Laboratory measurement of osmolality
Osmolality is a concentration that can be measured after osmosis has occurred. Osmosis is a physical law corresponding to the passage of a solution from a hypotonic medium to a hypertonic medium through a semipermeable membrane. Osmolality this therefore defined as the number of osmoles of solutes per kilogram of solvent, measured in osmol/kg.
Osmolality is used because the volume of solvent stays constant in any conditions (temperature, pressure, etc.) . FILAB laboratory realise mesurement of osmolality.
Measurement of osmolality for the cosmetics industry
In the cosmetics industry, osmolality measurements can be needed to measure the effectiveness of active ingredients. While making a cosmetic crème, the osmolality of raw materials can give an indication of the quantity of particles capable of seeping through semipermeable cell walls. It is therefore possible to determine if a crème containing the active ingredient will be effective or not. It is also possible to determine if the active ingredient disturbs the balance in a cell, which would disqualify the sample.
As an industrialist in the cosmetics industry, you are looking to measure the osmolality of your solutions.
Measurement of osmolality for the pharmaceutical industry
Osmolality therefore applies to any element (ion, molecule) capable of attracting water molecules though a membrane. That is why this property is often sort after for a better tolerance (ex. injectable solutions).
The European Pharmacopeia 2.2.35 “Osmolality Standards USP 785” describes the principle behind analytical methods, provides a clear and detailed description of a sampling procedure et provides precision requirements for sampling.
FILAB laboratory is able to assist you in measuring osmolality in accordance with the European Pharmacopeia
FILAB is able to measure osmolality in its laboratory and can assist you with your analytical needs
FILAB is an independent laboratory situated in Dijon, France and can assist you in measuring osmolality to resolve your quality, safety and performance problems.
Our experts provide multiple analytical services centered around osmolality measurements :
our services
Osmolality measurements in accordance with the European Pharmacopeia
Detection of elemental impurities in excipients in accordance with the USP 233 (ICH Q3D)
Analytical development and validation of methods for quantifying substances in accordance with various standards : ICH, USP, EP, ISO…
Expertise to understand osmolality differences between samples
Particulate count and analysis
Compatibility testing between active ingredients and excipients
Reverse engineering of finished products
Osmolality and osmolarity are both measurements that refer to the concentration of solutes in a solution, but they are measured in different ways.
Osmolality is a measure of the total number of particles in a solution per unit of solvent, typically expressed as osmoles per kilogram of solvent (osmol/kg). Osmolality is determined by measuring the freezing point depression of the solution using an osmometer. This method takes into account all solutes present in the solution, regardless of whether they dissociate in water or not.
Osmolarity, on the other hand, is a measure of the total number of particles in a solution per unit of volume of solution, typically expressed as osmoles per liter of solution (osmol/L). Osmolarity is calculated based on the concentrations of individual solutes and their contributions to the overall osmotic pressure of the solution. This method assumes that all solutes in the solution are fully dissociated in water.
The main difference between osmolality and osmolarity measurement is the way they take into account the presence of non-dissociating solutes (such as urea), which contribute to osmolality but not osmolarity. Osmolality is considered to be a more accurate measure of the effective osmotic pressure of a solution, while osmolarity is useful for calculating the expected movement of water across cell membranes.
In summary, osmolality measures the total number of particles in a solution per unit of solvent, while osmolarity measures the total number of particles per unit of volume of solution.
Osmolarity can be measured using several methods, including:
- Freezing point depression: This method involves measuring the freezing point depression of a solution compared to a pure solvent. Osmometers are specialized instruments that use this method to calculate the osmolarity of a solution based on its freezing point depression.
- Vapor pressure: Vapor pressure osmometry measures the decrease in vapor pressure caused by the presence of solutes in a solution. This method is commonly used for measuring the osmolarity of biological fluids such as blood and urine.
- Calculation: Osmolarity can also be calculated based on the concentrations of individual solutes in a solution, using the formula:
Osmolarity = (sum of [solute] x number of particles per molecule) / volume of solution
For example, a 0.9% saline solution contains 9 grams of NaCl per 1000 ml of solution. The osmolarity of NaCl is 2, so the osmolarity of the solution can be calculated as:
Osmolarity = (9 g/L x 2) / 0.1000 L = 180 Osm/L
- Conductivity: Another method for measuring osmolarity is by measuring the electrical conductivity of a solution. The conductivity of a solution is proportional to the concentration of ions present, which can be used to calculate the osmolarity.
Overall, choosing how to measure osmolarity depends on the type of solution being tested and the equipment available in the chemical analysis laboratory.
Whether to measure osmolality or osmolarity depends on the type of sample being tested and the purpose of the test. When making a request to a chemical analysis laboratory, it is important to provide as much information as possible about the sample being tested and the purpose of the analysis. Based on this information, the laboratory professionals can recommend whether osmolality or osmolarity measurement is more appropriate for the specific needs of the experiment or analysis.
Osmolality measurement is often preferred in clinical settings and for biological samples such as blood, urine, and other bodily fluids, as it is a more accurate measure of the solute concentration in a solution. This is because osmolality is not affected by changes in temperature or pressure, which can affect osmolarity measurements. Additionally, certain solutes present in biological samples, such as urea, contribute to osmolality but not osmolarity, making osmolality a more comprehensive measure of solute concentration.
On the other hand, osmolarity may be more appropriate for solutions with well-characterized solutes, such as salt solutions used in cell culture. In these cases, specific solutes are known, and their contributions to the total osmotic pressure can be accurately calculated using osmolarity measurements.
Ultimately, the choice between osmolality and osmolarity measurements depends on the specific needs of the experiment or analysis being conducted. If you are unsure which measurement to use, consulting with a laboratory professional or an expert in the field can help determine the best approach.
