Determination Of Trace Amounts Research Articles

Determination of iron in water by flame atomic absorption spectrometry with sorption preconcentration

Determination and monitoring of pollutants in the natural environment is an urgent task because of their impact on living organisms as a result of numerous anthropogenic impacts. For this reason, a large number of publications are devoted to the development, modification or optimization of analytical methods that can solve these problems. When determining trace elements present in various samples, such as natural and waste water, biological samples and alloy samples, direct determination by various instrumental methods is often impossible due to the matrix effect and rather low concentration of metal ions in the sample. The atomic absorption method is one of the methods widely used for the determination of iron ions, which has such advantages as simplified sample preparation, low probability of contamination and loss of elements, increased analytical productivity, the detection limit of components in the analyzed mixture reduced by several orders of magnitude, and the ability to determine trace amounts of elements in small samples. The aim of the study was to develop a technique for the preliminary concentration of Fe (III) ions in waters of various origins using a sorbent immobilized with sulfosalicylic acid and their further determination by flame atomic absorption spectrometry. Sorbents obtained on the basis of polyacrylonitrile modified with polyethylene polyamine (PPF-1 and PPA-1) with sulfosalicylic acid immobilized on their surface were used for selective sorption of Fe (III) ions. Optimal conditions for the immobilization of sulfosalicylic acid on sorbents and the formation of complexes with Fe (III) ions were studied. The developed sorption-atomic absorption technique provided determination of low concentrations of Fe (III) ions in various waters. The use of PPF-1 as a sorbent with immobilized sulfosalicylic acid for pre-concentration of iron has a number of advantages compared to traditional atomic absorption procedure, i.e., the simplicity, high degree of iron extraction, high sensitivity and selectivity of iron determination, as well as a low cost. The detection limit of iron ions is 0.01 μg/L, Sr does not exceed 0.033.

Ecofriendly ratiometric colorimetric determination of mercury(II) ion in environmental water samples using gallic acid-capped gold nanoparticles

Today, the monitoring and determination of heavy metal pollutants in the environment is an essential requirement for the environmental and research communities. Mercury ion is one of the most hazardous heavy metals, and scientists are trying to develop new methods for its detection. In this study, a new colorimetric sensor based on aggregation gallic acid-capped gold nanoparticles (GA-AuNPs) for the determination of mercury ions in environmental water samples was presented. The green synthesized GA-AuNPs exhibited a sharp surface plasmon resonance peak at 515 nm. The addition of mercury ions changed the surface properties of GA-AuNPs, resulting in the formation of a new peak near 670 nm due to the aggregation of GA-AuNPs, and an obvious color change from red to purple occurred. Thus, mercury ions were detected based on the change in the absorbance ratio (A670/A515). The developed sensor can determine the mercury ions in the concentration range of 78.0 nM to 8.3 µM with a detection limit of 5.5 nM. Based on the Environmental Protection Agency (EPA) and the World Health Organization (WHO) reports, the amount of Hg2+ ions in fresh water should be between 10.0 and 30.0 nM. The results indicate that the developed sensor can detect and determine trace amounts of Hg2+ ions in environmental water samples.

Dual-chromic cellulose paper modified with nanocapsules containing leuco dye and spiropyran derivatives: A colorimetric portable chemosensor for detection of some heavy metal cations

Heavy metal cations are important in our daily life and may cause serious disorders and diseases. Colorimetric portable cellulosic sensors with high selectivity and sensitivity toward metal cations are preferred relative to those based on small molecules which operate mostly in organic media and difficult test methods. Here, dual-chromic stimuli-responsive cellulose paper (TPL@T-Cell) was produced by modification of the paper with the designed and prepared epoxy-functionalized polyacrylic nanocapsules via dip-coating and subsequent heat treatment processes. The capsules contained thermochromic leuco-dye derivative and photochromic hydroxyl-functionalized spiropyran and were prepared through semi-continuous miniemulsion polymerization. Chemical structure of the synthesized dyes, nanocapsules and modified cellulose fibers were identified by FTIR and UV-Vis analyses. Spherical morphology of the prepared nanocapsules with average particles size of 121 nm were observed by SEM and DLS analyses. The effective wetting of the cellulose fibers by nanocapsules with proper diffusion and deposition through the establishment of physical and chemical interactions were evaluated by SEM and ATR-FTIR analyses, respectively. The prepared TPL@T-Cell sensor revealed distinct color changes toward Fe2+, Pb2+ and Sn2+ ions. Opto-chemical results indicated that detection limit of TPL@T-Cell for Sn2+ (0.0028 µM, 0.326 ppb), Fe2+ (0.0013 µM, 0.15 ppb), and Pb2+ (0.0023 µM, 0.268 ppb) are lower than their critical permitted levels announced by WHO. These exhibited applicability of TPL@T-Cell sensor for determining trace amount of some heavy metal ions with instant responsivity, wide linear detection range, high sensitivity, and low detection limit via colorimetric and spectroscopic responses.

