Table 2.
Analytical parameters for the identification of Labrasol® and Transcutol® by GC-MS with EI ion source, and LC-MS with ESI ion source. tR denotes retention time, Mr denotes relative molecular mass.
| Sample | tR(min) | Mr(m/z) | Precursor and product ion of EI in GC-MS, ESI negative in Labrasol® and positive in Transcutol® in LC-MS | Compound |
|---|---|---|---|---|
| Labrasol® by GC-MS | 10.31 | 186.3 | 186[M]+, 155[M–O–CH3]+, 143[M–C3H7]+, 87[M–C7H15]+, 74[M–C8H16]+ | Methyl caproate |
| Labrasol® by GC-MS | 7.43 | 158.2 | 158[M]+,127[M–O–CH3]+,115[M–C3H7]+, 87[M–C5H11]+,74[M–C6H12]+ | Methyl caprylate |
| Transcutol® by GC-MS | 5.60 | 134.2 | 134 [M]+,133[M−H]+, 117[M−OH]+, 104[M–O–CH2]+,72{[M−H]–O–C2H4–OH}+ | 2-(2-Ethoxyethoxy)-ethanol |
| Labrasol® by LC-MS | 21.16 | 172.3 | 171.1[M−H]−, 130.1[M–C2H6]−, 127.1[M–COOH]−, 87.1[M–C6H13]− | Capric acid |
| Labrasol® by LC-MS | 17.13 | 144.2 | 143.1[M−H]−,130.2[M–CH2]−, 98.2[M–COOH]−,56.3[M–C3H6–COOH]− | Caprylic acid |
| Transcutol® by LC-MS | 7.11 | 134.2 | 135.2[M+H]+,117.3[M–OH]+, 103.2[M–CH2–OH]+, 73.1[M–O–C2H4–OH]+ | 2-(2-Ethoxyethoxy)-ethanol |