Sample Flow Rate Research Articles

Effect of process parameters on separation efficiency in a deterministic lateral displacement device

Deterministic lateral displacement (DLD) is a hydrodynamic method known for its high-resolution sorting of particles. It achieves this through a periodic array of obstacles and laminar flow that passively directs particles along in two different directions depending on the particles’ diameter. Many prior publications have been dedicated to the structural and geometrical development of DLD arrays to improve separation performance; however, a successful separation requires much more than a well-designed array. This paper shows how separation performance is affected by process parameters. For this purpose, the design and fabrication of a DLD device are described. Then three experiments show how process parameters affect the performance of the device. The first experiment uses dye solutions to visualize the formation of a hydrodynamically focused sample stream. The second experiment shows that the particle separation performance (of 7- & 15-µm particles) is affected by the way output fluids are collected. Finally, the third experiment looks at the particle separation efficiency as the input flow rates and the ratio of buffer to sample are changed. The results show that the proper range for buffer and sample flow rate in this device is 1–10 and 0.1–1 (µl/min), respectively. The buffer to sample flow rate ratio of 10 gives the highest separation efficiency, but at a lower sample throughput. The optimized values are specific for our device but demonstrate processes that we believe are universal for DLD separations.

Recovery of cobalt from spent lithium ion batteries utilizing surface modified graphene oxide

Metal content present in the spent lithium ion batteries (LIBs) make their recycling vital for resources conservation and environmental sustainability. Cobalt, grouped among critical, valuable and strategic metals, is the basic part of the LIBs cathode and defines its recycling economic capacity. In the present work, an attempt has been made to develop an efficient hydrometallurgical technique based on solid phase extraction method for the recovery of cobalt from leach solution of waste LIBs. An adsorbent was synthesized by diazotization of p-phenylenediamine modified graphene oxide (GO-PPDA) sheets with disodium 1-nitroso-2-naphthol-3-6-disulphonate (nitroso R-salt, NRS) in one pot process of Mill's reaction. Maximum retention of cobalt (99.9%) was achieved at pH 5.5–6.5. Adsorption kinetics favour complexation as a separation mechanism following second order kinetics model with R2 value of 0.9999 with sample flow rate of 1.5 mL/min. Langmuir isothermal model (R2 = 0.998) also confirm monolayer chemisorption mechanism with 29.7 mg/g adsorption capacity. The two-step elution mechanism enables us to achieve 99.5% extraction efficiency with ~98% purity. The chelating adsorbent was found reasonably stable even after the 30th cycle of adsorption and desorption with <2% decrease in removal efficiency. The results show that the proposed adsorbent is successful in terms of selectivity, reusability, analytical merit and stability.

A low cost, easy-to-assemble, open-source modular mobile sampler design for thermal desorption analysis of breath and environmental VOCs

Exhaled breath vapor contains hundreds of volatile organic compounds (VOCs), which are the byproducts of health and disease metabolism, and they have clinical and diagnostic potential. Simultaneous collection of breath VOCs and background environmental VOCs is important to ensure analyses eliminate exogenous compounds from clinical studies. We present a mobile sampling system to extract gaseous VOCs onto commercially available sorbent-packed thermal desorption tubes. The sampler can be connected to a number of commonly available disposable and reusable sampling bags, in the case of this study, a Tedlar bag containing a breath sample. Alternatively, the inlet can be left open to directly sample room or environmental air when obtaining a background VOC sample. The system contains a screen for the operator to input a desired sample volume. A needle valve allows the operator to control the sample flow rate, which operates with an accuracy of −1.52 ± 0.63% of the desired rate, and consistently generated that rate with 0.12 ± 0.06% error across repeated measures. A flow pump, flow sensor and microcontroller allow volumetric sampling, as opposed to timed sampling, with 0.06 ± 0.06% accuracy in the volume extracted. Four samplers were compared by sampling a standard chemical mixture, which resulted in 6.4 ± 4.7% error across all four replicate modular samplers to extract a given VOC. The samplers were deployed in a clinical setting to collect breath and background/environmental samples, including patients with active SARS-CoV-2 infections, and the device could easily move between rooms and can undergo required disinfection protocols to prevent transmission of pathogens on the case exterior. All components required for assembly are detailed and are made publicly available for non-commercial use, including the microcontroller software. We demonstrate the device collects volatile compounds, including use of chemical standards, and background and breath samples in real use conditions.

