Sample Preparation - Copper (Cu) / Zirconium (Zr) alloy method

I was wondering if I would be able to get some technical help on method development for ICP-OES and the possibility of having some custom standards ordered. We are needing to test a Cu/Zr(50/50) alloy. The material can occasionally have up to 1.5% Nb or Hf. The other traces we would be interested in would be Sn, Cr, Ti, and V. We also need to analyze for Cu and Zr. We had previously analyzed by taking 0.5g and digested with 4ml HF +4 mls HNO3 and 4 mls of H2O. This method did not create any problems besides a very long digestion time by hot block digestion. I recently came across the information on your website concerning Zr and Hf sample preparation. Alloys containing Zr + some combination of Ti, W, Nb, Ta, and Hf (0.5g): 5 mL HNO3 + 5 mL HF + 15 mL 1:1 H2SO4 I have recently tried analyzing using the matrix ratio as stated above at the volume of 10 mls for 0.5 grams diluted up to 50 mls and when I analyze my internal standard numbers drop dramatically as each sample goes on. My calibration standards seem not to drop, but I also do not have Cu or Zr in the calibration standards. I am wondering if you could recommend a good digestion matrix for this alloy and provide me a quote for some custom calibration standards? Our levels would be Hf - 1.5% max Nb - 1.5% max Cr - 150 ppm max Ti - 600 ppm max V - 150 ppm max Sn - 5000 ppm max For the Cu and Zr I have been diluting my samples, but the specs are Cu/Zr 48-52% I would appreciate any information you would be able to help me out with.