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An innovative integrated paper-based microdevice was developed for protein separation by isoelectric focusing (IEF), allowing for robust design thanks to a 3D-printed holder integrating separation channel, reservoirs, and electrodes. To reach robustness and precision, the optimization focused on the holder geometry, the paper nature, the reservoir design, the IEF medium, and various focusing parameters. A well-established and stable pH gradient was obtained on a glass-fiber paper substrate with simple sponge reservoirs, and the integration of the electrodes in the holder led to a straightforward system. The separation medium composed of water/glycerol (85/15, v/v) allowed for reducing medium evaporation while being an efficient medium for most hydrophobic and hydrophilic proteins, compatible with mass spectrometry detection for further proteomics developments. To our knowledge, this is the first report of the use of glycerol solutions as a separation medium in a paper-based microdevice. Analytical performances regarding pH gradient generation, pI determination, separation efficiency, and resolution were estimated while varying the IEF experimental parameters. The overall process led to an efficient separation within 25 min. Then, this methodology was applied to a sample composed of saliva doped with proteins. A minimal matrix effect was evidenced, underscoring the practical viability of our platform. This low-cost, versatile and robust paper-based IEF microdevice opens the way to various applications, ranging from sample pre-treatment to integration in an overall proteomic-on-a-chip device., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The success of polymerase chain reaction (PCR) depends on the quality of deoxyribonucleic acid (DNA) templates. This study developed a cost-effective and eco-friendly DNA extraction system utilizing poly(3,4-dihydroxyphenylalanine)-modified cellulose paper (polyDOPA@paper). PolyDOPA@paper was prepared by oxidatively self-polymerizing DOPA under weak alkaline conditions and utilizing the adhesive property of polyDOPA on different materials. Compared to the uncoated cellulose paper, polyDOPA coating significantly enhances DNA adsorption owing to its abundant amino, carboxyl, and hydroxyl moieties. The DNA extraction mechanism using polyDOPA@paper was discussed. The maximum adsorption capacity of polyDOPA@paper for DNA was 20.7 μg cm -2 . Moreover, an automated extraction system was designed and fabricated using 3D printing technology. The device simplifies the operation and ensures the reproducibility and consistency of the results. More importantly, it eliminates the need for specialized training of operators. The feasibility of the polyDOPA@paper-based automated extraction system was evaluated by quantitatively detecting Escherichia coli in spiked milk samples via a real-time PCR. The detection limit was 10 2 cfu mL -1 . The results suggest that the system would have significant potential in detecting pathogens., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Competing Interests: Declaration of competing interest The author declares that he has no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Thermal papers (e.g. point of sale receipts, adhesive labels, tickets) significantly contribute to contamination of paper material cycles and the environment with substances of (eco-) toxicological concern. In particular, they contain color developers like endocrine disrupting bisphenols in typical concentrations of about 1-2 percent per weight (wt%). Bisphenol A (BPA) was used as the common color developer over the last decades, but it will be restricted for thermal paper application in the European Union to a limit of 0.02 wt% from 2020 onwards. Consequently, a variety of BPA substituents such as bisphenol S (BPS) and its derivatives gain importance in thermal paper application. In this study, a rapid, reliable and cost-effective method for identification and quantification of BPA, alternative color developers and related substances like sensitizers is presented based on HPLC separation coupled with diode array detection (DAD) and Corona charged aerosol detection (CAD). Quantification was performed with regard to the intended use of the substances in thermal papers. Besides traditional UV external calibration using reference standards, alternative quantification approaches, in particular UV chromophore concentration for BPS derivatives and CAD universal response technique for low-volatile color developers, were applied and compared in order to allow quantification without reference substances. A market analysis for intended used color developers and sensitizers was performed on thermal paper samples (n = 211) collected in Germany during 2018 and 2019. Pergafast 201 (in 41.7% of the samples) was the most common color developer with concentrations above 0.02 wt%, followed by BPA (36.0%), BPS (13.3%) and other BPS derivatives known as D8, D-90, BPS-MAE and TGSA, that are mainly present in adhesive labels. Sensitizers were determined in over 90% of the samples., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Fluoro-functionalized paper was prepared and applied in solid phase extraction (SPE) for the analysis of trace-level perfluorinated compounds (PFCs). The proposed fluoro-functionalized paper-based solid-phase extraction (Fp-SPE) exhibits significant advantages for sample preparation, such as the biodegradability of paper-based adsorbent, simple manipulation and low cost. Owing to the fluorous affinity, the Fp-SPE technique with high sensitivity and high selectivity is more suitable for the selective enrichment of fluorine-containing molecules from the background of non-fluorinated organic compounds in a real water sample. Combined with high-performance liquid chromatography coupled with electrospray ionization-tandem mass spectrometry analysis (HPLC-MS/MS), the linear range of the PFCs, including perfluorobutyric acid (PFBA), perfluorooctanic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and perfluorodecanoic acid (PFDA), was 0.20-5.0 ng/L with the limits of detection (LOD) ranging from 0.04-0.05 ng/L and the limits of quantification (LOQ) ranging from 0.15-0.20 ng/L. The method was then applied to the analysis of tap water, river water and waste water samples. The results of the actual sample analysis are consistent with that by reverse phase SPE (RP-SPE)., (Copyright © 2019. Published by Elsevier B.V.)