Ferrozine colorimetry and reverse flow injection analysis (rFIA) based method for the determination of total iron in aqueous solutions at nanomolar concentrations

Iron is one of the most microbiologically and chemically important metals in natural waters. The biogeochemical cycling of iron is significantly influenced by the redox cycling of Fe(II) and Fe(III). Because of the unique chemistry of iron, it is often needed to analyze iron at nano-molar concentrations. This article describes a reverse flow injection analysis (rFIA) based method with ferrozine spectrophotometric detection to quantify total iron concentration in stream water at nanomolar concentrations. The rFIA system has a 0.65 nM detection limit and a linear dynamic range up to 1.40 μM for the total iron analysis. The detection limit was achieved using a 1.0 m long liquid waveguide capillary flow cell, 1.50 m long knotted reaction coil, 87.50 μL injection loop and a miniature fiber optics spectrophotometer. The optimized colorimetric reagent has 1.0 mM ferrozine, 0.1 M ascorbic acid, 1.0 mM citric acid and 0.10 M acetate buffer adjusted to pH 4.0. The best sample flow rate is 2.1 mL min−1 providing a sample throughput of more than 15 samples h−1. The linear dynamic range of the method can be adjusted by changing the volume of the injection loop. The rFIA manifold was assembled exclusively from commercially available components.

Development and validation of a reverse phase High Performance Liquid Chromatographic method, using standard addition calibration, for determination of risperidone in human plasma

Risperidone is a drug of choice in the management of psychosis and high performance liquid chromatography (HPLC) is regarded as the most sensitive and accurate method for quantitative analysis of risperidone, as well as other drugs having low plasma concentrations in biological fluids. A simple and accurate HPLC method was developed for the determination of risperidone in human plasma using the standard addition calibration technique to augment the weak signals due to low plasma concentrations of risperidone. Risperidone was eluted using isocratic mode with a mobile phase of methanol: acetonitrile (60:40) on a Chemisil ODS C18 column (250 mm×4.6 mm i.d., 5 μ particle size). The sample injection volume, flow rate, column temperature and wavelength of detection were set at 10 µl, 1.0 ml/min, 35 ˚C and 280 nm respectively. The run time for the method was 7 minutes, with risperidone having a retention time of 3.566 minutes. The method was linear within the concentration 10-50 ng/ml (R2= 0.998), with LOD and LOQ of 0.13 and 0.40 ng/ml respectively. The precision and relative error was 3.44 % and 3.38 % respectively. The developed method can be employed in the quantitative determination of risperidone in pharmacokinetic and bioequivalence studies.

A low-cost flow cell for flow cytometry

Flow cytometry is an essential analytical technique used in biomedical diagnostics to measure properties of cells, micro-organisms, and particles. Laser light is scattered from particles focused in a flow cell and collected by light sensors, where the intensity of the scattered light is a function of the scattering angle, the refractive index of the particle and surrounding medium, the wavelength of light, and the size and the shape of the particle. One of the critical parts of the cytometer is the flow cell where the particle stream is constrained into a tight region within 10–30 μm using hydrodynamic focusing. The conventional flow cells use thick quartz flow cells, which are expensive and therefore not suitable for instruments targeted for resource-constrained settings. We demonstrate a compact, economical, bio-compatible flow cell assembly design that incorporates inexpensive and easily available capillaries attached to sturdy polymer fixtures in a simple manner that performs the focusing of a sample stream of particles. The flow cell has been tested by studying the relation between sample core diameter, and sample and sheath flow rates. Small-angle scattering (forward scatter) and wide-angle scattering (side scatter) have been captured for the enumeration and characterization of particles. We show excellent agreement between the size distribution obtained via direct imaging and that obtained from light scattering. The flow cell was also used to successfully size white blood cells in human blood samples.

