GC Injection Port Research Articles

Study of components in crude drugs by headspace gas chromatography. II. Components of atractylodes

Determination of volatile components in essential oils from Atractylodis plants was studied by headspace gas chromatography. The crude drug of 0.20 g with 1.0 ml of water in a capped vial was heated at 130 degrees C for 45 min. Then 0.5 ml of vaporized components were collected by gas tightsillinge, and were applied into the injection port of GC or GC/MS. Consequently we could analyze and confirm the following components; hinesol and beta-eudesmol were found to be contained in Atractylodis Lanceae Rhizoma and atractylon in Atractylodis Rhizoma. beta-Eudesmol was analyzed by headspace gas chromatography, and the obtained calibration curve showed good linearity over the range from 2.5 micrograms to 10.0 mg. The result agreed with those obtained using numerical analyses by the steam distillation method. Atractylodis was found to have a wide variety of components depending on the available sources and on the stored conditions. This method was, therefore, more rapid and simpler determination of essential oils in crude drugs using headspace gas chromatography than those used previously. The method was useful means of the analyses of components in crude drugs such as Atractylodis plants and quality control.

The conversion of ephedrine to methamphetamine and methamphetamine-like compounds during and prior to gas chromatographic/mass spectrometric analysis of CB and HFB derivatives

Ephedrine and methamphetamine standards were separately derivatized with heptafluorobutyric anhydride (HFBA) and carbethoxyhexafluorobutyryl chloride (CB) and analyzed by full-scan gas chromatography/ion trap mass spectrometry with electron ionization (EI) and chemical ionization (CI). Using EI, a high-concentration ephedrine standard produced a total ion gas chromatogram containing several minor HFB derivatives in addition to ephedrine. One of these had the same retention time as the derivative of methamphetamine, while another eluted 3 s later. Both contained the same major mass fragmentation ions that could be erroneously used in targeted selected ion monitoring gas chromatographic/mass spectrometric analysis for methamphetamine. The full-scan EI and CI spectra showed that these derivatives were not methamphetamine. CI mass spectrometric studies of ephedrine scanning up to m/z 700 demonstrated that reaction with HFBA caused acylation of both the hydroxyl and secondary amino groups. The HFBA used in this study was contaminated with pentafluoropropionic anhydride and tri-fluoroacetic anhydride and produced mixtures of derivatives, some with retention times near or identical to that of methamphetamine. In contrast, CB derivatization of ephedrine produces a single methamphetamine-like compound that has the same retention time and mass spectra as methamphetamine, and is produced only when high gas chromatograph injector temperatures are used ( > 260°C). Collision-induced decomposition tandem mass spectrometric studies for the CB derivative verified that methamphetamine is produced from ephedrine at elevated GC injection port temperatures. In view of these findings, substance abuse testing for methamphetamine in urine must proceed with caution when ephedrine and other sympathomimetic amines are present. Definitive analyses can be accomplished by full-scan CI gas chromatographic/mass spectrometric analysis with HFB derivatives, or by lowering gas chromatograph injector temperatures with CB derivatives.

Solution and gas phase deuterium derivatization reactions for gas chromatography/microwave emission detection

Deuterium is monitored and quantitated in the presence of hydrogen in organic molecules with the helium microwave emission detector (MED). Various functional groups are tagged utilizing deuterated reagents which also serve to modify the components' Chromatographic characteristics. Lithium aluminum deuteride (LAD) will reduce aldehydes, carboxylic acids, esters, amides and acid halides to non-exchangeable CD 2-tagged alcohols which can be further derivatized with multi-element reagents such as chlorodifluoroacetic anhydride. Other reagents include D 9-BSA (N, O-bistrimethylsilylacetamide) for silylation, Deuter-8 TM for esterifications, D 3-acetylchloride for acetylation, and D 2-diazomethane for generalized N and O alkylations. Gas phase derivatization utilizes an on-line deuteration reactor in series with the GC injection port. The reactor contains catalysts such as nickel, platinum, or palladium coated on a suitable substrate in a deuterium atmosphere. This technique is used to tag olefins, alkanes, aromatics, nitriles and other functionalities subject to D-H exchange, reduction, isomerization, and a variety of cleavage reactions. The element-selective MED provides qualitative and quantitative information for a variety of compounds in which deuterium is incorporated.

Liquid Chromatographic and Gas Chromatographic Determination of N-Nitrosodiethanolamine in 2,4-D Diethanolamine Pesticide Formulations

Abstract A method for the determination of N-nitrosodiethanolamine (NDE1A) in diethanolamine formulations of 2,4-D herbicide has been developed. The NDE1A fraction was isolated from the formulation by 2 disposable ion exchange columns followed by an extraction column to remove the acid and amine that might be deleterious to the analytical system and to concentrate the NDE1A solution. The isolated fraction was then further purified on a silica gel disposable column and analyzed for NDE1A by using a liquid chromatographic (LC) apparatus connected to an ultraviolet (UV) detector in series with a thermal energy analyzer (TEA) detector. NDE1A was derivatized to the trimethylsilyl (TMS) derivative, the identity of which was confirmed by gas chromatography- mass spectrometry (GC-MS) and analyzed by gas chromatography with TEA detection (GC-TEA). The limit of detection of NDE1A by LC-TEA and LC-UV is 1 ng and by GC-TEA 0.08 ng. These values correspond to 0.1 ppm relative to the active ingredient in the formulation. The recoveries for this analytical method averaged from 91 to 100% when the samples were spiked at the 0.30-3.47 ppm level. The specificity and reproducibility of these 3 methods of determination were compared; results suggest that NDE1A was not generated during cleanup or in the GC injection port.

Aromatization and catecholization of the A-ring of nor-19-methyl steroidal 3-keto-epoxides by trimethylsilylation

The reaction of 3-keto-nor-19-methyl-4,5 or 1,2-epoxy steroids with trimethylsilylating reagents has been investigated by NMR and GC-MS. Aromatization of the A-ring was found to be induced not only by thermal effects in the GC injection port but also as a function of the silylation reaction conditions. The strength of the silylating reagent was influential in the type of product formed in the reaction of 17β-hydroxy-4β,5β-epoxyestr-1-ene-3-one.