigated. The adsorbed amounts were then fitted into different adsorption isotherm equations; finally, the Langmuir equation was selected. Then the imidazolium silica with the highest adsorption capacity of lactic acid was packed into a cartridge for solid phase extraction. The loading volume of the cartridge was optimized by the Langmuir equation and geometry. After washing with distilled water and eluting with 0.25 mol L⁻¹ of an HCl solution, the lactic acid was separated from interference with a recovery yield of 91.9%. Furthermore, this kind of anion-exchangeable material exhibited potential for industrial applications and separation of other anionic bioactive compounds.     

Solid phase extraction using silica gel functionalized with Sulfasalazine for preconcentration of uranium(VI) ions from water samples

Silica gel surface was chemically functionalized by reaction the silanol from the silica surface with 3-chloropropyltrimethoxysilane followed by reaction with Sulfasalazine. This new sorbent has been used for the preconcentration of low levels of U(VI) ions from an aqueous phase. Parameters involved in extraction efficiency such as pH, weight of the sorbent, volume of sample and eluent were optimized in batch and column methods prior to determination by spectrophotometry using arsenazo(III) reagent. The results showed that U(VI) ions can be sorbed at pH range of 5.0–6.0 in a minicolumn and quantitative recovery of U(VI) (>98.0?±?1.6%) was achieved by stripping with 2.5 mL of 0.1 mol L^?1 HCl. The sorption capacity of the functionalized silica gel was 1.15 mmol g^?1 of U(VI). A linear calibration graph was obtained over the concentration range of 0.02–27.0 μg mL^?1 with a limit of detection of 1 μg L^?1 in treatment with 1000 mL of the U(VI) solution in which the preconcentration factor was as high as 400. The method was employed to the preconcentration of U(VI) ions from spiked ground water and synthetic sea water samples.     

Solid phase extraction and preconcentration of some metal ions using Schiff base immobilised silica gel followed by ICP-OES

ABSTRACT

In this study, a simple and efficient solid phase extraction procedure was developed for simultaneous separation and preconcentration of Ba, Cd, Co, Cu, Mn and Ni. The methodology was based on preconcentration of the target analytes on N,N’-bis(4-methoxysalicylidene)-1,3-propanediamine modified silica gel prior to inductively coupled plasma optic emission spectrometry detection. The experimental conditions were as follows: pH of sample 5.00; sample and eluent flow rates 3 mL min^?1; sample volume 25 mL; eluent 0.5 mol L^?1 HNO₃; eluent volume 3.0 mL. Preconcentration factor was achieved as 33.3 for Ba, Co, Mn; 83.3 for Cd, Ni; 166.7 for Cu. Limits of detection were found as 0.33, 0.26, 0.27, 0.36, 0.27 and 0.19 µg L^?1 for Ba, Cd, Co, Cu, Mn and Ni, respectively. The relative standard deviations of 2.6–3.8% were obtained via nine parallel analyses. The suggested procedure was successfully validated by the analysis of TMDA-53.3 Lake Ontario water and ERM-CA022a soft drinking water certified reference materials and applied to various natural water samples.     

Solid phase extraction of ultra-trace amounts of Ag+ by using octadecyl silica membrane disks modified with a new fulvalen derivative.

A simple method for the rapid extraction and determination of ultra-trace amounts of Ag+ ions using octadecyl-bonded silica membrane disks modified with a recently synthesized fulvalen (tetramethyltetrathiafulvalen) (TMTTF) and graphite furnace atomic absorption spectrometry is presented. The extraction efficiency and influence of the flow rate, pH, nature of the counter ion and type and the least amount of eluent for the stripping of Ag+ from disks and breakthrough volume were evaluated. The maximum capacity of the membrane disks modified by 5 mg of TMTTF used was found to be 482 +/- 6 micrograms Ag+. The detection limit of the proposed method is 1.0 ng/dm3. The method was applied to the recovery of Ag+ ions from different synthetic and water samples.     