Trace mercury in wate were measured by dispersion-liquid microextraction combined with spectrophotometry

An experimental method was developed for the determination of trace amounts of mercury by dispersion-liquid microextraction combined with spectrophotometry. Undea buffer medium of hydrochloric acid and sodium acetate at pH=4, mrcury ions in the water were extracted by dispersion-liquid microextraction at the wavelength of 410nm, carbon tetrachloride was used as an extractant, methanol was used as a dispersant, dithizone-methanol solution was used as a chelating agent, the optimum conditions for extraction were obtained, Carbon tetrachloride 70uL, methanol 0.75mL, dithizone methanol solution 200uL. Under the optimal conditions, Lambert-Beer's law was satisfied at concentrations of 0.1-20μg/L,the detection limit is 64.2ng /L, The correlation coefficient of the standard curve was R2 =0.9983, the relative deviation was about 4.64%. Three water samples were measured, the recoveries were 96.8%-109.2%.

Voltammetry in Determination of Trace Amounts of Lanthanides—A Review

This paper presents an overview of approaches proposed in the scientific literature for the voltammetric determination of rare earth elements (mainly cerium and europium individually, as well as various lanthanides simultaneously) in manifold kinds of samples. The work is divided into chapters describing the most important aspects affecting the sensitivity of the proposed methods: the technique adopted (AdSV, ASV, CSV), complexing agents used, the kind of working electrode (mercury-based, noble metal or carbon electrodes) and the most popular electrode modifiers (e.g., metal film, carbon nanotubes, molecularly imprinted polymers). Analytical parameters of the procedures presented in the paper are collected in tables. The subsequent chapters are devoted to a detailed discussion of potential inorganic and organic interfering factors. The possibilities of simultaneous determination of several lanthanides in one sample and the influence of other lanthanides on the determined rare earth element were also discussed. Finally, the applications of the voltammetric procedures to the determination of rare earth metals in real samples with miscellaneous matrix is described. All analytical results were tabulated in order to compare the analytical suitability of the proposed procedures.

CATALASE AND PEROXIDASE BIOMIMETIC SENSOR BASED ON Ag-ELECTRODE

Research has been carried out on the development of a biomimetic sensor of the catalase and peroxidase type to determine trace amounts of peroxide hydrogen and low concentrations of ethyl alcohol in an aqueous solution. By potentiometric research, the physicochemical feature of the catalase and peroxidase biomimetic sensor was studied, the transducer of which was Ag. Rapid and accurate determination of hydrogen peroxide is very important, but no less important side of this issue is associated with the determination of trace amounts of C2H5OH in aqueous media of various origins. The need to develop express methods for determining the concentration of C2H5OH in aqueous solutions follows from the requirements for the quality of wine and alcohol products. As you know, the taste and drinking qualities of the product depend on the ratio of methyl and ethyl alcohols. In this work, biomimetic sensors of the catalase and peroxidase types based on an Ag electrode were developed for determining trace amounts of hydrogen peroxide and ethanol. Biomimetic sensors of the catalase and peroxidase types based on an Ag electrode have been developed for the determination of microquantities of hydrogen peroxide and ethyl alcohol. The applicability of a biomimetic sensor for determining trace concentrations of hydrogen peroxide, as well as for determining microquantities of ethyl alcohol in an aqueous solution with a low detection limit, high sensitivity, wide recognition range, high stability, and repeated use, is shown. The developed and synthesized biomimetic sensor of the catalase and peroxidase types based on TPhPFe3+/Al2O3/Ag have high sensitivity, stability, and do not lose their activity for a long time

