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• Recent advances in paper/thread-based zone and capillary electrophoresis techniques. • Various sample pretreatment methods using electrophoresis on wicking substrates. • Review of unmodified and modified microfluidic paper/threat -based chromatography. • Application of paper/threat -based chromatography in blood separation. Paper and thread are widely used as the substrates for fabricating low-cost, disposable, and portable microfluidic analytical devices used in clinical, environmental, and food safety monitoring. Concerning separation methods including chromatography and electrophoresis, these substrates provide unique platforms for developing portable devices. This review focuses on summarizing recent research on the miniaturization of the separation techniques using paper and thread. Preconcentration, purification, desalination, and separation of various analytes are achievable using electrophoresis and chromatography methods integrated with modified or unmodified paper/thread wicking channels. A variety of 2D and 3D designs of paper/thread platforms for zone electrophoresis, capillary electrophoresis, and modified/unmodified chromatography are discussed with emphasis on their limitation and improvements. The current progress in the signal amplification strategies such as isoelectric focusing, isotachophoresis, ion concentration polarization, isoelectric focusing, and stacking methods in paper-based devices are reviewed. Different strategies for chromatographic separations based on paper/thread will be explained. The separation of target species from complex samples and their determination by integration with other analytical methods like spectroscopy and electrochemistry are well-listed. Furthermore, the innovations for plasma and cell separation from blood as an important human biofluid are presented, and the related paper/thread modification methods are explored. [ABSTRACT FROM AUTHOR]

Widening the methodology of chromophore analysis in pulp and paper science, a sensitive gas-chromatographic approach with electron-capture detection is presented and applied to model samples and real-world historic paper material. Trifluoroacetic anhydride was used for derivatization of the chromophore target compounds. The derivative formation was confirmed by NMR and accurate mass analysis. The method successfully detects and quantifies hydroxyquinones which are key chromophores in cellulosic matrices. The analytical figures of merit appeared to be in an acceptable range with an LOD down to approx. 60 ng/g for each key chromophore, which allows for their successful detection in historic sample material. [ABSTRACT FROM AUTHOR]

This article details the study of electrochemical behavior of new carbon electrodes based on pyrolysis of different paper sources to be used in biosensor applications. The resistivity of the pyrolyzed papers was initially used as screening parameters to select the best three paper samples (imaging card paper, multipurpose printing paper, and 3MM chromatography paper) and assemble working electrodes that were further characterized by a combination of microscopy, electrochemistry, and spectroscopy. Although slight differences in performance were observed, all carbon substrates fabricated from pyrolysis of paper allowed the development of competitive biosensors for uric acid. The presented results demonstrate the potential of these electrodes for sensing applications and highlight the potential advantages of 3MM chromatography paper as a substrate to fabricate electrodes by pyrolysis. [ABSTRACT FROM AUTHOR]

In this study we investigated the underlying mechanisms of coffee stain formation on paper – a porous substrate. When a drop of aqueous liquid containing dispersed materials dries on paper, the faster water evaporation rate at the edge of the drop drives the redistribution of the dispersed materials to the edge of the drop-covered area on paper. Deegan׳s discovery has been accepted as the “coffee ring” phenomenon, which has wide implications. However, stains left by dried aqueous liquids on paper are not always ring-shaped. This is because, besides Deegan׳s coffee ring effect, the transport of dispersed materials in porous media is affected by chromatographic and filtration effects, which are highly dependent upon the properties of the substrates. In this work we clarify the influences of different mechanisms to the dispersed materials redistribution in paper. [ABSTRACT FROM AUTHOR]

Abstract: Iron gall inks were the most often used inks from the Middle Ages until the 20th century; examples include the drawings by Leonardo and scores by Bach. These masterpieces are threatened by the corrosive properties of the ink. In order to increase the longevity of the materials, stabilisation treatments have been developed during the last two decades. Their effectiveness has often been determined by comparing rates of degradation during accelerated tests. However, such evaluation using historical materials is limited by the amount of material required by various analytical methodologies. The paper describes the use of size exclusion chromatography (SEC) of cellulose containing iron gall ink, derivatised using phenyl isocyanate. A linear correlation is observed between the weight average degree of polymerisation obtained with SEC and the one obtained using viscometry, with a slope of 1.4. The method was used to evaluate the extent of stabilisation of historic documents containing iron gall inks during accelerated degradation. Despite considerable uncertainty, also caused by the heterogeneity of historic materials, it is demonstrated that efficient stabilisation by factors of 10 and 20 times is achievable using a calcium phytate treatment. [Copyright &y& Elsevier]

Abstract: A quick and direct method for identifying organic components of papers in library and archival collections with minimal destructive sampling is needed for preservation, forensic, and general purposes. Direct analysis in real time mass spectrometry (DART-MS) is used for characterizing 16 reference papers of known manufacture in terms of their pulp composition and pitch contaminants. Unique mass spectra are obtained from bleached kraft, chemithermomechanical, and stone groundwood pulp papers in real time without extractions, derivatizations, chromatographic separations, and other time- and chemical-consuming sample preparations. Phytosteroids are volatilized from bleached hardwood kraft but not from bleached softwood kraft papers, which differentiates the two of them. The kraft papers are in turn differentiated from chemithermomechanical pulp papers by lignin-derived thermolyis products: syringyl products arise from hardwood, but guaiacyl and coumaryl products arise from softwood, chemithermomechanical pulp papers. Stone groundwood papers contain a number of extractives that are volatilized, which serve to differentiate them from all the other papers. Papers that contain rosin vs. alkyl ketene dimer (AKD) sizings are immediately differentiated. The DART-MS methodology is fast and simple, and the spectra are repeatable. Microsamples as small as ∼10μg tweezed from the paper surface may be analyzed. These benchmark spectra are the prelude to further applications of DART-MS in paper research and the beginning of the development of a searchable library of DART-MS spectra of printing and writing papers by the Library of Congress. [Copyright &y& Elsevier]

