HUMAN SALIVA

V. A TECHNICAL PROCEDURE FOR PHOSPHORUS ANALYSIS

¹ The George Williams Hooper Foundation for Medical Research and Division of Dental Medicine, College of Dentistry, University of California, San Francisco.

1. The available surveys of the literature on the calcium and phosphorus composition of mixed human saliva indicate the need for further clarification of the rôle of salivary electrolytes in oral conditions. 2. One obstacle in this process has been the lack of a satisfactory method for salivary inorganic phosphorus analysis. The adopted method must be not only thoroughly tested and compared with others of proven accuracy and worth in the biological field, but must satisfy the peculiar conditions of salivary analysis. 3. The popular methods of Tisdall; Bell and Doisy; stannous chloride; and Fiske and Subbarow were tested on known solutions of inorganic phosphate with satisfactory recoveries. When these methods were tried on saliva several difficulties were encountered which interfered with accurate checks. 4. Poor color development was pronounced by the methods of Bell-Doisy; and Fiske and Subbarow. 5. The stannous chloride procedure, as modified by A. Bodansky, was found to give the most satisfactory results over the widest possible range of conditions. 6. Bodansky's procedure adapted to saliva made possible the use of the smallest sample of saliva (average 0.1 cc.) for a single determination; gave the best color development when tested on selected cases developing poor color by the Bell-Doisy and Fiske-Subbarow technics; and was found suitable over a range of amounts of inorganic phosphorus from 0.0090 to 0.0560 mg. 7. Preliminary centrifugation of the saliva sample was adopted after testing and discussing the findings of Becks; and Clark and Levine. Losses due to preliminary centrifugation were shown to involve principally the organic phosphorus fraction. This does not support the hypothesis of Clark and Levine, who state that the losses in centrifuged saliva are not due to the removal of cells, debris, etc., but to the formation of a "calcium-phosphorus-mucin complex." If this were true the losses would occur in the inorganic fraction as well. Clark and Levine's findings, based upon the analysis of only the total phosphorus content, were insufficient to permit this conclusion. 8. Trichloracetic acid was used to precipitate proteins and permit the determination of the inorganic phosphorus fraction. 9. A nomogram was constructed to lessen the labor of calculation. On the chart the result in mg. per cent phosphorus can be found directly from the calorimetric reading. 10. A complete description of the recommended method according to the modified Bodansky procedure is given for the determination of salivary inorganic phosphorus. Modifications for the determination of total phosphorus and the total acid-soluble fraction are also noted.