Modern/ Sophisticated Instruments

Instrument discussed above are general purpose instruments which provide useful information regarding physicochemical properties and microbiological analysis of milk and milk products (proximate analysis). However, development of more sophisticated instruments has enabled the estimation of pesticide residues, toxins, antibiotic residues etc in part per billion (ppb) levels which was impossible with classical instruments. Some of these instruments are discussed below in brief.

i. Flame Photometer: Flame photometer is used for the quantative chemical analysis for the determination of alkali and alkaline earth metals (Sodium and Potassium etc.) present in solution. Flame photometer is must when concentration of the element is very low, say of the order of 1ppm as ordinary method, such as gravimetric or volumetric will not respond. The principle of flame photometer is based on the fact that different eliments emits light of different wave length on burning in a flame. This characteristics wave length by a particular element isolated to the characteristics wave band by an optical filter is allowed to fall on a photocell whose output is measured by a suitable deflection for instant an electronic amplifier and a meter or glavnometer. The intensity of the emitted light is proportional to the concentration of the element in the solution. Thus the concentration of an eliment can be determined in the solution through determination of the intensities of solutions of different but known concentrations and preparation of a standard curve.

ii. Atomic Absorption Spectrophotometer: This instrument employ special light source (hollow cathode lamps) constructed for the specific element to be analyzed. A sample is dissolved in a solvent and burnt for atomization and light from the specific cathode lamp is passed through the flame. The proportion of light absorbed is proportional to the concentration of the element in the sample.

Thus by comparison of the extent of absorbed light of the unknown sample and a series of standard solutions it is possible to calculate the concentration of the element in the unknown sample. The instrument is widely used and accepted technique for determining trace (hg/ml) or ultra trace (sub-hg/ml) levels of an element in a wide variety of samples.

iii. High Precision Thin Tayer Chromatography (HPTLC): In chromatography the solution are resolved by differential rates of elution as they passes through the plate or column. Their separation is governed by their distribution between the stationary and mobile phases. HPTLC is a more sensitive, adaptable and rapid technique than paper chromatography. It has wide application in quantifying as well as qualitative analysis of various biomolecular. It is the cheapest and the best method for isolating and identifying minor components of food.

iv. Gas Liquid Chromatography (GLC): It is the most elegant and useful method in analytical chemistry. It is a form of partition chromatography in which the stationary phase is a film held in place on a solid support and the mobile phase is a carrier gas flowing over the surface of a liquid film in a controlled fashion. The vaporized sample is fractionated as a consequences of being partioned between the mobil gas phase and liquid stationary phased held in a column. Analysis of food using GLC is concerned with the assay of lipid, proteins, carbohydrates, preservatives, flavours, colorants and texture modifiers. It is particularly suitable for determination of fatty acid profile of the food lipids and flavours compounds of a food. It is also usefull in the analysis

of vitamins, steroids drugs and pesticide residues.

v. High Pressure liquid chromatography (HPLC): This is a very fine and high precision technique but the successful use of the techniques for a given problem requires the right combination of a variety of operating conditions such as the type of column, packing and mobile phase, column length and diameter, flow rate, column temperature and sample size. In fact newer columns and packing materials offer high performance at moderate pressure (although still high relative to gravity flow). HPCL methods have been developed in a variety of areas including organics, biological, small molecules, macromolecules, pollutants, polymers, and many others. Chromatography can be done in a number of modes. The best mode for a particular separations depends on the structural characteristics of the solutes to be separated and the analysis requirements. HPLC methods can be selected based on the molecular weight and the solubility of the substance. In many samples separation can be achieved by reverse phase chromatography using a bonded silica, stationary phase.Reverse phase HPLC is the first choice because it is often faster, cheaper and easier than other alternatives.

vi. Rancimate: This is a modern, PC-controlled instrument which is used to determine the oxidative stability of a fatty food. The determination of the oxidative stability in natural fat and oils is a method of quality control in food industry. This method has been developed as an automated version of the extremely demanding AOM method (active oxygen method) for the determination of the induction time of fats and oils. In this method the highly volatile organic acids produced by oxidation are absorbed in water and used to indicate the induction time.

vii. Liquid Chromatography Mass Spectrophotometer (LCMS): Its an indispensable tool for problems solving in virtually all analytical fields requiring “information rich” chemical analysis. Its use is must when the concentration of residues and contaminants is in PPB levels.

viii.Gas Chromatography Mass Spectrophotometer (GCMS): It involves high resolution capillary gas chromatography with mass spectral detection,aids in the analysis of residual volatiles in polymers, pharmaceuticals and packing materials. It is must for the pesticide analysis.