Table 1.

The advantages and limitations of the GC-based hyphenated MS techniques.

Instrument	Advantages	Limitations
GC-MS	Capable of providing detailed data from complex matrices. The most cost-effective method of hyphenated GC-based MS analysis. Can tailor pre-concentration methods to suit the sample being analysed. Generally easy to operate once set up and data easy to analyse. Good reproducibility. Miniaturisation efforts were achieved.	Samples require pre-processing and pre-concentration, which can be time consuming and expensive. Sample analysis can typically range from 30–60 min and requires blank runs and QC qualification, limiting throughput. The lowest sensitivity among MS techniques used with GC. Commonly, problems with identification if run without standards. Standards required for quantification.
GC-MS/MS	Much greater selectivity and sensitivity versus GC-MS. Can measure a wide mass range, including peptides. Enhanced signal-to noise ratio. Can provide more accurate identification of compounds versus GC-MS.	Both expensive and has a large lab. footprint. Requires experienced personnel for both method development and data analysis. Low mass resolution.
GC-TOFMS	Great mass resolution allows for more accurate identification of compounds. Has a theoretically unlimited upper mass range. Very high sensitivity. More consistent performance for low concentration compounds. Rapid acquisition rates.	At high signal-to-noise levels, reproducibility suffers. Poor detector linearity compared to a standard quadrupole MS. Limited dynamic range.
GC × GC-TOFMS	Retains the same advantages as GC-TOFMS in addition to the following: Compatible with single GC injection techniques. Can provide sharper and better resolved peaks. Solves some issues of co-elution compared to GC-MS. Higher and more effective use of peak capacity when compared to one-dimensional GC methods and results in improved signal-to-noise ratios due to increased signal (focusing/band compression at modulator). Decreased noise (separation of analytes from primary column bleed and coeluting analytes). Therefore, spectra are cleaner, allowing improved compound identification. The combination of GC × GC with a TOFMS is considered the most powerful tool for qualitative VC analysis.	Retains the same disadvantages of GC-TOFMS in addition to the following: Long sample run times compared to techniques with single chromatographic separation. If the modulation between the two columns is not properly set, then separation is compromised. Much higher per sample costs. Higher cost of the instrument.