Solid phase ligand-less extraction of cadmium(II) using a silica gel modified with an amino-functionalized ionic liquid

A method was developed for the determination of cadmium(II) by ligand-less solid phase extraction that is based on the direct retention of Cd(II) in a mini-column filled with a silica gel modified with an amino-functionalized ionic liquid. The effects of pH, sample volume and its flow rate, eluent concentration and its volume, the flow rate of eluent, and of potential interferences on extraction and desorption were optimized. Following its determination by electrothermal atomic absorption spectrometry, the detection limit for Cd(II) is 8.9 ng L^?1, and the relative standard deviation is 2.3 % (at 1.0 ng mL^?1; for n?=?5). The method was applied to the analysis of Cd(II) in a certified reference material (laver; GBW10023), and the recoveries ranged from 97.0 to104.0 %

Solid phase extraction of metal ions using carbon nanotubes

The sorption behaviour of carbon nanotubes (CNTs) toward some divalent metal ions such as Cu(II), Co(II), Ni(II), Zn(II), Pb(II), Mn(II) and Cd(II) has been investigated systematically. The affinity order of the metal ions towards CNTs at pH in the range of 7.0-9.0 was: Cu(II) > Pb(II) > Zn(II) > Co(II) > Ni(II) > Cd(II) > Mn(II). The experimental parameters for preconcentration of copper, which exhibits the highest affinity towards carbon nanotubes, on a microcolumn packed with CNTs prior to its determination by flame atomic absorption spectrometry have been investigated. Copper can be quantitatively retained at pH 8.2 from sample volume up to 150 mL and then eluted completely with 0.1 mol L^− 1 HNO₃. The limit of detection limit for Cu(II) determination with FAAS detection was 2.1 μg L^− 1, and the RSD was 3.5% at the 50 μg L^− 1 level. Under the optimal conditions for copper enrichment also Zn(II), Pb(II) and Ni(II) could be quantitatively preconcentrated from water samples. The method was validated using a certified reference materials BCR-610 and SRM 1640.     

Solid phase extraction of Pb(II) in water samples using a new hybrid inorganic-organic mesoporous silica prior to its determination by FAAS

A mesoporous silica has been chemically modified with 5-mercapto-1-methyltetrazole. The newly synthesized material was characterized by powder X-ray diffraction, N₂ adsorption, FT-IR, ¹³C-NMR spectroscopy and elemental analysis, and used to preconcentrate Pb(II) from aqueous solutions. The effect of several variables on the adsorption capacity (i.e. stirring time, pH, interfering ions, presence of other heavy metals in the medium, etc.) has been studied using batch and column techniques. The adsorption capacity of the material followed the order: Pb(II) >> Cu(II) > Cd(II) >>Mn(II) > Ni(II) > Co(II). In column experiments a pre-concentration factor of 200 was obtained for Pb(II). Spiked tap water, mineral water and river water were used for the preconcentration and determination of Pb(II) by flame atomic absorption spectrometry, and a 101–103% recovery was obtained. The limit of detection and quantification values of the method were found to be 2.22·10^?6 mM and 8.20·10^?6 mM, respectively. The relative standard deviation for four preconcentration experiments was found to be ≤9% in all cases.     

Selective solid-phase extraction of dibutyl phthalate from soybean milk using molecular imprinted polymers

An analysis method is reported for dibutyl phthalate and related compounds with high selectivity and sensitivity by using the selective molecularly imprinted solid-phase extraction (MISPE) technique. In this report, dibutyl phthalate (DBP) is employed as the template molecule, and the molecularly imprinted polymers (MIPs) are synthesized through the bulk polymerization of methacrylic acid (MAA). The Scatchard plot suggests that the template-polymer system has two-site binding behavior with the dissociation constants of 0.5187 and 0.01898 mmol L⁻¹, respectively. The rebinding test, based on the MISPE column technique, shows the recoveries of soybean milk samples spiked with 5 phthalates are in the range of 75.8-107.5% with the relative standard deviations of 1.80-10.08%, indicating the feasibility of the prepared MIPs for phthalates extraction. Finally, the method is used to analyze the trace level of phthalates in commercial soybean milk.     

Simultaneous determination of paracetamol and caffeine by flow injection-solid phase spectrometry using C18 silica gel as a sensing support.

