GC was once commonly called “GLC,” where the “L” stands for liquid. Inside GC columns are particles of a ceramic or inert material coated with a viscous liquid stationary phase that interacts with the analyte. By contrast, HPLC stationary phases are bonded to the base material. New GCs are sold with software that integrates peaks, stores methods, assists in report writing, and controls instrument functions.
GC detectors have been evolving rapidly to provide greater sensitivity. Flame ionization detectors (FIDs) have been the most widely used, as they detect any molecule containing carbon. Numerous other detector types have been introduced over the years, but the most interesting is the mass detector, which is essentially a miniaturized mass spectrometer. Mass detectors provide unequivocal identification of peaks emerging from the chromatograph based on the molecules’ molecular weights and fragmentation patterns.
High-throughput analysis was once associated with commercial labs, but today even academic groups value productivity, says Jim Edwards, business development manager at Thermo Fisher Scientific (Austin, TX). Instruments that perform faster separations are available, but this has introduced a detection bottleneck. “Vendors who place a premium on accelerating chromatography should similarly speed up detection to acquire data at a speed appropriate to good precision and performance.” Less easily achieved is the design of instruments that do not suffer from “fatigue effects,” that is, show signs of slowing down or require maintenance after one or two thousand cycles. Maintenance downtime, Edwards observes, is a productivity killer that easily negates the benefits of more rapid analysis or cycling.
GC systems have become faster and more selective to the point where analysts now look to dead times during analytical runs to eliminate inefficiencies. Alessandro Baldi, business manager for chromatography software at PerkinElmer (Waltham, MA), says this is best achieved by avoiding changes that will disrupt workflows or force analysts to alter established methods.
Oven equilibration is one obvious bottleneck. PerkinElmer tackled equilibration by designing an oven with very low mass that cools down rapidly by fast-moving, non-recirculated air.
Next, the company went after autosampling by implementing lookahead functions. “It takes time to inject, clean the needle, and load and unload the sample,” Baldi says. In an optimal configuration, the autosampler engages not at the precise moment it is needed, but when the oven is almost at the right temperature.
A third approach is to integrate the GC with sample prep devices to provide greater flexibility and less of a hardwired configuration. PerkinElmer has recently collaborated with Tekmar (Mason, OH) on purge-and-trap sample concentration and with CTC (Zwingen, Switzerland) on solid-phase microextraction. Baldi says the goal is to minimize sample preparation.
Reductions in per-injection cycle times may be achieved through the use of flow-splitting techniques that divert eluent to multiple columns or post column to one of several detectors. Splitting allows analysts to switch columns or detectors on the fly without having to turn off the instrument, allow components to cool down, and swap them out. In essence, splitting creates “multiple” chromatographs from one instrument.
Recently Released GC Systems
490 Micro GC
- Engineered to deliver lab-quality GC performance in the field, on the production line, or wherever you need fast accurate GC measurements
- Provides fast, accurate on-line gas analysis at ppm-level sensitivity
- Extensive remote control and I/O capability for seamless integration with existing operations and reliable unattended operation
- Features flame ionization and flame photometric detectors with flame out sensors that shut off the hydrogen if the flame goes out
- Includes a 7-inch color touch screen
- Low and high set-points (depends on the options) can be customer-programmed for each point and/ or compound
FAME in AVTUR Analyzer
- Can be used by the average technician and doesn’t require a chemist to operate
- Requires no sample preparation; no Internal standard (ISTD), no dilutions, and no Solid Phase Extractions techniques are used
- Excellent stability and repeatability of the instrument minimizes calibration and maintenance of the instrument
Forston Mini GC
- Based on Seacoast’s sensing and sampling technology and is integrated with the Forston Labs LabNavigator
- Provides real-time data on-site, or can send data to supervising chemist via cell phone
- Has the ability to acquire, monitor and analyze data from up to 5 simultaneous sensor inputs
- Suitable for various applications, such as soil and water remediation, security and safety, industrial processing and quality control