Spectral interference is a major disadvantage that hinders the application of ICP-OES. This is not a serious problem in the
traditional AAS method because the single-element HCL in the AAS system always provides an excellent line source. Although introducing multi-element HCLs may achieve cost savings and avoid the complication of carrying many lamps for operation or as spares, some criteria should be followed during the multielement merging process, including spectral overlap, compatibility
between elements, and acceptability of emission. The cathode materials and their relative ratios require careful adjustment for an optimum design lamp.