Determination Of Chlorine Research Articles

Highly sensitive solution-gated graphene transistor based sensor for continuous and real-time detection of free chlorine

The concentration of free chlorine used for sterilizing drinking water, recreational water, and food processing water is critical for monitoring potential environmental and human health risks, and should be strictly controlled. Here, we report a highly efficient solution-gated graphene transistor (SGGT) device, for the detection of free chlorine in a real-time and convenient manner with excellent selectivity and high sensitivity. The detection mechanism of the SGGT with Au gate electrode is attributed to two combined effects: the reduction of the free chlorine on Au gate electrode; and the direct oxidization of graphene by the free chlorine in solution. The SGGT device shows a linear response range of free chlorine from 1 μM to 100 μM, with detection limit as low as 100 nM, far beyond the sensitivity required for practical applications. Finally, we also demonstrate the performance of the SGGT for determination of free chlorine in local tap water samples. The results presented herein have important implications in the development of portable and disposable devices based on SGGT sensing platform for the simple, real-time, and selective determination of free chlorine.

Method development for the determination of chlorine by high-resolution graphite furnace molecular absorption spectrometry via GaCl

In this study, a method was developed for the determination of chlorine via molecular absorption of GaCl at 249.060 nm generated in a graphite furnace of a high-resolution continuum source atomic absorption spectrometer. For this purpose, 25 μg of Ga and standard solutions or samples were mixed on the platform. The optimized pyrolysis and vaporization temperatures were 500 and 1100 °C, respectively, which were uncommonly low compared to other diatomic molecules between chlorine and molecule forming reagents of chlorine and non-metals. The limit of detection for the method was 2.3 ng which was sufficient to determine chlorine in samples to be analyzed in this study as well as in many matrices. The Cl concentration was determined in uncertainty limits of a certified wastewater sample. Finally, Cl concentrations in some milk and mineral water samples were determined using aqueous standards for calibration. The results were compared with those found by analyte addition technique and no significant difference was found.

Chlorine determination in cement-bound materials with Laser-induced Breakdown Spectroscopy (LIBS) – A review and validation

The determination of chloride is still one of the main tasks for the evaluation of reinforced concrete structures. The corrosion of the reinforcement induced by the penetrating chlorides is the dominant damage process affecting the lifetime of concrete structures. In the recent years different research groups demonstrated that LIBS can be a fast and reliable method to quantify chlorine in cement-bound materials. Because chlorine in concrete can only occur as solved ions in the pore solution or bound in salts or hydrated cement phases, the detected emission of chlorine can be correlated with the chloride concentration determined e.g. with potentiometric titration. This work inter alia describes the production of reference samples and possible side effects during the production process. Due to transport processes in the porous matrix of the cement a misinterpretation of the concentrations is possible. It is shown how to overcome these effects and higher precisions of the single measurements can be realised. Using the calibration method, blank sample method and noise method, three different ways of calculating the limit of detection (LOD) and limit of quantification (LOQ) are compared. Due to the preparation of the reference samples a precision of the whole calibration model of sx0 = 0.023 wt% is determined. The validation of the model is based on different test sets, which are varying in their composition (different Cl-salts, water-to-cement ratios and additives). The determined mean error of the validation is 0.595 ± 0.063 wt%, which is comparable to standardised methods like potentiometric titration, direct potentiometry or photometry (0.40 ± 0.06 wt%) [1].

Sols of Silver Nanoparticles as Analytical Reagents for the Determination of Active Chlorine in Water Samples by Spectrophotometry and Photometric Titration

Sols of silver nanoparticles surface-stabilized by cetyltrimethylammonium bromide or polyvinylpyrrolidone can be used for the determination of active chlorine in water samples. As analytes modeling active chlorine in water, we used freshly prepared sodium hypochlorite solutions. Because of the high values of standard electrode potentials of reduction half-reactions, active forms of chlorine can oxidize silver nanoparticles, exhibiting the effect of surface plazmon resonance with an absorption maximum near 400 nm. The absorption intensity of silver nanoparticles correlates with the concentration of sodium hypochlorite. This effect was used for the qualitative and quantitative determination of active chlorine in water samples. The quantitative characteristics of the described method were obtained for two versions of analysis, spectrophotometry and photometric titration. The calibration graphs for both versions were similar and linear in the range of sodium hypochlorite concentrations 0.1–2.5 mM.

Copper Ion Assisted Photochemical Vapor Generation of Chlorine for Its Sensitive Determination by Sector Field Inductively Coupled Plasma Mass Spectrometry.

