Application Ion Selective Potentiometry (ISP) for Determination Chloride Ion in Natural and Drink Water

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1 European Journal of Scientific Research ISSN X Vol.62 No.1 (2011), pp EuroJournals Publishing, Inc Application Ion Selective Potentiometry (ISP) for Determination Chloride Ion in Natural and Drink Water Amra Odobašić Selma Tuzlak Sead Ćatić Husejin Keran I. Šestan Abstract Water is the wealth of the planet. First life forms were created in the water. Water is the source and condition of the planet's existence. Like all living beings, man is composed of water, and its survival depends on water. For accurately understanding of the analysis of water and for proper evaluation and classification of water, it is required to have good knowledge of chemical processes, analytical methods as well as changes that are possible in the sample and the consequences they can have on water quality. Water used for drinking must be chemically and biologically correct. This means that its structure and the presence of microorganisms have to be in certain limits defined by its regulations. If the content of microorganisms in water is above the allowed limits, the water disinfection has to be undertaken. Water disinfection is the basic process of water treatment for removing (inactivating) pathogenic microorganisms from water to prescribed level. Methods of water disinfection: 1. reagentive (oxidative) processes: chlorination, ozonization, the use of other halogens, hydrogenperoxidant permanganate disinfection 2. nonreagentive procedures: ultrasound disinfection, disinfection with ultraviolet rays and heat disinfection Chlorine is the oldest and most effective way of water disinfection. The aim of this paper, speaking about the content of chlorid ion in natural and drinking water, is to demonstrate the concept and methodology of the analysis, control and monitoring of water quality. Content of chloride ion in drinking and natural water will be

2 Application Ion Selective Potentiometry (ISP) for Determination Chloride Ion in Natural and Drink Water 71 tested on the particular sample. Also, aim of this paper is to show advantage of ISP for determination the concentration of chlorid ion in relation to standard method analysis like Mohrov method. Keywords: Water disinfection, chloride ion, ionselective potentiometry, chloride ionselective electrode. 1. Introduction Water is essential part of every human being and forms about 65% of our body. Water takes part in biochemical processes ranging from digestion through circulation of matters in the body, excretion, respiration, transpiration, etc [1]. On the other hand, water is a risk because of the possible input and transmission of infectious pathogens and parasitic diseases. The most common pollutants in water are chemical (pesticides, phenols, heavy metals such as Pb, Cu, Cr, Cd and Hg and bacteriological [2]. According to the U.S. Environmental Protection Agency, there are 6 groups which cause contamination of drinking water: microorganisms, disinfectants, disinfection byproducts, inorganic chemicals, organic chemicals, radioactive substances. Disinfectants that are added to reduce the number of microorganisms, as well as disinfection byproducts can cause a series of disorders in body (anemia, impaired function of liver, kidneys, nervous system), so it is necessary to perform constantly control of them. Chemical disinfection is economically most favorable when it comes to processing large amounts of water, for the preparation of drinking water and wastewater treatment. That is why this type of disinfection is used almost exclusively in B&H. Most frequently used method is chlorination. As an active substance it contains threechlorozansodium, which acts on bacterial and virus pathogens, and the fungi and parasites. Chlorination as a method of disinfecting water is used in 99% cases of the disinfection of municipal water. It is applied so chlorine is directly introduced into the water. While in process of chlorination we should strive for water to be slightly acidic, this means that as much chlorine is in the form of hypochloric acid. Permissible concentration of chlorine as a means of disinfections is up to 3 mg / L. Chloride ions in large quantities are present in sea water and sediments of the Earth's crust where it is associated with ions Na +, K + ; Mg 2+. In the human body it is also found in the form of chloride ions. Daily requirements for intake of chloride are up to the age range, from newborn to 500 mg to 2000 mg for adults. Chloride in water can be determined using ionselective potentiometry (ISP). [5] Ionselective potentiometry (ISP) is a nondestructive method, which means that the sample can be used for further analysis. Ionselective electrode (ISE) such as chloride, which is used in this article, as detector provides a range of possibilities in the analysis of samples of biological material [3]. Work of ionselective electrode is based on the fact that there is a linear relationship between the electrical potential established between the ISE and reference electrode and the logarithm of activity (or effective concentration) of ions in the solution. This relationship is described by Nernst equation: E = E o + (2.303RT/zF) log a (1) The function of ionselective electrode is based on selective leakage of positively charged specie from one phase to another, creating a difference in potential. Working principle is based on measuring the electrode potential (mv) depending on the concentration of tested ions in the solution. The reference electrode has a constant potential, and potential of ISE is changing with the concentration of certain ions. Measuring electrode is consisted of a body of electrode, ionselective membrane, the internal electrolyte and the internal reference electrode [4]. ISP has a high sensitivity to 10 5 mol/l and a short response time, from several seconds to 15 minutes for lower concentrations.

