TABLE 1. Comparison of Molar Concentration Ratios of Reagents to Iron for the Three Analytical Methods Used.
| Reagent | Orig. Ref. Method | Opt. Ref. Method | Sensor Method |
|---|---|---|---|
| Ascorbic acid |  |
 |
 |
| Citric acid |  |
 |
 |
| Thiourea |  |
 |
 |
| Ferene |  |
 |
 |
| Iron | 1.0 | 1.0 | 1.0 |
Note for Table 1: Ascorbic acid, citric acid, and thiourea are far in excess (2,700–55,000 times larger than the iron concentration), whereas the ferene is in excess rendering ~1:220–320 ratio. The calculations were for practical examples, e.g., 50 
of iron standard (100 
/dL) added to 200 
of total assay reagents in the optimized method, 36 
of the same iron standard was added to 214 
of total assay reagents in the original method. 30 
of 100 
/dL iron sample was delivered to the dry sensing channel in the sensor strip method.