Ml Of Eluate Research Articles

Determination of chloropropanol esters and glycidyl esters in nutritional foods by gas chromatography–tandem mass spectrometry based on acid hydrolysis and solid-phase extraction

This study presents a method based on acid transesterification and the purification by solid-phase extraction (SPE) coupled with gas chromatography–tandem mass spectrometry for quantifying 3- and 2-monochloropropanediol esters (3-MCPDE, 2-MCPDE) and glycidyl esters (GE) in nutritional foods. The fat was extracted by liquid–liquid extraction with petroleum ether and diethyl ether after the sample was hydrolysed with ammonia. Then the extract was purified by a SPE cartridge filled with the aminopropyl sorbents. It was demonstrated that the optimal elution volume for 3-MCPDE, 2-MCPDE and GE greatly depended on the sample matrix and varied from 6 to 12 mL for four different kinds of food matrices. All three analytes in the sample solution could be fully collected in the first 10–12 mL of eluate. By this way, monoacylglycerols commonly present in the samples were fully removed. Therefore, the overestimation of GE quantification was effectively eliminated. The modified analytical procedure was fully validated in a single laboratory and has been recommended as a Chinese Food Safety National Standard. In addition, two derivatisation agents, heptafluorobutyrylimidazole and phenylboronic acid, were proved to be equivalent in method accuracy and precision for the quantification of three analytes.

Development of 225Ac/213Bi generator based on α-ZrP-PAN composite for targeted alpha therapy

BackgroundRadioligand therapy using alpha emitters has gained more and more prominence in the last decade. Despite continued efforts to identify new appropriate radionuclides, the combination of 225Ac/213Bi remains among the most promising. Bismuth-213 has been employed in clinical trials in combination with appropriate vectors to treat patients with various forms of cancer, such as leukaemia, bladder cancer, neuroendocrine tumours, melanomas, gliomas, or lymphomas. However, the half-life of 213Bi (T½ = 46 min) implies that its availability for clinical use is limited to hospitals possessing a 225Ac/213Bi radionuclide generator, which is still predominantly scarce. We investigated a new Ac/Bi generator system based on using the composite sorbent α-ZrP-PAN (zirconium(IV) phosphate as active component and polyacrylonitrile as matrix). The developed 225Ac/213Bi generator was subjected to long-term testing after its development. The elution profile was determined and the elution yield, the contamination of the eluate with the parent 225Ac and the contamination of the eluate with the column material were monitored over time. ResultsThe high activity (75 MBq of parent 225Ac) generator with a length of 75 mm and a diameter of 4 mm containing the composite sorbent α-ZrP-PAN with a particle size of 0.8 to 1.0 mm as the stationary phase, eluted with a mixture of 10 mM DTPA in 5 mM nitric acid, provided 213Bi with yields ranging from 77 % to 96 % in 2.8 mL of eluate, with parent 225Ac contamination in the order of 10−3 %, up to twenty days of use. ConclusionAll the results of the monitored parameters indicate that the composite sorbent α-ZrP-PAN based separation system for the elution of 213Bi is a very promising and functional solution.

Improved purification of cyclotron [68Ga]GaCl3 for the production of 68Ga radiopharmaceuticals

