Translation. Region: Russian Federation –
Source: Peoples'Friendship University of Russia
An important disclaimer is at the bottom of this article.
Imagine needing to measure the size of a dust particle, which is a thousand times thinner than a human hair. What's more, the dust particle doesn't stay still, but moves chaotically through the liquid. This is precisely the challenge pharmacists face every day, monitoring the quality of modern medications. And now—for the first time in Russia—they will have a single, legally approved measurement method.
The Russian Ministry of Health has approved a draft general pharmacopoeial monograph developed by the Department of Pharmaceutical and Toxicological Chemistry at the RUDN University Institute of Medicine. The document establishes a state quality control standard for an entire class of drugs—colloidal solutions, emulsions, nanoparticles, and even vaccines.
Team: Who Created the Quality Standard?
Anton Vladimirovich Syroeshkin is a Doctor of Biological Sciences, Professor, and Head of Department. Tatyana Vadimovna Pletneva is a Doctor of Chemical Sciences and Professor. Olga Valeryevna Levitskaya is a Candidate of Chemical Sciences and Associate Professor. Elena Valeryevna Uspenskaya is a Doctor of Pharmaceutical Sciences and Professor.
What is a "colloid" and why can't it be seen?
When we buy drops, sprays, or injection solutions at the pharmacy, we think the liquid in the ampoule is completely transparent and homogeneous. But this is not entirely true. Many modern medications are colloidal systems. Simply put, tiny solid particles or oil droplets float in the liquid, so small that they are invisible to the naked eye.
Examples from life:
Protargol (nasal drops) is a colloidal silver solution; Polyglucin and Hemodesis, which are used to treat blood loss, are also colloids; even some new-generation vaccines are based on virus-like particles smaller than 150 nanometers.
The problem is that particles up to 400 nanometers in size are invisible to optical microscopes—they're smaller than the wavelength of light. Inspecting their quality is like checking the straightness of a seam while wearing very thick mittens.
Laser magic: how to "catch" the invisible man?
The method standardized by RUDN scientists is called dynamic light scattering (DLS).
A colloidal solution is illuminated by a laser, and a special sensor records how the brightness of the scattered light changes over time. The particles in the liquid are in constant thermal motion. Large particles "tremble" slowly, while small ones vibrate rapidly. By analyzing this "tremble," a computer calculates the precise size.
Particle size in a drug is a factor in safety and effectiveness
"Particles that are too large can clog capillaries or not be absorbed. Uneven size means the active substance dose will fluctuate from ampoule to ampoule. And in vaccines based on virus-like particles, size critically affects how the immune system 'sees' the enemy," says Elena Uspenskaya.
RUDN University sets the standard. The DLS principle itself has been used in science and industry since the 1990s. However, it was only included in the EU list of mandatory drug control methods in 2023–2024. Russia is not copying Western regulations, but is developing its own, more in-depth and precise ones. The European version describes the method in a fairly general way. The RUDN University version contains a comprehensive section on theory and mathematical models, eliminating any misunderstandings. It outlines sample preparation requirements, down to how to filter the solvent and at what temperature to measure. Furthermore, the article is tailored to the national regulatory framework and uses terminology familiar to Russian pharmacists.
"The development of a general pharmacopoeial monograph transforms the DLS method from a convenient analytical tool into a mandatory element of regulated control. The general pharmacopoeial monograph introduces universal criteria: what polydispersity index is considered acceptable, what Z-average value should be recorded in the drug passport. This will reduce the variability of methods and associated errors in determining particle sizes in solutions for medical use. It will also facilitate the comparability of results both at the drug registration stage and during the publication of scientific results in the form of uniform terminology, test parameters, and experimental quality criteria," says Elena Uspenskaya.
Regarding the impact on the educational process, changes to the course content of "Physical and Colloid Chemistry" are possible after the article's approval. However, as Elena Valeryevna notes, the courses "Methods of Pharmacopoeial Analysis" and "Quality Control of Medicines" at the RUDN University Institute of Medicine already include modules on dynamic light scattering.
The draft general pharmacopoeial monograph is currently undergoing scientific and technical editing at the Institute of Pharmacopoeia and Standardization. It is expected that in the first quarter of 2026, an order from the Ministry of Health will approve this monograph as part of the State Pharmacopoeia of the Russian Federation.
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