Development and evaluation of a low thermal mass gas chromatograph for rapid forensic GC–MS analyses

Abstract

Field as well as laboratory gas chromatography-mass spectrometry (GC-MS) systems are limited in several ways. Laboratory systems with air circulation ovens are bulky, power inefficient, and have a narrow range of temperature programming rates. Commercial field-portable GC-MS systems are too heavy, and many are limited to isothermal column temperature control. A resistively heated low thermal mass (LTM) GC system has been developed that can overcome most of these limitations, offering laboratory-level performance, or better, in a small, lightweight package. A prototype LTM GC was developed and evaluated in parallel with a commercial laboratory GC-MS used as a benchmark. A series of hydrocarbons, a Grob mixture, and a drug mixture critical pair of cocaine and nortriptyline were analyzed under different chromatographic conditions, and the performance of both systems was compared in terms of speed, efficiency, temperature control, resolution, precision, and power demand. The LTM GC was found to provide performance that was equivalent to the lab-based commercial GC when conventional temperature ramp rates were used (up to 30 • C/min). The LTM GC provided additional advantages over the conventional GC system in terms of positive or negative temperature ramping rates and range, cool-down time reduction, and lower power requirements (1-5 W/m). This new GC system demonstrated a capability for a wider range of linear temperature programming rates providing analysts flexibility when performing established forensic methods. Method development and implementation of the LTM GC was successful in demonstrating GC analyses that are controllable, reproducible, and fieldable.

Direct resistively heated column gas chromatography (Ultrafast module-GC) for high-speed analysis of essential oils of differing complexities

“…The temperature programming rates of 1-20 • C/s for UFM-GC can only be achieved through direct resistive heating of the capillary columns. Different approaches to direct resistive heating have been described [5,6]. The Ultrafast module (UFM) adopted here was that described by Magni et al [5] affording temperature programming rates up to 20 • C/s.…”

“…This system incorporates heating and temperature sensing elements distributed along the column. In UFM-Trace-GC, the Overton's system has been modified in agreement with Mustacich's patents [6,[9][10][11] extending its use to modules containing capillary columns with a broad range of lengths and diameters and enabling it to be assembled it inside a conventional GC oven. Moreover, the column module can quickly be cooled-down at the end of the analysis (about 1 min from 350 to 40 • C) by activating the oven fan.…”

Cromatografia gasosa ultrarrápida: uma visão geral sobre parâmetros, instrumentação e aplicações

“…19,28,40 A ideia do aquecimento resistivo direto da coluna surgiu na década de 60, mas teve sua eficácia experimental comprovada somente a partir dos anos 90, quando diferentes propostas deste sistema foram publicadas na literatura. [40][41][42][43][44][45][46][47][48][49][50] A partir do trabalho de Ehrmann et al 40 e das patentes de Mustacich et al [47][48][49] e Magni et al 50 foram concebidos os diferentes módulos de aquecimento ultrarrápidos comercializados atualmente, projetados para comportar colunas de vários comprimentos e que podem ser instalados tanto em cromatógrafos convencionais quanto em sistemas portáteis de análise cromatográfica. Esses módulos de aquecimento resistivo da coluna permitem atingir taxas de aquecimento de até 20 o C s -1 , sendo que o resfriamento da coluna é rápido, indo de 350 a 50 °C em cerca de 1 min.…”

“…Por não necessitar do aquecimento do forno do cromatógrafo, o consumo de energia é menor (200 W) quando comparado ao modo convencional. [44][45][46]51 Em CG, a temperatura afeta de forma significativa os aspectos cinéticos e termodinâmicos relacionados ao equilíbrio existente entre a fase móvel-analito-fase estacionária, alterando, dentre outros parâ-metros citados nas Equações 1 e 2, a seletividade da fase estacionária e o espalhamento das zonas cromatográficas, provocando, consequentemente, variações no desvio padrão dos tempos de retenção dos componentes da amostra. Deste modo, quando altas taxas de aquecimento são necessárias para promover separações ultrarrápidas, o programa de temperatura deve ser controlado com grande precisão.…”

Performance Evaluation of a Loeb-Eiber Mass Filter at 1 Torr

“…Related to the rapidly growing interest in field-and person-portable mass spectrometers [3], the forensic science community has also shown an active interest in pursuing a variety of applications using portable mass spectrometers [4][5][6][7]. Terrorism and security concerns have precipitated an increased awareness for the ability of mass spectrometers to be broad-spectrum threat detection devices.…”