Whatman no 4 filter paper

Manufactured by Cytiva

Sourced in United Kingdom, United States, Germany, Switzerland, Japan, India

Whatman No. 4 filter paper is a general-purpose filtration medium designed for a wide range of laboratory applications. It is made of high-quality cellulose and offers consistent performance with good flow rates and retention capabilities. The filter paper is available in various sizes to accommodate different filtration needs.

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Whatman filter paper (1892 citations) Filter paper (419 citations) Whatman paper (338 citations) Whatman filter (94 citations) No. 4 paper (60 citations) Whatman No. 4 (57 citations) No. 4 filter (14 citations) Whatman #4 paper (7 citations)

267 protocols using whatman no 4 filter paper

Extraction and Crystallization of Orange Pigments

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The fermentation broth was filtered through Whatman filter paper (No. 4). The resulting filter cake was resuspended in an ethanol aqueous solution (70 %, v/v, pH 2.0 adjusted with formic acid), homogenized using the FSH-II high speed homogenizer (Jiangsu Huanyu Scientific Instrument Co., Ltd, Changzhou, China) and extracted for 12 h at 4 °C in dark. Subsequently, the undissolved culture debris were removed by filtration with Whatman filter paper (No. 4), and the filtrate was collected as crude MPs extract.
The concentration of crude MPs extract was addjusted to an OD_{470 nm} of 45.0 ± 1.0 with 70 % ethanol aqueous solution (pH 2.0 adjusted with formic acid). Then, orange MPs rubropunctatin and monascorubin were crystallized from the crude MPs extract by adding 0.5 vol of acidic water (pH 2.0 adjusted with formic acid) and keeping at −20 °C for 2 h. Subsequently, the orangish red crystal particles were harvested by filtration through Whatman filter paper (No. 4), washed with acidic water (pH 2.0 adjusted with formic acid), dried by hot air drying at 40 °C and stored at −20 °C in dark.

He L., Liu C., Chen S., Zhang J., Gao M, & Li L. (2023). Precursor-directed production of water-soluble red Monascus pigments with high thermal stability via azaphilic addition reaction-based semi-synthesis. Food Chemistry: X, 20, 100940.

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Extraction and Analysis of Phenolic Acids

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The extraction was performed according to a previously described method with some modifications [19 (link)]. Ethanolic and water extracts prepared from 1.0 g of the powdered formula were added with 30 ml of 2 N NaOH and stirred for 12 min at room temperature. The mixture was centrifuged at 2800 x g for 20 min and then filtered through Whatman filter paper (No.4). The supernatant was extracted three times with 60 mL of diethyl ether with the aqueous extract containing unbound phenolics collected. The pH of the aqueous extract was adjusted to 1.5 by using 12 M HCl. The acidic aqueous solution was filtered through Whatman filter paper (No.4) and extracted three times with 60 ml of diethyl ether with the diethyl ether extract collected. The diethyl ether solution contained unbound phenolics and was dried over Na₂SO₄ (anhydrous) and filtered through Whatman filter paper (No.4). The filtrate was evaporated by rotary evaporation and then blowing N₂ gas over the sample. The phenolic extract was dissolved in 1 ml of 50% methanol solution and filtered through 0.2 μm syringe filter. The phenolic acid content was analyzed by HPLC.

Kumnerdkhonkaen P., Saenglee S., Asgar M.A., Senawong G., Khongsukwiwat K, & Senawong T. (2018). Antiproliferative activities and phenolic acid content of water and ethanolic extracts of the powdered formula of Houttuynia cordata Thunb. fermented broth and Phyllanthus emblica Linn. fruit. BMC Complementary and Alternative Medicine, 18, 130.

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Extraction and Analysis of FB and HFB1 from Maize

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FB and HFB₁ were extracted from maize according to the method of Sewram et al. [43 (link)] with minor modifications. Briefly, 100 mL of extraction solvent [methanol: acetonitrile: water (25:25:50; v/v/v)] was added to ground maize kernels (10 g) and placed on a shaker (80 rpm) for 20 min. The extracts were subsequently centrifuged (4000× g) in a refrigerated Sorvall RC-3B centrifuge (DuPont, Norwalk, CT, USA) at 4 °C for 10 min. The supernatant (20 ml) was diluted (1:1) with methanol:water (25:75), filtered (Whatman No 4 filter paper) and filtrates analyzed by direct injection into the LC-MS/MS. FAPAS (London, UK) quality control reference maize samples (Cat no T22123QC), containing the mycotoxins in known concentration ranges were included. For analyses of the residual solutions, samples were filtered (Whatman No 4 filter paper) and filtrates analysed directly by LC-MS/MS. Matrix-matched standard solutions for calibration curves were prepared utilising an extract prepared from control maize.