Mineral oil saturated and aromatic hydrocarbons (MOSH/MOAH) are food contaminants, mainly due migration from packaging materials made from recycled fibers, but other routes of entry into food have also been identified. Legal limits for MOSH and MOAH in food and food contact materials currently are not set, but are to be expected in the near future. For the analysis of MOSH and MOAH, the very well developed and highly automated on-line liquid chromatography-gas chromatography with flame ionization detection (LC-GC-FID) is commonly used. However, this approach is time-consuming, and data interpretation is a very challenging task. Therefore, a planar solid phase extraction (pSPE) method was developed for a rapid and efficient MOSH and MOAH screening in paper and cardboard. Based on high-performance thin-layer chromatography (HPTLC), pSPE offers the simultaneous clean-up and analysis of up to 20 samples in parallel, while MOSH and MOAH analytes were focused in two distinct target zones on silica gel HPTLC plates after a twofold development. Plate impregnation with primuline allowed the detection of MOSH by fluorescence, while MOAH were detected by UV light absorption. The pSPE screening approach provided limits of detection of 7.2 and 2.3 ng/zone for MOSH and MOAH, respectively, corresponding to 1.8 and 0.6 mg/kg paper. Coupling of pSPE with GC revealed the common MOSH and MOAH peak humps, while marker substances offered the identification of the mineral oil origin or information about recycled fiber materials. As compared to SPE-GC-FID analyses, the determined quantities of MOSH and MOAH in cardboard samples indicated pSPE as a rapid and suitable screening tool. The co-migration of polyolefin oligomeric saturated hydrocarbons, native n-alkanes, terpenes and possibly essential oils or sterol esters, however, can result in an overestimation of MOSH and MOAH. Hence, samples with pSPE results above a given limit are subsequently analyzed by GC (pSPE-GC) for confirmation and detailed evaluation., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The generation of concentration gradients is an essential operation for several analytical processes implemented on microfluidic paper-based analytical devices. The dynamic gradient formation is based on the transverse dispersion of chemical species across co-flowing streams. In paper channels, this transverse flux of molecules is dominated by mechanical dispersion, which is substantially different than molecular diffusion, which is the mechanism acting in conventional microchannels. Therefore, the design of gradient generators on paper requires strategies different from those used in traditional microfluidics. This work considers the foundations of transverse dispersion in porous substrates to investigate the optimal design of microfluidic paper-based concentration gradient generators (μPGGs) by computer simulations. A set of novel and versatile μPGGs were designed in the format of numerical prototypes, and virtual experiments were run to explore the ranges of operation and the overall performance of such devices. Then physical prototypes were fabricated and experimentally tested in our lab. Finally, some basic rules for the design of optimized μPGGs are proposed. Apart from improving the efficiency of mixers, diluters and μPGGs, the results of this investigation are relevant to attain highly controlled concentration fields on paper-based devices., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This paper presents a multiple headspace extraction (MHE) analysis technique to determine the water vapor transmission rate of cellulose-based papers. The water vapor passing through the sample in a closed headspace vial is determined by MHE-gas chromatography. The results show that the employed method offers good precision (the relative standard deviation < 3.49 %) and good accuracy. The method is rapid and accurate, and is promising for the determination of the water vapor transmission