Chromatographic speed classification for liquid chromatography using average theoretical peak time (ATPT).

BACKGROUND: The development of analytical techniques in the field of liquid chromatography has brought new frontiers in performance and analytical speed for the technique. The proper evaluation of the analytical boundaries achieved with those developments was not addressed in the literature, since different liquid chromatography (LC) techniques have not yet received any classification regarding their chromatographic speed. Defining chromatographic analysis speed based simply on analysis time is an outdated concept since it is sample and analyte-dependent. In this context, the application of the Average Theoretical Peak Time concept (ATPT) is proposed as a unified metric for chromatographic speed classification. RESULTS: This metric was evaluated using PCA analysis in a group of more than 50 publications, which generated the classification of LC methods in normal, high, hyper, and ultra-high-speed separations using ATPT. Normal speed (ATPT values greater than 18000 ms/peak) was found in HPLC, nano-LC, SFC, and CEC methods. Therefore, high-speed methods (ATPT values between 4000 and 18000 ms/peak) were found in UHPLC techniques, while LC × LC methods presented higher ATPT values between 1000 and 4000 ms/peak being classified as hyper-speed separations. ATPT can also be used as an optimization parameter, since older methods show higher ATPT values, while recent published papers show lower values of this metric. This behavior is justified due to the improvement of the LC methods over the years. SIGNIFICANCE: This work fulfills the gap in chromatographic definitions and metrics, regarding analytical speed in one-dimensional and multidimensional liquid chromatographic techniques and shows that ATPT metrics is a robust parameter that can be used to classify the separation speed as well as a metric to evaluate the LC Method optimization. It also corrects the historical application of separation time as a metric for chromatographic speed.

Influence of acquisition rate on performance of fast comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry for coconut fiber bio-oil characterization.

Comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC/TOFMS) is used to characterize complex bio-oil samples because of the high peak capacity associated with the high acquisition rate and mass spectra deconvolution capability of TOFMS. A recent application of fast GC × GC for this type of analysis improved sample throughput while achieving the same peak capacity without the use of cryogenic liquids. This work evaluates the effect of the TOFMS data acquisition rate on the quality of the analytical information obtained by GC × GC/TOFMS. In the analysis of coconut fiber bio-oil under fast GC × GC/TOFMS conditions, use of high data acquisition rates (200-300 Hz) increases the number of identifiable peaks by more than 50% compared with that achieved at the conventional rate of 100 Hz. The acquisition rate can affect the peak capacity by a factor of 3 or more. This is the first study to demonstrate the importance of optimizing the data acquisition rate, a parameter that has previously been neglected in the literature, in GC × GC/TOFMS development.

Towards the determination of an equivalent standard column set between cryogenic and flow-modulated comprehensive two-dimensional gas chromatography.

This preliminary research is focused on the task of defining an equivalent standard column set between cryogenic and flow-modulation comprehensive two-dimensional gas chromatography (GC × GC) combined with mass spectrometry (MS). Cryogenic modulation (CM) was carried out by using a loop-type device, while the flow modulator used was a seven-port wafer chip, equipped with an external accumulation loop. Initially, a common low-polarity + mid-polarity CM GC × GC column set was selected (30 m × 0.25 mm ID × 0.25 µm df + 1.5 m × 0.25 mm ID × 0.25 µm df), a method was developed, and a GC × GC-MS fingerprint was attained (on a sample of bio-oil derived from coconut fibers). After, a column set with the same stationary phases was selected for the flow modulation GC × GC-MS method (20 m × 0.18 mm ID × 0.18 µm df + 5 m × 0.32 mm ID × 0.25 µm df), with the capability to provide a-similar-as-possible separation. A side-by-side measurement of several chromatography parameters (efficiency, peak capacity, resolution, peak widths, retention factors, elution temperatures) was made.

Preliminary studies of bio-oil from fast pyrolysis of coconut fibers.

This work studied fast pyrolysis as a way to use the residual fiber obtained from the shells of coconut ( Cocos nucifera L. var. Dwarf, from Aracaju, northeastern Brazil). The bio-oil produced by fast pyrolysis and the aqueous phase (formed during the pyrolysis) were characterized by GC/qMS and GC×GC/TOF-MS. Many oxygenated compounds such as phenols, aldehydes, and ketones were identified in the extracts obtained in both phases, with a high predominance of phenolic compounds, mainly alkylphenols. Eighty-one compounds were identified in the bio-oil and 42 in the aqueous phase using GC/qMS, and 95 and 68 in the same samples were identified by GC×GC/TOF-MS. The better performance of GC×GC/TOF-MS was due to the possibility of resolving some coeluted peaks in the one-dimension gas chromatography. Semiquantitative analysis of the samples verified that 59% of the area on the chromatogram of bio-oil is composed by phenols and 12% by aldehydes, mainly furfural. Using the same criterion, 77% of the organic compounds in the aqueous phase are phenols. Therefore, this preliminary assessment indicates that coconut fibers have the potential to be a cost-effective and promising alternative to obtain new products and minimize environmental impact.