A novel, reliable, and sensitive approach for the determination of chlorine by sector field inductively coupled plasma mass spectrometry (SF-ICPMS) using photochemical vapor generation for sample introduction is presented. Methyl chloride is generated from different chlorine species in a flow-through photochemical reactor using a 1% solution of acetic acid containing 7.5 μg g-1 of Cu2+. The volatile product is directed by an argon carrier gas to a gas-liquid separator and introduced into the instrument. A sample flow rate at 1.7 mL min-1 and a 45 s irradiation time provided a 74-fold enhancement in sensitivity compared to conventional nebulization. A blank-limited detection limit of 0.5 ng g-1 for chloride, suitable for quantitation at trace levels, was achieved. The proposed method was validated by analysis of two certified reference materials, NIST SRM 1568b rice flour and SRM 1571 orchard leaves, with satisfactory results, as well as three varieties of bottled water, achieving spike recoveries between 101% and 105%.

Fast and Simple Analytical Method for Direct Determination of Total Chlorine Content in Polyglycerol by ICP-MS.

The fast and simple method for total chlorine determination in polyglycerols using low resolution inductively coupled plasma mass spectrometry (ICP-MS) without the need for additional equipment and time-consuming sample decomposition was evaluated. Linear calibration curve for 35Cl isotope in the concentration range 20–800 µg/L was observed. Limits of detection and quantification equaled to 15 µg/L and 44 µg/L, respectively. This corresponds to possibility of detection 3 µg/g and determination 9 µg/g of chlorine in polyglycerol using studied conditions (0.5% matrix-polyglycerol samples diluted or dissolved with water to an overall concentration of 0.5%). Matrix effects as well as the effect of chlorine origin have been evaluated. The presence of 0.5% (m/m) of matrix species similar to polyglycerol (polyethylene glycol—PEG) did not influence the chlorine determination for PEGs with average molecular weights (MW) up to 2000 Da. Good precision and accuracy of the chlorine content determination was achieved regardless on its origin (inorganic/organic). High analyte recovery level and low relative standard deviation values were observed for real polyglycerol samples spiked with chloride. Additionally, the Combustion Ion Chromatography System was used as a reference method. The results confirmed high accuracy and precision of the tested method.

PENETAPAN KADAR KLORIN PADA BEBERAPA MERK PEMBALUT WANITA YANG ADA DI PASARAN DENGAN METODE IODOMETRI

Sanitary napkin is a device product used by women during menstruation, sanitary napkins function to absorb blood from the vagina so that the blood that comes out does not interfere. Currently, there are many problems that arise in sanitary napkins, due to the presence of chlorine additives which function as an ingredient in the initial bleaching process of sanitary napkins. The purpose of this study was to identify the color reaction test, and to determine the chlorine content by iodometry method in sanitary napkins on the market. This research is an experimental study using a sample of sanitary napkins on the market. Sampling by random sampling (random). Determination of chlorine in sanitary napkins by testing qualitatively with a color reaction and quantitatively using the iodometric method.Based on the results of the study, it was found that of the 5 (five) samples used, 3 (three) positive samples contained chlorine, namely samples A, B and sample C. The chlorine content obtained in sample A was 0.0035%, sample B was 0.0014 % and sample C is 0.0027%. According to YLKI, the normal threshold for the use of chlorine in sanitary napkins is 5-55 ppm, so the samples tested still meet the stipulated conditions.

Towards highly selective detection using metal nanoparticles: A case of silver triangular nanoplates and chlorine

The article describes a novel approach towards improving selectivity of volatile compounds detection using metal nanoparticles. It is based on combination of sensitive optical detection using convenient nanoparticle-modified paper test strips and dynamic gas extraction improving selectivity to volatile compounds. A simple and inexpensive setup allowing for realization of this combination is described. Analytical prospects of the approach are shown by the example of chlorine determination in highly salted aqueous solutions using silver triangular nanoplates and digital colorimetry. The limit of detection is equal to 0.03mgL−1 and the determination range is 0.1–2mgL−1. This determination can be successfully carried out in solutions containing at least 2·105 greater molar amounts of Na+, K+, Zn2+, Cl–, SO42–, and H2PO4– with no sample pretreatment. The approach seems to be compatible with different types of nanoparticles with respect to detection of various analytes, thus having good opportunities for further development.