A sustainable magnetic γ-Fe2O3@Escherichia coli (E. coli) bio-sorbent for determination trace amounts of thymol in pharmaceutical, food and cosmetic samples

Due to the need for environmentally friendly technologies, using microorganisms such as bacteria as a biosorbent for the solid phase extraction (SPE) technique has paid attention. These biosorbents have advantages, such as good performance, abundance and accessibility, operation over a wide range of environmental conditions, regeneration, and not producing secondary contaminations. This study examines a biotechnological application using Escherichia coli (E. coli), as a highly efficient adsorbent for separation, preconcentration, and determination of thymol. The E. coli was immobilized to γ-Fe2O3 magnetic nanoparticles, as a solid-phase biosorbent, for magnetic dispersive micro-solid phase extraction (MDμ-SPE) to provide an efficient and rapid recovery after the sorption process. Characterization of the prepared biosorbent was carried out using the Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscope (FE-SEM), and vibrating sample magnetometer (VSM). The MDμ-SPE as a green and sensitive method proposed for the separation and determination of trace quantities of thymol. Some experimental factors, such as sample pH, amount of sorbent, adsorption time, and temperature affecting the MDμ-SPE efficiency, were tested by the experimental design method. Under optimal conditions, linear range, detection limit, and the relative standard deviation for extraction and preconcentration of thymol were obtained; 30–500, 9.1 ng mL−1, and 1.4 %, respectively. Finally, the proposed method was successfully applied to the preconcentration and determination of target analyte in pharmaceutical, food, and cosmetic samples.

Preparation of Some as-Triazines, Their Evaluation as Spectrophotometric Reagents and Determination of Trace Amount of Iron in Certain Food and Natural Samples

Spectrophotometric reagents 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT) and 3-(2-pyridyl)-5,6-bis(p-methoxyphenyl)- 1,2,4-triazine (PBMPT) were prepared from commercially available reactants simply by condensing pyridyl-2-hydrazidine with 1,2-dicarbonyl compounds. These organic reagents were used further to determine the trace amount of iron in various natural and food samples by spectrophotometric method. The absorptiometric features of iron (II) complexes of PDT and PBMPT were determined. The molar absorptivites of iron (II) complexes of PDT and PBMPT were found to be 24,181 L mol-1 cm-1 (at 556.0 nm) and 32,091 L mol-1 cm-1 at (561.8 nm) respectively. The reliability of these absorptivities were verified by standard addition technique and also by comparing the results of atomic absorption spectroscopy method. The complexes of both the reagents obey Beer’s law within the experimental concentration range 0.032mg/L - 0.159 mg/L.
 Dhaka Univ. J. Sci. 71(2): 111-116, 2023 (July)

A heteropore covalent organic framework for highly selective enrichment of aryl-organophosphate esters in environmental water coupled with UHPLC−MS/MS determination

The identification of an increasing number of aryl organophosphate esters (aryl-OPEs) in environmental samples has led to growing attention recently. Due to the potential adverse effects on human health and environment, development of new analytical methods for sensitive and selective determination of aryl-OPEs in complex matrices is urgently needed. Here, a novel analytical method for the identification and determination of trace amounts of aryl-OPEs in water samples is developed by using melamine sponge@heteropore covalent organic framework (MS@HCOF) based on vortex-assisted extraction (VAE) prior to UHPLC−MS/MS analysis. The MS@HCOF was rationally designed and synthesized through an in-situ growth strategy and exhibited superior selectivity toward aryl-OPEs compared with that of MS@single-pore COF (MS@SCOF) due to steric effect. A systematic optimization was conducted on important parameters of VAE, resulting in the successful extraction of nine aryl-OPEs in just 6 min. Under optimized conditions, the limits of detection (S/N = 3) and quantification (S/N = 10) were within the ranges of 0.001−0.027 and 0.005−0.091 ng/L for nine aryl-OPEs, respectively. The validated method was proven applicable to real water samples, i.e., the recoveries were 65.3−119.5 % for seawater, 59.4−112.9 % for effluent, and 76.0−117.4 % for tap water. Furthermore, the adsorption mechanisms were explored through density functional theory (DFT) calculations. DFT results revealed that a notable selective enrichment capacity of MS@HCOF towards aryl-OPEs stems from π-π conjugation and hydrogen bonding. The established method benefits from the advantages of high selectivity and sensitivity for the ultra-trace determination of aryl-OPEs.