Rapid sampling and determination of phthalate esters in indoor air using needle trap device

Sensitive detection of trace Phthalate esters (PAEs) in ambient air has great significance for environmental supervision and human health. In this research, a sensitive analytical method was established to determine trace PAEs in ambient air by combining the needle trap device (NTD) with gas chromatography-mass spectrometry (GC–MS). The operating parameters were optimized for the PAEs detection. In addition, the preservation capacity and repeatability of the sampling needle were also investigated. Under the optimized conditions of sampling flow rate of 5 mL min-1, breakthrough volume of 100 mL, desorption temperature of 290 ºC, and desorption time of 150 s, the satisfactory extraction stability (intraday and daily) of PAEs with relative standard deviations (RSDs) was less than 10%, and the average recovery was ranged from 88.89% to 93.77% within seven days. The wide linear concentrations of 0.04 µg L−1-10 µg L−1 and low detection limits of 0.050–3.6 ng m−3 demonstrated that the established method based on the micro-extraction device of NTD was competitive and had a potential application for trace PAEs in ambient air.

A rapid and label-free platform for virus enrichment based on electrostatic microfluidics.

Virus surveillance and discovery are crucial for virus prediction and outbreak preparedness. Virus samples are frequently bulky and complicated so that effective virus detection remain challenging. Herein, we develop an 3D electrostatic microfluidic platform to rapidly and label-free enrich viruses from bulky samples at low concentrations. The platform consists of double microchannels for streamlining large volume processing and electrodes for enriching viruses by electrostatic interaction. The trajectories of simulation show that particle is successfully enriched under different forces of electrostatic field and different sample flow rates. We demonstrate that the electrostatic microfluidic platform can increase the limit of detection in 100-fold higher based on real-time PCR quantified analysis. Our design thus provides a simple, rapid, label-free and high-throughput viruses concentration platform and would thus have significant utility for various viral detection.

Identification of Unknown Substances in Ambient Air (PM10), Profiles and Differences between Rural, Urban and Industrial Areas.

A fast and automated strategy has been developed for identifying unknown substances in the atmosphere (concretely, in the particulate matter, PM10) using LC-HRMS (MS3). A total of 15 samples were collected in three different areas (rural, urban and industrial). A sampling flow rate of 30 m3 h−1 was applied for 24 h, sampling a total volume of around 720 m3. A total of 49 compounds were tentatively identified using very restrictive criteria regarding exact mass, retention time, isotopic profile and both MS2 and MS3 spectra. Pesticides, pharmaceutical active compounds, drugs, plasticizers and metabolites were the most identified compounds. To verify whether the developed methodology was suitable, 11 substances were checked with their analytical standards and all of them were confirmed. Different profiles for industrial, rural and urban areas were examined. The Principal Component Analysis (PCA) model allowed us to separate the obtained data of the three assessed area. When the profiles obtained in the three evaluated areas were compared using a Volcano plot (the rural area was taken as reference), 11 compounds were confirmed as being discriminant: three of them (3-hydroxy-2-methylpyridine, 3-methyladenine and nicotine) were more likely to be found in industrial sites; ten compounds (3-hydroxy-2-methylpyridine, 3-methyladenine, azoxystrobin, cocaine, cotinine, ethoprophos, imidacloprid, metalaxyl-M, nicotine and pyrimethanil) were more probable in the case of urban sites; finally, triisopropanolamine was more likely to be detected in rural locations.

