REPORT FOR ANALYTICAL CHEMISTS
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ANALYTICAL CHEMISTRY
ized nature having essentially no other use in our work t h a n for the one food additive in question." Certainly there is legitimate question as to whether a method requiring five or six days for completion is a practicable one. I t m a y be t h a t there is no reasonable expectation of developing a faster one. B u t there are other points also to be considered. If the additive is highly toxic or if there is but small difference between the amount specified for use and the maximum safe level of use, then there is clearly a need for close policing. This dictates a rapid and accurate method of analysis and even, perhaps, the use of inexpensive or portable equipment. On the other hand, use of the additive m a y be so self-limiting for one reason or another t h a t no regulatory problem is likely to arise. Methodology offered by the petitioner is unquestionably one of the most frequent reasons why F D A refuses to accept a petition until alterations are made. Mr. Ramsey tells of the case where one petitioner offered validation data on several foods and said t h a t his method was generally applicable t o all foods in which the additive was proposed for use. F D A requested samples of one food covered by the petition on which the method had not been tried. After laboring over a period of 35 m a n - d a y s , F D A was unable to get any recovery whatever; the method had failed completely. " T h e crowning cap of this fruitless study," adds Mr. Ramsey ruefully, "was a subsequent statement of regret by the petitioner t h a t his chemists also had failed in their attempts to analyze the particular food furnished us." H e can cite m a n y cases where methods caused rejection of a petition through their failure on individual points. To give a single example, one petitioner submitted a colorimetric method which relied on an absorbance of about 0.050 in a 1-cm. cell, with half the absorbance being contributed by a blank on an untreated food. I n m a n y cases the petitioner must be requested to revise his method to spell out the procedural steps in detail to avoid misunderstanding, and thus to improve reproducibility as well as accuracy.
Air. Ramsey says t h a t the requirement for a practicable analytical method can be met by having it officially adopted by an organization like the Association of Official Agricultural Chemists or the American Oil Chemists Society. This would be done, where time permits, through a collaborative study done under their auspices. F D A recommends in general t h a t the style used in the AOAC Book of Methods be followed in describing procedures. The National Research Council suggests t h a t replicate analyses and recovery experiments should be done to establish accuracy and precision, no m a t t e r w h a t t y p e of analytical approach is used. A relatively lower precision can be tolerated a t high sensitivity t h a n at low; for example, a method sensitive to 0.01 p.p.m. m a y have ± 2 5 % or more error, while a method sensitive to no less t h a n 10 p.p.m. should be reproducible within perhaps 5 or 1 0 % . Recovery should be reasonably good—for example, 9 0 % for concentrations of 1 to 10 p.p.m. Blank tests should also be run. Excessively high blanks or poor recoveries, of course, tend to lower the quality of the data.
The D e l a n e y C l a u s e
Probably the Delaney clause of the Food Additives Amendment is the most controversial statement in the whole bill. In effect, this clause specifies t h a t no substance shall be used as a food additive if it has been shown to be carcinogenic in m a n or animal when applied in any amount whatever—that is, all carcinogenic substances have a "zero" tolerance. This concept of zero tolerances is immediately attacked as being completely unrealistic, since it raises questions as to the sensitivity of analytical methods. There is no method known, nor does it seem likely t h a t there ever will be, which makes possible the demonstration of an absolute zero quantity of substance in a mixture. The best answer t h a t any method can come up with is t h a t , with regard to the substance in question, there is "none detectable." The only thing indicated with any certainty in a finding of this