Simultaneous determination of trace amounts of dopamine and uric acid in human plasma samples with novel voltammetric biosensor (GCE/Ppy/DEA MIP) following the thin film-µSPE method based on electrospun nanofibers

In order to achieve the aim of this study, i.e., simultaneous measurement of trace amounts of dopamine (DA) and uric acid (UA) following their preconcentration, a novel sorbent with high performance was prepared. Hence, herein, poly vinyl chloride/Mg-Al layered double hydroxide (PVC/Mg-Al LDH) electrospun nanofibers were synthesized for the thin film- micro solid phase extraction (TF-µSPE) and then, simultaneous extraction of trace amounts of DA and UA was done. Finally, DA and UA were determined simultaneously from two different human plasma samples; afterwards, glassy carbon electrode/Poly pyrrole/diethylamine (DA, UA) molecularly- imprinted polymer (GCE/Ppy/DEA (DA, UA) MIP) electrochemical biosensor was constructed. The synthesis confirmation of PVC-Mg-Al LDH electrospun nanofibers was accomplished by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) and attenuated total reflection-Fourier transform infrared (ATR-FTIR). In addition, the GCE/Ppy/DEA MIP and GCE/Ppy/DEA (non-imprinted polymer) NIP nanocomposites were characterized with field emission-scanning electron microscopy (FE-SEM). PVC, as a polymer with a large surface area and high porosity, is an appropriate candidate in the sorbent preparation process with electrospinning. The flexible interlayer region is accessible to various anionic and polar molecular species. Adding Mg-Al LDH led to an extensive surface area of electrospun nanofibers. In the case of Ppy and DEA MIP as GCE surface modifiers, Ppy increased the electroactive sites, leading to the high conductivity of the electrochemical biosensor. Besides, DEA MIP has high selectivity and sensitivity. Optimization of impressive factors on the extraction procedure was conducted by one at-time (OAT) method, and optimum conditions for the construction of electrochemical biosensor were attained with experimental design (design-expert 12.0 software). According to the optimum conditions, the wide linear range was obtained 76.6–268.1 µg mL−1 for DA and 84.1–378.2 µg mL−1 for UA with R2≥ 0.96, low detection limits ranged from 22.3 µg mL–1 for DA and 24.8 µg mL−1 for UA based on S/N = 3 and large enrichment factors. The intra-day (n = 3) and inter-day (n = 3) RSDs% were obtained in the span of 5.3% − 6.1% for DA and 4.0% − 5.6% for UA. Eventually, the efficiency of the TF-µSPE-voltammetric biosensor method was evaluated for the measuring of DA and UA in human plasma samples with satisfactory recoveries (90.2%–99.7%).

Evaluation of thallium ion as an effective ion in human health using an electrochemical sensor

Exposure to thallium (Tl), a noxious heavy metal, poses significant health risks to both humans and animals upon ingestion. Therefore, monitoring Tl levels in the environment is crucial to prevent human exposure and reduce the risk of developing severe health problems. This paper presents the development of a highly sensitive Tl ions sensor through surface modification of a glassy carbon electrode with a nanocomposite comprising MnO2 magnetic sepiolite and multi-walled carbon nanotubes (MnO2@Fe3O4/Sep/MWCNT/GCE). Multiple methodologies were employed to assess the performance of the newly developed sensor. By employing square wave anodic stripping voltammetry (SWASV) to optimize the measurement conditions, notable enhancements were observed in the stripping peak currents of Tl (I) on the MnO2@Fe3O4/Sep/MWCNT/GCE surface. The effectiveness of the nanocomposite in facilitating electron transfer between the Tl (I) ions (guest) and the electrode (host) was demonstrated from the enhanced signals observed at the different modified electrode surfaces under optimal conditions. The developed sensor displayed a wide linear range of 0.1–1500 ppb for Tl (I) and a low detection limit of 0.03 ppb for Tl (I). It was found to be selective for Tl (I) ions while remaining unaffected by interfering non-target ions in the presence of the target ions. Despite its simple preparation procedure, the modified electrode exhibited high stability and excellent reproducibility for measuring Tl (I). The outstanding electroanalytical performances of the MnO2@Fe3O4/Sep/MWCNT/GCE electrode enabled its successful use as an ultrasensitive sensor for determining trace amounts of Tl in environmental samples.

