| Popis: |
A method for the analysis of organic acids in vanilla extracts has been developed. The lead salts of the organic acids are separated, trimethylsilylated derivatives are formed directly from the lead salts, and the trimethylsilylated de rivatives are separated by GLC. Typical vanilla chromatograms show about 20 acid peaks, with 8 major ones. The main vanilla acid shows up as the largest peak, identified as 7. Malic acid occurs naturally in vanilla and is measured by Peak 2. Tahiti extracts are distinguished from other extracts by the smaller Peak 2, and the ratio of Peak 7 to Peak 2 can be used to identify these extracts. To measure the peak heights on a standard basis, known quantities of glutaric acid are added to the vanilla extract sample; this internal standard appears between vanilla acid Peaks 1 and 2. Gross deficiency in vanilla solids in the extract is detected by low peak heights; additions of foreign acids are readily shown by abnormal peak heights or by foreign peaks. This method was studied by ten collaborators and the unknowns were identified correctly. The proposed method provides more information in a shorter time than any method or combination of methods now available. However, since each GLC instrument has different responses to the same set of empirical conditions given in the method, each analyst must test authentic extracts and establish the characteristics to be used for the basis of comparison. The method is recommended for adoption as official, first action. |