Silver ion functionalized covalent organic polymer for selective online solid phase microextraction of unsaturated fatty acid methyl esters

In this work, silver ion functionalized covalent organic polymer (COPTAPB-BPDA@SA@Ag+) was fabricated via the introduction of silver ion to COP, and utilized as selective sorbent for online SPME of unsaturated fatty acid methyl esters (UFAMEs). The synthesis of COPTAPB-BPDA@SA@Ag+ was confirmed by using the SEM, EDS, FT-IR, XRD and XPS characterization techniques. Due to the charge-transfer interaction between silver ion and C = C double bonds, COPTAPB-BPDA@SA@Ag+ displayed satisfactory extraction ability towards UFAMEs. Several SPME factors, such as ACN content in the sampling solution and eluent, sampling and elution flow rate, were investigated with respect to the extraction efficiency of UFAMEs. Under the optimized conditions, an online Ag+-SPME-Ag+-HPLC method for analysis of target trans-UFAMEs was proposed. A good linearity was established in the range of 0.04 ∼ 2 mg/kg for two target trans-UFAMEs in milk tea samples. The limits of detection (LODs) and limits of quantitation (LOQs) were not more than 8.8 μg/kg and 19 μg/kg respectively, while the intra-day RSDs (n = 3) and the inter-day RSDs (n = 3) were less than 2.1% and 2.9% respectively. The recoveries for the proposed method was ranged from 82.3% to 93.5% with RSDs (n = 4) less than 5.9%. The above results demonstrated the selective extraction of COPTAPB-BPDA@SA@Ag+ towards UFAMEs from complex real samples, as well as the satisfactory detection sensitivity for trans-fatty acids of the proposed method. This study provided a facile approach for the preparation of metal ion functionalized COP sorbent and showed its wide potential for sample preparation.

Simultaneous analysis of six inorganic anions in urine by double-suppress ion-exchange chromatography.

This study is aimed to establish a simple, rapid, and accurate ion chromatography approach for the simultaneous detection of six inorganic anions in urine. Various performance parameters affecting the determination of anions were optimized, including the selection of sample protein precipitation agent, eluent, and flow rate. The final eluent was 3.6mmol/L sodium carbonate and 12% isopropanol with a flow rate of 0.6mL/min. Acetonitrile was used for pretreatment to precipitate proteins, and the volume ratio of urine to acetonitrile was 1:4. The correlation coefficient of the target anion calibration curve ranged from 0.9973 to 0.9999. The limit of detection ranged from 1.50 to 12.0 μg/L, and the method detection limit ranged from 15.0 to 120 μg/L. The standard recovery rate for low, medium, and high concentrations ranged from 90 to 110%. The inter-day and intra-day relative standard deviations were<5%. The method has high accuracy and good reproducibility and is suitable for the separation and determination of anions in urine.

An experimental method for efficiently evaluating the size-resolved sampling efficiency of liquid-absorption aerosol samplers

Aerosol samplers are critical tools for studying indoor and outdoor aerosols. Development and evaluation of samplers is often labor-intensive and time-consuming due to the need to use monodisperse aerosols spanning a range of sizes. This study develops a rapid experimental methodology using polydisperse solid aerosols to evaluate size-resolved aerosol-to-aerosol (AtoA) and aerosol-to-hydrosol (AtoH) sampling efficiencies. Arizona Test Dust (diameter 0.5–20 µm) was generated and dispersed into an aerosol test chamber and two candidate samplers were tested. For the AtoA test, aerosols upstream and downstream of a sampler were measured using an online aerodynamic particle sizer. For the AtoH test, aerosols collected in sampling medium were mixed with a reference sample and then measured by the laser diffraction method. The experimental methodology were validated as an impressive time-saving procedure, with reasonable spatial uniformity and time stability of aerosols in the test chamber and an acceptable accuracy of absolute mass quantification of collected particles. Evaluation results showed that the AGI-30 and the BioSampler sampler had similar size-resolved sampling efficiencies and that efficiencies decreased with decreasing sampling flow rate. The combined evaluation of AtoA and AtoH efficiency provided more comprehensive performance indicators than either test alone. The experimental methodology presented here can facilitate the design and choice of aerosol sampler.

