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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]

The article looks at paper versus electronic records in the context of complete data under the U.S. Food and Drug Administration's (FDA) Good Manufacturing Practice (GMP) regulations for quality control (QC) laboratories in the U.S. It considers whether complete data includes the electronic files generated from a chromatographic analysis or just the signed paper printouts. The requirements for complete data for laboratories working under the FDA GMP regulations are highlighted.

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]

This paper reports on an inkjet printing method for the fabrication of lateral flow immunochromatographic devices made from a single piece of filter paper by patterning microfluidic channels and dispensing immunosensing inks, requiring only a single printing apparatus. This “paperfluidic” immunosensing device allows for a less time-consuming and more low-cost fabrication compared with the conventional immunochromatographic strips requiring multiple pads, plastic or nylon backing, and a plastic case. A sandwich immunoreaction was performed on the patterned immunosensing paper device, and the sensitivity of the device was optimized with an IgG model analyte. Inkjet-printed antibodies on the test line and the control line were immobilized by physical adsorption, resulting in a very simple fabrication method applicable for pure cellulose surfaces. The color intensity in the test line and the control line was determined both by naked eye and by means of a color scanner in combination with a simple computer program. With the resulting paperfluidic immunosensing device, human IgG concentrations at least down to 10 μg/l could be detected within 20 min. Additionally, in order to demonstrate the feasibility of a total multianalyte sensing system, a combined immuno-chemical sensing device was also fabricated by patterning an additional microfluidic channel for a chemical assay onto the same paper substrate. This low-cost multianalyte paperfluidic sensing device thus demonstrates the feasibility of simple, portable, and disposable tools for pathogen detection in the field of medical, environmental, and food analyses, possibly resulting in useful devices in remote settings and less-industrialized countries. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

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]

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]