The phrase "all classes of substances" is correct and usable in written English.
It can be used when referring to different categories or types of materials or chemicals in a scientific or technical context.
Example: "The study examined the effects of pollutants on all classes of substances found in the ecosystem."
Alternatives: "all types of substances" or "every category of substances".
First, high levels of public stigma were reported for all classes of substances investigated in this study.
Self-reported withdrawal symptoms was rated using the DSM-5 Withdrawal Symptom Check List with withdrawal symptoms from all classes of substances, with no indication that the described symptoms should be attributed to withdrawal.
This study revealed high levels of public stigma across all classes of substances, the cannabis user was considered significantly less dangerous than someone who uses alcohol, there were gender differences in attitudes towards people who use substances, and the more an individual used substances the more likely they were to hold a negative attitude.
Health Canada's Straight Facts about Drugs and Drug Abuse [ 1] outlines the health consequences of high doses of all classes of psychoactive substances, including stimulants, hallucinogens, cannabis and central nervous system depressants (opioid analgesics, alcohol, inhalants/solvents, benzodiazepines, barbiturates).
Materials that strongly absorb visible radiation belong to a class of substances known as semiconductors.
Other specialties may be centred not on a class of substances but rather on their interactions and transformations.
Intermetallic compound, any of a class of substances composed of definite proportions of two or more elemental metals, rather than continuously variable proportions (as in solid solutions).
That is the crux of a debate over adjuvants — a class of substances that somewhat mysteriously increase the potency of vaccines.
Organometallic compound, any member of a class of substances containing at least one metal-to-carbon bond in which the carbon is part of an organic group.
Alkanes are compounds that consist entirely of atoms of carbon and hydrogen (a class of substances known as hydrocarbons) joined to one another by single bonds.
