Author Archives: gowrimanoja

About gowrimanoja

I am working as an assistant professor in a pharmacy college.

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Determination of density and specific gravity of foods

DETERMINATION OF DENSITY OF FOODS

Aim: To determine the density of given food samples (Solid and Liquid).

Requirements:

  • Chemicals: Distilled water, Acetone and Dil. Nitric acid for cleaning.
  • Apparatus: 100 mL Measuring cylinder, 100 mL Beaker.

Principle:  Density of a substance or material is its mass per volume at fixed temperature (If the temperature increases, the volume expands and the density of an object decreases) and pressure. UNITS: Kg/m3 or g/cm3. For solids, it is determined diametrically from the liquid displaced by the submerged solids.

When a solid mass is immersed in a liquid (Solid must be insoluble in this liquid), it displaces equal amount of liquid. So, the apparent weight of an object immersed in a liquid decreases by an amount equal to the weight of the volume of the liquid that it displaces.

Density is an absolute quantity.

Procedure:

Density of solid sample:

  • Weigh the desired solid sample on the weighing balance and note down its weight as W1.
  • Take a clean 100 mL measuring cylinder with 50 mL of water in it, note down the volume as initial volume V1.
  • Immerse the solid sample in the beaker. The weight of the solid sample raises the water level to another mark. Note down the final volume of water to which it has been raised as final volume V2.
  • Subtract V1 from V2 and note down the value as V.
  • Now calculate density as

Density = mass/ volume

Density = W1/ V

Density of Liquid sample:

  • Take a clean empty beaker and weigh it on a weighing balance. Note down its weight as W1.
  • Fill this empty beaker with 50 mL (V) of desired liquid sample. Now, weigh it on a weighing balance and note down its weight as W2.
  • Calculate the difference between W2 and W1 and note down as W, it is the actual weight of the liquid sample.
  • Density of the liquid food can be calculated as
  • Density = Mass/ Volume
  • Density = W/ V

Note:

  1. Clean the apparatus used in the experiment thoroughly with dilute nitric acid and then with acetone and then with distilled water thrice.
  2. The experiment must be done in a constant temperature and pressure area.
  3. All the values noted down must be accurate.

Calculations:

 Report:

DETERMINATION OF SPECIFIC GRAVITY OF FOODS

Aim: To determine the specific gravity of the given food samples.

Requirements:

  • Chemicals: Distilled water, Acetone and Dil. Nitric acid for cleaning.
  • Apparatus: 100 mL Measuring cylinder, 100 mL Beaker. Specific gravity bottle.

 

Principle:  Specific gravity is the ratio of the density of a substance to the density of a reference substance. At a same given volume, specific gravity is the ratio of the mass of a substance to the mass of a reference substance. UNITS: It is a dimensionless quantity.

Specific gravity of a substance is measured by two means: By hydrometer and by specific gravity bottle. Both methods are used to measure specific gravity of liquids. Specific gravity of solids is calculated by use of a weighing balance.

Substances with a specific gravity of 1 are neutrally buoyant. The substances neither sink nor float. Those with SG greater than 1 are denser than reference substance and will sink. Those with an SG less than 1 are less dense than reference substance and will float on it.

Specific gravity is a relative quantity.

Procedure:

Specific gravity of solids:

  • Calculate the density of the solid substance from the method illustrated in the experiment (DETERMINATION OF DENSITY OF FOODS)
  • Calculate specific gravity as

Specific gravity = Density of substance/ Density of reference substance

If reference substance is water, then its density is  1.0 g/cm3.

Specific gravity of Liquids:

By Hydrometer:

  • Take the liquid sample in a clean empty beaker up to the half.
  • Dip hydrometer in the sample and let it float freely.
  • Note down the reading on the hydrometer as
  • S is the specific gravity of the liquid substance.

By Specific gravity bottle:

  • Take a clean specific gravity bottle and note down its weight as W1.
  • Fill the same specific gravity bottle with distilled water up to its brim. Put on the lid and wipe the outer surface of the bottle with absorbent paper or tissue paper. Then, weigh it on a weighing balance and note down its weight as
  • Empty the specific gravity bottle.
  • Dry it in oven.
  • Fill the same specific gravity bottle with the desired liquid sample up to the brim. Put on the lid and wipe the outer surface of the bottle with absorbent paper or tissue paper. Then, weigh it on a weighing balance and note down its weight as W3.
  • Note down the difference of W2 and W1 as W. W is the weight of distilled water.
  • Note down the difference of W3 and W1 as Ws. Ws is the weight of sample.
  • Density of sample = Mass of sample/ Volume

Density of sample = Ws/ W × density of water

Density of water is 1.0 g/cm 3.