Alberts J., Schatzmayr G., Moll W.D., Davids I., Rheeder J., Burger H.M., Shephard G, & Gelderblom W. (2019). Detoxification of the Fumonisin Mycotoxins in Maize: An Enzymatic Approach. Toxins, 11(9), 523.

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Cryo-SXT Sample Preparation Protocol

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HZB-2 grids were glow-discharged and a thin line of liquid blocker (PAP pen) was placed next to the observation region of the grid [20] (link). Grids were placed into cell growth medium in 12-well dishes and cells were seeded and allowed to settle overnight. A confluency of about 50% ensured that cells were sparse enough that they would not overlap at high tilt during cryo-SXT data collection.
Immediately prior to freezing, grids were blotted from the rear using Whatman filter paper no.4 to remove excess medium, and 1.75 μl of an aqueous solution containing 250 nm gold particles was added to the grid tip for use as fiducial markers (BBI). Grids were then plunge frozen in a Vitrobot Mk IV (FEI Company). Briefly, grids were clamped into Vitrobot tweezers taking care that the tweezer tips remained below the PAP-pen line. The tweezers were placed into the plunge freezer, held at 70% relative humidity and 37 °C. The grid was manually blotted from behind using Whatman no.4 filter paper, and the grid was plunge frozen in liquid nitrogen-cooled liquid ethane. Grids were transferred to 2 ml cryotubes and stored in cryocanes under liquid nitrogen.

Duke E.M., Razi M., Weston A., Guttmann P., Werner S., Henzler K., Schneider G., Tooze S.A, & Collinson L.M. (2014). Imaging endosomes and autophagosomes in whole mammalian cells using correlative cryo-fluorescence and cryo-soft X-ray microscopy (cryo-CLXM). Ultramicroscopy, 143(100), 77-87.

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Antioxidant Extraction from Cacao Beans

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The cacao beans were grounded and pulverized, two 1 g of which were accurately weighed out and transferred, respectively, into the centrifugation tubes. To the two samples 10 mL of solvent ethanol (95%) and deionized water were, respectively, added, ultrasonicated for 2 h, and to each tube original fresh solvent 10 mL was added, ultrasonicated for 1 h, and filtered through 0.45 μm Whatman No. 4 filter paper with the aid of suction. The ethanolic and the aqueous extracts were, respectively, concentrated at 65 °C and 85 °C under vacuum until dry. The residues were, respectively, redissolved in the original fresh solvent to make up a final volume 10 mL, agitated well, decolorized with appropriate amount of active carbon, filtered through the 0.45 μm Whatman No. 4 filter paper with the aid of suction into the fresh centrifugation tubes, and subjected to the antioxidative assay.

Lin L.Y., Chen K.F., Changchien L.L., Chen K.C, & Peng R.Y. (2022). Volatile Variation of Theobroma cacao Malvaceae L. Beans Cultivated in Taiwan Affected by Processing via Fermentation and Roasting. Molecules, 27(10), 3058.

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Extraction and Purification of Plant Compounds

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Briefly, 0.2 g powder sample was mixed in 10 mL of 80 % methanol and stirred for 24 h at room temperature. Then, the mixture was filtered with whatman No.4 filter paper before washing two times and the supernatants were combined. The residues were re-extracted again according to the method described by Laya and Koubala (2020) . The residues were mixed in 4 mL of 2 M of NaOH and incubated for 15 min in a water bath at 80 °C. The mixture was cooled at room temperature and 2.5 mL HCl (2 M) were added before incubating in a water bath for 45 min at 80 °C. Then, 2.5 mL of 95 % MeOH were added in order to wash and stirred for 15 min before filtering through the whatman No. 4 filter paper and washed once more with 2.5 mL (95 %) methanol. The two filtrates were combined and kept at -20 °C until analysis.

Kolla M.C., Laya A., Bayang J.P, & Koubala B.B. (2021). Effect of different drying methods and storage conditions on physical, nutritional, bioactive compounds and antioxidant properties of doum (Hyphaene thebaica) fruits. Heliyon, 7(4), e06678.

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Extraction and Quantification of Phytochemicals

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Fifty grams of each grinded brown rice sample was weighed accurately and dispersed in 250ml of acetone: water (85: 15; v/v). Sample suspension was blended for 3 min at 5000 rpm using Eberbach 8017 explosion–proof blender (Haverhill–Massachusetts, USA). The blended extract was filtered through Whatman no. 4 filter paper. An aliquot of 150 ml of sample extract was taken and mixed with 3 g of cupric carbonate for 20 s. The sample mixture was then added into a conical flask already contained 170 ml sodium hydroxide (0.2 M) and 30ml ferric chloride (0.41 M), mixed well and filtered through Whatman no. 4 filter paper. An aliquot of 250 ml filtrate was taken into a separating funnel, vigorously shake in the presence of 150 ml sulfuric acid (0.03%; v/v) and 10 ml chloroform and allowed to settle–down for 2min. The lower layer of chloroform was transferred into another separating funnel already contained 1g potassium chloride and 100 ml potassium hydroxide (0.02 M) solution. After a gentle swirling of 30 s, the lower chloroform layer was separated and re–collected into a graduated cylinder after passing through a bed of anhydrous Sodium sulfate (1 g). Finally 8mlof chloroform extract was evaporated to dryness at 45°C under gentle stream of nitrogen and stored at -20 °C till the further quantification by TLC.

