University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Chlorine, free

  • InChI: InChI=1S/Cl

@ ChemSpider@ NIST@ PubChem

Citations 7

"Determination Of Free And Combined Residual Chlorine By Flow Injection Spectrophotometry"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 233-240
Krishna K. Verma, Archana Jain and Alan Townshend*

Abstract: Optimized conditions are described for determining free and combined residual Cl. For 0.5 to 40 µg mL-1 of free Cl, 50 µL of sample solution is injected into 0.25 M HCl (1 mL min-1) as carrier and the stream is merged with 16 mM 4-nitrophenylhydrazine (I) in 60 mM HCl (0.5 mL min-1). After passage through a 75-cm coil, the stream is merged with aqueous 0.3% N-1-naphthylethylenediamine hydrochloride (1 mL min-1) coupling reagent and passed through a 70-cm coil before detection at 532 nm. To determine similar concentration. of total residual Cl, the I reagent also contains 20 g L-1 of KBr, with which both types of residual Cl react; the Br thus produced acts as the oxidizing agent. Combined residual Cl is determined by difference. A reagent-injection variant is used to determine 0.05 to 10 µg mL-1 of analyte. Response is rectilinear over both the cited ranges, and the detection limit is 0.03 µg mL-1 by the reagent-injection method. Sample throughput is 110 h-1. Chlorine dioxide interferes, but ClO3-, ClO2-, NO3-, up to 3 µg mL-1 of NO2- and a range of other ions are tolerated. The method does not distinguish between chloramine and dichloramine. The method was applied to Cl-doped model samples, and results agreed well with those obtained by flow injection spectrophotometry with NN-diethyl-p-phenylenediamine and by iodimetric titration. A new reaction scheme to determine free residual Cl in the presence of other Cl species, viz. ClO2-, ClO3-, and ClO2, was evaluated. The scheme is based on the oxidation of 4-nitrophenylhydrazine by free Cl to the 4-nitrophenyldiazo cation and its electrophilic coupling with N-(1-naphthyl)ethylenediamine dihydrochloride to give an azo dye with an absorption max. at 532 nm. Flow injection systems are proposed to determine 0.05-10 µg/mL free Cl by the reagent-injection technique, and 1-40 µg/mL free Cl by sample injection. The limits of detection of free Cl and mean relative standard deviation (range) were 0.03 µg/mL and 0.9% (0.6-1.2%), and 0.4 µg/mL and 0.6% (0.4-0.8%), respectively. Only ClO2 interferes. The results were in good agreement with those obtained by flow -injection N,N-diethyl-p-phenylenediamine spectrophotometric and classical iodometric titration methods. Since chloramines do not interfere in free Cl determination, a method was developed to determine total Cl (and hence of combined Cl by difference after determination of free Cl) utilizing a secondary reaction of both free and combined Cl with Br- to yield Br which then acts as oxidizing agent. The sample throughput was 110/h in both methods.
Spectrophotometry Optimization Interferences Method comparison

"Improvements In The NN-diethyl-p-phenylenediamine Method For The Determination Of Free And Combined Residual Chlorine Through The Use Of FIA"
Talanta 1991 Volume 38, Issue 2 Pages 145-149
G. Gordon, D. L. Sweetin, K. Smith and G. E. Pacey

Abstract: Buffer solution (pH 6.3) was mixed sequentially with NN-diethyl-p-phenylenediamine (I) solution and a stream of water containing the sample. After passage of the mixture through a 30-cm reaction coil, the absorbance of the solution was measured at 520 nm to give free Cl. For the determination of total Cl, the eluate was mixed with KI solution, passed through a 40-cm reaction coil and the absorbance of the solution was measured at 520 nm; combined Cl was determined by difference. The rectilinear range of the calibration graph was extended (to 0.1 to 8 mg L-1 of Cl) and coefficient of variation were improved (to 0.5 to 3%), compared with colorimetric or titrimetric methods involving I. The detection limit was 0.07 mg L-1 of Cl.
Water Spectrophotometry Buffer Method comparison

"Investigation Into The Detection Of Chlorine Species By Rhodamine 6G Chemiluminescence With Electrochemical Modification"
Analyst 1995 Volume 120, Issue 2 Pages 477-483
Gordon P. Irons and Gillian M. Greenway

