Iodometric And Iodimetric Titration Pdf 14
Iodometric And Iodimetric Titration Pdf 14 >>> https://urlgoal.com/2sVr6m
Iodometry, known as iodometric titration, is a method of volumetric chemical analysis, a redox titration where the appearance or disappearance of elementary iodine indicates the end point.
Redox titration using sodium thiosulphate, .mw-parser-output .template-chem2-su{display:inline-block;font-size:80%;line-height:1;vertical-align:-0.35em}.mw-parser-output .template-chem2-su>span{display:block;text-align:left}.mw-parser-output sub.template-chem2-sub{font-size:80%;vertical-align:-0.35em}.mw-parser-output sup.template-chem2-sup{font-size:80%;vertical-align:0.65em}Na2S2O3 (usually) as a reducing agent is known as iodometric titration since it is used specifically to titrate iodine. The iodometric titration is a general method to determine the concentration of an oxidising agent in solution. In an iodometric titration, a starch solution is used as an indicator since it can absorb the I2 that is released. This absorption will cause the solution to change its colour from deep blue to light yellow when titrated with standardised thiosulfate solution. This indicates the end point of the titration. Iodometry is commonly used to analyse the concentration of oxidizing agents in water samples, such as oxygen saturation in ecological studies or active chlorine in swimming pool water analysis.
The volatility of iodine is also a source of error for the titration, this can be effectively prevented by ensuring an excess iodide is present and cooling the titration mixture. Strong light, nitrite and copper ions catalyse the conversion of iodide to iodine, so these should be removed prior to the addition of iodide to the sample.
For prolonged titrations, it is advised to add dry ice to the titration mixture to displace air from the Erlenmeyer flask so as to prevent the aerial oxidation of iodide to iodine. Standard iodine solution is prepared from potassium iodate and potassium iodide, which are both primary standards:
Demonstration of titration on paper microfluidics. (a) Ascorbic acid (concentrations are in µM); (b) citric acid; (c) nitrite (concentrations are in mM); (d) glucose (concentrations are in M); (e) Intensity Profile of a; (f) Intensity Profile of c; (g) Intensity Profile of d. (Scale bar: 3 mm).
To detect titration end point we will use a standard indicator for iodine titrations - starch. We start with a solution containing relatively high concentration of iodine, so indicator has to be added close to the end point. See iodometric titration end point detection for a more detailed explanation.
As it often happens in the case of multistage procedures, equation that describes whole process is only an oversimplification of the real procedure. What is important is that it preserves the stoichiometry of the process, so it can be used for the calculation of titration results:
Apart from general sources of titration errors, when titrating with iodine we should pay special attention to titrant. Thiosulfate solutions are not stable and they should be standardized every 2-3 months. It is also important to keep the flask closed during the reaction, as iodine is volatile and it can be lost from the mixture. For the same reason titration before indicator is added should be performed reasonably fast. After that iodine concentration is low and there is no need to hurry, although leaving the solution can be still source of serious errors.
The Winkler Method uses titration to determine dissolved oxygen in the water sample. A sample bottle is filled completely with water (no air is left to skew the results). The dissolved oxygen in the sample is then "fixed" by adding a series of reagents that form an acid compound that is then titrated with a neutralizing compound that results in a color change. The point of color change is called the "endpoint," which coincides with the dissolved oxygen concentration in the sample. Dissolved oxygen analysis is best done in the field, as the sample will be less altered by atmospheric equilibration.
Community based cross-sectional designs on selected 318 household food caterers were interviewed and salt samples were accordingly collected. Data was analyzed by the SAS-9.2 statistical software package. The iodine concentrations of the salt samples were determined by using the golden standard iodometric titration technique. Logistic Generalized Estimating Equation (GEE) statistical analysis method was used to assess factors affecting proper iodized salt utilization at household level.
Data was collected using structured questionnaires which sought information on socio-demographic and economic variables, availability and accessibility of iodized salt, practice of salt utilization, concentration of iodized salt, Knowledge and attitude regarding to iodized salt and IDDs. The questionnaires were adapted from different studies taking into account the local situation of the study area [10, 21] (Additional file 1). The collected salt samples were tested by using an iodometric titration technique to measure the iodine concentration. This process was done in Tigray Health Research Laboratory.
To ensure data quality and consistency of the measurement tool, the questionnaire that was in Tigrigna was translated back to English. About 5% of the total participants of the study were pre-tested by similar households to check any discrepancy. Data was collected under close supervision and data was checked for completeness daily by the principal investigators. The quality of the test of the iodometric titration technique was checked to positive and negative controls.
Descriptive statistics were done to determine the proportion of households using adequately iodized salt, socio demographics and concentration of iodine in the salt. An inter observer variation of the iodized salt between self report of the respondents and iodometric titration was measured by using kappa statistics. The Kappa agreement was interpreted according to the scale [22]. Specificity, sensitivity, positive predictivity, negative predictivity and predictive validity of self-report on the use of iodized salt were calculated to check its validity with iodometric titration.
The main aim of this study was to assess adequately iodized salt coverage, iodine concentration in salt and factors affecting proper iodized salt utilization among the households of Ahferom District, North Ethiopia. This in-depth community-based study revealed that 52.83% of the respondents have self-reported as they use adequately iodized salt, however, only 17.5% of the households were using adequately iodized salt when tested using an iodometric titration technique. The kappa agreement of iodometric titration test and validity of predicting adequately iodized salt by using perceived self report was poor. This indicates either there was a problem in identification of iodized salt during the purchasing or there might be a loss of iodine more than expected during storage and/ or transportation of the iodized salt in the whole sellers, shops and others where salt was sold.
The strengths of this study were: Iodine concentration in salt was determined by quantitative golden standard iodometric titration technique, statistical analysis and modeling was done by logistic GEE, which can handle intra class correlation within the clustered data and this study have used to combine both household practice and quantitative concentration of iodine in salt as the outcome variable. However, this study was not without limitation; the study was done in one region and the findings may not generalize to national levels. In addition to that design effect was not considered during sample size determination and the cross-sectional study design limits the factors to establish temporal relationship; hence inference of causation is not possible. 2b1af7f3a8