rate of cellulose-based papers in future studies., Competing Interests: Declaration of Competing Interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In this work, a method for measuring polychlorinated biphenyls (PCBs) in contaminated solid waste was investigated. This waste includes paper that is used in electric transformers to insulate electric components. The PCBs in paper sample were extracted by supercritical fluid extraction and analyzed by gas chromatography-electron capture detection. The recoveries with this method (84-101%) were much higher than those with conventional water extraction (0.08-14%), and were comparable to those with conventional organic solvent extraction. Limit of detection was 0.0074 mg kg(-1) and measurable up to 2.5 mg kg(-1) for 0.5 g of paper sample. Data for real insulation paper by the proposed method agreed well with those by the conventional organic solvent extraction. Extraction from wood and concrete was also investigated and good performance was obtained as well as for paper samples. The supercritical fluid extraction is simpler, faster, and greener than conventional organic solvent extraction., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The paper deals with the application of size exclusion chromatography (SEC) for the studies of paper degradation phenomena. The goal is to solve some of the technical problems connected with the calibration of multi-detector SEC system and to find the correlation between SEC and viscometric results of degree of polymerization of cellulose. The results gathered for the paper samples degraded by acidic air pollutant (NO(2)) are used as an example of SEC-MALLS application. From the correlation between intrinsic viscosities and absolute value of molecular masses obtained with SEC/MALLS (Multi Angle Laser Light Scattering) technique, Mark-Houwink coefficients for cellulose in cupri-ethylenediamine solution were determined. Thus obtained coefficients were used for the determination of viscometric degree of polymerization (molecular mass) of the aged samples. An excellent correlation was found between the chromatographic values of molecular masses obtained with SEC-UV/VIS detection and the viscometric ones utilizing the improved values of Mark-Houwink coefficients., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Lactic acidemia is commonly associated with severe diseases in pediatric patients. Quantitation of blood lactate and pyruvate is important for the diagnosis and clinical management. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method using dried blood spots (DBS) was developed and could be used for simultaneous quantification of blood lactate and pyruvate. The applicability of the developed method was tested and confirmed by the regression analysis between LC-MS/MS method and enzymatic assay. Lactate and pyruvate were extracted from DBS obtained from 580 full-term, 120 pre-term infants (gestations ranging from 24 to 36 weeks), and 65 patients with suspected lactic acidemia, with methanolic internal standard (IS) solutions of sodium L-lactate-(13)C(3) and pyruvate-(13)C(3). An API-2000 LC-MS/MS system with multiple reaction monitoring (MRM) mode was applied. The within-run and between-run precisions (CV%) were determined and the results were 1.9% and 3.9% for lactate (n=20) and 5.7% and 7.3% for pyruvate (n=20). The linearity of lactate (r=0.9986) and pyruvate (r=0.9973) based on the IS was excellent. The parameter r squared (r(2)) of linear regression between LC-MS/MS method and enzymatic assay was 0.9405 for lactate and 0.9447 for pyruvate, respectively, and the agreement between these methods was consistent and acceptable. The stability of lactate and pyruvate on DBS was also confirmed. The LC-MS/MS method we developed is a specific, sensitive, and reproducible method for measuring blood lactate and pyruvate concentrations. The use of DBS in this method makes it particularly attractive for pediatric patients.

