GAS-LIQUID CHROMATOGRAPHY IN THE ANALYSIS OF PERFUMES !83 The importance of analysing the sample on more than one column, using a different stationary phase and/or operating temperature, is demonstrated by composite peaks which separate into two components under different conditions. Examples are given in Table $. Table 3 Resolution of composite peaks Column (Table 1) Column (Tabl• 1) Compound pairs giving a single giving two composite peak separate peaks Menthol/pulegone 2 3 Camphor/linalol 2 1 Linalyl acetate/ bornyl acetate 1 2 Bornyl acetate/ linalyl propionate 2 1 Note that even using two columns, the presence of bornyl acetate cannot be ensured in the presence of linalyl esters. It can only be confirmed by preparative-scale isolation of the composite peak under the operating con- ditions of column No. 2 and then re-analysis on column No. 1. Col. 2 22. 40 •0 20 lb Figur• 5 Peppermint oil using 60-100 mesh firebrick support. Compare resolution with Fig. 4b for Celit•.

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Col.2 18 I 22 3•0 20 0 ..... Minutes Figure 6 Peppermint oil with 0-5•tl charge (10 x normal) at reduced sensitivity (1/5 x normal) showing non-linearity of response. Compare relative peak heights with those in Fig. 4b. Col. 2 22 Minutes Figure Peppermint oil recovered from toothpaste. Compare relative peak heights with those shown in Fig. 4b.