3. Supplemental Materials Table S-3. Comparison of Limit of Detection Differences by Preparation Method and Analytical Platform for 9 Replicate Analyses of a Single Serum Sample Spiked with 0.5 µg Co/L Co Conc. by ICP-CRC-MS (µg/L) Co Conc. by ICP-DRC-MS (µg/L) Co Conc. by ICP-CRC-MS (µg/L) Co Conc. by ICP-DRC-MS (µg/L) Preparation MethodAcid Digestion Detergent Dilution Mean Serum Co Conc. with No Spike0.420.600.220.42 Replicate 10.880.820.700.80 Replicate 20.911.110.750.85 Replicate 30.831.010.730.94 Replicate 40.950.880.700.93 Replicate 50.890.960.800.90 Replicate 60.961.060.710.83 Replicate 71.071.190.750.95 Replicate 80.831.030.710.85 Replicate 90.771.060.690.89 Corrected Mean + SD0.48 + 0.090.41 + 0.110.51 + 0.030.46 + 0.05 Limit of Detection0.360.460.140.21 Corrected mean is the average of each replicate Co concentration after subtracting the mean value with no spike (n = 9). Limit of detection is determined according to the analytical solution detection limit (ASDL) calculation reported by the Association of American Chemists: ASDL = 2 x t0.95 x SqrRt [1+(1/n-1)] x SD Where: t 0.95 = one-sided Student's t at 95% confidence level; n = number of replicates; SD = standard deviation of replicates.

4. Supplemental Materials Table S-4. Comparison of Pre-Spiked/Frozen Serrum Co Concentrations by Preparatory Method and Mixing Status After Thawing Serum Code Co Spike Conc. (µg/L) Co Conc. by ICP-DRC-MS (µg/L) Mean + SD Relative Percent Difference (%) Unmixed/Detergent DilutionMixed/Acid Digestion 100.41 + 0.020.60 + 0.1037% 10.50.79 + 0.0050.95 + 0.1319% 15.04.8 + 0.064.5 + 0.117% 11000873 + 29847 + 163% 200.49 + 0.0070.63 + 0.0926% 20.50.81 + 0.020.93 + 0.0314% 25.05.0 + 0.055.0 + 0.181% 21000870 + 21838 + 7.34% 300.50 + 0.110.60 + 0.1318% 30.50.79 + 0.050.81 + 0.022% 35.04.9 + 0.024.9 + 0.081% 31000866 + 18876 + 111% ICP-DRC-MS was operated without DRC correction and reported Co concentrations were not adjusted for 0 ug/L spike value. Mean values are based on n = 3. Each serum sample was mixed after initial Co spiking and then frozen for 8 days, then aliquots were taken with or without mixing; an aliquot was prepared by detergent dilution without mixing the thawed sample, and another aliquot after mixing was prepared by acid digestion. Comparison of mean values between the two test conditions revealed no significant differences using the unpaired Student's t-test with a significance criterion at p < 0.05.

