Automatic prediction of retention times in multi-linear programmed temperature analyses

Vezzani, S.; Moretti, Paolo; Castello, Gianrico

doi:10.1016/s0021-9673(96)01043-6

Cited by 29 publications

(10 citation statements)

References 19 publications

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“…Small imperfections in the temperature calibration, column dimensions, or the flow rate/inlet pressure can cause large errors in projected retention times. Some researchers have successfully taken these imperfections into account by making meticulous measurements of them [13,18], but the amount of effort required is impractical for most users. Moreover, these measurements would have to be re-made every time the experimental conditions are deliberately or inadvertently changed.…”

Section: Introductionmentioning

confidence: 99%

“…al. [13] where they calculated the sensitivity of conventional retention projections to small errors in a number of experimental factors including the ramp rate, inlet pressure, and column length. However, these were all factors that would affect the temperature and hold-up time profiles—the multi-lab study showed that the back-calculation methodology can take those types of errors into account.…”

Section: Introductionmentioning

confidence: 99%

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What experimental factors influence the accuracy of retention projections in gas chromatography–mass spectrometry?

Wilson

Barnes

Boswell

2014

Journal of Chromatography A

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Programmed-temperature gas chromatographic (GC) retention information is difficult to share because it depends on so many experimental factors that vary among laboratories. Though linear retention indexing cannot properly account for experimental differences, retention times can be accurately calculated, or “projected”, from shared isothermal retention vs. temperature (T) relationships, but only if the temperature program and hold-up time vs. T profile produced by a GC is known with great precision. The effort required to measure these profiles were previously impractical, but we recently showed that they can be easily back-calculated from the programmed-temperature retention times of a set of 25 n-alkanes using open-source software at www.retentionprediction.org/gc. In a multi-lab study, the approach was shown to account for both intentional and unintentional differences in the temperature programs, flow rates, and inlet pressures produced by the GCs. Here, we tested 16 other experimental factors and found that only 5 could reduce accuracy in retention projections: injection history, exposure to very high levels of oxygen at high temperature, a very low transfer line temperature, an overloaded column, and a very short column (≤ 15 m). We find that the retention projection methodology acts as a hybrid of conventional retention projection and retention indexing, drawing on the advantages of both; it properly accounts for a wide range of experimental conditions while accommodating the effects of experimental factors not properly taken into account in the calculations. Finally, we developed a four-step protocol to efficiently troubleshoot a GC system after it is found to be yielding inaccurate retention projections.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

What experimental factors influence the accuracy of retention projections in gas chromatography–mass spectrometry?

Wilson

Barnes

Boswell

2014

Journal of Chromatography A

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“…The equation treats a programmed-temperature run as the sum of a series of infinitesimally small isothermal temperature steps that, taken together, closely approximate the true temperature program. It can be accurately solved for t R [15] if the following three relationships are precisely known: (1) the isothermal k vs. T relationship for compound x , (2) the T vs. time relationship produced by the GC instrument (the temperature profile), and (3) the t M vs. T relationship produced by the GC instrument (the hold-up time profile).…”

Section: Introductionmentioning

confidence: 99%

“…In a retention projection system, users can calculate retention times of compounds from their measured isothermal k vs. T relationships (which would be stored in a central database) along with the temperature profile and hold-up time profile produced by their instrument. In fact, several researchers [13,15–20] have attempted to use retention projection to predict retention times in programmed-temperature runs, but unless the temperature and hold-up time profiles produced by the GC instrument are known with great precision, the accuracy of retention projections suffer . In one report, Vezzani and co-workers [15] found that even when the hold-up time profile was precisely measured, errors in the calibration of their GC oven of less than 1 °C (affecting the accuracy of the temperature profile they used in their calculations) were enough to cause considerable error in retention projections.…”

Section: Introductionmentioning

confidence: 99%

“…In fact, several researchers [13,15–20] have attempted to use retention projection to predict retention times in programmed-temperature runs, but unless the temperature and hold-up time profiles produced by the GC instrument are known with great precision, the accuracy of retention projections suffer . In one report, Vezzani and co-workers [15] found that even when the hold-up time profile was precisely measured, errors in the calibration of their GC oven of less than 1 °C (affecting the accuracy of the temperature profile they used in their calculations) were enough to cause considerable error in retention projections. This remains an important problem as modern GC ovens are specified with oven temperature accuracies of ±3–5 °C (not to be confused with temperature “precision” or “resolution”, which are often specified to 0.01 °C).…”

Section: Introductionmentioning

confidence: 99%

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Easy and accurate calculation of programmed temperature gas chromatographic retention times by back-calculation of temperature and hold-up time profiles

Boswell¹,

Carr²,

Cohen³

et al. 2012

Journal of Chromatography A

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Linear retention indices are commonly used to identify compounds in programmed-temperature gas chromatography (GC), but they are unreliable unless the original experimental conditions used to measure them are stringently reproduced. However, differences in many experimental conditions may be properly taken into account by calculating programmed-temperature retention times of compounds from their measured isothermal retention vs. temperature relationships. We call this approach “retention projection”. Until now, retention projection has been impractical because it required very precise, meticulous measurement of the temperature vs. time and hold-up time vs. temperature profiles actually produced by a specific GC instrument to be accurate. Here we present a new, easy-to-use methodology to precisely measure those profiles: We spike a sample with 25 n-alkanes and use their measured, programmed-temperature retention times to precisely back-calculate what the instrument profiles must have been. Then, when we use those back-calculated profiles to project retention times of 63 chemically diverse compounds, we found that the projections are extremely accurate (e.g. to ±0.9 s in a 40 min ramp). They remained accurate with different temperature programs, GC instruments, inlet pressures, flow rates, and with columns taken from different batches of stationary phase while the accuracy of retention indices became worse the more the experimental conditions were changed from the original ones used to measure them. We also developed new, open-source software (http://www.retentionprediction.org/gc) to demonstrate the system.

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Prediction of retention times of polycyclic aromatic hydrocarbons and n-alkanes in temperature-programmed gas chromatography

2007

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We have developed an iterative procedure for predicting the retention times of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes during separations by temperature-programmed gas chromatography. The procedure is based on estimates of two thermodynamic properties for each analyte (the differences in enthalpy and entropy associated with movements between the stationary and mobile phases) derived from data acquired experimentally in separations under isothermal conditions at temperatures spanning the range covered by the temperature programs in ten-degree increments. The columns used for this purpose were capillary columns containing polydimethylsiloxane-based stationary phases with three degrees of phenyl substitution (0%, 5%, and 50%). Predicted values were mostly within 1% of experimentally determined values, implying that the method is stable and precise.

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Automatic prediction of retention times in multi-linear programmed temperature analyses

Cited by 29 publications

References 19 publications

What experimental factors influence the accuracy of retention projections in gas chromatography–mass spectrometry?

What experimental factors influence the accuracy of retention projections in gas chromatography–mass spectrometry?

Easy and accurate calculation of programmed temperature gas chromatographic retention times by back-calculation of temperature and hold-up time profiles

Prediction of retention times of polycyclic aromatic hydrocarbons and n-alkanes in temperature-programmed gas chromatography

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