Carrier gas flow-rate and injection system in capillary gas chromatography of unconjugated and glycine-conjugated bile acids.
The first description of successful capillary gas chromatography of intact glycine-conjugated bile acid derivatives used an automatic solid injection system and required very high carrier gas flow-rates (approximately 20 ml/min) to obtain satisfactory peak shape. Peak heights of unconjugated bile acid derivatives using this injection system and the low flow-rates (1-2 ml/min) usually used for such gas chromatographic analyses were very susceptible to small changes in flow-rate. This system has been re-examined in an attempt to explain this anomalous behaviour. An alternative injection system, the all-glass dropping needle, was also investigated. No explanation for the very high carrier gas flow-rates required when using the automatic solid injection system was found. The dropping needle injection system, however, produced excellent separation of bile acids and their glycine conjugates as dimethylethylsilyl ethers-methyl esters on non-polar wall-coated capillary columns using normal carrier gas flow-rates of 1-2 ml/min. It is clear that the automatic solid injection system originally used has some problem associated with it which can only be overcome, in the case of bile acids and their glycine conjugates, by increasing the carrier gas flow-rate to very high levels.
Street
J M
JM
Division of Pediatric Gastroenterology and Nutrition, Children's Hospital Medical Center, Cincinnati, OH 45229-2899.
Trafford
D J
DJ
Makin
H L
HL
D001647:Bile Acids and Salts / Q000032:analysis*; D002849:Chromatography, Gas / Q000379:methods; D005998:Glycine
D001647:Bile Acids and Salts; D005998:Glycine