5. Supplemental Materials Table S-5. Interference Removal Comparison for Three Serum Sources Between Dynamic Reaction Cell and Collision Reaction Cell Technologies Serum Code Co Spike Conc. (µg/L) Co Conc. By ICP-CRC- MS (µg/L) Mean + SD Co Conc. By ICP-DRC- MS (µg/L) Mean + SD 100.33 + 0.300.29 + 0.0230.20 + 0.0300.36 + 0.0603.0 + 0.030.51 + 0.0230.46 + 0.080.44 + 0.098 10.50.78 + 0.0050.62 + 0.0400.64 + 0.0330.83 + 0.0993.3 + 0.090.97 + 0.100.91 + 0.0960.89 + 0.066 15.05.4 + 0.085.0 + 0.0075.1 + 0.075.0 + 0.167.3 + 0.135.0 + 0.105.1 + 0.175.1 + 0.12 110001000 + 27960 + 25970 + 19960 + 4.7920 + 16930 + 11930 + 8.4940 + 6.1 200.37 + 0.0160.22 + 0.0140.23 + 0.0120.39 + 0.0313.0 + 0.080.55 + 0.0120.46 + 0.0080.48 + 0.033 20.50.84 + 0.0120.69 + 0.0300.70 + 0.0170.80 + 0.0133.3 + 0.070.93 + 0.0270.91 + 0.0960.87 + 0.056 25.05.6 + 0.095.1 + 0.095.3 + 0.085.2 + 0.097.3 + 0.265.0 + 0.195.0 + 0.115.0 + 0.27 21000940 + 60890 + 55900 + 5.9920 + 21860 + 21870 + 14870 + 25880 + 19 300.31 + 0.0320.18 + 0.0550.18 + 0.0490.31 + 0.0072.7 + 0.140.45 + 0.0220.40 + 0.0100.36 + 0.007 30.50.77 + 0.0780.61 + 0.0260.62 + 0.0350.83 + 0.0603.1 + 0.060.93 + 0.0410.90 + 0.0880.85 + 0.094 35.05.3 + 0.134.9 + 0.045.1 + 0.085.0 + 0.097.2 + 0.225.0 + 0.174.9 + 0.065.0 + 0.24 31000930 + 112890 + 105900 + 110930 + 12900 + 2.2910 + 8.8920 + 8.6930 + 4.0 Cell gasNoneHelium NoneAmmonia (RPq = 0.6)Ammonia (RPq = 0.7)Ammonia (RPq = 0.8) Ammonia (RPq = 0.85) Cell Gas FlowNot Applicablelowhigh

6. Supplemental Materials Table S-6. MS-MS Data for Serum Samples from ICP-QQQ-MS Transition Blank10 ppb 200 ppm Ca,MgBlank Serum Code 1 Serum Code 2 21 -> 59 [ NH3 Scan ]CPS000000 22 -> 59 [ NH3 Scan ]CPS000000 23 -> 59 [ NH3 Scan ]CPS000003 24 -> 59 [ NH3 Scan ]CPS003000 25 -> 59 [ NH3 Scan ]CPS0053000 26 -> 59 [ NH3 Scan ]CPS000000 27 -> 59 [ NH3 Scan ]CPS000000 28 -> 59 [ NH3 Scan ]CPS000000 29 -> 59 [ NH3 Scan ]CPS000000 30 -> 59 [ NH3 Scan ]CPS000000 31 -> 59 [ NH3 Scan ]CPS000000 32 -> 59 [ NH3 Scan ]CPS000000 33 -> 59 [ NH3 Scan ]CPS000000 34 -> 59 [ NH3 Scan ]CPS000000 35 -> 59 [ NH3 Scan ]CPS000000 36 -> 59 [ NH3 Scan ]CPS000000 37 -> 59 [ NH3 Scan ]CPS000000 38 -> 59 [ NH3 Scan ]CPS000000 39 -> 59 [ NH3 Scan ]CPS000000 40 -> 59 [ NH3 Scan ]CPS006670323 41 -> 59 [ NH3 Scan ]CPS000000 42 -> 59 [ NH3 Scan ]CPS00203302750 43 -> 43 Ca [ NH3 Scan ]CPS207501286859203336535108 43 -> 59 [ NH3 Scan ]CPS00197301357 44 -> 44 Ca [ NH3 Scan ]CPS171013151213276901383554835577772 44 -> 59 [ NH3 Scan ]CPS00130000 45 -> 59 [ NH3 Scan ]CPS000000 46 -> 59 [ NH3 Scan ]CPS000000 50 -> 59 [ NH3 Scan ]CPS000000 51 -> 59 [ NH3 Scan ]CPS000000 52 -> 59 [ NH3 Scan ]CPS000000 53 -> 59 [ NH3 Scan ]CPS000000 54 -> 59 [ NH3 Scan ]CPS000000 55 -> 59 [ NH3 Scan ]CPS000000 56 -> 59 [ NH3 Scan ]CPS000000 57 -> 59 [ NH3 Scan ]CPS000000 58 -> 59 [ NH3 Scan ]CPS011320000 59 -> 59 [ NH3 Scan ]CPS10700787900203193 118 -> 59 [ NH3 Scan ]CPS000000 CPS = Counts per second