3 72 Amra Odobašić, Selma Tuzlak, Sead Ćatić, Husejin Keran and I. Šestan 2. Experimental 2.1. For the Determination of Chloride by Mohr Method Following Solutions are Being Used 1. AgNO3, mol/l and 0.01mol/l 2. NaCl 3. 5 % solution K2CrO4 (indicator) 4. For the determination of chloride by ISP following solutions are being used: 5. NaCl concentration 1 g/l as standard solution for preparation of solution for calibration curve, 6. KCl 7. 2 % ISA/FK 0.5M NaNO3 adjustment and maintenance of ionic strength Apparatus In the experimental work ISP as a choice method was used, and Mohr's method as a standard was the control method for the determination of chloride ions in natural water and drinking water. Chloride electrode type 500, was used as the ISE. The electrode consists of a PVC membrane based on o nitrofeniloctyleter. As a reference electrode WTW electrode type R502 was used. In this paper was determined the contents of chloride ions in natural and drinking water by using the chloride ISE on ionmetar type Microprocessor ph / ION Meter PMX 3000 WTW. In the process of preparing and analyzing, used chemicals were of high purity (CP) by manufacturers Merck and Kemika. 3. Results and Discussion In the experimental study the five different samples from the area of the Federation of Bosnia and Herzegovina as follows are being analyzed: 1 sample from city water Tuzla (TW), 1 sample from Lake Modrac (MW), 1 sample from city water Gradačac (GW), 1 sample from salt lake Panonica( PW) and 1 sample of bottled water (FW). For the determination of chloride ions in water it is not required prior sample preparation. Two calibration curves are recorded. For determination of chloride ions ISP the two calibration curves are being recorded. The first calibration curve (KK1) was recorded for solutions of higher concentrations of Cl ions, and second calibration curve (KK2) for solutions of lower concentrations of Cl ions. This was necessary due to large differences in the concentrations of Cl ions in drinking water and the waters of the lake Modrac and salt lake Panonica. Based on the calibration curve concentrations in the tested samples was calculated. To all samples was added 2% ISA/FK, whose concentration was 0.5 mol/l. Each sample was performed by three measurements and all samples were mixed for 5 minutes. Calibration curve was obtained with high accuracy. Error for calibration curve 1 was R 2 = and for calibration curve 2, R 2 = In Table 1 are given the concentration of chloride solutions for KK1 and read off the highest potential values in mv, and in Figure 1 is given KK1. Table 1: Values for calibration curve

Application Ion Selective Potentiometry (ISP) for Determination Chloride Ion in Natural and Drink Water 73 Diagram 1: Calibration Curve 1 (KK1) 160 E (mv) 155 150 145 y = 0,0874x + 159,79 R 2 =

Table 2: Values for calibration curve 2 1 1 183.3 2 3 179.6 3 5 177.8 4 10 171.5 5 15 166.8 6 20 161.

