Osmometer

Make:- Advance Instrumentation Model no. Advanced model3D3

Principle :- An osmometer is a device for measuring the osmotic strength of a solution, colloid or compound.

Colligative properties are properties of solutions that depend on the number of molecules in a given amount of solvent. Colligative properties include: relative lowering of vapour pressure; elevation of boiling point; depression of freezing point  osmotic pressure.

πV = nRTi

Freezing Pointsolution = Freezing Pointsolvent - ΔTf

Boiling Pointtotal = Boiling Pointsolvent + ΔTb

ΔTf = b * Kf * i, (Kf = cryoscopic constant, which is 1.86°C kg/mol for the freezing point of water; b = molality; i = Van 't Hoff factor)

π = (ΔTf /1.86)*1000

Types of osmometers

 There are three major types of osmometers commerically available, each leveraging a particular colligative property to achieve their analytical results

Freezing Point Osmometers – determine the osmotic strength of solution by utilizing freezing point depression

Vapor Pressure Osmometers – determine the concentration of osmotically active particles that reduce the vapor pressure of the solution

Membrane Osmometers – measure the osmotic pressure of a solution separated by a semi-permeable membrane.

The freezing point technique operates by rapidly Super Cooling the sample to a predetermined temperature below the expected Sample Freezing Point.  This is identified in the diagram as theFast Cool and Slow Cool regions of the freeze curve.  While the sample is in the super-cooled state, crystallization is initiated by some external means, such as the rapid vibration of a stirring rod or a solenoid knocking. This external catalyst is called the Freeze Pulse.  As a result of the initial freezing caused by the freeze pulse, only part of the sample crystallizes, forming a layer of slush around the temperature probe.

The Heat of Fusion resulting from the crystallization process raises the sample temperature to a Plateau where ice/water equilibrium is maintained. This equilibrium temperature is the Sample Freezing Point of the solution. The sample remains at this temperature for prolonged periods of time.  During this time, the osmometer uses a thermistor probe to sense the sample temperature, control the degree of super cooling and freeze induction, and measure the freezing point of the sample.  This information is calculated and the Readout displayed in milliosmoles per kilogram of water (mOsm/Kg H20).

Eventually, all of the liquid in the sample freezes out and the sample assumes the temperature of its environment. This is seen in the gradually decreasing temperature of the freeze curve after the readout has occurred.

Operation

Switch on (run-up time 3 minutes)

Transfer 0 .25ml of sample into the sample tube

Attached the tube to the measuring head

Slide the measuring head down, insert tube into the cooling cone

Supercooling is reached in about 1 minute and shortly after, the seeding needle is automatically inserted into the sample vessel

The freezing point is determined and osmolarity is shown on the digital display. An audible signal indicates the measurement has been completed.The measurement value is stored in the memory

Raise the measuring head, remove sample tube and wipe thermistor with a soft tissue

CALIBRATION

The sample volume may be 0.25ml but calibration and measurement must always be carried out on the same volume. Zero is set using distilled water, and the instrument is calibrated against a 100 m/Osm/kg water standard 3times and than 3 times with 1500 m/Osm/kg . Only occasional checks are necessary.

Applications

Osmolality is a valuable and cost-effective measurement tool which is used in a wide range of clinical, biotechnology, pharmaceutical, industrial, food testing, athletic, and forensic applications. Freezing point determination has virtually limitless applications where there is a need to determine concentations of solutes in a solutions. We have attempted to provide you with example applications illustrative of the variety and range of the uses for osmolality.

Pharmaceutical and biotechnology companies can use Advanced Instruments osmometers for osmolality testing extensively in their R&D, production, quality and process control operations to ensure product safety and the efficiency of their production capabilities.  Freezing point technology has proven to be the industry-preferred method due to its accuracy, performance and reliability.

Media Preparation and Quality Control, Improved Cell Culture Yield

Pharmaceutical Formulation Development

Salts or non-electrolytes (e.g. glycerin) are often added to protein formulations to achieve an isotonic solution. Non-electrolytes are often preferred to salts as tonicity adjustors because of potential issues salts cause with protein precipitation. Intrathecal and epidural injection drugs require very precise specifications for the product to be isotonic. Osmolality testing provides these stringent assurances.Osmolality is a rapid and accurate QC measurement for a number of pharmaceutical and biopharmaceutical applications, including: finished product testing, infant formulas, ophthalmic solutions, electrolyte solutions, tissue cultures, culture media, IV solutions and other parenterals.