IntroductionIncreased demand for NetSpot and Illuccix as requirement to receive the respective Lutathera and Pluvicto radiotherapies, and monitor subsequent response to treatment, have reinforced the need to develop alternative ways of producing gallium-68 (68Ga). Building on our efforts to produce 68Ga in a liquid target on a GE PETtrace, the goal of this work is to modify the current GE Gallium Chloride cassette using the FASTLab 2 synthesis module to produce [68Ga]GaCl3 equivalent to a 1.85 GBq generator and demonstrate compatibility with FDA-approved kits for production of 68Ga-labeled radiopharmaceuticals. Methods68Ga was produced in a liquid target via the 68Zn(p,n)68Ga reaction. 68Ga was loaded onto various sizes of ZR resins (ZR Load, 0.3 mL, 1 mL, or 2 mL). The loading efficiency was determined using a dose calibrator. After washing with HNO3, 1.75 M HCl was used to elute the ZR Load resin through various sizes of a second ZR resin (ZR CG, 0 mL, 2 mL, 4 mL). Using 0.5 mL fractions, the elution profile was determined. Compatibility of the [68Ga]GaCl3 with NetSpot and Illuccix kits was investigated. Radiochemical purity (RCP) and 4 h stability were determined using radioTLC and radioHPLC. Using a modified [68Ga]GaCl3 cassette and new FASTLab program, 6 validation preparations were conducted using NetSpot and Illuccix kits for which RCP, stability, sterility and suitability were determined. Dual irradiation of 2 liquid targets was also performed, which was used to simultaneously prepare 1 NetSpot and 2 Illuccix kits by diluting the required activity with 0.1 M HCl. ResultsThe commercially available GE Cassette gave low RCP using commercial FDA kits. To optimize this, the loading efficiency onto ZR Load and the ratio of ZR resin used to load the initial activity and subsequent elution were explored. When using a 2:4 ratio of ZR Load to ZR CG, 97.89 % RCP was observed when a 3.8 mL [68Ga]GaCl3 solution was used. For Dotatate validation, 0.55 mL of buffer was added to 4.2 mL of [68Ga]GaCl3 which gave 1.35 GBq of formulated product. For Illuccix validation, [68Ga]GaCl3 was added to 2.5 mL of buffer which gave 1.52 GBq of [68Ga]Ga-PSMA-11. Formulated products passed package insert quality control (QC) requirements. When dual target irradiations were performed, 2.84 GBq was delivered to an external vial and used to label 1 NetSpot and 2 Illuccix kits simultaneously, and each kit also met or exceeded established QC criteria. ConclusionMethods are reported for using cyclotron-produced 68Ga from a liquid target in conjunction with FDA-approved NetSpot and Illucix kits. By employing a 2 mL ZR Load resin with a 4 mL ZR CG resin, adequate resolution between residual 68Zn and desired 68Ga was achieved. By modifying the FASTLab procedure to retain the final 2.5 mL of eluate from the ZR CG resin, [68Ga]GaCl3 equivalent to a new 1.85 GBq generator was obtained. This was suitable for labeling NetSpot and Illucix kits, resulting in high incorporation of 68Ga (RCP >95 %), which has not previously been demonstrated. Delivering [68Ga]GaCl3 into an external vial and diluting with 0.1 M HCl makes it possible to prepare multiple kits simultaneously. These new procedures should facilitate use of cyclotron-produced [68Ga]GaCl3 for clinical production going.

Small nanofibrous disks for preconcentration of environmental contaminants followed by direct in-vial elution and chromatographic determination

A novel method for the extraction of river water contaminants as model analytes of ranging polarities, including bisphenols A, C, S, Z, fenoxycarb, kadethrin, and deltamethrin, using small compact fibrous disks has been developed and validated. Polymer nanofibers and microfibers prepared from poly(3-hydroxybutyrate), polypropylene, polyurethane, polyacrylonitrile, poly(lactic acid), and polycaprolactone doped with graphene were evaluated in terms of extraction efficiency, selectivity, and stability in organic solutions. Our novel extraction procedure comprised preconcentration of analytes from 150 mL river water to 1 mL of eluent using a compact nanofibrous disk freely vortexed in the sample. Small nanofibrous disks with a diameter of 10 mm were cut from a compact and mechanically stable 1–2 mm thick micro/nanofibrous sheet. After 60 min extraction in a magnetically stirred sample located in a beaker, the disk was removed from the liquid and washed with water. Then, the disk was inserted into a 1.5 mL HPLC vial and extracted with 1.0 ml methanol upon short intensive shaking. Our approach avoided the undesired problems related to the manual handling typical of “classical” SPE procedure since the extraction was carried out directly in the HPLC vial. No sample evaporation, reconstitution, or pipetting was required. The nanofibrous disk is affordable, needs no support or holder, and its use avoids creation of plastic waste originating from disposable materials. Recovery of compounds from the disks was 47.2–141.4% depending on the type of polymer used and the relative standard deviations calculated from 5 extractions ranged from 6.1 to 11.8% for poly(3-hydroxybutyrate), 6.3–14.8% for polyurethane, and 1.7–16.2% for polycaprolactone doped with graphene. A small enrichment factor was obtained for polar bisphenol S using all sorbents. A higher preconcentration reaching up to 40-fold was achieved for lipophilic compounds such as deltamethrin when using poly(3-hydroxybutyrate) and graphene-doped polycaprolactone.

