Source stability, viii

Clinical trials have demonstrated excellent efficacy with recombinant human factor VIII concentrates available as Recombinate and Kogenate. These recombinant factor VIII products are purified from the cell culture of plasmids, not viral DNA-transfected hamster cells and therefore do not express viral sequences. The addition of human serum albumin for stabilization, constitutes the sole possible source for human viral contamination. More recently recombinant factor IX has been genetically engineered by insertion of the human factor IX gene into a Chinese hamster ovary cell line. It has been proved to be safe and effective in the treatment of patients with hemophilia B. 

Since atomic absorption spectroscopy utilizes the ground state atom population for its measurements, it would appear that atomic absorption has a great advantage over flame emission in terms of detection limits and sensitivities of detection. An inspection of Appendix VIII, where detection limits are given for a number of elements for flame emission and atomic absorption, indicates this is not true. The reason for this apparent discrepancy lies in the relative stabilities of ground state and excited state atoms. An excited atom has a lifetime of the order of 10 -10 sec, and thus emits its energy very quickly after being excited. The usual flame emission source has an upward velocity of from 1 to 10 m/sec, so the excited atom will move only about 10 -10 m between the time of excitation and emission. 

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