4 Application Ion Selective Potentiometry (ISP) for Determination Chloride Ion in Natural and Drink Water 73 Diagram 1: Calibration Curve 1 (KK1) 160 E (mv) y = 0,0874x + 159,79 R 2 = 0, c (mg/l) In Table 2 are given the concentration of chloride solutions of KK2 and read off the highest potential values in mv, and in Figure 2 is a data KK2. Table 2: Values for calibration curve Diagram 2: Calibration Curve 2(KK2) Table 3 shows average concentrations of chloride ion on the basis of equations derived from the direction of the calibration curve KK1, and in Table 4 the average concentrations of chloride ion obtained from the calibration curve KK2. Table 3: Concentration of chloride in water calculated from KK1 FW 341, ,9 PW 1569,679 22,6

5 74 Amra Odobašić, Selma Tuzlak, Sead Ćatić, Husejin Keran and I. Šestan Table 4: Concentration of chloride in water calculated from KK2 GW 4, ,4 TW 10, ,9 MW 6, ,6 After all samples were analyzed using ionselective potentiometry, Mohr's method was used as a comparative method for some sample. Mohr's method is a standard method for the determination of Cl. By this method following samples are being tested: TW, PW, and MW. For all three samples titration with AgNO 3 was performed three times. The calculated values of the concentration of chloride using Mohr method are given in Table 5. Table 5: Concentration of chloride obtained by Mohr method Sample C Cl mg/l TW MW PW Samples of lake water Modrac (MW) and salt lake water Panonica (PW) were taken during same weather conditions and with both ISP and Mohr method same results are obtained. Sample of TW shows a deviation in results between the two methods used,but this deviation is not significant. The difference is caused by interference that may occur while working with chloride electrode. Interference can be caused by complexes with Bi 3+, Cd 2+, Mn 2+, Pb 2+, Sn 2+, Ti 2+, reducing means as well as interfering ions. The obtained results for the GW and TW indicate that the chloride content is in the acceptable limits prescribed by WHO. The results for the sample FW show that the concentration of chloride ions is extremely high and exceeds the maximum allowed line. According to the regulations of the Republic of Serbia (Bosnia and Herzegovina has no defined Regulation on permissible concentrations of cations and anions in water), for chloride, the set limit is 200 mg / L (Fig. list SRJ, 42/98). The diagram 3 shows the results of a complete analysis of all water samples performed by ISP (samples GW, FW, MW and PW) and Mohr's method (samples TW, MW and PW ). Diagram 3: The comparative results of a complete analysis of samples of water ISP and Mohrov method 44, , ,01 ISP 341,99 10,12 6,836 14,811 6,747 Mohrov mg/l GW FW TW MW PW type of sample

6 Application Ion Selective Potentiometry (ISP) for Determination Chloride Ion in Natural and Drink Water Conclusion Based on the results obtained it can be concluded that the ISP has advantages over the standard Mohr's method, because measurements with the ISP are faster, efficient and reliable. Measurements are possible in a wide concentration range where the examined samples can still be use, meaning that this method is a nondestructive, unlike standard Mohr method. It does not require the use of many different chemicals, and does not require any preparation of samples before analysis, which directly affects the economic availability. References [1] C. Chieh: Water Chemistry and Biochemistry, (Blackwell Publishing, USA, ). [2] Roger M. Rowell: Removal of metal ions from contaminated water using agricultural residues, 2 nd International Conference on EnvironmentallyCompatible Forest Products, Fernando Pessoa University, Oprorto, Portugal (2006), [3] S. Mentus: Electrochemistry, (Belgrade, 2001). [4] A.Odobašić, S.Ćatić, H.Keran, H.Pašalić, I.Šestan,: ISP method of selecting of control content for Ca in milk, Journal for manifacturing, tehnology, bioingeneering and marceting, Vol.20 (2009), issues 12, p [5] M.Campbell: Sensor systems for environmental monitoring, Chapman & Hall, First Edition (1997)

Chapter 3 Electrochemical methods of Analysis-Potentiometry

Chapter 3 Electrochemical methods of Analysis-Potentiometry Electroanalytical chemistry Contents Introduction Galvanic and electrolytic cells Salt bridge Electrode potential and cell potential Indicator