Voltammetric Determination of Trace Amounts of Lead With Novel Graphite/Bleaching Earth Modified Electrode

Modified composite electrodes have gained considerable interest in the detection of heavy metal ions due to their excellent sensitivity, selectivity, stability, and rapid response. Generally, these sensors consist of binder, conductive substance, and modifier. This study examined into the performance of a novel modified electrode that used a graphite–bleaching earth (BE-MCPE) composite performed while detecting trace amounts of Pb(II) using a differential pulse voltammetric technique (DPASV). In order to investigate the properties of BE-MCPE, we employed several analytical techniques, including SEM, SEM-EDX, FTIR, and XRD. These techniques were used to characterize the physical, chemical, and elemental properties of BE-MCPE, as well as its Pb(II) adsorption capacity, providing a comprehensive understanding of its composition and structure. The electrochemical results showed that the modified electrode demonstrated superior sensitivity and selectivity, in detecting Pb(II) ions, with a linear response range of 2.10-7 M to 10.10-7 M, limit of detection (LOD) of 4,89x10-8 mol.L-1, and limit of quantification (LOQ) of 1,63x10-7 mol.L-1. This novel modified electrode can achieve the sensitive detection of trace amounts of Pb(II) in a wide range of wastewater applications.

A Simple, Stable, and Highly Sensitive Spectrophotometric Method for the Determination of Arsenic(III) from Different Biological Media in the Presence of Nanosilica-Cysteine Composite

This paper describes a selective and fairly stable colorimetric approach to determine trace amounts of arsenic conjugated with nanosilica-cysteine composite in various aqueous and biological samples in milligram per liter (mg/L) using Leucocrystal Violet (LCV) as a chromogenic reagent. Attenuated total reflectance-Fourier-transform infrared (ATR-FTIR) spectroscopy analysis was applied to characterize the composite. Novelty of this method is dealing with the presence of nanosilica which is reflected in the difficulty of obtaining a clear solution. The maximum absorbance is measured and Beer's law shows linearity over the concentration range of (0.75 to 5.00 mg/L) of As(III) at 590 nm. The molar absorptivity, Sandell’s sensitivity, and detection limit of the method were found to be 6.00 × 105 L/mol.cm, 8.55 × 10-2 μg/cm2, and 0.043 mg/L, respectively. The optimum reaction conditions and other analytical parameters were evaluated. Arsenic was successfully detected in a variety of aqueous and biological samples using the proposed method.

Photometric Determination of Trace Amounts of Aluminum in Nearly Saturated Rock Salt Solutions Used by Chlor-alkali Industry

The previously widespread mercury cell technology in chlorine production has now been replaced by more environmentally friendly membrane cell electrolysis which is a Best Available Techniques (BAT) technology. However, this requires a much cleaner brine containing contaminants (Al, Ca, Mg, etc.) in the order of ng/g at most. For this reason, it’s very important to detect trace amounts of aluminum in concentrated saline media in the simplest and fastest way. To the best of our knowledge, no one has previously developed a spectrophotometric method capable of detecting aluminum in ionic forms selectively in the order of ng/g in concentrated saline media, without any preconcentration or separation step. Our advanced analytical method provides an opportunity for this. During the analytical procedure, a colored complex ion is formed from the dissolved aluminum content of the sample with eriochrome cyanine R (ECR) ligand in buffered pH medium. The sensitivity of the measurement is increased by adding quaternary ammonium salt. The colored complex ion is formed in 15 minutes, then the absorbance measurement can be performed for 90 minutes. The effect of rock salt interference was eliminated by proper calibration. In our work the dependence of the signal on temperature, pH, time elapsed after the addition of reactants, the dosing sequence, the salinity of the medium was examined, furthermore, we studied which wavelength-absorbance values give the best fit (highest R2 value) and the highest sensitivity in case of linear calibration. Surprisingly, increasing the salinity significantly improves the sensitivity of the measurement.