Influence of E-Liquid Humectants, Nicotine, and Flavorings on Aerosol Particle Size Distribution and Implications for Modeling Respiratory Deposition.

Electronic cigarette, or vaping, products are used to heat an e-liquid to form an aerosol (liquid droplets suspended in gas) that the user inhales; a portion of this aerosol deposits in their respiratory tract and the remainder is exhaled, thereby potentially creating opportunity for secondhand exposure to bystanders (e.g., in homes, automobiles, and workplaces). Particle size, a critical factor in respiratory deposition (and therefore potential for secondhand exposure), could be influenced by e-liquid composition. Hence, the purposes of this study were to (1) test the influence of laboratory-prepared e-liquid composition [ratio of propylene glycol (PG) to vegetable glycerin (VG) humectants, nicotine, and flavorings] on particle size distribution and (2) model respiratory dosimetry. All e-liquids were aerosolized using a second-generation reference e-cigarette. We measured particle size distribution based on mass using a low-flow cascade impactor (LFCI) and size distribution based on number using real-time mobility sizers. Mass median aerodynamic diameters (MMADs) of aerosol from e-liquids that contained only humectants were significantly larger compared with e-liquids that contained flavorings or nicotine (p = 0.005). Humectant ratio significantly influenced MMADs; all aerosols from e-liquids prepared with 70:30 PG:VG were significantly larger compared with e-liquids prepared with 30:70 PG:VG (p = 0.017). In contrast to the LFCI approach, the high dilution and sampling flow rate of a fast mobility particle sizer strongly influenced particle size measurements (i.e., all calculated MMAD values were < 75 nm). Dosimetry modeling using LFCI data indicated that a portion of inhaled particles will deposit throughout the respiratory tract, though statistical differences in aerosol MMADs among e-liquid formulations did not translate into large differences in deposition estimates. A portion of inhaled aerosol will be exhaled and could be a source for secondhand exposure. Use of laboratory-prepared e-liquids and a reference e-cigarette to standardize aerosol generation and a LFCI to measure particle size distribution without dilution represents an improved method to characterize physical properties of volatile aerosol particles and permitted determination of MMAD values more representative of e-cigarette aerosol in situ, which in turn, can help to improve dose modeling for users and bystanders.

Ultra-sensitive speciation analysis of tellurium by manganese and iron assisted photochemical vapor generation coupled to ICP-MS/MS

Photochemical vapor generation (PVG) of Te4+ was undertaken with a simple reactor consisting of a polytetrafluoroethylene reaction coil wrapped around a low-pressure mercury tube lamp and using a flow-injection for sample delivery. The composition of a reaction medium, the influence of irradiation time and the effect of added sensitizers and interferents were investigated using high-resolution continuum source atomic absorption spectrometry and a miniature diffusion flame atomizer. A mixture of 5 M acetic acid and 3.5 M formic acid and sample flow rate of 4 mL min−1 permitting a 36 s irradiation time were found optimal for PVG of Te4+. The addition of 250 mg L−1 Mn2+ and 15 mg L−1 Fe2+ ions as sensitizers enhanced the overall PVG efficiency 2.75-fold to 50 ± 2%. In order to achieve higher sensitivity necessary for determination of Te in real environmental samples, PVG was coupled to inductively coupled plasma triple quadrupole mass spectrometer and detection was performed with O2 in the reaction cell utilizing a mass shift mode of measurement (m/z 128 → m/z 144) to ensure interference free ion detection. A limit of detection 1.3 ng L−1 and repeatability (RSD) 0.9% at 250 ng L−1 were achieved. This ultrasensitive methodology was validated for speciation analysis of Te in water samples of various matrix complexities (fresh water, well water, seawater and contaminated water). Since no response was observed from Te6+ under optimal PVG conditions, Te4+ was selectively determined by direct PVG. The sum of Te4+ and Te6+ was determined after pre-reduction of Te6+ in 6 M HCl (95 °C), evaporation to dryness and reconstitution in the reaction medium containing sensitizers. Very good accuracy was demonstrated by spiked recoveries for both Te4+ and total Te in water samples and also by total Te determination in fresh water Standard Reference Material NIST 1643f.