Graphene oxide/Fe3O4@β-lactoglobulin nanocomposite for the enrichment of trace Pb(II) from real samples

A new GO/Fe3O4@β-lactoglobulin sorbent was prepared for selective extraction of trace Pb(II). The GO/Fe3O4@β-lactoglobulin packed column advantageously permeates samples faster than nascent GO column ca. 5 fold. We experimentally demonstrated the developed SPE method for the enrichment of Pb(II) from real samples (tap, river and packaged drinking water) before ICP-OES determination. The sulfhydryl groups of the vicinal cysteine and the carboxylic groups were led to successful chelate formation with Pb(II) ions. The method shows a detection limit of 0.30 ng mL−1 for Pb(II) ion. The prepared sorbent has a surface area and pore volume of 1460.37 m2g−1 and 1.36 ccg−1, respectively. The preconcentration limit and preconcentration factor for Pb(II) was found to be 0.37 μg L−1 and 900, respectively using 3 mL of eluent. At 95% confidence level, the Student's t-test was less than the critical Student's t value (4.303). A coefficients of variation for five replicate measurements is 3.45%, indicates good precision of the method.

Rapid Elution of 226Th from a Two-Column 230U/226Th Generator with Diluted and Buffer Solutions.

A radionuclide generator of the short-lived alpha emitter 226Th was proposed. An original scheme consisting of two in-series chromatographic columns was developed for rapidly producing a neutral citric-buffered eluate of high purity 226Th. The first column filled with TEVA resin retained the parent 230U, while 226Th was eluted with 7 M HCl solution to be immediately adsorbed on the second column containing DGA resin or UTEVA resin. Having substituted the strongly acidic medium of second column with neutral salt solution, 226Th was desorbed with diluted citric buffer solution. One cycle of generator milking took 5-7 min and produced >90% of 226Th in 1.5 mL of eluate (pH 4.5-5.0) appropriate for direct use in radiopharmaceutical synthesis. The 230U impurity in 226Th eluate was less than 0.01%. The proposed two-column 230U/226Th generator was tested over 2 months including a second loading of 230U additionally accumulated from 230Pa.

Determination of new carmine in beverages by one step rapid solid phase extraction based on metal organic framework extractant

胭脂红是一种广泛应用的偶氮类色素,我国对其在食品中的添加量有严格规定。由于食品基质的复杂性,针对这类痕量色素很难建立一种灵敏度高、富集性强且高效便捷的检测方法。研究利用卟啉环中的羧基与金属锆离子的配位作用制备了一种高比表面积的金属有机骨架材料(PCN-222),并将纳米材料填入注射式固相萃取装置中,以简化前处理过程,用于快速萃取饮料中胭脂红色素。采用多种表征手段研究了PCN-222纳米材料的形貌、结构及性能。较高的比表面积和静电作用共同决定了新型萃取剂对胭脂红色素具有极强的富集性能。通过优化萃取剂用量、样品溶液pH值、洗脱条件和洗脱剂体积等萃取条件,使目标物实现瞬时吸附,样品前处理时间缩短至5 min。在最佳条件下,该方法可使样品在高、中、低3个水平的加标回收试验中的回收率达到99.5%~109.4%,相对标准偏差小于3%,方法的检出限为0.1 μg/L(S/N=3),定量限为0.3 μg/L(S/N=10)。此外,针对所合成的材料进行萃取-解吸后发现,PCN-222在重复使用4次后仍保持90%以上的萃取能力,表明材料具备可循环性。该方法通过制备的新型金属骨架材料建立了一种高效、便捷、绿色环保的前处理技术,极低的检出限、较高的准确度和较好的重复性表明方法适用于饮料中痕量色素胭脂红的富集和检测。新型固相萃取技术的开发为食品安全检测提供了新思路。

Separation of 44Sc from 44Ti in the Context of A Generator System for Radiopharmaceutical Purposes with the Example of [44Sc]Sc-PSMA-617 and [44Sc]Sc-PSMA-I&T Synthesis.