The determination of perfluorooctanoate (PFO) in articles of commerce has become increasingly important to understand if treated products are a possible source of PFO. An LC-MS/MS method for the determination of PFO in paper and textile using a dual labeled 13C-PFOA internal standard was successfully developed and validated. Residues of PFO were determined using an isocratic, reversed-phase high-performance liquid chromatography (HPLC) method with an ammonium acetate/methanol buffer. Ions monitored were 413 (parent) and 369 (daughter) for PFO and 415 (parent) and 370 (daughter) for dual labeled 13C-PFOA internal standard. As a precaution against ubiquitous PFO that occasionally occurs in mobile phase or instrument components, two Hypercarb cartridges (4 mm) were placed before the HPLC injector. Any PFO that was captured by the cartridges was removed before each injection by flushing the system with 100% methanol prior to equilibration with the isocratic mobile phase. Overall recovery and standard deviation over a 3 day validation regimen for samples (n=54-55) fortified with PFOA at 5, 50, and 200 ng g(-1) were 114+/-4.9% for textile and 110+/-7.6% for paper. The results also established a limit of detection (LOD) of 1 ng g(-1) in textile and 2 ng g(-1) in paper based upon S/N of the 5.0 ng g(-1) fortification versus the untreated paper and textile.

A comprehensive method for the determination of four stilbene-type disulfonate and one distyrylbiphenyl-type fluorescent whitening agents (FWAs) in paper materials (napkin and paper tissue) and infant clothes was developed. FWAs were extracted from paper material and cloth samples using a hot-water extraction, and the aqueous extracts were then preconcentrated with the newly developed Oasis WAX (mixed-mode of weak anion exchange and reversed-phase sorbent) solid-phase extraction cartridge. The analytes were unequivocal determined by ion pair chromatography coupled with negative electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS-MS), applying a di-n-hexyl-ammonium acetate (DHAA) as the ion-pairing reagent in mobile phase. Limits of quantitation (LOQ) were established between 0.2 and 0.9 ng/g in 2 g of samples. Recovery of five FWAs in spiked commercial samples was between 42 and 95% and RSD (n = 3) ranging from 2 to 11%. The method was finally applied to commercial samples, showing that two stilbene-type disulfonates were predominant FWAs detected in napkin and infant cloth samples.

A solid-phase microextraction (SPME) method has been developed for the determination of pentachlorophenol (PCP) in paper and board samples. The analytical procedure involves direct extraction of PCP from paper and board samples and determination by gas chromatography with electron capture detection (GC-ECD). Two kinds of commercially available fibres; 100 microm polydimethylsiloxane (PDMS), apolar, and 85 microm polyacrylate (PA), quite polar, were evaluated to determine the extraction efficiency of pentachlorophenol. Parameters affecting the extraction process, such as temperature and time, were studied. Moreover, time of desorption and the effect of addition of salt were also investigated. The optimized procedure was applied to the analysis of pentachlorophenol (PCP) in five samples of virgin and recycled paper and board. The PCP content was determined by GC-ECD. To evaluate the effectiveness of the proposed method, it was compared with conventional extraction method with liquid-liquid extraction and derivatization. Detection limit of 0.015 microg/g for PCP in paper was achieved with a RSD of 14%.

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 (1.25-125 microg kg(-1) for OP and 9.50-950 microg kg(-1) for NP) and showed good level of precision, with a RSD lower than 10% and detection limits at 0.10 and 4.56 microg kg(-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 211 microg kg(-1).

Two low-volume solvent continuous extraction methods are applied to the extraction of paper matrices. In the methods reported here, a complex mixture of fluorescent whitening agents (FWAs) and azo dyes (AZOs) used in paper materials intended to come into contact with foodstuffs was extracted by using subcritical water extraction (SWE) and dynamic sonication-assisted solvent extraction (DSASE). Rationale for the work is based upon migration concerns of these groups of analytes from the packaging to the packaged items, thus compromising their subjective and/or objective quality. In SWE, sample was extracted in 21 min with 0.5 mL of water, whereas the DSASE method required 11 min and used 7 mL of water. DSASE was further developed by incorporating an organic modifier in order to change water polarity, thus improving extraction of moderately polar analytes. This way, modified-DSASE used a total organic volume of 0.9 mL which represents a reduction of 200 times in organic solvent consumption (200 mL versus approximately 1.0 mL) and 11 times in extraction time (2h versus 11 min) compared to the existing methods. SWE was able to extract only 9 out of 12 test analytes with average recoveries between 10 and 25% whereas modified-DSASE succeed in extracting all the target analytes with an average recovery of 89%. Complete discussion and explanation concerning these differences are provided in the text.

Hydrolytic degradation of cellulose was shown to take place during the activation procedure in distilled water during the dissolution procedure of cellulose samples from papers for size-exclusion chromatography analyses in the lithium chloride-N,N-dimethylacetamide (DMAc) solution system. The use of dilute aqueous sodium hydroxide solution in the activation procedure prevents hydrolytic degradation of cellulose during the dissolution procedure, especially in the case of samples of aged papers with low pH. The use of the freeze-drying technique provides samples of cellulose ready-made for dissolution in lithium chloride-N,N-dimethylacetamide solution.

