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A note on stability of emulsions and evaluation.

Stability of Emulsions and Evaluation of Stability 1) Stability of Emulsions There are two principal requirements for the stability of an emulsion : i) There should not be changes in mean droplet size and size distribution of the droplets in an emulsion. ii) The suspended droplets should remain homogeneously dispersed in the continuous phase throughout it's shelf life. Stability/ instability of the emulsions can be seen by observing following phenomenon: a) Flocculation : It is the aggregation or clumping of dispersed droplets. This aggregation is re-dispersible by shaking. As the aggregates form due to electrical charges on the droplets/ globules where interfacial film remains intact, flocculation is reversible. Sometimes, flocculation further results into coalescence where the number of globules come together and form a large globule (interfacial film breaks). b) Creaming : In o/w emulsion, dispersed oil globules migrate at the top and accumulate, whereas in w/o emulsi...

Linctuses: Monophasic Liquid Dosage Form

LINCTUSES What is a Linctus? Linctuses are sweet, viscous liquid oral preparations containing medicinal substances which have demulscent, expectorant or sedative properties. These contain high proportions of syrup and glycerin which exert demulscent effect on the mucous membrane of throat. In order to obtain prolonged local action, linctuses should be administered slowly in undiluted form. Formulation of Linctus 1. Vehicle : Syrups are mostly used as vehicles in the linctuses. Tolu syrup is preferred in cough preparations due to its aromatic odor and flavour. Glycerol syrup and invert syrup are also used as vehicles. Linctus preparation for diabetic patients contain sorbitol syrup (vehicle). Medicament is first dissolved in little amount of water and then added into vehicle. Syrups are viscous and contain less amount of water, this limits (affects) the dissolution of medicament in syrup. 2. Additives: Colouring agents : Amaranth, Erythrosin, Tartrazine. Flavouring agents : ...

UV-Visible spectroscopy: Basics

Ultraviolet Spectroscopy In this anaytical technique, ultraviolet radiations are used. Wavelength ranges of radiations: Visible light : 400 - 800 nm Near UV radiations : 200 - 400 nm Far/ Vacuum UV : below 200 nm Generally, we carry out UV analysis in near UV region of radiations. PRINCIPLE : Electronic transitions When a molecule absorbs UV radiations, the electronic excitation occur where electrons go from lower to higher energy state. Electronic excitation causes the electron to go from electron bonding orbital to antibonding orbital. After some time electron returns to its original state (stable). While returning to its stable form (into bonding orbital) it releases excess energy. That energy is measured by the detector to access the wavelength (λmax) /absorption pattern. TRANSITIONS: σ → σ* (126-135 nm) n → σ* (180-200 nm) π → π* n → π* ALLOWED TRANSITION: π → π* FORBIDDEN TRANSITIONS: n → π* ENERGY OF VARIO...

DOWNLOAD CHROMATOGRAPHY [PDF] NOTES

Chromtography is an interesting section in Pharmaceutical Analysis subject. Here, I have compiled various chromatographic techniques in one/ two documents. INDEX 1. Classification of chromatography 2. Thin layer chromatography (TLC) 3. High Performance Liquid Chromatography (HPLC) 4. Ion Exchange Chromatography Following pdf also contains various sub-sections with detailed information about chromatographic techniques. Click on the following link to download pdf. DOWNLOAD CHROMATOGRAPHY [PDF]

TABLETS

Short notes on tablets I In this first article on tablets I am going to provide some important points regarding tablet formulation. ü I : Advantages, disadvantages, tablet defects and the excipients used in the formulation of tablets ü II : Evaluationparameters and types & classes of tablets . Second part of this topic will be provided in the next post. So, for short notes on second point please refer the next post. Let’s start with the first point in this topic. ADVANTAGES OF TABLETS Oral route of administration is the most preferred route for the administration of drugs for their systemic effects. Tablets are mostly preferred for this due to following advantages: · Unit dosage forms · Greatest dose precision · Least content variability · ...

EVALUATION PARAMETERS OF TABLETS

Evaluation of tablets Notes on tablets II Tablets are evaluated for their physical, chemical and bioavailability properties. Stability testing is also an important evaluation parameter. Theset are divided into official and unofficial tests. Unofficial tests : 1. Appearance 2. Size and shape 3. Organoleptic properties (color, odor, taste) 4. Hardness 5. Friability Official tests : 1. Drug content 2. Weight variation 3. Disintegration 4. Dissolution Let's see important parameters in all the test (from GPAT point of view): Measurement of crown thickness : Instruments used are Micrometer and Caliper scale . Tablet thickness values variations: ±5% variation of a std value. Instruments used for color evaluation : Reflectance spectrophotometry Tristimulus colorimetric measurements Microreflectance photometer (measure the color uniformity and gloss on a tablet surface) Hardness and Friability Hardness : tablet crushing str...