Capillary columns with immobilized stationary phases. Part 4: A moderately polar phase,OV-1701

Whereas the immobilization of apolar silicone phases is essentially understood and mastered, the corresponding treatment of even moderately polar phases remains problematical. Upon attack by peroxide radicals, these phases respond by forming active transformation products rather than by bonding to the support surface or to neighboring molecules. OV-1701 is at present the most polar stationary phase which can reasonably be immobilized. An essential feature of the practical procedure is the prevention of film breakage after coating the inert support surface and before immobilization. Two ways of overcoming this problem are presented.     

Stabilization of Ucon LB-550-X stationary phase film by hydrogen chloride

The influence of gaseous hydrogen chloride on the efficiency and thermal stability of a Ucon LB-550-X stationary phase film has been studied under various working conditions. The efficiency of capillary columns was found to be unchanged or even increased, and the upper working temperature increased by 40–50°C. Nor did the action of hydrogen chloride change the polarity of the columns studied.     

Device for filling of small diameter capillaries with stationary phase solutions in liquefied gases

This paper describes a high pressure device for filling small diameter capillaries with stationary phase solutions is described. A liquid is forced into the capillary column with the help of high pressure syringe whose needle (provided with a side opening) is tightened in a PTFE seal. The device allows use of liquefied gas as solvent. A detailed procedure is given for filling the capillary with stationary phase solution. The performance of the device was evaluated by filling 12 m × 15 μm i. d. glass capillary with 6.5 % (w/v) SE-54.     

Behavior of fused silica capillaries subjected to gamma radiation. Part 1: Chromatographic performance

Fused silica capillaries deactivated with D₄ and coated with OV-1 were subjected to cobalt-60 gamma radiation in order to elucidate the effect of incident radiation on column performance. The chromatographic performance of these open tubular columns in which OV-1 was polymerized in situ was found to be dependent on the dosage of radiation and was evaluated before and after the irradiated columns were rinsed with solvent. Of the radiation dosages employed, 3 MRad produced superior chromatographic performance coupled with very favorable residual surface activity.     

Liquid crystal stationary phases for gas chromatography and supercritical fluid chromatography

Novel monomeric and polymeric liquid crystalline compounds were synthesized as stationary phases for gas chromatography (GC) and supercritical fluid chromatography (SFC). Monomeric liquid crystalline compounds were used in packed column gas chromatography for the separation of isomeric aromatic compounds and insect sex pheromones. Liquid crystalline polymers possess long nematic ranges and a uniform coating was easily achieved in glass and fused silica capillaries, which could stand temperatures up to 250°C in GC and pressures of 200 MPa at 160°C in SFC. The columns provide excellent selectivity and resolution for fused ring aromatic compounds such as the isomers anthracene and phenanthrene or triphenylene and chrysene.     

Chromatographic properties of various polysiloxane stationary phases for separation of 2,3,7,8–chloro-substituted dibenzo-p-dioxin and dibenzofuran isomers–a systematic comparison

Glass capillaries coated with four crosslinked and surface-bonded OH-terminated polysiloxanes [PS 347.5, OV-17-OH, OV-225-OH, and OV-240-OH] were compared with commonly used methyl-terminated SP-2330-coated columns with respect to their selectivity for the separation of 2,3,7,8-chloro-substituted dibenzo-p-dioxins and dibenzofurans. The methyl- and phenyl-substituted phases [PS 347.5 and OV-17-OH] exhibit only moderate isomer selectivity which limits their applicability in this field. The examined 3-cyanopropyl-substituted phases [OV-225-OH, OV-240-OH, and SP-2330] allow complete separation of all 2,3,7,8-chlorosubstituted PCDDs and PCDFs. With SP-2330 longer columns are required (50 m) for baseline separation of critical groups of isomers. OV-225-OH was found to be the most suitable phase as to isomer selectivity. In comparison to SP-2330, the analysis times can be reduced by a factor of two.     

Preparation of inert and high-temperature stable apolar and medium polar glass-capillary columns using OH-terminated polysiloxane stationary phases

Coating intensively leached silica surfaces with OH-terminated phases provides a new way of producing, by simple means, columns with substantially increased inertness and thermostability. In addition, their separation efficiency is found to be typically higher than that of columns with traditional coatings. The underlying basic effect is a condensation process between terminal silanol groups of the phase and residual silanols, of the glass surface, thus producing the mentioned inertness. Moreover, the surface-bonded molecules are immobilized without addition of a radical generator. If required, crosslinking can also be effected using a volatile azo compound. No vinyl groups are required for this additional immobilization process. The paper discusses all processes involved, and gives detailed working directions for the following medium polar phases. OV-1701-OH, OV-31-OH (new, 17% cyanopropyl), OV-61-OH, and OV-17-OH, and the apolar phases PS-347.5 and PS-086. There is no doubt so far that the principle of terminal silanol groups is applicable to all silicone phases, and may replace the traditional endcapped stationary phases in the future.     

Topical administration of ibuprofen in man. Simultaneous determination of the drug and its metabolites in urine by high resolution gas chromatography

A selective and sensitive high resolution gas chromatography assay for simultaneous determination of Ibuprofen and its major metabolites in urine is described. Biological samples were collected from healthy volunteers after a single topical administration of the drug in gel form. The chromatographic system, developed on a WCOT OV-1 glass capillary column, ensured a clear separation of Ibuprofen and its metabolites and their quantitative evaluation.     

Preparation of inert glass capillary columns coated with UCON 50 HB-5100. An attempt to rediscover industrially produced α, ω-polyethylene/polypropyleneglycol ethers as stationary phases in capillary gas chromatography

Using UCON 50 HB-5100, one of the most successful stationary phases in capillary gas chromatography during the past decade, as an example, we wish to redirect attention to the excellent properties of the polyethylene/polypropyleneglycol ether copolymer coatings. Based on experience gained in work with OH-terminated polysiloxanes, a method is described for preparing inert and relatively temperature stable chemically bonded and crosslinked coatings in a single working step. Methyltrimethoxysilane was used as coupling agent, and trifluoroacetic acid was introduced as an acidic catalyst. The reaction mechanisms involved as well as the influence of additional crosslinking on the column behavior are discussed, particularly with respect of the inertness of the coatings.