Chlorine determination via MgCl molecule in environmental samples using high resolution continuum source graphite furnace molecular absorption spectrometry

This paper describes a method development for chlorine determination through the formation of MgCl molecule, applied for the first time for Cl quantification, by high resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) in environmental samples. Pyrolysis and vaporization temperatures were optimized as well as the use of chemical modifier. Determinations were carried out at the wavelength of 377.010 and the compromise conditions of the graphite furnace temperature program were 500°C and 2500°C for pyrolysis and vaporization, respectively, using 10µg of chemical modifier Pd. The concentration of reactants for the generation of MgCl molecule was optimized through Box-Behnken experimental design, using MgCl2 solution as source of chlorine. The optimum values according to the surface response were 5gL−1 Mg, 25mgL−1 of chlorine and 2% vv−1 of HNO3, condition in which the amount of Mg is at least 200 times higher than that of chloride. This excess of the forming agent ensures the complete formation of MgCl molecular species, since Cl is the limiting reactant. Certified reference materials, BCR 182 and NIST 8414, and addition and recovery tests were used to evaluate the accuracy of the method and good results were achieved at a 95% confidence level. The method was applied to direct determination of Cl in five produced water samples from offshore oil wellbore, high complex matrix, whose conventional methods require tedious treatment before the analysis.

Effect of TiO2/GAC and water vapor on chloroform decomposition in a hybrid plasma-catalytic system

ABSTRACTThis paper presents the combination of TiO2/GAC catalyst and NTP for the decomposition of chloroform using a DBD reactor. The experiments were performed using an AC transformer as the power supply system to determine the optimal conditions of the chloroform conversion in the presence of a hydrogen-rich substance, that is, water vapor. TiO2/GAC enhanced the removal efficiency and also CO2 selectivity significantly, leading to an acceptable conversion rate at SIEs higher than 400 J L−1. The adsorption property of GAC was noticed to be an effective factor for catalytic activity by increasing the residence time, although the higher retention time prevented the accurate determination of chlorine and carbon balance. Selectivity toward HCl was improved considerably from 24.3% to 64.3% over catalyst when water was fed as a hydrogen-rich compound. At the same time, the harmful chlorinated by-products such as TCBA and TCE declined significantly. A noticeable enhancement in the selectivity toward CO2 was observed when both catalyst and water were introduced, regardless of the inlet concentration. Our findings suggest that the hybrid of NTP with TiO2/GAC will highly be effective in the abatement of chloroform, and the addition of H2O will successfully decline harmful chlorinated by-products.

Orthogonal and Collinear Configurations in Double-Pulse Laser-Induced Breakdown Spectrometry to Improve Sensitivity in Chlorine Determination

We consider collinear and orthogonal beam-convergence configurations in double-pulse laser-induced breakdown spectrometry (LIBS, also known as laser-spark emission spectrometry) for chlorine determination in plants and concrete from the Cl I 837.59 nm line. We have observed that the signal-to-noise ratio is not much lower for the orthogonal configuration due to spatial instability in the second breakdown. At the same time, suppression of interfering molecular bands in this configuration lets us improve the sensitivity of LIBS for chlorine determination in plant material.

Determining the chlorine content in the blast-furnace system

The production of ferrous metals and the extraction and processing of raw materials are environmentally hazardous. Besides atmospheric and water pollution, many solid wastes are formed. Chlorine plays a special role in blast-furnace processes. The chlorine compounds present in the blast-furnace gas lead to the corrosion of pipelines, air heaters, and tuyeres in the furnace. The behavior of chlorine in the blast furnace determines the sinter properties during the reduction process. If the content of mineral chlorine (chlorine bound with metals) in residues at filters and dust traps is monitored, the toxicity of the wastes may be assessed, and the production processes may be evaluated. The chlorine content is determined by various physical methods: atomic-emission spectrometry, mass spectrometry with inductively bound plasma, and neutron-activated analysis. However, chemical methods have been widely adopted: titrimetric, photometric, electrochemical, and ion-chromatographic methods. It is important to develop fast and inexpensive methods of determining chlorine for the analysis of materials encountered in technological systems, including metallurgical systems. In the present work, attention focuses on samples of blast-furnace slag from PAO Tulachermet and dusty wastes from PAO Kosogorskii Metallurgicheskii Zavod. X-ray fluorescent methods are used for preliminary analysis of the sample composition. The interfering influence of other components is considered. Ionometric determination of chlorine by means of a crystalline chloride-selective electrode is proposed. The samples are decomposed by high-temperature sintering in a mixture with Na2CO3 and ZnO and subsequent leaching with water. The details of this method are described. The results of the analysis are confirmed by variation in the sample weight (n = 10; t tab = 2.26, P = 0.95) and also by comparison with X-ray fluorescent data. The precision of ionometric determination of chlorine in the blast-furnace system is assessed. The working range of the chlorine concentrations observed is 0.037–1.340 wt %.