ASGHAR M.A., IQBAL J., AHMED A, & KHAN M.A. (2014). Occurrence of Aflatoxins Contamination in Brown Rice from Pakistan. Iranian Journal of Public Health, 43(3), 291-299.

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Extraction and Analysis of Polyphenols

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The polyphenols were extracted as described by Laya and Koubala [13 (link)]. The amount of 0.2 g of fruit powder was mixed with 10 mL of 80% methanol and stirred for 24 hours at room temperature. After shaking, the mixture was filtered with No. 4 Whatman filter paper, and the filtrate was collected. Then, the residue was washed one more before combining the filtrates for the free phenolic fraction and kept at -4°C. For the bound phenolics, the residues were hydrolyzed with 4 mL of 2 M NaOH and incubated for 15 min in a water bath at 80°C. The mixture were cooled at room temperature and added to 2.5 mL of 2 M HCl before incubating again in a water bath for 45 min at 80°C. Then, 2.5 mL of 95% methanol was added, and the mixture was stirred for 15 min. The mixture was filtered through Whatman No. 4 filter paper before washing two times with 2.5 mL of 95% methanol. The filtrates obtained were combined for the bound phenolics and kept at -4°C until analysis.

Koubala B.B., Bayang J.P., Wangso H., Kolla M.C, & Laya A. (2021). Variation of Phenolics (Bound and Free), Minerals, and Antioxidant Activity of Twenty-Eight Wild Edible Fruits of Twenty-Three Species from Far North Region of Cameroon. BioMed Research International, 2021, 4154381.

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Extraction Methods for Plant Bioactives

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The plant material was used to prepare hydroethanolic extracts, infusions, and decoctions preparations. The preparation/extraction methods were selected according to the traditional/empirical uses of the different parts of the plant [13 (link),20 (link)]. Hydroethanolic extractions were performed by stirring the plant material (~3 g) with 45 mL of ethanol/water solution (80:20, v/v) under constant magnetic stirring, at room temperature, for 1 h. The preparation was filtered through a Whatman filter paper No. 4 and the residue was re-extracted and the combined filtrates were then evaporated under pressure at 40 °C (rotary evaporator Buchi R-2010, Flawil, Switzerland) and subsequently lyophilized.
Approximately 3 g of plant material was infused with 100 mL of freshly boiled distilled water (heating plate, VELP scientific), left aside for 5 min, and subsequently filtered through Whatman filter paper No 4. The resulting extracts were frozen and lyophilized.
The plant material was decocted by adding 100 mL of distilled water (~3 g), and boiled for 5 min. Subsequently, the mixtures were left to stand for 5 min and then filtered through Whatman No. 4 paper. The obtained decoctions were frozen and lyophilized.

Rodrigues J.P., Fernandes Â., Dias M.I., Pereira C., Pires T.C., Calhelha R.C., Carvalho A.M., Ferreira I.C, & Barros L. (2021). Phenolic Compounds and Bioactive Properties of Ruscus aculeatus L. (Asparagaceae): The Pharmacological Potential of an Underexploited Subshrub. Molecules, 26(7), 1882.

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Extraction of Medicinal Plant Leaves and Stems

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Two types of extracts were prepared, namely a decoction and a hydroethanolic extract. To prepare the decoction, 3 g of lyophilized leaves and stems were extracted with 300 mL of deionized water by boiling for 5 min. After standing at room temperature for another 5 min, the mixture was filtered through Whatman filter paper no. 4 and then subjected to freeze-drying (FreeZone 4.5, Labconco, USA).
For the hydroethanolic extract, 3 g of the lyophilized leaves and stems were extracted with 90 mL of ethanol : water (80 : 20, v/v) under stirring at room temperature, for 1 hour. The mixture was filtered through Whatman paper filter no. 4 and the residue was re-extracted by repeating the procedure. After gathering the two filtrates, ethanol was eliminated under vacuum at 40 °C by using a rotary evaporator (Buchi R-2010). The obtained solution was frozen and further lyophilized.

Spréa R.M., Fernandes Â., Calhelha R.C., Pereira C., Pires T.C.S.P., Alves M.J., Canan C., Barros L., Amaral J.S, & Ferreira I.C.F.R. (2020). Chemical and bioactive characterization of the aromatic plant Levisticum officinale W.D.J. Koch: a comprehensive study. Food & function, 11(2).

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