Refer to Table 4.4 of selectivity coefficients for cations that interfere with the creatinium ISE described. At what concentration of creatinine would \(0.3 \mathrm{M}\) ammonium interfere to cause a \(10 \%\) error in the measured creatinine concentration?

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TABLE 4.4 Selectivity coefficients for cations interfering with the creatinine ISE and threshold creatinine levels where typical activity of these cations in urine samples leads to a 10% error Interferant Selectivity coefficient Typical urine Creatinine concentration (ac, min) (mol/l) (mol/l) Sodium 2.00 x 10-4 0.16 3.19 10-4 Potassium 3.16 x 10-3 0.06 1.90 x 10-3 Ammonium 5.01 x 10-3 0.035 1.75 x 10-3 Calcium 1.58 x 10-5 0.005 7.92 x 10-7