Development of a fast screening method for the direct determination of chlorinated persistent organic pollutants in fish oil by high-resolution continuum source graphite furnace molecular absorption spectrometry

The occurrence of persistent organic pollutants (POPs), mainly organochlorine pesticides and polychlorinated biphenyls, was directly associated with several diseases and environmental endocrine disrupting. In the aquatic environment, POPs can accumulate in fish lipoid tissues due to their high hydrophobicity, and become this way one of the main sources of human exposure to POPs through the consumption of fish meat and oil as Omega-3 source. Chlorine might serve as a proxy for the presence of POPs, and a fast screening of chlorine in a complex matrix, such as fish oil, could provide substantial information about the contamination with POPs. Therefore, a method has been developed in this work for the determination of total chlorine in fish oil samples via molecular absorption of the strontium mono-chloride molecule in the gas phase using high-resolution continuum source graphite furnace molecular absorption spectrometry. The effect of zirconium as permanent chemical modifier in the pyrolysis and vaporization stages was optimized in order to avoid the need for any kind of sample preparation prior to the determination of total chlorine, using just a dilution with 1-propanol. The accuracy has been evaluated using micro-coulometric titration after sample combustion, and the values were statistically in agreement (95% confidence level) between both techniques. The method has been applied for the determination of total chlorine in five different fractions of a commercial pooled marine fish oil sample collected from the Pacific Ocean, where the majority of the fish is Peruvian anchovy (Engraulis ringens), two commercial oils from Brazil and three Omega-3 supplements acquired in Germany. The limit of detection of the procedure is 1.8 ng Cl absolute or 0.9 μg g−1 Cl in the fish oil. The time required for a single determination is less than 5 min, and less than 15 min for a triplicate determination.

Simple and convenient analytical method for the direct determination of chlorine species by ETV-ICP-AES using tungsten boat furnace vaporiser and exchangeable small sample cuvettes

A tungsten boat furnace vaporiser and an exchangeable sample cuvette system were applied for the direct determination of chlorine in plastic samples by electrothermal vaporisation inductively coupled plasma atomic emission spectrometry. Each piece of plastic samples was moulded into a thin film, and weighed into small sample cuvettes. An ethanolic solution of the modifier potassium hydroxide and an organic solvent were added to each sample cuvette. The contents including the plastic piece were spread over the bottom of each sample cuvette by warming on a hotplate. After the preparation, one of the cuvettes was placed in the tungsten boat furnace equipped with the electrothermal vaporiser. The temperature was gradually elevated. At the flash vaporisation step of 1800 °C, the analyte was vaporised and introduced into the ICP to measure an atomic emission assignable to Cl I 134.724 nm. A widely spread thin layer of the plastic facilitated its rapid evaporation and introduction into an ICP atomic emission spectrometer. Since all the chlorine species were on-furnace decomposed to form potassium chloride during the pretreatment, the solid samples were analysed using a calibration curve prepared from the aqueous standard solutions. By using this system, a detection limit of 1.5 μg g−1 of chlorine in solid plastic samples was established when a sample amount taken of 2 mg was studied. The exchangeable sample cuvette technique makes it possible to measure a number of sample sequentially by preparing a lot of sample cuvettes prior to analysis. Approximately 20 batches could be vaporised per hour. Analytical results of some plastic samples that were analysed by this technique are given in this report.

A LED-based fiber-optic sensor integrated with lab-on-valve manifold for colorimetric determination of free chlorine in water

In this work, a colorimetric methodology was developed for free chlorine determination by constructing a fiber-optic sensor (FOS) which was designed by using a small LED as light source and two silica fibers as light transmission elements. Then the FOS was integrated with the sequential injection lab-on-valve (SI-LOV) manifold to fabricate a FOS-SI-LOV system for free chlorine detection. The colorimetric determination was based on the reaction between N,N-diethyl-p-phenylenediamine (DPD) reagent and free chlorine, which would produce a chromophore showing maximum absorbance at 511 and 551nm and detected by a micro spectrometer detector. By choosing a green LED with emission wavelength at 520nm as light source, the chlorine concentration could be simply evaluated according to Beer's law. The developed FOS-SI-LOV system showed improved performances of wide linear range (10–400μgL−1), low detection limit (3.5μgL−1, 3σ), fast analysis (6.85s) and excellent repeatability (0.0083 RSD, n=8) for chlorine determination. The proposed FOS-SI-LOV system has been applied to on-line and real-time chlorine determination in different water samples with excellent selectivity. Furthermore, this FOS-SI-LOV methodology provided a colorimetric and fluorescence detection platform for other hazardous species monitoring in water environment based on Beer's law and Stern-Volmer relationship, respectively.