A continuous and simple UV-photometric flow-through biparameter-sensing device has been developed for the simultaneous determination of paracetamol and caffeine at 275 nm. The sensor is based on temporary sequentiation in the arrival of the analytes to the sensing zone by on-line separation using C18 bonded phase beads (the same as that used in the sensing zone) placed into a minicolumn just before the flow cell. The sample containing these compounds is injected into the carrier solution; paracetamol is determined first because it passes through the minicolumn, while caffeine is strongly retained in it. Then, caffeine is conveniently eluted from the precolumn and develops its transitory signal. Using 200 microl of a sample and deionized water as a carrier, the analytical signal showed a very good linearity in the ranges of 10-160 microg ml(-1) and 3.5-50 microg ml(-1) with detection limits of 0.75 and 0.56 microg ml(-1) for paracetamol and caffeine, respectively. If deionized water with the pH adjusted at 12 was used as a carrier solution, these parameters were 25-400 and 4-55 microg ml(-1) with 2.0 and 0.50 microg ml(-1) as the detection limits, respectively. The biparameter optosensor was satisfactorily applied to the simultaneous determination of these two analytes in pharmaceuticals.     

Ionic imprinted polymer for nickel recognition by using the bi-functionalized 5-vinyl-8-hydroxyquinoline as a monomer: Application as a new solid phase extraction support

A new ionic imprinted polymer (IIP) for Ni(II) recognition/pre-concentration was prepared via precipitation polymerization using 2-(diethylamino) ethyl methacrylate (DEM) and divinylbenzene (DVB) as a crosslinking agent in the presence of nickel(II) and 5-vynil-8-hydroxyquinoline (5-VHQ) as a bi-functionalized ligand. An important increase on the selectivity of the synthesised IIP for nickel(II) ions was obtained when comparing to the use of 8-hydroxyquinoline (8-HQ) as a ligand. The synthesised IIP was used as a new support for solid phase extraction (SPE) of nickel(II) from seawater before inductively coupled plasma optical emission spectrometry (ICP-OES) detection. Variables affecting the SPE process, such as pH, load and elution flow rates, and concentration and volume of the eluting solution, were fully evaluated. The optimised procedure consists of a sample loading (100 mL of seawater at a pH of 9.0 ± 0.1) through IIP-SPE cartridges containing 300 mg of the synthesised IIP at a flow rate of 3.0 mL min^{− 1}. Elution was performed by passing 2.5 mL of 2.0 M nitric acid at a flow rate of 1.5 mL min^{− 1}, which gave a pre-concentration factor of 40. The limit of detection (LOD) of the method was 0.26 µg L^{− 1}, while the relative standard deviation (RSD) for eleven replicated measurements was 3%. Accuracy of the method was assessed by analyzing SLEW-3 (estuarine water) and TM-23.3 (lake water) certified reference materials. In addition to the selectivity of the synthesised material for nickel(II) ions against other transition metal ions and major alkaline and alkaline-earth metals (Na⁺, K⁺, Mg²⁺ and Ca²⁺) in seawater, it can be stated that the salt matrix is efficiently removed by using the proposed IIP-SPE procedure.     

Fast extraction of amphenicols residues from raw milk using novel fabric phase sorptive extraction followed by high-performance liquid chromatography-diode array detection

A simple, sensitive, reliable, and fast analytical method was developed for the simultaneous determination of amphenicols residues in raw milk by combining fabric phase sorptive extraction (FPSE) and high-performance liquid chromatography-diode array detection. FPSE, a new generation green sample preparation technique, efficiently incorporates the advanced and tunable material properties of sol–gel derived microextraction sorbents with the rich surface chemistry of a cellulose fabric substrate, resulting in a flexible, highly sensitive, and fast microextraction device capable of extracting target analytes directly from complicated sample matrices. Due to the strong chemical bonding between the sol–gel sorbent and substrate, the microextraction device demonstrates a very high chemical and solvent stability. Therefore, any organic solvent/solvent mixture can be used as the eluent/back-extraction solvent.     

Solid phase versus solvent extraction of pesticides from water

The average recovery for 12 pesticides spiked into 100 ml of water at 0.1 ppb was 90% when cartridges containing 100 mg of C-18 bonded porous silica were used for adsorption. Flow rates of up to 200 bed volumes per minute were employed for the adsorption step. Quantitative desorption of the pesticides was accomplished with less than 100l of solvent, thus eliminating the need for a solvent reduction step. The pesticides from samples of surface waters were adsorbed onto C-18 bonded porous silica at the sampling site and the cartridges containing the bonded phase were returned to the laboratory for elution and analysis. The analytical results obtained from use of this procedure agreed with those obtained for duplicate samples of the water that were processed in the laboratory using standard solvent extraction procedures.     