Development of Three-Stage Bioaerosol Sampler for Size-Selective Sampling.

In this study, a three-stage bio-aerosol sampler with a sampling flow rate of 170 L/min was designed and fabricated for sampling the bio-aerosols released during human breathing and coughing, and its performance was evaluated. The sampler was constructed using a cyclone separator with a cutoff size of 2.5 μm as a preseparator, a multinozzle virtual impactor with a cutoff size of 0.34 μm as an aerosol concentrator, and a Bio-Sampler, which is a commercial product, for collecting bio-aerosols in a collection fluid. The collection efficiency of the sampler was evaluated through simulations and experiments. Only particles with sizes of 0.1-4 μm were selectively collected in the collection fluid. Bacteriophage bio-aerosols were sampled using the developed sampler and ACD-200 Bobcat sampler, which is a commercial product. The amounts of collected bacteriophages were compared using the polymerase chain reaction (PCR) technique. The sampling performance of the developed sampler was similar to that of the ACD-200 Bobcat sampler. Moreover, the developed sampler showed its ability to sample bio-aerosols of a specific size range and collect them directly in a collection fluid for the PCR analysis. Therefore, the developed sampler is expected to be useful for indoor environmental monitoring by effectively sampling the bio-aerosols released indoors during human breathing and coughing.

Determination of ten iodinated X-ray contrast media by solid-phase extraction and ultra-high performance liquid chromatography coupled with high-resolution orbitrap mass spectrometry

A highly sensitive method for the simultaneous determination of ten iodinated X-ray contrast media (ICM) in environmental water samples was developed, in which samples were pretreated using solid-phase extraction and analyzed by ultra-high performance liquid chromatography coupled with high-resolution orbitrap mass spectrometry. A combination of two ENVI-Chrom P cartridges was selected due to its high recoveries of ICM. The optimized sample pH, flow rate, eluent type, and volume of eluent were 2.0, 6 mL/min, MeOH/ACN (50:50, v/v), and 6 mL, respectively. The developed method was used for the tap, surface, and waste water sample analysis, and exhibited satisfactory accuracy (80.8-118.5%), high precision (0.1-11.6%), and low detection limits (0.3-1.0 ng/L). These results indicate that this method is highly effective for the simultaneous determination of trace-level ICM in the aquatic environment.

Development of method for determination and preconcentration of uranium in water samples using XAD-4 resin loaded with Br-PADAP

In the present work, a minicolumn of XAD-4 loaded with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) is proposed as a preconcentration system for uranium determination in well, tap and mineral water samples by spectrophotometer using arsenazo III as the chromogenic reagent. Initially, a two-level (23) full factorial design was used for the preliminary evaluation of three factors, involving the following variables: sampling flow rate, elution flow rate, and pH. This design has revealed that, for the studied levels, buffer concentration and pH were significant factors. When the experimental conditions established in the optimization step were pH = 8.6, and an elution flow rate of 8.6 mL min−1 using 0.5% m/v ascorbic acid, this system has allowed for the determination of uranium with a detection limit (LOD) (3σ/S) of 0.05 μg L−1 and a quantification limit (LOQ) (10σ/S) of 0.16 μg L−1. The precision expressed as the relative standard deviation (R.S.D.) of 0.8% and 1.9% at 10.0 and 1.0 μg L−1, respectively- and a preconcentration factor of 184.5 for a sample volume of 50.0 mL. Accuracy was confirmed by uranium determination in the standard reference material, NIST SRM 1566b trace element units in Oyster Tissue samples, and spike tests with recuperations ranging from 93.2 to 105%; the procedure were applied for uranium determination in tap water, well water, and drinking water samples collected from Caetité and Cruz das Almas Cities, Bahia, Brazil. Five water samples were analyzed the uranium concentrations varied from 0.50 to 2.07 μg L−1

Conductive polymer sorbent for extraction and determination of resveratrol and polydatin in Polygonum cuspidatum root samples.

