These are of two types:-

  1. Monophasic liquids. Ex:- Solutions, Syrups, Elixirs, etc.
  2. Biphasic liquids. Ex:- Emulsions, Suspensions.

 

  1. MONOPHASIC LIQUIDS:-
  • CLEAN AND PURIFIED VEHICLE (WATER):- Quality control technicians test the water frequently to ensure that it is clean and pure before the syrup is made. The syrup is also thoroughly filtered before filling in bottles.
  • LIGHT TRANSMITTANCE TEST:- A light transmittance meter is a newer tool that is used to check syrup colour. In a light transmittance meter, a syrup sample is checked for colour by passing light through the sample. The percent of light transmission is compared to light transmission rates set for different grades.
  • VISUAL INSPECTION:- The ingredients and the final products are carefully examined for purity and for appearance. Physical appearance of products for patient adherence and compliance is critical so it should be Good looking, Elegant in appearance.
  • pH MEASUREMENT:- The measurement and maintenance of pH is also very important step in the Quality control testing. Generally there are 2 different types of methods used in the measurement of pH:-
  • The simplest and cheapest is to dip a piece of pH paper into the sample.
  • By using pH meter (for greater accuracy)
  • DETERMINATION OF SUCROSE CONCENTRATION (FOR SYRUPS ONLY):- If the concentration of Sucrose in the syrup is very high it may crystallize the syrup, less sucrose concentrations give favor for the microbial growth. For the determination sucrose in syrup, HPLC and UV -spectroscopy are used.
  • DETERMINATION OF ALCOHOL CONCENTRATION (FOR ELIXIRS ONLY):- Elixir usually contains 5 to 40% alcohol. Distillation, Specific gravity.
  1. BIPHASIC LIQUIDS:
  • EMULSIONS
  • SUSPENSIONS
  • DETERMINATION OF VISCOSITY:- Determination of viscosity is done to assess the changes that might take place during aging. The viscometers used are cone and plate viscometers , Brookfield viscometer .
  • DETERMINATION OF PARTICLE SIZE:- It is performed by optical microscopy and Coulter counter apparatus. 
  • DETERMINATION OF PHASE SEPARATION (for emulsions):- Phase separation may be observed visually or by measuring the volume of the separated phases or by subjecting the emulsions to various stress conditions like boiling, temperature variations etc.
  • STABILITY OF SUSPENSIONS:-
  1. SEDIMENTATION METHOD:- The measurement of sedimentation volume is the most important parameter in the evaluation of stability of suspensions.
  2. RHEOLOGICAL METHOD:- The viscosity of the suspension is studied at different time intervals by using a good quality of viscometer.

 

  • ELECTRO KINETIC METHOD:- The determination of surface electric charge or zeta potential of suspension is helpful to find out the stability of suspension.
  • MICROMERITIC METHOD:- The stability of a suspension depends on the particle size of the dispense phase. A change in particle size distribution & crystal habit may be studied by microscopy & counter coulter method.

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Reference links

https://www.slideshare.net/mobile/bhatti106/quality-control-tests-for-syrups-and-elixirs

https://www.researchgate.net/profile/Md_Sahab_Uddin/publication/292130182_Pharmacopoeial_Standards_and_Specifications_for_Pharmaceutical_Oral_Liquid_Preparations/links/56d26fca08ae85c8234ae7fc/Pharmacopoeial-Standards-and-Specifications-for-Pharmaceutical-Oral-Liquid-Preparations.pdf