Physico-chemical analysis: understanding, measuring and characterizing matter

Definition of physicochemical analysis

A physicochemical analysis studies the characteristics of the materials or raw materials being analyzed, in the case of natural elements such as soil, water, or air. Its aims are multiple: to ensure the quality of natural products or components, but also to comply with current regulations. This work can only be carried out in a laboratory using scientific instruments such as a scanning electron microscope and a spectroscope.

Different types of physicochemical analyses are possible:

• Analysis of the composition and structure of the raw material: chemical composition and characteristics.
• Analysis of the material's behavior and its physical, thermal, or mechanical properties. The sample is subjected to different temperature or pressure conditions.

Difference with a pure chemical analysis

Physicochemical analysis does not simply search for the chemical compounds of a material or raw material. Unlike a pure chemical analysis, which only detects chemical elements such as heavy metals (mercury, lead, arsenic, etc.), pesticides, PFAS, or nitrogen, phosphorus, or potassium—all components commonly found in soils—it also involves a broader range of other analyses.

Why is it indispensable in many sectors?

Physicochemical analysis is carried out in a wide range of sectors to verify the quality and performance of products, as well as to ensure they are safe and comply with current regulations. The most frequently tested raw materials are soil, water, and air, particularly to detect potential pollutants.

The sectors most affected by these tests are those in which chemical products and industrial processes are used, such as the design of cosmetics and medicines, metallurgy, energy production, automotive, aeronautics or defense.

Quality control of raw materials or finished products

The primary motivation for conducting a physicochemical analysis is to control the quality of the raw materials used in the manufacture of a product. It also plays a role at the end of the supply chain to verify that the finished product is compliant and poses no danger to the end consumer. Physicochemical analysis is therefore performed several times throughout the life cycle of the drug, cosmetic product, vehicle, jewelry, or electronic device.

Regulatory compliance (standards, REACH, food safety, etc.)

This type of analysis also serves to verify that the product complies with standards. One example is the European REACH regulation (Registration, Evaluation, Authorisation and Restriction of Chemicals), which came into force on June 1, 2007. It protects humans and the environment from potentially harmful chemical substances. REACH analysis applies to facilities that produce or import at least one tonne of chemical substances per year.

Other physico-chemical analyses can be carried out. For example, to look for the presence of prohibited substances such as Bisphenol A, heavy metals or solvents.

Finally, these tests also aim to verify that the product is safe and cannot break, crack, or corrode. To this end, it is subjected to various mechanical, pressure, and temperature stresses to verify its behavior.

Environmental assessment: water, soil, air

This type of analysis also serves environmental diagnostic purposes. The composition of water, soil, or air can be analyzed. Most often, the focus is on detecting pollutants harmful to human health and ecosystems. For example, PFAS or pesticides in water, heavy metals or pesticides in soil, and fine particulate matter (PM2.5, PM10), ozone, or nitrogen dioxide in the air.

Research & Development (R&D)

Finally, a physicochemical analysis can be carried out for research and development (R&D) purposes to design a new product or improve an existing one. It can also be used to test new materials or alloys of materials that are not yet widely used.

Physical properties

A physicochemical analysis is primarily used to measure the physical properties of a finished material or a raw material such as soil. This allows us to assess the pH, which indicates the level of acidity. For example, acidic soil has a pH between 5.5 and 7, while acidic water has a pH below 7. We can also check conductivity, density, temperature, and turbidity. Turbidity, in water, measures the presence of suspended materials such as soil or algae.

Chemical properties

The table below lists several chemical elements, often sought in physicochemical analyses, as well as the materials or raw materials in which they are most present and their characteristics.

This list is not exhaustive. We can also mention VOCs, which are volatile organic compounds, found particularly in soils and indoor air. They are produced by cooking, cigarette smoke, certain furniture and floor coverings, exhaust fumes, and cleaning products.