Toward the Development of an Electromechanical Ion-Specific Conveyer Belt

Bromide (Br−) is ubiquitous both in natural waters and those impacted by anthropogenic activities, such as, the discharge of treated or untreated wastewaters, releases from coal-fired power plants and hydraulic fracturing operations, and sea water intrusion. The development of methods for the extraction and purification of Br−, particularly from Br− -rich brines, is regarded as of great economic interest owed to the uses of bromine in many industrial processes. In fact, the removal of Br- from drinking water is beneficial from a public health perspective, as it can lead to the formation of regulated disinfection byproducts (DBPs) during water treatment. Although various alternatives have recently been proposed to remove halide anions, such as bromide, from drinking water, none of them have proven sufficiently effective for large-scale application (see e.g. Ref. 1).The present contribution describes a strategy for the removal and purification of bromide from an aqueous solution containing chloride in amounts that closely mimic those found in natural brine sources. As will be described, this tactic relies on the selective electrosorption of Br− on Au, an inert metal electrode material from such a synthetic brine, and its subsequent desorption into a second aqueous solution devoid of Br−.The all glass multi compartment cell employed for these experiments ‘shown schematically in the figure above consists of a central cylindrical cup filled with 0.01 HClO4 supporting electrolyte, which houses the reference, RE, and counter electrodes connected on either side to two identical cups of smaller diameter, C1 and C2 are separated from the central cup by glass frits so that diffusion between C1 and C2 is negligible. At the start of a regular experiment, C1 is filled with a solution containing 28 mM KCl and 12.5 mM KBr, the synthetic brine, in the supporting electrolyte, and C2 is filled with only supporting electrolyte. In the initial stage of this protocol, a gold foil is immersed in C1, which together with the RE and CE would form a conventional 3-electrode cell and a potential of 1.3 V vs RHE is then applied to the Au foil using a potentiostat to induce anion adsorption for ca.10 s. which is sufficient for Br-(aq) and Cl-(aq) to achieve their equilibrium coverages under the specific conditions of the experiment, as represented by the blue arrow. Based on the results of independent optical measurements, Br-(aq) would be the predominant ion adsorbed on the Au surface at this high potential. Subsequently, the Au foil is emersed from the solution without disconnecting the potentiostat, immersed into C2, and a potential of 0.2 V applied, which is just positive of the onset of hydrogen evolution but negative enough for adsorbed Br- to fully desorb, as represented by the red arrow. This process is then repeated tens of times, at the end of which the composition of the solution in C2 is analyzed using the methylene blue (MB) spectroscopic method described by Uraisin, et al. (2) to determine specifically Br-(aq), and a slightly modified Mohr’s turbidimetry technique, which employs K2CrO4 as the indicator, to determine the total amount of Br-(aq) and Cl-(aq).Four independent runs involving 50 to 75 sequential transfers were performed in order to assess the efficiency of this process, and found to yield an increase in the Br-(aq) concentration from an initial 30% in C1, up to higher than 75% in C2. Overall, the efficiency of this process can be increased by a corresponding increase in the area of the electrode. Alternatively, one can envision a continuous process involving a segmented electrode in the form of a belt and appropriate potential controls, that would be continuously emersed and immersed into C1 and C2, acting as a virtual ionic conveyer. Various aspects of this unique technology and its prospects for large scale implementation will be discussed. Acknowledgements This work was supported by a grant from NSF, CHE-1412060 References Sanchez-Polo, J. Rivera-Utrilla, E. Sahli, U. von Gunten, Ag-Doped Carbon Aerogels For Removing Halide Ions In Water Treatment, Water Res., 41, 2007,1031-1037Uraisin, T. Takayanagi, M. Oshima, D. Nacapricha, S. Motomizu, Kinetic-Spectrophotometric Method For The Determination Of Trace Amounts Of Bromide In Seawater, Talanta, 68, 2006, 951-956 Figure 1

Investigation and elimination of surfactant-induced interferences in anodic stripping voltammetry for the determination of trace amounts of cadmium

This article aims to investigate in detail to what extent surfactants affect the determination of cadmium by anodic stripping voltammetry. In recent years, the production and use of surfactants have been steadily increasing, so that their concentration in environmental water samples is rising. At the same time, it is known that organic compounds, such as surfactants, often hinder the voltammetric determination of trace elements by stripping. Non-ionic (Triton X-100, Brij 35, Tween 20, Tween 60, Tween 80), cationic (CTAB, CTAC, DTAB, HPC) and anionic (DSS, SDS) compounds were selected to investigate the effect of surfactants on the voltammetric signal of cadmium. At the same time, the extent to which the addition of Amberlite resins to the analysed solution eliminates the interfering effect of surfactants was tested. Three types of Amberlite resins XAD-2, XAD-7 and XAD-16 were selected for the study and the ratio of resin weight to solution volume was determined. Finally, the determination of cadmium in surfactant-enriched environmental samples was carried out. The recoveries obtained between 95.5 and 107%, with RSD between 3.4 and 6.2%, confirm the validity and correctness of the proposed procedure All measurements were carried out by anodic stripping voltammetry using a CNTs/SGC electrode modified with a bismuth film as the working electrode.

