The model 206M provides quick and accurate measurement of the ratio of zinc protoporphyrin to heme in whole blood. No volume measurement is needed. The sample is optically dense and front surface illumination is used. As little as 5 x 10-12 grams of zinc protoporphyrin can be detected in a single drop of whole blood. Simply puncture a finger, toe or ear lobe which has been cleaned with alcohol. Place a glass cover slide (AVIV No. 1, 25mm sq.) into the sample holder. A drop of whole blood is then placed in the center of the cover slide, sufficient to cover the aperture. No additional preparation is needed and no volume measurement is required. With the sample in place, operate the Model 206M by simply depressing the measure button located on the front of the instrument. The instrument will pause for a second to calibrate itself, automatically draw the sample holder with the whole blood sample into the measuring compartment, analyze the sample, display the results and return the sample for easy disposal. Although the instrument always measures the molar ratio of ZPP to Heme, the instrument can be ordered calibrated to display this result in any one of several units. Many instruments in the USA are calibrated to display weight/ volume concentration units using assumed hematocrits as specified by OSHA (ZPP, Hct 42) or CDC (equivalent EP, Hct 35). These calibrations are fully acceptable to the respective agencies. We strongly recommend the use of molar SI units µmole/mole Heme or µg ZPP/gram Hb for all other purposes.