Today, 44Sc is an attractive radionuclide for molecular imaging with PET. In this work, we evaluated a 44Ti/44Sc radionuclide generator based on TEVA resin as a source of 44Sc. The generator prototype (5 MBq) exhibits high 44Ti retention and stable yield of 44Sc (91 ± 6 %) in 1 mL of eluate (20 bed volumes, eluent—0.1 M oxalic acid/0.2 M HCl) during one year of monitoring (more than 120 elutions). The breakthrough of 44Ti did not exceed 1.5 × 10−5% (average value was 6.5 × 10−6%). Post-processing of the eluate for further use in radiopharmaceutical synthesis was proposed. The post-processing procedure using a combination of Presep® PolyChelate and TK221 resins made it possible to obtain 44Sc-radioconjugates with high labeling yield (≥95%) while using small precursor amounts (5 nmol). The proposed method takes no more than 15 min and provides ≥90% yield relative to the 44Sc activity eluted from the generator. The labeling efficiency was demonstrated on the example of [44Sc]Sc-PSMA-617 and [44Sc]Sc-PSMA-I&T synthesis. Some superiority of PSMA-I&T over PSMA-617 in terms of 44Sc labeling efficiency was demonstrated (likely due to presence of DOTAGA chelator in the precursor structure). It was also shown that microwave heating of the reaction mixture considerably shortened the reaction time and improved radiolabeling yield and reproducibility of [44Sc]Sc-PSMA-617 and [44Sc]Sc-PSMA-I&T synthesis.

Semiautomatic method for the ultra-trace arsenic speciation in environmental and biological samples via magnetic solid phase extraction prior to HPLC-ICP-MS determination

A novel magnetic functionalized material based on graphene oxide and magnetic nanoparticles (MGO) was used to develop a magnetic solid phase extraction method (MSPE) to enrich both, inorganic and organic arsenic species in environmental waters and biological samples. An automatic flow injection (FI) system was used to preconcentrate the arsenic species simultaneously, while the ultra-trace separation and determination of arsenobetaine (AsBet), cacodylate, AsIII and AsV species were achieved by high performance liquid chromatography combined with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). The sample was introduced in the FI system where the MSPE was performed, then 1 mL of eluent was collected in a chromatographic vial, which was introduced in the autosampler of HPLC-ICP-MS. Therefore, preconcentration and separation/determination processes were automatic and conducted separately. To the best of our knowledge, this is the first method combining an automatic MSPE with HPLC-ICP-MS for arsenic speciation, using a magnetic nanomaterial based on MGO for automatic MSPE. Under the optimized conditions, the LODs for the arsenic species were 3.8 ng L−1 AsBet, 0.5 ng L−1 cacodylate, 1.1 ng L−1 AsIII and 0.2 ng L−1 AsV with RSDs <5%. The developed method was validated by analyzing Certified Reference Materials for total As concentration (fortified lake water TMDA 64.3 and seawater CASS-6 NRC) and also by recovery analysis of the arsenic species in urine, well-water and seawater samples collected in Málaga. The developed method has shown promise for routine monitoring of arsenic species in environmental waters and biological fluids.

Separation and determination of cadmium in water samples based on functionalized carbon nanotube by syringe filter membrane- micro solid-phase extraction

A simple and fast separation of cadmium (Cd) based on functionalized carbon nanotubes with 2,3-dimercapto-1-propanol (CNTs@DHSP) was achieved in water samples before a determination by atom trap flame atomic absorption spectrometry (AT-FAAS). In this study, Cd(II) ions were extracted by syringe filter membrane-micro solid phase extraction procedure(SFM-μ-SPE). Firstly, 20 mg of the CNTs@DHSP as solid-phase added to 20 mL of water sample in a syringe, then dispersed for 3 min after adjusting pH up to 7 and pass through SFM very slowly. After extraction, the Cd(II) ions were back-extracted from SFM/CNTs@DHSP by 1.0 mL of eluent in acidic pH. Finally, the cadmium concentration was measured by AT-FAAS. Under the optimal conditions, the linear range (2–90 µg L−1), LOD (0.75 µg L−1) and enrichment factor (19.6) were obtained (RSD&lt;1.5%). The adsorption capacity of Cd(II) with the CNTs@DHSP was obtained about 152.6 mg g-1. The method was validated by certified reference materials (SRM, NIST) and ET-AAS in water samples.