  • Specific gravity of sample = Density of sample/ Density of water

Note:

  1. Clean the apparatus used in the experiment thoroughly with dilute nitric acid and then with acetone and then with distilled water thrice.
  2. Hydrometer will sink in low density liquids and float in high density liquids.

 

Calculations:

  

 Report:

 

Standard operating Procedures

DIGITAL BALANCE

  • Purpose: To lay down the procedure for the operation of Digital balance.
  • Scope: This procedure for the operation of Digital balance.
  • Responsibility:
  • Accountability:
  • Precaution: Avoid any kind of water contact with the instrument.
  • Procedure:
  • 6.01: Clean the pan thoroughly prior to calibration.
  • 6.02: Switch ON the balance & allow it to stabilize for 15 mins.
  • 6.03: Place the Butter paper and tare it.
  • 6.04: Weigh the sample.

DIGITAL pH METER

  • Purpose: To lay down the procedure for the operation of Digital pH Meter.
  • Scope: This procedure for the operation of Digital pH meter.
  • Responsibility:
  • Accountability:
  • Precaution: Always keep the electrode in distilled water.
  • Procedure:
  • 6.01 Connect the power cable to 230 V A/c 3 pin power socket.
  • 6.02 Fix the electrode in to the stand clip.
  • 6.03 Insert the combined Electrode in buffer solution.
  • 6.04 Keep the temp.  at 30 ºC.
  •  6.05 Switch ‘ON’ the instrument.
  • 6.06 It will read 7.00 if not adjust with set 7.0.
  • 6.07 Wash the electrode with distilled water and wipe of the moisture.
  • 6.08 Dip electrode in standard 4.00 pH buffer, stir the beaker for while.
  • 6.09 Bring the switch to read position, the reading shall be 4.01 at 30 ºC.
  • 6.10 If it is not happening adjust SET-BUFFER Knob, to do so.
  • 6.11 Keep the switch in check position. Remove the Electrode from buffer, wash wipe of moisture and dip in unknown solution. After a minute put the switch to read position and read pH of the solution.

DIGITAL COLORIMETER

  • Purpose: To lay down the procedure for the operation of Digital Colorimeter.
  • Scope: This procedure for the operation of Digital Colorimeter.
  • Responsibility:
  • Accountability:
  • Procedure:
  • 5.01 Switch the instrument ‘ON’ by the main switch provided at the back and allow  instrument to stabilize for 5-10 minutes.
  • 5.02 Select proper filter by rotating turret.
  • 5.03  Insert ‘BLANK’ in sample holder and adjust meter read out to 000 with the ‘SET ZERO’ control.
  • 5.04  Remove the Blank and insert the test tube containing sample solution to coincide the marks.
  • 5.05 Note the OD reading of the sample solution.

DIGITAL POTENTIOMETER

  • Purpose: To lay down the procedure for the operation of Digital Potentiometer.
  • Scope: This procedure is for the operation of Digital Potentiometer.
  • Responsibility:
  • Accountability:
  • Procedure:
  • 5.01 Connect the mains cable to 230V single phase mains and switch ON the instrument.
  • 5.02 Keep Switch in Hold to read 000mv.
  • 5.03 Connect Calomel reference electrode to Terminal.
  • 5.04 Connect Platinum Electrode to Terminal.
  • 5.05 Dip the electrode in the solution to be titrated.
  • 5.06 Keep the Switch in Read to measure the EMF.

DIGITAL FLOURIMETER

  • Purpose: To lay down the procedure for the operation of Digital Flourometer.
  • Scope: This procedure is for the operation of Digital Flourometer.
  • Responsibility:
  • Accountability:
  • Procedure:
  • 5.01 Connect the instrument power cable to AC 230V mains. Switch ON the instrument.
  • 5.02 Select the primary and secondary filters from the range of filters available and insert them in the instrument.
  • 5.03 Take Blank in a cuvette and insert in sample holder.
  • 5.04 Press the knob beside the sample holder and adjust SET ZERO to read display ZERO.
  • 5.05 Remove the cuvette of Blank.
  • 5.06 Take sample in the cuvette, insert it in the sample holder.
  • 5.07 Press the knob and record the reading displayed.

CONDUCTIVITYMETER

  • Purpose: To lay down the procedure for the operation of Conductivity meter.
  • Scope: This procedure for the operation of Conductivity meter.
  • Responsibility: 
  • Accountability
  • Precaution: The electrode should always be immersed with DI water when not in use.
  •  Procedure:
  • 6.01 Press the power switch and allow the conductivity meter to warm up and equilibrate for at least 15 minutes.
  • 6.02 Rinse the electrode chamber three times with DI water and shake-out any excess after the last rinse.
  • 6.03 Then fill the electrode chamber with sample, allow the instrument to equilibrate  and record the measurement.

