Fast, very fast, and ultra-fast gas chromatography-mass spectrometry of thermally labile steroids, carbamates, and drugs in supersonic molecular beams

Abstract

Aviv 69978, Tel Aviv, Israel Gas chromatography-mass spectrometry (GC-MS) analyses of thermally labile compounds have been studied by using a short column fast gas chromatograph, coupled with fly-through electron ionization in supersonic molecular beams. Thirty-two compounds, which include steroids, carbamate pesticides, antibiotic drugs, and other pharmaceutical compounds, have been analyzed and the details of their GC-MS analysis are provided. The ability to analyze thermally labile compounds is discussed in relation to the speed of analysis. A new term, "speed enhancement factor" (SEF), is defined as the product of column length reduction and the carrier gas linear velocity increase, as compared with normal GC-MS conditions. Fast, very fast, and ultra-fast GC-MS are defined with a SEF in the ranges of 5-30,30-400, and 400-4000, respectively. Trade-offs in the degree of dissociation, speed, gas chromatograph resolution, and sensitivity were studied and examined with thermally labile molecules . The experimental factors that affect the dissociation are described with emphasis on its reduction. We claim that the use of supersonic molecular beams for sampling and ionization provides the ultimate capability in the GC-MS of thermally labile compounds. The obtained 70-eV electron ionization mass spectra are shown, and an enhanced relative abundance of the molecular ion is demonstrated together with library search capability of these mass spectra, which is better than that reported with particle beam liquid chromatography-mass spectrometry. The performance of fast GC-MS in supersonic molecular beams is compared with other methods of fast GC-MS and with particle beam liquid chromatography-mass spectrometry. (J Am Soc Mass Spectrom 1996, 7, 737-752) G as chromatography-mass spectrometry (GC-MS) is the central technique employed today for the analysis of organic compounds, which includes analysis at trace levels in complex mixtures. However, GC-MS is limited in its scope and therefore is often replaced by liquid chromatography-mass spectrometry (LC-MS), although LC-MS analysis is more complicated to operate, exhibits poorer performance, and costs more .The scope of conventional GC-MS is limited owing to two main reasons:1. Relatively nonvolatile molecules (such as large polycyclic aromatic hydrocarbons) are incompatible with gas chromatography and especially incompatible with the mass spectrometer ion source. The ion source-limited temperature results in an early onset of chromatographic peak tailing.Address reprint requests to Professor Aviv Am irav, School of Chemistry, Sadder Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.

Gas chromatography‐mass spectrometry with supersonic molecular beams

“…The considerably lower elution temperatures achieved enabled the analysis of an extended range of thermally labile and low‐volatility compounds, which otherwise could not be analyzed by standard GC‐MS. We have demonstrated5–7, 23, 48 the analysis of large polycyclic aromatic hydrocarbons (PAHs) such as decacyclene with ten fused rings, well above the current GC limit of PAHs with six rings. Even a metaloporphirin such as magnesiumoctaethylporphin was easily analyzed with elution temperatures below 300 °C.…”

“…The range of Supersonic GC‐MS applications that we explored include the analysis of pesticides in agricultural products, which is described in detail in Ref. 22; fast analysis of drugs in raw urine;54 the analysis of heroin and cocaine in single, untreated hair;52 the analysis of several types of organic contaminants on surfaces by laser desorption fast GC‐MS;51 ultrafast analyses of lead in gasoline, caffeine in coffee and drugs in tablets;5 the application of the ChromatoProbe sample introduction device for extract‐free dirty sample analysis;65 the analysis of large phthalates and large PAHs;6 fast analysis of thermally labile drugs, underivatized steroids, explosives and carbamate pesticides;23, 48 the analysis of testosterone in alligator blood;7 the analysis of hydrocarbons in fuels43 and the analysis of triglycerides in biodiesel 43…”

Detecção em cromatografia gasosa rápida e cromatografia gasosa bidimensional abrangente

“…A GC rápida pode ser classificada de acordo com a largura do pico à meia altura e com o tempo total da análise [21] . Outros autores levam em conta um fator para quantificar o aumento de velocidade, o qual é o resultado da multiplicação da diminuição do tamanho da coluna pelo aumento na velocidade do gás de arraste (ambos em relação às condições convencionais) [22] . Embora não exista um acordo entre as classificações, os termos GC rápida, muito rápida e ultrarrápida são relatados na literatura, nos quais as larguras de pico típicas são da ordem de 200-1000 ms, 30-200 ms e 5-30 ms, respectivamente.…”

Faster gas chromatography and its utilization in brewing. Part 1. - Theoretical and practical aspects.

“…The definition of fast or faster gas chromatography has been discussed for some time [9][10][11][12][13][14]. Concepts relating fast gas chromatography to run time clearly indicate the bottom-line of getting results roč.…”