Comparing the predictions by NIR spectroscopy based multivariate models for distillation fractions of crude oils by F-test.

The whole range of distillation fractions in industrially relevant crude oil samples is predicted by using two multivariate models based on near-infrared (NIR) spectra. The first versions of the models as well as the respective model updates are considered, with the updates largely aimed at expanding the models. The prediction results are compared across all the fractions and F-test is used to critically compare the performance of the models and the effectiveness of the limited updates. The results suggest that both multivariate methods perform very comparably, and the updates do not lead to statistically significant changes, which differs from what one could conclude from the nominal prediction errors. The near-equivalency of the prediction accuracy of the updated models is additionally illustrated by perusing predictions of a number of batches from one sour and one sweet crude arriving at the refinery during a four month period.

Lubricant-Infused Surfaces for Low-Surface-Tension Fluids: The Extent of Lubricant Miscibility.

Lubricant-infused surfaces (LISs) and slippery liquid-infused porous surfaces (SLIPSs) have shown remarkable success in repelling low-surface-tension fluids. The atomically smooth, defect-free slippery surface leads to reduced droplet pinning and omniphobicity. However, the presence of a lubricant introduces liquid-liquid interactions with the working fluid. The commonly utilized lubricants for LISs and SLIPSs, although immiscible with water, show various degrees of miscibility with organic polar and nonpolar working fluids. Here, we rigorously investigate the extent of miscibility by considering a wide range of liquid-vapor surface tensions (12-73 mN/m) and different categories of lubricants having a range of viscosities (5-2700 cSt). Using high-fidelity analytical chemistry techniques including X-ray photoelectron spectroscopy, nuclear magnetic resonance, thermogravimetric analysis, and two-dimensional gas chromatography, we quantify lubricant miscibility to parts per billion accuracy. Furthermore, we quantify lubricant concentrations in the collected condensate obtained from prolonged condensation experiments with ethanol and hexane to delineate mixing and shear-based lubricant drainage mechanisms and to predict the lifetime of LISs and SLIPSs. Our work not only elucidates the effect of lubricant properties on miscibility with various fluids but also develops guidelines for developing stable and robust LISs and SLIPSs.

Characterization and quantitative analysis with GC/TOFMS comparing enhanced separation with tandem-column stop-flow GC and spectral deconvolution of overlapping peaks.

Time-of-flight mass spectrometry is unique in that ion abundance ratios are constant over the chromatographic peak profile provided that the peak contains only one component. This provides the means for the automated finding and spectral deconvolution of overlapping chromatographic peaks from completely unknown mixtures if the mass spectra for the overlapping components are sufficiently unique. This can greatly reduce the chromatographic resolution requirements, which allows for very rapid quantitative analysis as well as for high-speed mixture characterization. High-speed GC with stop-flow operation of a series-coupled column ensemble can be used to completely separate some component pairs that coelute from the column ensemble, thus eliminating the need for spectral deconvolution of those mixture components. This provides two options for high-speed qualitative and quantitative analysis, using either the mass spectra from deconvoluted overlapping peaks or the mass spectra from the completely separated peaks obtained with stop-flow operation of the tandem column ensemble. These options are compared with respect to the similarity for spectral matching with a library and to peak area linearity with concentration, calibration plot correlation coefficients, and shot-to-shot reproducibility.

High-speed characterization and analysis of orange oils with tandem-column stop-flow GC and time-of-flight MS.

High-speed GC with time-of-flight (TOF) MS detection is used for the characterization and analysis of oils rendered from the peel of five diverse species of orange including bergemot orange, bitter orange, tangerine, mandarin orange, and sweet orange. With a user-defined signal-to-noise threshold of 100, 44 peaks were found and 36 compounds identified in the various oils. Some major constituent components show large concentration ranges over the five species. A 14-m-long, 0. 18-mm-i.d. column ensemble consisting of 7.0-m lengths of a trifluoropropylmethyl polysiloxane and a 5% phenyl dimethyl polysiloxane column was temperature-programmed at 50 degrees C/min starting at the time of injection to achieve analysis times under 140 s. The TOFMS was operated with a spectral acquisition rate of 25 spectra/s, and automated peak finding software successfully found all of the components, with the exception of one severely overlapping peak pair in bitter-orange oil. Of the 44 peaks, 25 were identified by use of a TOFMS library created for this study; another 11 were identified with a commercial terpene library, and 8 were not identified. A quantitative comparison (percent of total peak area) is presented for 16 components, which comprise 98.8-99.5% of the total peak area for the five orange species. Stop-flow operation of the column ensemble is used to enhance selectivity for targeted component pairs to facilitate single-channel detection for QA/ QC analysis of characterized samples and to enhance column selectivity for TOFMS characterization in cases in which peak overlap is so severe that only a single peak is observed.