A miniaturized evanescent-wave free chlorine sensor based on colorimetric determination by integrating on optical fiber surface

Chlorine is a powerful oxidizing agent extensively used in water disinfection and blanching processes. Too low or too high chlorine concentration in water supplies would cause hazards for water usage. In this work, a miniaturized microfluidic evanescent-wave sensor was developed for colorimetric determination of free chlorine in water. A microfluidic channel with narrow dc (50μm) was constructed to act as both flow cell and detection cell in this sensor. When light propagated by total internal reflection (TIR) in the fiber core, evanescent wave produced on the fiber surface could interact with the DPD reagents and produce absorption change. The free chlorine could be determinated by colorimetric method and evaluated by absobance according to Beer’s law. This miniaturized sensor showed improved performances of small detection volume (1.2μL), fast analysis (4.42s), low detection limit (1.5ppb) and excellent repeatability (1.59%) for chlorine determination. The sensor was applied to chlorine determination in different water samples. The results obtained were compared with those obtained by conventional spectrophotometry and iodometry, showing agreement and validating the sensor’s potential applications. Meanwhile, the fabrication of this sensor provides a miniaturized and portable detection platform for other hazardous species monitoring by simple modular design.

Determination of chlorine in cement via CaCl molecule by high-resolution continuum source graphite furnace molecular absorption spectrometry with direct solid sample analysis

The use of a new molecule the calcium mono-chloride (CaCl) with absorption band head at 621.145nm was evaluated in the development of a method for Cl determination in cement by high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GFMAS) employing direct solid sample analysis. Calcium compounds present in cement samples acted as CaCl-forming reagent. Pyrolysis and vaporization curves were established to optimize the atomizer temperature program. The optimum pyrolysis and vaporization temperatures were 1000°C and 2200°C, respectively. These values provided higher thermal stability of the CaCl molecule which allows reducing matrix effects and the calibration with aqueous standard solutions in the range of 10–200ng Cl. Correlation coefficient of 0.995 and a slope of 0.00159sng−1 were obtained, with a calculated limit of detection of 1.4ng Cl. Sample masses in the range 0.65–1.05mg can be accurately weighed and assayed. Commercial cement samples were analyzed by the proposed method and the concentrations of Cl were in the 159–540μgg−1 concentration range. Samples were also analyzed by the Brazilian Association of Technical Norms (ABNT) and results were in agreement at a 95% confidence level (paired t-test). Recoveries of Cl added to samples were in the range 101–118% and the relative standard deviations (n=12) were in the 3.4–11.2% interval.

The determination of chlorine in plastic using isotope dilution inductively coupled plasma mass spectrometry

The determination of chlorine (Cl) in plastic using isotope dilution inductively coupled plasma mass spectrometry (ID-ICPMS) combined with different sample pretreatment procedures was examined in the present study.

Determination of Chlorine in Crude Oil Emulsified via the MgCl Molecule by HR‑CS MAS

A method for chlorine determination in crude oil samples, through the formation of MgCl molecule, by high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) was developed and is described in this paper. The use of this molecule for chlorine determination in crude oil has not been reported up to now. Measures were carried out at the wavelength 377.010 nm and the samples were submitted to a simple treatment as emulsion, whose composition was optimized applying a simplex-centroid experimental design. Magnesium was used as molecule forming agent at the concentration of 10 g L-1, at least 500 times higher than the concentration of chlorine. This excess is required to ensure the molecule formation of all content of Cl present in the sample. Chemical modifier Pd was used and improved greatly the signal intensities. Optimized pyrolysis and vaporization temperatures, applied for determination, were 800 and 2300 °C, respectively. Accuracy was evaluated through analysis of certified reference materials, NIST 1848 and NIST 1634c, and addition and recovery tests with recoveries between 92 and 117%. Limits of detection and quantification were 3.0 and 9.0 µg g-1, respectively. The method was applied to eight crude oil samples.

Electrocatalytic Reduction of Free Chlorine at an N,N-Diethylaniline-grafted Carbon Electrode for Improved Sensitivity in Amperometric Detection.

The electrocatalytic activity of an N,N-diethylaniline-grafted carbon (DEA/PFC) electrode was utilized to improve the sensitivity in the cathodic detection of free chlorine. Voltammetric curves showed a well-defined cathodic peak of free chlorine on DEA/PFC, lowering the overlap with that of dissolved oxygen. Amperometric measurements were applied for the determination of free chlorine for a concentration range of 4 orders of magnitude. The results showed that measurements of the amperometric response with DEA/PFC can be used as the basis for a simple, accurate, and rapid method to determine free chlorine.