PH tunable anionic and cationic heavy metal reduction coupled adsorption by thiol cross-linked composite: Physicochemical interpretations and fixed-bed column mathematical model study

Over the past, extensive works executed to treat anionic and cationic heavy metal ions from wastewater. Although very few adsorbents were developed to adsorb anionic and cationic heavy metal ions from the same system. In this study, we explored the pH tunable complete reduction plus adsorption mechanism of Pb2+ and Cr2O72− by dithiocarbamate-based composite. The pH study recommended that; adsorption of Pb2+ occurred at pH 5.5, besides Cr2O72− reduction coupled adsorption executed at pH 3. Furthermore, quick adsorption occurred within 60 min with adsorption capacities of 228.69 and 219.75 mg g−1 for Pb2+ and Cr2O72−, respectively. Adsorption isotherm well described by the Redlich-Peterson model, also adsorption processes were fitted by pseudo-second-order kinetics model. Interestingly, characteristic techniques, a physical monolayer model and thermodynamic models were applied to the experimental results to further understand the adsorption mechanisms. The results indicated that the physical model with two types of interaction energies was more appropriate to interpret the adsorption mechanism. Based on the physical model, three thermodynamic functions were calculated and interpreted to attribute new macroscopic interpretations at the molecular level of the adsorption systems. Inspiringly, the metal-composite system highly effective for 5 regeneration cycles and fixed-bed column could decontaminate 17.2 L of ~10 mg L−1 Pb2+ and 7.3 L of ~10 mg L−1 Cr2O72− to the EPA’s wastewater discharge limit by 5 g of CSC@SDBC with the yielding of 400 and 346 mL of eluent, respectively. Theoretically, a liter of CSC@SDBC column may efficiently adsorb 145,646 mg of Pb2+ and 57,518 mg of Cr2O72− from industrial effluent, these were calculated from the Bohart-Adams model. These collective batch and fixed-bed systems were cost-effective and environmentally tolerable techniques to remove anionic and cationic heavy metal ions from industrial wastewater.

Influential Factors in the Preparation of 68Ga-DOTATATE.

Acceptable and reproducible radiochemical purity (RP) for 68Ga-DOTATATE was difficult to obtain with the NETSPOT kit because the manufacturer instructions lacked details on the heater or needles used. Methods: The drug was prepared in an International Organization for Standardization (ISO) 5 environment. Multiple dry baths and needle types were used to investigate the effects of reaction temperature and metal contamination, respectively. Temperature curves were obtained with a calibrated thermocouple. The influence of the accuracy of the NETSPOT reagent volume and its effect on outcome were investigated. Results: The AccuBlock dry bath required recalibration for the ISO 5 environment; after calibration, the temperature was stable (only ±0.1°C from the set point). When we followed package insert recommendations (dry bath temperature set to 98°C, reaction time of 8 min), the reaction temperature was 90.6°C. When Becton Dickinson needles were used for reconstitution, 15 of 18 runs (83%) did not meet the RP specification. However, B. Braun Medical needles achieved satisfactory and stable RP. When the 68Ga generator was eluted with 5.0 mL of 0.1 M hydrochloric acid (HCl), only 3.8-3.9 mL of eluate reached the reaction vial; this volume did not impact labeling (final pH was 3.8). The labeling success rate increased markedly if the 68Ga eluate was passed through a conditioned silica gel cartridge or if no cartridge was used; then, RP was more than 99%. HCl contact with the septum of the labeling vial reduced RP. Conclusion: The needle type and the temperature setting of the dry bath have critical roles in 68Ga-DOTATATE preparation. The AccuBlock dry bath has excellent stability and accuracy and can be used for reliable preparation. By using a conditioned silica gel cartridge or by eliminating the cartridge altogether, the RP is reliably high and stable.

225Ac/213Bi generator based on inorganic sorbents

Abstract A scheme of an “inverse” generator based on an inorganic sorbent (annealed zirconium and yttrium mixture oxides) has been proposed and tested. The generator demonstrated high yield of the 213Bi product (up to 97 % in 0.5 mL of eluate), high degree of purification from the actinium isotopes (up to 10−2 % of initial 225Ac in 3 M NaNO3 solution), as well as the products of 227Ac decay, and low radiation impact on the sorbent. Application of circulating approach to the sorption of 213Bi provides decreasing processing time to 5 min at higher yield of the product.

