In this study, we applied a portable near-infrared spectrophotometer (MicroNIR) for in-line monitoring of the synthesis of 5-hydroxymethylfurfural (5-HMF) in a continuous flow microreactor. Under the best reaction conditions using isopropyl alcohol/dimethyl sulfoxide as the reaction solvent and a fixed-bed reactor packed with solid acid catalyst, total conversion of D-fructose was observed, and 5-HMF was obtained in 95% yield with a residence time of just 11.2 min. Principal component analyses and construction of multivariate control charts based on Hotelling's T 2 and Q residuals were also performed and proved the excellent response of the compact MicroNIR device for in-line monitoring of 5-HMF production without variation in the yield over 8 h/day during 5 days. Our results demonstrate the great potential for the application of this compact device in the monitoring of laboratory-scale reactions, which can be extended to industrial scales.

The effect of selenate and selenite enrichment on mineral composition of a red type of lettuce cv. "Veneza roxa" was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP OES), molecular modeling and principal component analysis (PCA). Both Se species did not show toxicity, while selenate promoted the greatest Se accumulation by the plant. There was an increase of 886 µg of Se per 100 g of fresh sample at different concentrations of selenate, but for selenite the maximum variation was only of 114 µg per 100 g. Selenate promoted the absorption of Mo and S and the reduction of K, Mn and P, meanwhile selenite increased Mn and decreased Mo accumulation. Copper and Fe absorption was negatively affected, Ca and Mg showed a slight increase, and Na and Zn were not affected by Se species. Despite the changes in the nutritional balance, Se-enriched lettuce can still be considered a potential dietary source of this essential element.

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A novel heart-shaped substrate-integrated hollow waveguide (hiHWG) was integrated with a near-infrared micro-spectrometer (μNIR) for sensing natural gases, resulting in an ultra-compact near-infrared gas sensing system - iHEART. The iHEART system was evaluated using two different μNIR spectrometers, and the performance was compared with a laboratory NIR spectrometer for gas analysis based on an acousto-optic tunable filter (AOTF). The spectral data were pre-processed using the 1(st) derivative Savitzky-Golay algorithm, and then used for establishing multivariate regression models based on partial least squares (PLS). The root mean square errors of prediction (RMSEPs) obtained for major components of natural gas with both iHEART systems were similar to those associated with the AOTF spectrophotometer combined with a conventional long-path measurement cell. It was demonstrated that the iHEART system has significant potential for the development of compact in-line gas sensing systems, thus facilitating monitoring of (petro)chemically relevant processes and products. However, the flexibility and modularity of the system also allows tailoring iHEART to a wide range of other relevant analytical measurement scenarios requiring short response times and minute gas sample volumes.