Cyclodextrin derivatives in GC separation of racemic mixtures of volatiles: Part III

Abstract

The gas chromatographic performance of differently derivatized a-, p-, and y-cyclodextrins in the separation of racemic mixtures of volatile is investigated. The performances of 2,3,6-permethylated a-, p-, and y-cyclodextrins and 2,6-dimethyl-3-trifluoro-acetyl a-, p-, and y-cyclodextrins mixed with different ratios of OV-1701 or OV-1701-OH terminated were tested with racemates with widely differing structures. The influence of the percentage of cyclodextrins in polysiloxane, of film thickness of the stationary phase, of the length of the column, of column conditioning, and of the operating temperatures in the separations of different racemates has been evaluated.

Chiral stationary phases and applications in gas chromatography

“…The identically functionalized αand γ-CDs were introduced by the Bicchi group. [175][176][177] Li et al 178 synthesized 2,6-di-O-pentyl-3-O-trifluoroacetyl functionalized α-, βand γ-CDs (commercially available as, e.g., Astec…”

“…The first 2,6‐dialkyl‐3‐trifluoroacetyl functionalized CD was reported by Nowotny et al 173 and Schurig et al, 174 who prepared and investigated the properties of heptakis(2,6‐di‐O‐methyl‐3‐O‐trifluoroacetyl)‐β‐CD 49 (Figure 17). The identically functionalized α‐ and γ‐CDs were introduced by the Bicchi group 175–177 . Li et al 178 synthesized 2,6‐di‐O‐pentyl‐3‐O‐trifluoroacetyl functionalized α‐, β‐ and γ‐CDs (commercially available as, e.g., Astec CHIRALDEX A‐TA 50 , Astec CHIRALDEX B‐TA 51 , Astec CHIRALDEX C‐TA 52 ).…”

“…Bicchi and Schurig diluted the 2,6‐di‐O‐methyl‐3‐O‐trifluoroacetyl‐CDs in polysiloxane OV‐1701 and successfully applied the CSP in the separation of racemic compounds such as lactones, dioxolanes, spiroketals and terpenes, often showing complementary selectivity to their permethylated analogs 175–178,180 . However, they also observed faster degradation of column performance for 2,6‐di‐O‐methyl‐3‐O‐trifluoroacetyl functionalized α‐ and β‐CDs compared to their permethylated counterparts 180 .…”

Improved separation of γ‐ and δ‐lactones on a popular phase

“…The column descnbed in Section 2 1 was used for routine quahty control on a HP 5898A GC equipped with the HP 5970 mass selective detector (MSD) Hehum was used as carner gas at a velocity of 27 cm/s The test mixture contained racemic y-lactones C5, ca 2 mg/l, CS-ClZ, ca 1 mg/l of each, and &lactones C7, Cg CIO, and Cl2, ca 1 mg/l each 1 pl was iqected at 50 "C ma the BP 7673A automatic hquid sampler in the sphtless mode Followlng a purgeoff time of 80 s, the oven was rapidly heated to 110 "C, then programmed at 0 5 "/mn to 185 "C and kept at 190 "C for another 10 m n Detection was performed by selected ion momtonng (SIM), y-lactones at 85 amu, &lactones at 99 amu Results were confirmed by multiple ion monitoring (MIM) as hsted in Tables 1 and 2 Table 1 shows intensities of mass fragments relative to the base peak at 85 amu for y-lactones, Table 2 the same for &lactones (base peak at 99 amu) 3 Results Figure 1A shows the FID chromatogram of a solution of y-and 6-lactone standards Each peak represents about 1 3 ng of the substance To emphasize the quahty of the separation, an expanded mew of the nona-and decalactones is shown above the chromatogram The separation number (TZJ between y-nonalactone and y-decalactone was 32, Rs for y-decalactone was 14 3, that for 6-decalactone 2 44 ( Figure 1B) The 6-lactones are situated between the two y enantiomers of the corresponding carbon number The elution temperature of the last peak (S-6-dodecalactone) was 181 "C ~~ Figure 2 shows a GC-MS chromatogram of the test solution described in Section 2.3. R-and S-6-heptalactone were not well separated from R-y-octalactone; R-and S-6-octalactone overlapped with S-y-octalactone.…”

Cyclocholates as Chiral Selectors for Capillary Gas Chromatography - Effect of Temperature Conditioning on the Chromatographic Behavior of the Stationary Phase

“…The thermal behavior of cyclocholate 4 a is very different to that of cyclodextrins derivatives, which are usually more enantioselective after column conditioning at high temperature [22]. Indeed, cyclodextrin derivatives need to be transformed into a supercooled liquid-like state to obtain their separation ability.…”