No, the Holmium Oxide Calibration Standard (cat# PQA-HOX-01) is quite variable in its absorbance and is intended as a wavelength accuracy standard only. The appropriate item for this purpose is the 0.06000 mg/mL potassium dichromate solution, which is Solution #3 in the current UV kit. This is the basis of the current EP regulations, and it is widely used both in the US and internationally. The reference solution will also be needed. This item is not currently sold separately apart from the Kit.
The NIST specifications for Holmium can be found in the attached document. Also attached is the Instruction Manual for the Chemical Solutions PQ Qualification Kit.