Quantitative evaluation of low-concentration OH impurities in quartz glass by infrared photothermal deflection spectroscopy

.Impurity control in materials is of great importance to achieve excellent performance, yet the quantitative determination of trace impurities, especially OH, is extremely difficult using today’s characterization techniques. Here we report the determination of trace amounts of OH in quartz glass plates by photothermal deflection spectroscopy (PDS) extended to the IR region. PDS detects trace OH based on the amount of heat generated during non-radiative processes during light irradiation. IR absorption spectra of quartz glasses with five different OH concentrations were investigated. In addition to the standard OH band around 3640 cm−1, we find that there are combination modes, overtones, and water-induced IR features. The presence and OH concentration dependence of these species reveal the role of impurities in quartz glass. The PDS is effective in quantifying OH concentrations below 1 ppmw (parts per million weight) in quartz glass plates.

Determination of trace amounts of thiabendazole in fruit juices using internal standard-based SERS method

Thiabendazole (TBZ) is widely used as a fungicide to prevent mold on citrus fruits. Uncontrolled use of TBZ can potentially harm the human health and contaminate the environment of aquatic organisms. In this work, we have developed an ultra-sensitive and low cost quantitative method for the determination of TBZ in juices (orange, apple, and peach) using surface-enhanced Raman scattering (SERS) on CaCl2-agglomerated silver nanoparticles. The recovery of analyte from juice with ethyl acetate was performed using liquid-liquid extraction. We used nitrothiabendazole (NTBZ), a closely related compound to TBZ, as an internal standard for improving accuracy and reproducibility of the results. This compound was obtained through a simple synthesis procedure. The structural similarity between TBZ and NTBZ allowed to obtain a practically identical recovery rate during the extraction and a relatively equal concentration dependence in the SERS mode. Application of NTBZ as an internal standard allowed to obtain a linear dependence of the SERS intensity signal at the TBZ concentration ranging between 100 and 1000 nM (R2 =0.9907). The recovery rate was between 90% and 113%, RSD was less than 3.5%. The LOD for TBZ specifically in juice samples was calculated to be between 1.2 and 5.1 nM. The dependence of the TBZ signal on the acidity of the medium was also studied. The enhancement factor was evaluated at 1.57 * 107.

Adsorptive Stripping Voltammetry for Determination of Vanadium: A Review.

The main purpose of this review is to present methods of adsorptive stripping voltammetry that can be used to determine trace amounts of VO2(+) in various types of samples. The detection limits achieved using different working electrodes are presented. The factors influencing the obtained signal, including the selection of the complexing agent and the selection of the working electrode, are shown. For some methods, in order to increase the range of applied concentrations in which vanadium can be detected, a catalytic effect is introduced to adsorptive stripping voltammetry. The influence of the foreign ions and organic matter contained in natural samples on the vanadium signal is analyzed. This paper presents methods of elimination associated with the presence of surfactants in the samples. The methods of adsorptive stripping voltammetry for the simultaneous determination of vanadium with other metal ions are also characterized below. Finally, the practical use of the developed procedures, mainly for the analysis of food and environmental samples, is summarized in a tabular version.

Determination of trace amount of some drugs as in its pure form and in its Pharmaceutical Preparations by using different spectroscopic methods

The present study includes analytical methods for determination of the drugs Chlorpromazine hydrochloride (CPZ) and trifluoperazine hydrochloride (TFPH) in some pharmaceuticals using molecular absorption, indirect AAS, in addition to investigating complexes obtained throughout. Chlorpromazine hydrochloride and trifluoperazine hydrochloride are widely used for the treatment of schizophrenia. Synthetic formulas for the prepared drug complexes were proposed through the results of the molar ratios of the combination between the drug and each of copper, lead, chrome and iron.