The quantitative analysis of trace resveratrol and polydatin in plant tissues is suitable for elucidation of the compounds' mechanisms of action. The main objective of this work was to develop a feasible and effective sample pretreatment method to measure the concentrations of resveratrol and polydatin in complex samples. A polymer sorbent, poly(2-mercaptobenzimidazole), was electrochemically prepared and utilized for selective extraction, while resveratrol and polydatin were used as target analytes. The sorbent was characterized by cyclic voltammetry, scanning electron microscopy and Fourier transform infrared spectroscopy. After extraction and elution, the analytes were analyzed by a Thermo U3000 HPLC system. Several affecting parameters, including the volume of elution solution, sample pH value, sample flow rate and sample volume, were evaluated and optimized. The proposed method showed good linearity with low limits of detection (from 0.5 to 0.8ng·mL-1 ) and ideal accuracy with spiked recoveries from 81.30% to 99.16%. A good enrichment factor (more than 200-fold) together with good sensitivity was obtained with this method. Analysis of resveratrol and polydatin in Polygonum cuspidatum samples by this method is efficient. The method developed in this work exhibits several significant merits, including easy operation and high extraction efficiency, indicating that electrochemically prepared polymer sorbent is useful for sample pretreatment and analysis of traditional Chinese medicine samples.

Determination of the Cadmium Ions from Aqueous Solution Using EDTA Functionalized Prunus Dulcis L. Peels by Solid-Phase Extraction Method.

In the present study, Prunus Dulcis L. Peels was modified with ethylenedinitrilo tetraacetic acid and used as the sorbent for the preconcentration of Cd(II) ions from aqueous media. To characterize the sorbent, scanning electron microscopy-energy dispersive X-ray spectrometer and Fourier transform infrared spectrometer analysis were used. The optimum preconcentration conditions such as pH, eluent type, sample volume, sample flow rate and foreign ions effect were determined. The mean recovery and relative standard deviation values were found to be 100.7 ± 1.5 and 4.01% for Cd(II) ions. The capacity of the sorbent was obtained 277.8mgg-1 from the Langmuir isotherm model. The limit of detection was calculated as 0.216µgL-1 (P.F:40). In order to test the accuracy and applicability of the method, certified reference material and spiked water samples were analyzed. The results demonstrated good agreement with the certified values (relative error < 10%).

Optimization and modeling of solid-phase extraction of rare earth elements with chert using design methodology

The cherty rocks, the most abundant byproduct of the mining industry, were applied as an adsorbent in the solid-phase extraction of six rare earth elements from aqueous solutions. Purified chert was characterized by various analytical methods. The adsorption and desorption steps were evaluated separately using experimental design methodology. Four variables (sorbent amount and sample volume, pH, and flow rate) were regarded as factors in the optimization of the adsorption step using an FFD 24−1 Design. While eluent volume, concentration, and flow rate were modeled and optimized by Box-Behnken design (BBD) combined with response surface methodology. The eluent volume followed by the eluent concentration was statistically significant parameters on the desorption step. The best results were obtained when an aqueous solution of REE (500 mL) was adjusted to pH 6 and passed, at 8 mL min−1 loading flow rate, through the cartridge containing 500 mg of chert. SPE method was evaluated statistically and showed good repeatability and reproducibility. The detection and quantification limits were found between 0.025 and 0.075 mg L−1 and 0.084 and 0.250 mg L−1, respectively. Extraction recovery percentages of all the REE were 80.13, 95.25, 97.30, 88.10, 82.80, and 91.99% for Eu(III), Yb(III), La(III), Gd(III), Ce(III), and Nd(III), respectively.