Measurement of Chloride in Water

Measurement of Chloride in Water

Chlorine is naturally occurring is found in the mineral form of sodium chloride (common salt) and other salts.

A strong oxidizing agent, chlorine (Cl 2),is an ideal disinfectant. Proper residual chlorine levels in drinking water ensure that water is safe for human consumption, but too much chlorine in water can have detrimental effects. It is one of the best and cheap water disinfectant solution compare to Ultraviolet and ozonisation options also maintain slow decay rate thereby enabling hygiene for longer period.

Chlorination is the water treatment disinfection process which uses dissolving chlorine gas in water. It is used for taste and odor control, prevention of algal growths and epidemics of water borne disease, maintaining clear filter media, removal of iron and manganese, destruction of hydrogen sulfide, cyanide and improving coagulation.

Residual chlorine must be continuously monitored to prevent both under- and over-chlorination and factors including pH, temperature and fouling must be considered as these also affect the disinfectant strength of residual chlorine

Methods for measuring chlorine can be specific for free chlorine (hypochlorous acid and hypochlorite) or combined chlorine (chloramines and chloro-organics).

Summary of Methods of Chlorine Detection

Method	Signal	Linear range ppm	LOD ppb	Error %	Known Interferences
Spectrophotometric	Colorimetric	0.01 - 5	4	4 - 7	Metal ions, Chloramines , Organic compounds , oxidants
Syringaldazine	Colorimetric	0.1 - 10	100	10	UV light , Monochloramine
Titration with FAS and DPD indicator	Colorimetric	0.02 - 5	11	5	Metal ions, Chloramines , Organic compounds , oxidants
Amperometric DPD	Amperometric	0.01 - 5	4	4 -7	Metal ions, Chloramines , Organic compounds , oxidants
Iodometric titration with sodium thiosulfate	Colorimetric	1 – 20	150	2 – 4	Nitrite , Oxidants , transition metal ions
Platinum Electrodes	Amperometric	0 - 20	5	2	Metal ions , oxidants, biofilm , scale
ABTS	Colorimetric	0.012 -0.70	2	4	Bromine and Brominated compounds
MnO2 nanosheets	Colorimetric	0.007-0.35	2.8	1.1 – 1.2	pH and temperature sensitive
BSA coated gold nanoclusters	Fluorometric	0.012-0.60	3.5	4.35	Must be refrigerated to prevent denaturation
Polyuminol based sensor arrays	Luminometric	0-1.4	18	6 - 10	Not Known
Gold film nano transducers	Amperometric	0.2 - 5	20	5	Biofilm
CdSe- Zns quantum dots	Fluorometric	0.018 -0.18	9	8 - 11	Not Known
Nitrogen and sulfur co-doped carbon dots	Fluorometric	0.00035-3.5	0.18	2.5 – 3.8	Not Known
Evanescent-wave analysis using fibre optics	Colorimetric	0.005 – 0.4	1.5	1.59	Microfluidic system
Chemresistive sensor	Chemresistive	1.5 -9	0.06	4.5 – 6.5	Not Known
Multiwalled carbon nanon tube	Amperometric	0.056 – 446.2	0.6	2.69 – 2.77	Not Known
Surfactant -modified Prussian blue sensor	Amperometric	0.009 – 10	9	4.2	Not Known

Article by Manmeet Singh Bhatti
Published 14 Jun 2022