Archive for July, 2014

TDS Meter

July 8th, 2014

TDS meter is an equipment which is used to measure the amount of Total Dissolved Solids i.e. TDS in an aqueous state/water. The instrument/equipment is convenient, accurate, portable and easy to operate, especially for field measurement.

What Are Total Dissolved Solids?

Total Dissolved solids” refer to mobile charged ions including minerals, salts, metals, cations or anions dissolved in given volume of water. This includes anything present in water other than the pure water (H20) molecule and suspended solids. (Suspended solids are any particles/substances that are neither dissolved nor settled in the water, such as wood pulp.) TDS is expressed in units of mg per unit volume of water (mg/L), also referred to as parts per million (ppm).

Principle of TDS meter

A TDS meter is based on the Electrical Conductivity (EC) of water. Pure H20 has virtually zero conductivity. Conductivity is usually about 100 times the total cations or anions expressed as equivalents. TDS is calculated by converting the EC by a factor of 0.5 to 1.0 times the EC, depending upon the levels. Typically, the higher the level of EC, the higher the conversion factor to determine the TDS. While a TDS meter is based on conductivity, TDS and conductivity are not the same thing.

Applications of TDS meter

  • To identify the Taste and effect of TDS on Health


High TDS results in undesirable taste which could be salty, bitter, or metallic. It could also indicate the presence of toxic minerals. The Environmental Protection Agency (EPA) recommended maximum level of TDS in water is 500mg/L (500ppm).

  • To meaure Hardness

High TDS indicates Hard water, which causes scale buildup in pipes and valves, inhibiting performance.

  • For the aquatic life

A constant level of minerals is necessary for aquatic life. The water in an aquarium or tank should have the same levels of TDS and pH as the fish and reef’s original habitat.

  • To measure the Hydroponics

TDS is the best measurement of the nutrient concentration in a hydroponic solution.

Soxhlet Extraction Overview

July 3rd, 2014

When a compound of low solubility such as lipid is need to be extracted from a solid mixture a Soxhlet extraction can be carried out. The technique places a specialized piece of glassware in between a flask and a condenser. The refluxing solvent repeatedly washes the solid extracting the desired compound into the flask. The Soxhlet extraction method was described by Soxhlet in 1879, in this procedure; oil and fat from solid material are extracted by repeated washing/percolation with an organic solvent usually hexane or petroleum ether, under reflux in a special glassware. Soxhlet extraction is only required where the desired compound has a limited solubility in a solvent and the impurity is insoluble in that solvent.

Lipids are a group of substances that, in general, are soluble in ether, chloroform, and other organic solvents but are relatively insoluble in water. An accurate and precise quantitative analysis of lipids in foods is important not only for nutritional labeling, but also for determining whether the food meets the standards for identity and uniformity, and for understanding the effects of fats and oils on the functional and nutritional properties of foods. The validity of the fat analysis of a food depends on many factors, including proper sampling and preservation of the sample before the analysis. Because of commercial regulations, it is important for food producers to be able to report fat content in a serving size of a food item.

Figure of Soxhlet extractor


1. Flask containing the solvent

2. Thimble placed in an extraction chamber

3. Funnel allows recovering the blog uploadsample

4. Condensor

In this method the sample is dried, ground into small particles and placed in a porous cellulose thimble. The thimble is placed in an extraction chamber, which is suspended above a flask containing the solvent and below a condenser. The whole unit is supported with the heating unit. The flask is heated and the solvent evaporates and moves up into the condenser where it is converted into a liquid that trickles into the extraction chamber containing the sample. The extraction chamber is designed so that when the solvent surrounding the sample exceeds a certain level it overflows and trickles back down into the boiling flask. At the end of the extraction process, which lasts a few hours, the flask containing the solvent and lipid is removed. In some device a funnel allows to recover the solvent at the end of the extraction after closing a stopcock between the funnel and the extraction chamber.