Abstract: Environment-responsive membranes were prepared by coating filter paper with poly (N-vinylcaprolactam) hydrogel. These membranes could be made to switch between hydrophobic and hydrophilic states in a reversible manner by the addition or removal of lyotropic salts. The effects of polymer loading and salt concentration on hydraulic permeability and human immunoglobulin G (hIgG) binding property of these membranes were studied. A candidate membrane possessing high hydraulic permeability and hIgG binding property was selected for carrying out protein purification experiments. This membrane demonstrated selective antibody binding, and could be used for hIgG purification from simulated cell culture supernatant. [Copyright &y& Elsevier]

Abstract: A novel and simple method for the determination of active endocrine disrupter compounds (octylphenol OP, and nonylphenol NP) in paper using microwave-assisted extraction (MAE) and headspace solid-phase microextraction, coupled with gas chromatography–mass spectrometry has been developed. Parameters affecting the efficiency in the MAE process such as exposure time and extraction solvent were studied in order to determine operating conditions. The optimised method was linear over the range studied (1.25–125μgkg-1 for OP and 9.50–950μgkg-1 for NP) and showed good level of precision, with a RSD lower than 10% and detection limits at 0.10 and 4.56μgkg-1 for OP and NP, respectively. The results obtained from six different types of paper revealed the presence of the target compounds in all samples analysed, at levels ranging between 3 and 211μgkg-1. [Copyright &y& Elsevier]

This study presents the research on the chemical analysis and genotoxicity of 28 virgin/recycled paper products in food-contact use. In the chemical analysis, paper products were extracted by reflux with ethanol, and analyzed by gas chromatography/mass spectrometry. 4,4′-bis(dimethylamino)benzophenone (Michler''s ketone: MK), 4,4′-bis(diethylamino)benzophenone (DEAB), 4-(dimethylamino)benzophenone (DMAB) and bisphenol A (BPA) were found characteristically in recycled products. Seventy-five percent of the recycled paper products contained MK (1.7–12 μg/g), 67% contained DEAB (0.64–10 μ g/g), 33% contained DMAB (0.68–0.9 μg/g) and 67% contained BPA (0.19–26 μg/g). Although, BPA was also detected in virgin paper products, the detection levels in the recycled products were ten or more times higher than those in the virgin products. The genotoxicity of paper and paperboard extracts and compounds found in them were investigated by Rec-assay and comet assay. Of the 28 products tested by Rec-assay using Bacillus subtilis, 13 possessed DNA-damaging activity. More recycled than virgin products (75% against 25%) exhibited such activity, which, of the compounds, was observed in BPA, 1,2-benzisothiazoline-3-one (BIT), 2-(thiocyanomethylthio)benzothiazole, 2,4,5,6-tetrachloro-isophthalonitrile, 2,4,6-trichlorophenol (TCP), and pentachlorophenol. The critical toxicant in one virgin paper product was concluded to be BIT. Eight samples with DNA-damaging activity were also tested by comet assay using HL-60 cells; six induced comet cells significantly (five times or higher than the control) without a decrease of viable cells. TCP, BZ, DEAB, and BIT also caused a slight increase in comet cells. In conclusion, we showed that most recycled paper products contain chemicals such as MK, DEAB, DMAB, and BPA, and possess genotoxicity. However, the levels of the chemicals in the recycled products could not explain their genotoxic effects. [Copyright &y& Elsevier]

We studied the aging behaviour of gelatin used to size paper. Thus far, research on the aging of paper has largely ignored the sizing agent. Degradation of the protein was characterised and the impact of paper components, such as cellulose, and aluminium potassium sulphate was evaluated. Whatman No. 1 filter papers sized with two types of gelatins (A and B) were prepared as model samples. Commercially sized modern papers (Arches) were also studied in order to compare laboratory samples with real artist papers. Both types of papers were artificially aged (80 °C, 50% relative humidity for 35 and 94 days). Historic papers were included in the study in order to compare artificially aged with naturally aged gelatin. The aqueous extracts from the papers were characterised by aqueous size-exclusion chromatography (SEC) using four PL-Aquagel-OH columns and UV photodiode array detection at 220, 254 and 280 nm. Results showed that gelatin undergoes hydrolysis upon aging, type A gelatin showing a faster degradation rate than type B. The result was an increase in the lower-molar-mass fractions, under 50 000 g mol−1, and especially in a characteristic fraction with a peak molecular mass (Mp) of 14 000 g mol−1. A significant decrease in the extraction yields of α-, β- and γ-chains occurred after aging. This was attributed to crosslinking, leading to the formation of less-soluble polypeptides with very high molar mass (>800 000 g mol−1). Less than 10% alum had no impact on the degradation rate; higher alum contents accelerated hydrolysis reactions. [Copyright &y& Elsevier]