Abstract: A flow system for free chlorine determination was developed. A portion (140 µL) of the sample (hypochlorous acid; I) in 0.1 M phosphate buffer of pH 6.7 was injected into a an aqueous carrier stream (2 ml/min) which merged with a stream (2 ml/min) of 2 mM Rhodamine 6G in 5% Tween 40. The chemiluminescence produced was measured. The detection limit was 90 µg/l of free chlorine and the calibration graph for up to 4 ppm I is shown. No RSD are given. The flow system was used to investigate whether other chlorine species, not normally detected by Rhodamine 6G chemiluminescence, could be detected by electrochemically-modified chemiluminescence in the presence of a charged Pt electrode. The analytes tested were NaCl, NH4Cl, KClO3, NaClO4, sodium hypochlorite and a mixture of chloramines. All the analytes tested except hypochlorite exhibited voltage-dependent chemiluminescence. The possibility of using Rhodamine 6G chemiluminescence combined with electrochemical modification to quantify a number of chlorine-containing species in water is discussed.
Water Chemiluminescence Optimization

"Selective Chlorine Determination By Gas Diffusion Flow Injection Analysis With Chemiluminescent Detection"
Anal. Chem. 1988 Volume 60, Issue 1 Pages 2-4
J. R. Gord, G. Gordon, and G. E. Pacey

Abstract: To determine dissolved free Cl (i.e., Cl2, ClO- and HClO) in water, the sample (0.35 ml) was injected into a donor stream (2.25 mL min-1) of 1 M HCl, from which Cl2 transferred through a 0.45 µm PTFE membrane into an acceptor stream (pH 11.75; 0.8 mL min-1) of 75 mM KOH, which was then mixed with 5 mM H2O2 - 1 mM lophine in ethanolic KOH (0.8 mL min-1) as chemiluminescence reagent to react with the ClO- formed. Rectilinear response was obtained for 175 ppb to 900 ppm of Cl, with a limit of detection of 75 ppb, and a coefficient of variation of 1.3%. Sample throughput was 120 h-1. A modified system was used for samples also containing ClO2.
Environmental Chemiluminescence Gas diffusion Teflon membrane

"Flow Injection Chemiluminescence Sensor For The Determination Of Free Chlorine In Tap Water"
Anal. Lett. 1997 Volume 30, Issue 1 Pages 11-19
Wei Qin; Zhujun Zhang; Shuna Liu

Abstract: A schematic diagram is given of the flow system. Luminol was immobilized on an anion-exchange column. A 0.15 M NaOH (200 µL) stream was mixed with a water carrier stream and injected via a six-way valve into the anion-exchange column. The alkaline aqueous solution eluted luminol from the column which was then mixed with a sample stream which had already passed through a cation-exchange column to remove interfering metal ions. The streams were mixed just before the flow cell and the resulting chemiluminescence was measured. The response of the sensor was linear from 10 ng/l to 40 µg/l with a detection limit of 8 ng/ml. The sample throughput was 60/h. The RSD (n = 7) was The effects of foreign ions on the determination were investigated. Recoveries ranged from 95-106%.
Water Chemiluminescence Ion exchange Sensor Immobilized reagent Resin Interferences

"Continuous-flow Method For Simultaneous Determination Of Monochloramine, Dichloramine, And Free Chlorine: Application To A Water Purification Plant"
Environ. Sci. Technol. 1989 Volume 23, Issue 1 Pages 46-50
Toyoaki Aoki

Abstract: A continuous-flow system is described and illustrated, for simultaneous determination of chloramide (I), chlorimide (II) and free Cl in water, which incorporates three double-tube separation units, each consisting of a PTFE outer tube and an inner tube of micro-porous PTFE. The three tubes were used for determination of I, I plus II, and I, II and Cl, respectively, by reaction with I- and absorbance measurement at 288 nm. Optimum pH and reagent concentration. for each reaction are given. Calibration graphs covered the ranges from 0.1, 0.02 and 0.02 mg L-1 of Cl for I, II and free Cl, respectively, to 71 mg L-1 for all Cl species. Within- and between-run coefficient of variation were 3.3% (n = 5) and 10% (n = 8), respectively. The method was applied in monitoring of I and II in water purification plants.
Water Spectrophotometry pH Tubular membrane Simultaneous analysis

"Use Of A Novel Apparatus Based On The Injection Principle For Automatic Voltammetric Analysis"
Hung. Sci. Instrum. 1979 Volume 45, Issue 1 Pages 1-8
Feher, Z.;Nagy, G.;Bezur, L.;Szovik, J.;Toth, K.;Pungor, E.

Abstract: The injection measuring principle, capable of rapid serial analysis of individual sample solutions, is described. As examples from the field of environmental analysis, the determination of free Cl content and the determination of phenol and phenolic compounds by using a novel app. based on the injection principle is described. The Modul Momatic 100 S voltammetric analytical application consists of a 28-channel peristaltic pump, an automatic sample changer, an analysis unit, a controller and integrator unit, a recorder, and a printer. Modes of operating the app. are described and shown in diagrams.
Environmental Voltammetry Apparatus Injector Review