NEPHELO TURBITY METER

  • Purpose: To lay down the procedure for the operation of Nephloturbidometer.
  • Scope: This procedure for the operation of Nephloturbidometer.
  • Responsibility: 
  • Accountability:
  • Procedure:
  • 5.01 Connect the instrument power cable to AC 220V mains. Switch ON the instrument.
  • 5.02 Take distilled water or blank solution in the test tube and cover it. Make sure that the mark on the test tube coincides with the mark on the panel.
  • 5.03 Switch ON the instrument and adjust SET ZERO knob to read display ZERO.
  • 5.04 After 5 minutes warm up re-adjust ZERO.
  • 5.05 Remove cuvette of distilled water.
  • 5.06 Thoroughly shake 100 NTU standard and pour it in another cuvette and insert in sample holder.
  • 5.07 Adjust set 100 to make the display 100.
  • 5.08 Repeat inserting cuvette of distilled water and readjust ZERO if necessary.
  • 5.09 Repeat inserting 100 NTU standards and check 100 again adjust if necessary.
  • 5.10 Take sample thoroughly shake and pour it in a cuvette and insert it in the sample holder.

 

Determination of Vitamin B12.

Vitamin B12 (cyanocobalamine)

Cyanocobalamine is a cobalt co-ordinated complex with composition C16O4H8692N14O13PC0.

Spectrophotometric method:

Cyanocobalamine occurs as dark red crystals or as a crystalline powder red pigments and pseudo vitamin B12 in general show similar UV absorption. The method is useful in determineermination of the concentration of crystalline vitamin B12 or its solutions in the absence of interfering substances. It exhibits maxima at 278nm and 361nm. The absorbance of solution of cyanocobalamine prepared for the assay are determineermined at the above maxima in a 1cm quartz cell with a suitable spectrophotometer by using water as a blank.

Counter current distribution (CCD) method:

By this procedure, one can determine cyanocobalamine in a mixture with cobalamine, pigments and pseudocobalamine by means of pre treatment with cyanide. The total cobalamine content can be determine by conversion of cobalamine to cyanocobalamine. This method is useful in determine of purity of crystalline cyanocobalamine, the concentration of B12 in infection and the assay of oral solids and crude cobalamine concentrates.

Procedure: Sample extraction.

Sample not more than 0.5µg but at least 50µg of vitamin B12 is weighed and put in a 250ml flask + 50ml water+ 5ml of 10%KCn + 5ml of 2% NaNO2 and boiled for 5mins. 1ml of HCHO is added and filtered through filter paper and the residue is washed with suffering water to make upto 100ml.

Cresol  butanol  extraction :

To 50ml clear filtrate, add 5ml of a 1:1 cresol solution mixture.   Shaken -> the lower part of mixture (cresol + CCl4) is drawn by 10ml syringe-> To the above ->add 4ml of 5NH2SO4 (crude pseudo cobalamine and pigments are removed in this step) -> To above, 74ml of Na2CO3+ 2%KCn solution and centrifuge. The top aqua layer is drawn by means of a syringe -> To washed cresol, add CCl4 solution + 20ml CHCL3 + 5ml butyl alcohol + 5mlwater shaken and centrifuged. The aqua layer is drawn into 25ml flask and solution is made upto 25ml with water.

Actual method:

Benzyl alcohol+ water are shaken, they are allowed to settle, and they are centrifuged before use to remove entrained liquid. The two liquids are referred to as the benzyl phase and the aqua phase respectively. The above extraction phase taken is treated with the benzyl phase and aqua phase. The aqua solutions are extracted and diluted to 10ml with water and vitamin B12 in the phases is determined spectrophotometrically or colourimetrically.

Cyanide colourimetric method:

Used to determine cyanocobalamine or total cobalamine in pharmaceutical products. The method is based on the Quantitative liberation of the cyano group of vitamin B12 by illumination with visible light and subsequent isolation and colourimetric determine of the liberated vitamin B12.

Di-cyanide colorimetric method:

This method which requires a sample of approximate 200µg is based on difference between the visible spectrum of vitamin B12 and the spectrum of di-cyanide complex formed in solutions containing excess cyanide ions.

Radioactive tracer method:

For the determination of vitamin B12 content of complex mixtures the use of a tracer form of the vitamin containing radioactive cobalt is used. It is used for determine of cyanocobalamin alone or to the determination of cyanocobalamin + those of vitamin B12 analogy which are readily convertible to cyanocobalamin by treatment with cyanide ion. The principle of the method depends upon the use of certain extractive and other procedures, designed to remove impurities which would interfere, and upon computing the percentage recovery of the vitamin from the percentage recovery of its radioactive compound. The method of measurement is by its absorption at 361nm.