Hints about safety gloves are found in safety data sheets oder in the GESTIS-Data base. Since there are usually lots of different chemicals in a lab it could be unreasonable to have safety gloves made of more than 2 different kinds of materials. Since as a rule only a protection from splashes is needed it should be a good idea to use cheap gloves, where it is easy to replace them even after a short time of usage.
If the risk assessment gives the result that there are no gloves with proper resistance the protection could be very enhanced if a second pair of gloves is pulled over the first ones. Use a disposable glove as the first one. It might be a little fiddly to pull over the second glove, but since both gloves are only partially in contact much more time is needed for chemicals to pass both gloves and reach the skin. You may use gloves made of different materials to further enhance the protection.
Suppliers of safety gloves offer information about the resistance of their products. Since the suppliers have the liability about their data you may trust the information.