Chemical Stability and Compatibility - Element compatibility in multi-element standards

At relatively low concentrations (<100 ppm) all of the elements you mention can be combined to create a stable mixture. Please note that IV-26 and IV-28 are at the upper limit of this concentration range (100 ppm) with the exception of Si, which is present at 50 ppm in these two stock products. The concentrations you request (250 ppm) are higher than we would recommend when mixing HF elements such as Si and Ti with alkaline earth elements such as Ca and Mg. A 250 ppm mixture of all of the elements you’re interested in might be stable or it might not; we don’t have long term data to support stability at these concentrations. And that is a key point: we design our standards to be stable for a minimum of 1 year (typically they are chemically stable indefinitely). It’s possible that a mixture of all the elements at 250 ppm in a ~5% v/v HNO3 / 0.5% v/v HF might be stable (this is the approximate matrix we would consider), but we’re not sure. We would recommend splitting the HF elements such as Si and Ti into a separate standard that could mixed together with the remaining elements at lower (<100 ppm ) concentrations.