returns a true unbiased answer to permit direct subtraction from any sample matrix the blank is unbiased as the blank is measured in any ionic strength different from that of the sample and no attempt is made to matrix match despite an increase or decrease in absolute signal intensity the isotopic ratio determines the true concentration of the element species or molecule independent of ionic content of the sample blank or matrix solution the true value is obtained without bias due to ionic yield in the electrospray ionization source the sample likewise has the same relative intensity dependence with ionization strength using electrospray and other techniques by using direct in process isotope dilution and speciated isotope dilution measurements the relative intensity of the signal no longer effects the quantification of the analytes in the sample a direct measurement of the concentration is established by the isotopic ratio and the unbiased concentration is achieved in this way can unknown samples of unknown ionic strength and composition be placed into the instrument without performing calibration curves and accurate concentrations enabled to be determined these concentrations are independent of ionic strength sample matrix composition and intensity fluctuations of the instrument in this example the spiking of isotopes in uncomplexed forms is demonstrated to permit formation and equilibration rapidly enough to tag both elemental and speciated forms of the element of interest in fig5 the natural abundance of natural copper is shown natural copper has for example a ratio of cu 63 and cu 65 of 69 09 and 30 91 respectively in fig5 this ratio can be observed in a dilute electroplating solution it will be appreciated that fig5 showing cu singly charged ions which exhibit the natural ratio while fig6 illustrates cu ions.