Safety cautions should be considered while using Soxhlet Extractor and Glass wares

  • To prevent the introduction of contamination into the sample and sample extracts at any time during the sample processing and analytical operation, it is vital that all glassware and other materials coming into contact with the sample should be clean properly.
  • All cleaned glassware should be stored prior to use under clean aluminum foil to prevent contamination by fallout from laboratory air, preferably in an enclosed cabinet.
  • To prevent the introduction of contamination to the cleaned glassware preparation and subsequent handling, it is important that suitable gloves should be worn. Disposable polyethene or latex gloves have been found suitable, however powdered gloves are not acceptable.


Soil Salinity And Its Measurement Soil Salinity Tester

July 2nd, 2014

Soil is the medium of growth of natural vegetation on earth’s surface. Various factors affect its composition such as climate, water level, biological properties and Salinity etc. The Salinity of soil refers to the amount of salts in the soil and it can be estimated by measuring the electrical conductivity (EC) of an extracted soil solution (EC increase with increase ion concentration). Salinity measurements are an important aspect of soil, crop and environmental protection, research and management.

Soil Salinity Tester measures the total amount of soluble salts in solution in a given soil sample. These tester based on electrical conductivity or total dissolved solids/ions measurements.

Applications of Soil Salinity Tester are:

  • Efficient monitoring of Soil Salinity.
  • Plant nutrient status and Fertigation.
  • Pollution and land reclamation.
  • Soil moisture mapping.

Two common ways for measuring Soil Salinity

  • Electrical Conductivity; EC meters measures how much electricity moves through a solution – the saltier the solution, the more the electricity moves through it, and higher the conductivity reading. EC for soil is measured in dS/m (deciSiemens/metre).
  • Total dissolved solids or total dissolved ions; measures how much salt is dissolved in soil solution. It is measured in units of mg/l (milligrams/litre) or ppm (parts per million). Higher readings mean more salt is present in the solution.

Effect of Soil Salinity on Plant Growth

Salinity can affect plant growth in several ways, directly and indirectly. High concentration of salt in soil can deteriorate the agricultural value of land.

Direct soil salinity damages

  • Decreased water uptake; High salts concentration results in high osmotic potential of the soil solution, so the plant has to use more energy to absorb water. Under extreme salinity conditions, plants may be unable to absorb water and will wilt, even when the surrounding soil is saturated.
  • Ion-specific toxicity
    When a plant absorbs water containing ions of harmful salts (e.g. Sodium, Chloride, excess of Boron etc.), visual symptoms might appear, such as stunted plant growth, small leaves, marginal necrosis of  leaves or fruit distortions.


Indirect soil salinity damages

  • Interference with uptake of essential nutrients
    An imbalance in the salts content may result in a harmful competition between elements. This condition is called “antagonism“, i.e. an excess of one ion limits the uptake of another ion.
  • Sodium effect on soil structure
    In saline soils, sodium replaces calcium and magnesium, which are adsorbed to the surface of clay particles in the soil. Thus, aggregation of soil particles is reduced, and the soil will tend to disperse. When wet, a sodic soil tends to seal, its permeability is dramatically reduced, and thus water infiltration capacity is reduced as well. When dry, a sodic soil becomes hard has the tendency to crack. This may result in damages to roots.

Factors affecting soil salinity

  • Irrigation water quality; the total amount of dissolved salts in the irrigation water, and their composition, influence the soil salinity. Therefore, various parameters, such as source water EC and its minerals content should be tested.
  • Fertilizers applied; The type and amount of fertilizers applied to soil, affect its salinity. Some fertilizers contain high levels of potentially harmful salts, such as potassium chloride or ammonium sulphate. Overuse and misuse of fertilizers leads to salinity buildup, and should be avoided.
  • Field’s characteristics;a poorly drained soil might reach salinity level that is harmful to the plants and to the whole crop. A soil that was not flushed after a previous growing cycle might contain high level of accumulated salts.