Different test cells cannot be used interchangeably. Taylor has designed test cells of different viewpaths to accommodate variable concentrations. There are exceptions to this rule, so you may need to check with a manufacturer's technical staff before choosing a test cell for your comparator. To change the equivalence of a drop test, you must change the sample size proportionally to the desired change in equivalence. Again, you may want to contact a manufacturer's technical staff before changing the equivalence of any test.
Different reagents have different shelf lives.
Because of this fact, storage conditions play a major role in determining the freshness of any reagent. As with most perishables, reagents must be stored under controlled environmental conditions. We prepare our liquid reagents to remain fresh for at least one year from the date of manufacture. In addition, powders and crystals have unlimited shelf lives. Store all reagents away from drums or bags of treatment chemicals.