As with handling of the lysate test reagents, the key word is cleanliness. Use aseptic and apyrogenic technique. Check the product for inhibition. Some products, especially members of the small volume parenteral family, may contain substances at great enough concentrations to inhibit the LAL gelation reaction. Check the pH of the sample to be tested. The pH should be in the range of 6.0-8.0. A pH that is too high or too low is one of the most common causes of product inhibition in the LAL test. The LAL reagent does have a certain amount of buffering capacity, but it must be assured that a product, when added to the LAL reagent, does not exceed that capacity. An easy way to determine whether or not a given product will require pH adjustment is simply to add a volume of the product in question to an equal volume of rehydrated LAL reagent. Check the pH of this mixture using a pH electrode or equivalent apparatus. The pH of this mixture must be within the range of pH 6.0-8.0. Remember that because of LAL reagent’s buffering capacity, you do no need to adjust the pH of Water for Injection or Saline for Injection USP. If a pH adjustment is necessary, pyrogen-free 0.1N HCl or 0.1N NaOH solutions may be easily made simply by dilution concentrated HCl or NaOH with pyrogen-free Water for Injection USP. Fortunately, endotoxin cannot exist in the presence of concentrated mineral acids or bases. Therefore, these will contain no contamination.