Magnetic solid phase extraction based on phenyl silica adsorbent for the determination of tetracyclines in milk samples by capillary electrophoresis

A magnetic solid phase extraction method coupled to capillary electrophoresis is proposed for the determination of tetracycline, oxytetracycline, chlortetracycline and doxycycline in milk samples. Five different magnetic phenyl silica adsorbents covered with magnetite were synthesized by varying the molar ratio of phenyltrimethylsilane and tetramethylorthosilicate; these adsorbents were evaluated in terms of their pH and degree of hydrophobicity for tetracycline retention. The optimal, selected combination of conditions was a pH of 10.0 and a magnetic sorbent ratio of 4:1; under these conditions, the retention capacity ranged from 99.7% to 101.2% for the four tetracyclines analyzed. The elution conditions and initial sample volume of the proposed extraction method were also optimized, and the best results were obtained with 1×10(-3) M acetic acid in methanol as eluent and a 200 ml of sample volume. Under optimal conditions, average recoveries ranged from 94.2% to 99.8% and the limits of detection ranged from 2 to 9 μg l(-1) for the four tetracyclines. After the proposed method was optimized and validated, 25 milk samples of different brands were analyzed, oxytetracycline residues were detected in five samples, in concentrations ranging from 98 to 213 μg l(-1). Subsequent analysis of positive samples by SPE-CE and magnetic solid phase extraction-HPLC revealed than no significant differences were found from results obtained by the proposed methodology. Thus, the developed magnetic extraction is a robust pre-concentration technique that can be coupled to other analytical methods for the quantitative determination of tetracyclines.     

Solid phase extraction of uranium and thorium on octadecyl bonded silica modified with Cyanex 302 from aqueous solutions

A simple and reliable method for rapid extraction and determination of uranium and thorium using octadecyl-bonded silica modified with Cyanex 302 is presented. Extraction efficiency and the influence of various parameters such as aqueous phase pH, flow rate of sample solution and amount of extractant has been investigated. The study showed that the extraction of uranium and thorium increase with increasing pH value and was found to be quantitative at pH 6; and the retention of ions was not affected significantly by the flow rate of sample solution. The extraction percent were found to be 89.55 and 86.27 % for uranium and thorium, respectively. The maximal capacity of the cartridges modified by 30 mg of Cyanex 302 was found to be 20 mg of uranium and thorium. The method was successfully applied to the extraction and determination of uranium and thorium in aqueous solutions. The percentage recovery of uranium and thorium in a number of natural as well as seawater samples of Iran were also investigated and found to be in the range of 85–95 %.     

Facile fabrication of hollow silica and titania microspheres using plasma-treated polystyrene spheres as sacrificial templates

By means of a plasma technique, the surfaces of monodisperse polystyrene (PS) colloids have been modified with hydroxyl groups. Using these surface-modified PS colloids as sacrificial templates, we have fabricated silica-coated PS colloids (PS@silica) and titania-coated PS colloids (PS@titania) composite microspheres as well as hollow and mesoporous silica and titania microspheres. This process not only demonstrated a facile, low-cost, environmentally benign way to fabricate hollow oxides structures but also offered a feasible alternative to the preparation of polymer/inorganic oxide composites by templating against the polymer substrate with hydrophobic surfaces.     

Solid phase extraction conditions for the selective isolation of drugs from biological fluids predicted using liquid chromatography

Summary A new method to predict the most suitable conditions for the solid phase extraction of 1,4-benzodiazepines and related compounds using C18 Sep-Pak carridges is proposed. The composition of the washing and elution solvents for the solid phase extraction of a test compound can be obtained from its capacity factor on a C18 HPLC column and an equation which relates capacity factors and solid phase extraction data of other similar compounds. The solid phase extraction data given in this paper can be used by others, there by saving considerable time and effort in the development of sample preparation methods. The suitability of the method was checked with two test compounds, showing good results.     

Solid phase synthesis of ribo-oligonucleotides on a polyacrylmorpholide support

A riboheptanucleotides G-C-A-A-C-C-A which has a sequence of the 3′-end of $\text{E. coli}$ formylmethionine tRNA has been synthesized on a polyacrylmorpholide resin by the triester approach using dinucleotide blocks.