7. Supplemental Materials Table S-7. Comparison of Limit of Detection Differences by Analytical Platform for 9 Replicate Analyses of a Single Whole Blood Sample Spiked with 0.5 µg Co/L Co Conc. by ICP-CRC-MS (µg/L)Co Conc. by ICP-DRC-MS (µg/L) Preparation MethodAcid Digestion Mean Serum Co Conc. with No Spike0.462.86 Replicate 11.093.26 Replicate 20.923.68 Replicate 30.882.52 Replicate 40.823.39 Replicate 51.023.72 Replicate 61.012.81 Replicate 70.853.40 Replicate 80.853.17 Replicate 91.312.64 Corrected Mean + SD0.51 + 0.160.32 + 0.44 Limit of Detection 0.621.7 Corrected mean is the average of each replicate Co concentration after subtracting the mean value with no spike (n = 9). Limit of detection is determined according to the analytical solution detection limit (ASDL) calculation reported by the Association of American Chemists: ASDL = 2 x t0.95 x SqrRt [1+(1/n- 1)] x SD Where: t 0.95 = one-sided Student's t at 95% confidence level; n = number of replicates; SD = standard deviation of replicates.

8. Supplemental Materials Table S-8. Interference Removal Comparison for Three Whole Blood Sources Between Dynamic Reaction Cell and Collision Reaction Cell Technologies Whole Blood Code Co Spike Conc. (µg/L) Co Conc. By ICP-CRC- MS (µg/L) Mean + SD Co Conc. By ICP-DRC- MS (µg/L) Mean + SD 100.54 ± 0.060.37 ± 0.090.49 ± 0.070.59 ± 0.143.17 ± 0.612.01 ± 0.492.9 ± 0.012.6 ± 0.49 10.51.17 ± 0.191.01 ± 0.251.14 ± 0.250.91 ± 0.012.99 ± 0.252.2 ± 0.143.39 ± 0.172.84 ± 0.34 15.04.45 ± 0.944.24 ± 0.914.35 ± 0.875.4 ± 0.377.49 ± 0.856.81 ± 0.357.6 ± 0.357.6 ± 0.7 11000909 ± 2.2916 ± 20.56943 ± 18.5896 ± 19.9882 ± 16.3874 ± 20.9850 ± 15.9887 ± 20.9 200.80 ± 0.0060.77 ± 0.070.73 ± 0.050.68 ± 0.0083.09 ± 0.12.25 ± 0.293.35 ± 0.062.76 ± 0.29 20.51.31 ± 0.051.18 ± 0.0161.18 ± 0.021.2 ± 0.142.97 ± 0.672.93 ± 0.133.34 ± 0.193.15 ± 0.27 25.05.07 ± 0.924.59 ± 0.524.99 ± 0.945.67 ± 0.687.51 ± 0.716.91 ± 0.397.53 0.297.3 ± 0.46 21000947 ± 9.13951 ± 15.21067 ± 156.3979 ± 11.1 954 ± 18.4952 ± 14.5927 ± 17.9937 ± 17.2 300.77 ± 0.040.55 ± 0.020.70 ± 0.040.61 ± 0.073.5 ± 0.282.54 ± 0.443.29 ± 0.362.99 ± 0.44 30.51.19 ± 0.231.07 ± 0.181.07 ± 0.101.09 ± 0.154.0 ± 0.653.22 ± 0.363.38 ± 0.283.34 ± 0.31 35.04.64 ± 0.354.44 ± 0.324.5 ± 0.385.67 ± 0.528.62 ± 1.07.34 ± 0.347.95 ± 0.327.95 ± 0.69 31000950 ± 9.6962 ± 47.66985 ± 33954 ± 39.9930 ± 48.4924 ± 45.9902 ± 41.6916 ± 40.3 Cell gasNoneHelium NoneAmmonia (RPq = 0.6)Ammonia (RPq = 0.7)Ammonia (RPq = 0.8) Ammonia (RPq = 0.85) Cell Gas FlowNot Applicablelowhigh