Synthesis of SDS micelles-coated Fe3O4/SiO2 magnetic nanoparticles as an excellent adsorbent for facile removal and concentration of crystal violet from natural water samples

In this research, a simple and rapid method for the separation and preconcentration of trace amounts of crystal violet (CV) from aqueous sample solutions by modified magnetic nano-particles (MNPs) has been developed. The modification of magnetite nanoparticles was conducted by tetra ethoxysilane (TEOS) followed by micelles of anionic surfactant (SDS) to enhance the preconcentration of CV. To characterize the shape and structure of the nanoadsorbent, FT-IR and XRD procedures were used. Also, the average size of the synthesized nanoparticles was achieved between 30 and 40 nm by TEM technique. The effects of some important parameters such as: aqueous solution pH, adsorbent dosage, contact time, temperature and desorption conditions on the separation and concentration of CV were investigated. So, under optimal experimental conditions: aqueous solution pH 6, solution temperature = 20 °C, 7 mg of adsorbent, 1 mL of eluent (0.8 mL of acetonitrile + 0.2 mL of acetic acid), the recovery of CV from river water samples was achieved 98.32 ± 0.056% (n = 5) in two short periods of time for extraction (5 min) and elution (2 min). The maximum sorption capacity of the nano-composite was determined to be 16.37 mg/g. Also linear dynamic range and limit of detection were calculated to be 10–2500 ppb and 1.82 ppb, respectively. Finally, the proposed method was successfully applied for the separation and concentration of CV from the real water samples and the results were satisfied.Graphical abstractUnder optimal conditions, a significant amount of nanocomposite was added to the dye solution. After dye removal in a short time, the nanoadsorbent-containing dye was magnetically separated from the solution and then the adsorbed dye was eluted into low volume of a suitable eluting solution.

Determination a variety of acidic gas in air of workplace by Ion Chromatography

To establish a method for determination of a variety of acid gas in the workplace air by Ion Chromatography. (hydrofluoric acid, hydrogen chloride or hydrochloric acid, sulfur anhydride or sulfuric acid, phosphoric acid, oxalic acid). The sample in workplace air was collected by the porous glass plate absorption tube containing 5 ml leacheate. (Sulfuric acid fog, phosphoric acid aerosol microporous membrane after collection, eluted with 5 ml of eluent.) To separated by AS14+AG14 chromatography column, by carbonate (2.0+1.0) mmol/L (Na(2)CO(3)-NaHCO(3)) as eluent, flow rate of 1 ml/min, then analyzed by electrical conductivity detector. The retain time was used for qualitative and the peak area was used for quantitation. The each ion of a variety of acid gas in the air of workplace were excellent in carbonate eluent separation. The linear range of working curve of 0∼20 mg/L. The correlation coefficient r>0.999; lower detection limit of 3.6∼115 µg/L; quantitative limit of 0.012∼0.53 mg/L; acquisition of 15L air were measured, the minimum detection concentration is 0.004 0∼0.13 mg/m(3). The recovery rate is 99.7%∼101.1%. In the sample without mutual interference ions. Samples stored at room temperature for 7 days. The same analysis method, the detection of various acidic gases in the air of workplace, simple operation, good separation effect, high sensitivity, high detection efficiency, easy popularization and application.

ON-LINE MINI-COLUMN SOLID-PHASE EXTRACTION COUPLED WITH SEQUENTIAL INJECTION FOR THE DETERMINATION OF CADMIUM IN ENVIRONMENTAL SAMPLES

□Trace cadmium(II) in environmental samples was separated and enriched in an automated fashion using a diphenylcarbazone-functionalized silica gel mini-column coupling with sequential injection. Cadmium was determined using a multicomponent system involving the analyte, potassium iodide, ethyl violet, and polyvinyl alcohol. Under the optimum conditions, the linear range for cadmium(II) was 0.015–0.50 µ g mL−1, and the detection limit was 0.012 µ g mL−1. The relative standard deviation of 11 determinations for 0.1 and 0.2 µ g mL−1 standard solutions was smaller than 3.5%. This method was applied for the determination of cadmium(II) in water, plant, soil, and electroplating wastewater. No statistically significant differences in the results were observed between the reported method and those obtained by atomic absorption spectrometry. The analysis was performed within 13 min and a total reagent volume of only 0.14 mL (0.07 mL of eluent and 0.07 mL of reagents) was consumed in each determination of cadmium(II).