The surface energies of various inorganic fillers including kaolin clay, titanium dioxide, and talc were examined using inverse gas chromatography (IGC). In an earlier investigation that examined calcium carbonate fillers, dehydration by heating under a dry nitrogen purge had a substantial influence on the apolar (gammaS(LW)) and polar (gammaS(AB)) components of surface energy as measured using IGC. Using the same approach, the influence of such conditioning on several inorganic fillers used in papermaking were determined using preconditioning IGC from 100 to 300 degrees C, and sequential isothermal analysis at 100 degrees C. Results from IGC analysis of titanium dioxides (rutile and anatase) were similar to precipitated calcium carbonate (PCC) for temperatures up to 200 degrees C. PCC was significantly more energetic after preconditioning at 300 degrees C, which may indicate the onset of significant thermal decomposition that titanium dioxides will not exhibit. Kaolin clay samples had relatively high apolar surface energy similar to that of the chalk samples. Calcination gave lower gammaS(LW) values that could not be accounted for by changes in the microporous structure. More likely the differences resulted from contamination of highly energetic surface sites with adsorbates other than water. Talc samples exhibited relatively high apolar surface energies that increased with preconditioning temperature. The results provided insight into the significance of water on the final adhesion properties of fillers in the sheet structure or coating layer.

Paper fiber was treated in a heterogeneous esterification reaction with four different fatty acids. This fiber was used to strengthen polyethylene (PE) composites. Modified and unmodified cellulose fiber was characterized with inverse gas chromatography. In previous work, characterization was also carried with X-ray photoelectron spectroscopy (XPS), solid-state NMR, differential scanning calorimetry and thermogravimetry. Individual fibers were found to be covered with the corresponding esters (cellulose undecylenate, undecanoate, oleate, stearate) with partial degrees of substitution of the cellulose. Comparison of XPS and NMR results showed that the surface degree of substitution of the cellulose fiber was higher than for the bulk, showing that the esterification reaction was a surface phenomenon. The aim of this work was to acquire information on the surface characteristics of the fiber and to see whether it could be correlated to PE composite mechanical strength results. The conclusions are that polar probes seem to diffuse more into the fibers than the non-polar probes, as the non-polar component of the surface tension of the modified fiber is much lowered towards that of PE, while donor-acceptor characteristics are hardly changed by esterification. The ester with the lowest non-polar component of the surface energy, the oleate, also gives the composite with the best mechanical properties.

Three analytical methods were developed for the determination of toxic compounds in recirculating waters of a paper-recycling industry. Three main groups of compounds were considered: (i) wood extractives originated from the raw material; (ii) biocides added during the production process and (iii) surfactants and other adjuvants present in the formulates of these biocides. Wood extractives considered in this study included fatty and resin acids. They were analysed by liquid-liquid extraction using methyl tert.-butyl ether, followed by gas chromatography-mass spectrometry for previous formation of the respective trimethylsilyl esters. Water samples were also extracted with Oasis HLB (copolymer [poly(divinylbenzene-co-N-vinylpyrrolidone]) solid-phase extraction cartridges of 60 mg and analysed by liquid chromatography-electrospray mass spectrometry for the determination of additives and biocides. Using these two approaches levels up to 15 mg/l for total resin and fatty acids, 5 mg/l for alkylbenzene sulfonates and 2-(thiocyanomethylthio)benzotiazol, 100 microg/l for bisphenol A and 2,2-dibromo-3-nitrilepropionamide, and 300 microg/l for nonylphenol ethoxycarboxylate were detected in process waters at different production treatment stages. These levels are of relevance since poor water quality affects the paper-recycling process, the primary water treatment process and eventually, the environmental water quality.

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 degrees 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 alpha-, beta- and gamma-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.

Abstract: The routine method of paper chromatography includes five steps: spotting, separating, drying, spraying/immersing and color development. In this paper, a pre-staining paper chromatography which only consisted of spotting, separating and color development was developed for quantitative analysis of γ-aminobutyric acid. Compared to the routine paper chromatography, the improved method is clean, rapid, inexpensive and reproducible. The effects of ninhydrin concentration, color temperature, color time and Cu2+ concentration on the color yield in the ninhydrin reaction were optimized. And then the pre-staining paper chromatography coupled with vis spectrophotometry was applied to γ-aminobutyric acid quantification. The results indicated that the limit of detection was 0.05mgmL−1 and the linear range was from 0.5 to 20.0mgmL−1. Furthermore, an excellent correlation coefficient was observed with an R 2 =0.998. The method is accurate (RSD<2.64%), and has good recoveries (102.7–103.9%). The validation of the modified technique was verified by a HPLC method. [Copyright &y& Elsevier]