With 1 ml 10 N NaOH for Cyanides Pack of 24 EP preserved containers EP Preserved Containers™ simplify field preservation. Level 1 Products include a certificate of analysis for the container and the added reagent. (Level 1 certified containers recieve full EPA quality assurance; each case is custody sealed and each container is lot numbered for tracibility) EP Preserved™ containers provide an extra measure of assurance that proper sampling protocols are followed especially when collecting for a number of parameters