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Process-monitoring laboratories in the pulp and paper industry generally use a combination of wet chemical analyses and physical measurements to certify the fitness of a production pulp for a specific end-use. These laboratory tests require time and the effort of trained personnel, limiting their utility for real-time process control. Here we show that Raman probes of unrefined cellulosic pulps, well-suited to the online measurement of in-process materials, can predict the quality attributes of manufactured papers. The accuracy of prediction improves when the covariance is modelled in a reduced measurement space selected by a data-driven, feature-selection technique referred to as a Template Oriented Genetic Algorithm (TOGA). TOGA, combined with discrete wavelet transform (DWT), isolates functional-group features that correlate best with mechanical properties paper derived from refined pulp. Paper makers refine market pulps to build sheet strength using a beating process that decreases freeness as it increases fibre-fibre bonding. Methods demonstrated here predict manufactured sheet properties obtainable after any specified degree of refining from the Raman spectrum of an unrefined pulp. This analysis capacity will enable both vendors of market pulp and makers of sheet paper to specify in advance the amount of beating required to produce a desired product, thereby saving cost and conserving resources.

Extra virgin olive oil provides an important intake of α-tocopherol, which is part of vitamin E complex. A fast analytical method for its quantification, based on paper spray mass spectrometry, has been developed. The methodology possesses the ability to record mass spectra without sample preparation or preseparation steps. The experiments were performed in Multiple Reaction Monitoring scan mode; in particular, the transitions m/z 429 → m/z 163 for α-tocopherol and m/z 435 → m/z 169 for the labeled internal standard were monitored, in order to obtain the greatest specificity and the best sensitivity. The accuracy of the method was tested analyzing spiked samples prepared at concentrations within the dynamic range of the calibration curve, which returned values near 100%. Furthermore, good values of LOQ and LOD were obtained, demonstrating that this approach can be applied for a rapid screening of tocopherols in different vegetable oils. The results were compared with analyses performed by traditional chromatographic methods. Graphical abstract.

As an analytical support, paper, being low cost, highly abundant, of high porosity, disposable or biodegradable, and easy to use, store, transport, and print, has excellent chemical compatibility with many applications. Since the first microfluidic paper-based analytical device (μ-PAD or lab-on-paper) was proposed, the paper-based assay has never attracted as much attention as it does now. There has recently been rapidly increasing interest in using sensitive luminescence methods, for example chemiluminescence (CL) and electrogenerated chemiluminescence (ECL), as the detection strategy for lab-on-paper devices. Because of their intrinsic characteristics, CL and ECL provide outstanding performance while retaining the simplicity, low cost, multifunctionality, versatility, flexibility, and disposability of μ-PADs. The objective of this review is to cover the development of lab-on-paper-based devices using CL and ECL detection, including fabrication of paper devices, construction of sensing interfaces, signal amplification strategies, external instruments used, and applications. We believe that lab-on-paper devices with CL and ECL detection methods will meet the diverse requirements of point-of-care diagnosis.

Bioluminescent Saccharomyces cerevisiae yeast-based bioreporters were used to monitor bisphenol A and other estrogenic chemicals in thermal paper samples collected mainly from Finland on two occasions in 2010/2011, and 2013. The bisphenol A-targeted (BPA-R) and the human oestrogen receptor (hERα) bioreporters were applied to analyse both non-treated and extracted paper samples. Bisphenol A was readily bioavailable to the yeast bioreporters on the non-treated paper samples without any pre-treatment. Detected concentrations ranged from a detection limit of 9-142 μg/g to over 20 mg/g of bisphenol A equivalents in the thermal papers. Low bisphenol A like activities were detected in many samples, and were considered to be caused by residual bisphenol A or other types of bisphenols, such as bisphenol S. Most of the thermal paper samples were toxic to the yeast bioreporters. The toxicity did not, however, depend on the bisphenol A concentration of the samples. The yeast bioreporters were demonstrated to be a robust and cost-efficient method to monitor thermal paper samples for their bisphenol A content and estrogenicity. Thermal paper was considered as a potential BPA source for both human exposure and environmental emission.

Despite recent advancements in the field of microfluidic paper-based analytical devices (μPADs), a key challenge remains in developing a simple and efficient μPAD with customized imaging capabilities for antioxidant assays. In the present study, we report a facile approach for μPAD fabrication through the application of transparent nail paint leading to creation of hydrophobic barriers and well-defined channels. The resultant μPADs were then characterized through scanning electron microscopy and contact angle measurements. The resolution and functional features of the fabricated μPAD were amenable to the intended assay. The μPAD's impregnated poly(methacrylic acid) (PMAA)-coated cerium oxide (CeO 2 ) nanoparticles oxidized the 3,3',5,5'-tetramethylbenzidine (TMB) leading to the formation of a blue-colored charge-transfer complex. The addition of different antioxidant standard solutions resulted in a reduction in the blue color in a dose-dependent manner which could be observed visually. The color intensity of the PMAA-CeO 2 nanoparticle@TMB oxidation product was inversely proportional to the antioxidant concentration and was measured using customized in-house MATLAB-based image processing software. Importantly, PMAA-CeO 2 nanoparticle-based μPADs demonstrated good analytical characteristics and were able to be stored for long periods without any loss of activity. Moreover, potential interferents did not pose any threat to the colorimetric signal read-out for determination of antioxidant activity. The developed method was further applied for the assessment of antioxidant activity in a variety of tea samples and performed satisfactorily in comparison with a commonly used antioxidant detection method. Collectively, the developed μPAD-based platform holds great potential as a low-cost, convenient, portable and reliable method for pursuing various on-site antioxidant assays. Graphical Abstract.