SPE coupled with dispersive liquid-liquid microextraction followed by GC with flame ionization detection for the determination of ultra-trace amounts of benzodiazepines

SPE combined with dispersive liquid-liquid microextration was used for the extraction of ultra-trace amounts of benzodiazepines (BZPs) including, diazepam, midazolam, and alprazolam, from ultra-pure water, tap water, fruit juices, and urine samples. The analytes were adsorbed from large volume samples (60 mL) onto octadecyl silica SPE columns. After the elution of the desired compounds from sorbents with 2.0 mL acetone, 0.5 mL of eluent containing 40.0 μL chloroform was injected rapidly into 4.5 mL pure water. After extraction and centrifugation, 2 μL of the sedimented phase was injected into a GC equipped with a flame ionization detector. Several parameters affecting this process were investigated and optimized. Under the optimal conditions, LODs ranged from 0.02 to 0.05 μg/L, a linear dynamic range of 0.1-100 μg/L and relative SDs in the range of 4.4-10.7% were attained. Very high preconcentration factors ranging from 3895-7222 were achieved. The applicability of the method for the extraction of BZPs from different types of complicated matrices, such as tap water, fruit juices, and urine samples, was studied. The obtained results reveal that the proposed method is a good technique for the extraction and determination of BZPs in complex matrices.

Analytical Solution of the Ideal Model of Chromatography for a Bi-Langmuir Adsorption Isotherm

The (closed-form) analytical solution of the ideal model of chromatography was derived in the case of a bi-Langmuir adsorption isotherm model. This explicit solution provides the sample concentration as a function of the elution time as the unique real and positive root of a quartic polynomial equation. Using this analytical solution, we could calculate the parameters of the bi-Langmuir adsorption model for phenol on a column packed with Poroshell 120 C18 core-shell particles, eluted with a mixture of methanol and water, and operated under high inlet pressure using the retention time method. The method permitted a rapid, economical determination of the best adsorption isotherm parameters for phenol. It required less than 32 mg of sample, 50 mL of eluent, and less than 4 h to complete the measurement of 20 adsorption data points. The relative precisions of the isotherm parameters were 5% for the equilibrium constant and 9% for the saturation capacity of the strong adsorption sites and 24% for the equilibrium constant and 5% for the saturation capacity of the weak adsorption sites. Compared with determinations made with the standard HPLC technology and frontal analysis experiments, the working time, eluent volume consumed, and mass of compound used were reduced by factors of 4, 20, and 400, respectively.

Multi‐residue determination of organophosphorus and organochlorine pesticides in environmental samples using solid‐phase extraction with cigarette filter followed by gas chromatography–mass spectrometry

A solid-phase extraction (SPE) method was developed to extract 14 pesticides simultaneously from environment samples using cigarette filter as the sorbent before gas chromatography-mass spectrometry (GC-MS) analysis. Parameters influencing the extraction efficiency, such as the sample loading flow rate, eluent and elution volume, were optimized. The optimum sample loading rate was 3 mL/min, and the retained compounds were eluted with 6 mL of eluent at 1 mL/min under vacuum. Good linearity was obtained for all the 14 pesticides (r(2) >0.99) from 0.1 to 20 μg/L for water and from 2 to 400 μg/kg for soil samples. The detection limits (signal-to-noise=3) of the proposed method ranged from 0.01 to 0.20 μg/L for water samples and from 0.42 to 6.95 μg/kg for soil samples. The developed method was successfully applied for determination of the analytes in real environmental samples, and the mean recoveries ranged from 76.4 to 103.7% for water samples and from 79.9 to 105.3% for soil samples with the precisions (relative standard deviation) between 2.0 and 13.6%.

MWCNT/nano-ZrO_2 as a new solid phase extractor: its synthesis, characterization, and application to atomic absorption spectrometric determination of lead

Nanoscale ZrO_2 was synthesized on a multiwall carbon nanotube (MWCNT) and designed as a new solid phase extractor for metal ion preconcentration. The characterization of the synthesized material was achieved by transmission electron microscope (TEM) and X-ray diffraction (XRD). Then the new nanoscale material was applied to preconcentration of lead(II) from various matrices. Different experimental factors including pH of the sample solution, sample volume, flow rate of the sample solution, and volume and concentration of the eluent for the preconcentration step were examined. The effect of interfering ions on the recovery of the lead(II) was also investigated. The recovery of lead(II) under the optimum conditions was found to be 104 \pm 2% at 95% confidence level. The preconcentration factor was 30 when 150 mL of sample solution and 5 mL of eluent were used. The analytical detection limit for Pb(II) was 0.80 \mu g L^{-1} after preconcentration. The adsorption capacity of the new nanosorbent was 115 mg g^{-1}. The accuracy of the method was confirmed by analyzing standard reference materials (Silty Clay 7003). The results demonstrated good agreement with the certified values. The method was applied for the determination of lead in tap water and clay samples.