Measurement and Results - Selection of Internal Standard and recommended concentration

I am conducting analysis of Cadmium, Lead, Arsenic, Mercury, Cobalt, Vanadium, Nickel, Thallium, Gold, Palladium, Iridium, Osmium, Rhodium, Ruthenium, Selenium, Silver, Platinum, Lithium, Antimony, Barium, Molybdenum, Copper, Tin and Chromium. Could anyone recommend the internal standards and their recommended concentration for these analytes? Are there any recommended ratio between the analyte signal and the internal standard signal? Thank you.