****************************************************************************** From: "Armando Silvestre" Date: Tue, 9 Feb 1999 09:42:19 +0100 Subject: amino acid analysis Organization: Universidade de Aveiro hello everybody: someone asked me for GC conditions for the analysis of aminoacids/dipepetides without derivatization (rather uncommon, I guess...). Does any one have a suggestion -- ARMANDO J.D.SILVESTRE DEPT OF CHEMISTRY UNIVERSITY OF AVEIRO 3810 AVEIRO PORTUGAL email: ARMSIL@DQ.UA.PT Phone: + 351 34 370 711 Fax: + 351 34 370 084 ****************************************************************************** From: Eric_Block@waters.com Date: Tue, 1 Jun 1999 14:36:21 -0400 Subject: Re: aminoacid analysis Organization: * It was my understanding that amino acids are converted to diketopiperazines in a hot injection port, which is why they are derivatized in the first place. Are you sure they didn't mean LC? Eric Block ****************************************************************************** From: Isabelle CARLETTI Date: Wed, 02 Jun 1999 08:16:52 +0200 Subject: Re: aminoacid analysis Organization: Universit de NICE Sophia Antipolis I think the best analysis conditions are by HPLC and not by GC ****************************************************************************** From: "David B. Hedrick" Date: Thu, 03 Jun 1999 21:50:13 -0400 Subject: Re: aminoacid analysis Organization: Hedrick Services Armando Silvestre: Hello, back. Without derivatization, amino acids will not come off the column. There are capillary GC methods available for amino acid analysis, as well as HPLC methods. -- ~DBH ****************************************************************************** From: gal@taloa.unice.fr (J.-F. Gal) Date: Sat, 5 Jun 1999 16:23:38 +0000 Subject: Amino acids Organization: * There is many possibilities to derivatize AAs for GC. Here we use esterification with propanol and acetylation with acetyl chloride. It is cheap and not very complicated, but takes time. Even with HPLC/MS needs derivatization to get good ESI spectra. Jean-Francois GAL ------------------------------------- Prof. J.-F. GAL Groupe FT-ICR*GRECFO-Chim. Phys. Org. Fac. des Sciences*Parc Valrose Univ. de Nice-Sophia Antipolis 06108 NICE Cedex 2*FRANCE Tel : (33) (0)4 92 07 61 10 Fax : (33) (0)4 92 07 61 11 E-mail : PLEASE USE : Jean-Francois.Gal@unice.fr (gal@unice.fr) ------------------------------------- ****************************************************************************** From: dnharring@aol.comzng (DanHarring) Date: 19 Jun 1999 17:13:33 GMT Subject: Re: aminoacid analysis Organization: AOL http://www.aol.com Hi, sorry I didn't notice this thread earlier. I think the amino acids/peptides have one too many polar groups for GC. But yes, the DKP diketopiperazines seem to make it thru a DB-1 or DB-5 non-polar GC column at normal temperatures (150-250 deg). I was skeptical, until I saw a report on their analysis in the J. Agric Food Chem in 1997, the August issue (+/- 1 month, I'm going on memory). It was cited in the latest mailer from (?)either HP Peak or J&W, the comparison chromatograms of NPD and FID were shown at top right of page. I see them by GC-MS in a few types of food extracts (usually foods that underwent fermentation or browning). The ones I see have a characteristic simple mass spectra (ions at 70,125 and 154, 194, 244 etc). I had seen the peaks for years, but couldn't figure out what they were until I got a newer spectral library. Some of them are listed as cyclic dipeptides (eg, cyclo-pro-leu ). I don't doubt they could also arise as injection port artifacts when the precursors are present in the extract. Overall I think liquid chromatography would be better. Only a small, small fraction of the peptides will show up by GC. I don't know about their behavior on polar columns. I would ask what amino acids/peptides are more likely to form DKPs or are most lipophilic, but the sparse elegant brevity that is the norm for most newsgroups (with good reason, probably) would seem to discourage in-depth replies. sigh hope that helped a little, dan h ****************************************************************************** From: dnharring@aol.comzng (DanHarring) Date: 21 Jun 1999 17:37:37 GMT Subject: Re: aminoacid analysis Organization: AOL http://www.aol.com }.. I saw a report on their analysis in the J. Agric Food }Chem in 1997, the August issue (+/- 1 month, I'm going on memory). It was }cited in the latest mailer from (?)either HP Peak or J&W, the comparison }chromatograms of NPD and FID were shown at top right of page. I was half-right. The original article was recently cited in Food Technology, March 99 p49-61 (not the HP or J&W mailers, sorry) "...DKPs corresponding to cyclic dipeptides..." was in: J Agric Food Chem, Aug 97 p 3183-3189, Gautschi, Peppard et al (of Givauden-Roure Flavors). They describe how they discovered the GC-able property of these molecules: "During the course of our continuing studies into the flavor of alcoholic beverages, we noted a series of unidentified late-eluting components which were evident in the gas chromatogram obtained on analysis of an extract of beer." Extraction consists of diluting the beer with water, adding NaCl, then a dichloromethane extraction. These DKP-cyclic dipeptides are the only intact aminoacids/dipeptides that can be analyzed by GC without derivatization, that I know of. dan h remove zng to reply