Basic methods

For physicochemical analysis, scientists use a few basic methods:

• Gravimetry allows us to measure the mass of a substance and thus verify the purity level of a sample.
• Spectrometry studies the spectra produced by the interaction between matter and radiation such as light, X-rays, or electrons. This allows us to analyze the concentration and distribution of the material's components.
• Titration aims to generate a chemical reaction between the analyzed product and the reagent used. An aqueous solution is most often used.

Advanced instrumental methods

There are also more advanced methods for performing physicochemical analysis. One such method is chromatography, which allows for the separation of the components of a mixture. It can be performed in the gas phase (GC) or in the high-performance liquid phase (HPLC).

ICP can also be mentioned for detecting chemical elements at very low concentrations, on the order of a few nanograms per liter. Infrared (or IR) spectroscopy is used to identify compounds or determine the composition of a sample. Ultraviolet spectroscopy is used for the analysis of liquid or gaseous solutions.

Standardized methods and accreditations for physicochemical analysis

The primary accreditation for physicochemical analysis is that issued by Cofrac. ISO 17025 is another relevant standard. It guarantees, in particular, reliable testing and calibration methods and the traceability of measurements. This type of laboratory is capable of verifying the purity of raw materials or ensuring that finished products comply with regulations.

Some analyses according to the sector of activity concerned:

• Search for THC (total hydrocarbons), TOC (total organic carbon) or inorganic residues for medical devices.
• Elemental impurity analysis for pharmaceutical products.
• Analysis of heavy metals in cosmetics.
  
  

Environment: soil, water, and air analysis

Through physicochemical analysis, the quality of the soil, water, and air is first tested. The most frequently analyzed elements are heavy metals, pesticides, hydrocarbons, and PFAS, which have a significant impact on human health and the preservation of ecosystems. In the air, particulate matter and nitrogen dioxide are the most frequently assessed compounds, especially with the establishment of air quality monitoring organizations such as Airparif for the Paris region and Atmo Auvergne-Rhône-Alpes for the Lyon region.

Agriculture: fertility, pollution, compliance

Agriculture is another sector where this analysis is crucial. Soil fertility , texture, acidity, and drainage capacity are assessed to determine corrective actions and the appropriate fertilizers. Soil pollutants are also detected, the most common being pesticides, PFAS, and heavy metals.

Industry: Raw material/finished product control

In industry, physicochemical analysis is used both upstream and downstream, at the raw material and finished product stages. This is to verify that the materials used are compliant and free of toxic residues, and that the production process is robust, free of defects, and safe for use by the end user.

Health, cosmetics, pharmaceuticals, construction

These analyses are most often carried out in specific sectors such as health: medicines, medical devices… But also cosmetics, construction and the design of everyday products such as clothing, jewelry, high-tech equipment or goods intended for babies and children.

Criteria: COFRAC accreditation, ISO standards, areas covered

Choose a laboratory accredited by Cofrac. This organization grants accreditation to laboratories, recognizing their impartiality and technical expertise. Accreditation is mandatory in certain situations, such as for organizations that certify products or services, or for medical biology laboratories. Various ISO standards are associated with this certification. For example, ISO 15189 for medical biology laboratories or ISO/IEC 17025 for testing laboratories.

Deadlines, result formats, interpretation provided or not

Turnaround times vary. Allow a few weeks for the most complex analyses, especially if the report is lengthy and you have an interview with the technician. The results must be transcribed in writing, including target values ​​and an interpretation of the indicators found.

Special case: laboratory for soil analysis

For soil analysis, Cofrac accreditation is not mandatory, but recommended. Especially for agricultural tests or those detecting soil pollutants, the independence of the results is crucial. This is the case with Pouryère, which offers soil sampling kits with testing in a Cofrac-accredited laboratory.

Solutions for individuals, farmers, communities and businesses

Each soil analysis kit is specialized and pursues a specific purpose:

• AGROKIT for agronomic soil analysis.
• POLLUKIT for pollutants.
• PESTIKIT for pesticide detection.
• PFASKIT for PFAS.
• METKIT for soil metals.
• SOLKIT for the complete health status of the soil (agronomic analysis, detection of pollutants and metals).
• ISDIKIT is aimed at construction professionals.