Nepheloturbidometry.pptx

Introduction, methodology and applications are discussed

1. Nepheloturbidometry By Dr. Nidhi Gupta Assistant Professor M.M. College of Pharmacy Maharishi Markandeshwar (Deemed to be University), Mullana , Ambala , India

2. Introduction Nephelometric and turbidometric methods depend on the scattering of light by particle suspended in a liquid. The suspended particles have refractive index values different from the suspending medium. The overall effect mimics Tyndal effect. Nephelometry is the measurement of scattered light as a function of concentration of suspended particles where the concentration is less than 100 mg/ litre . Turbidometry is the measurement of transmitted light as a function of concentration of suspended particles where the concentration is more than 100 mg/ litre that is high concentration samples

3. Principle At lower concentration of the suspension uniform scattering of particles is noticed. So the intensity of scattered light is directly proportional to the concentration of solute. The intensity of scattered light can be measured at 45°, 60°, 90° and 135°also. For higher concentration suspensions scattering is non uniform and light becomes scattered in all possible directions. Hence, it is difficult to measure the intensity of scatter radiation at specific angles . So, the intensity of transmitted light (that is unscattered ) direction is measured at 180°. The intensity of transmitted light (It) is a function of concentration i.e. when the concentration increases the intensity of transmitted light is less and when concentration is less the intensity in high . Depending on the sample concentration of the suspension either nephelometry or turbidometry is chosen. Suspensions with lower concentration nephelometry and for higher concentration turbidometry are utilised .

4. Factors that produce uniform turbidity: Order and rate of mixing of substances 2] Agitation of suspension 3] Temperature; as it affects solubility and viscosity of medium 4] Presence or absence of inert electrolyte and protective colloids such as gelatin, accacia etc. 5] Concentrations of solutions mixed Factors that produce scattered radiation: 1] Number of suspended particles 2] Size and shape of particles 3] Wavelength of radiation used 4] Difference in refractive index of particles and medium.

5. Instrumentation There are separate instruments available as nephelometer and turbidimeter . Also, they are combined to form a Nephloturbidometer . Following are the common instrumental components: Source of light Tungsten lamp is used when a polychromatic light is necessary and a Mercury arc lamp is used when a monochromatic light is necessary. 2. Filters and Monochromators When polychromatic light is used filters and monochromators are not required but when monochromatic light is necessary a filters or monochromator is used. In turbidimeter blue filter 530 nm is used and in a nephelometer visible filter is used as a secondary filter.

6. 3. Sample cells Various shapes of sample cells are used in a nepheloturbidimetry . They may be cylindrical with the path length of 1 cm. Also they may be rectangular cells but the cell walls may be coated with black to avoid any reflection that may interact detector response. Cells can also be prepared as per need to measure the scattered light at different angles of 45°, 90°, 135° and 180°. These cells are made up of glass . 4. Detectors Photometric detectors like photovoltaic cells photomultiplier tubes are used in such instruments. Photovoltaic cell or phototubes are used in turbidimeter . Whereas in nephelometer photomultiplier tubes are used as the scatter radiation is weak.

7. If is suspension is to be measured whose concentration is unknown then A nepheloturbidimeter can be effectively used as it can detect both low concentration as well as high concentration suspensions. It has two detectors one for measuring the scattered light at 90° and the other one at 180° for transmitted light. The ratio of the response of two detectors is displayed as nepheloturbidimetric units or NTUs which is proportional to the ability of the suspension .

8. Applications The nepheloturbidimeter can be effectively used for various purposes such as: Analysis of clarity of water Determination of carbon dioxide Determination of inorganic substances like phosphorus ammonia sulphate etc. For quantitative analysis of ions at ppm levels Analysis of petroleum products, sugar products and clarity of citrus juices In turbidimetric titration

9. Thank you………..