Paraformaldehyde solution preparation

Formaldehyde solutions prepared by dissolving and depolymerization of paraformaldehyde (a homopolymer of formaldehyde with empirical formula HO (CH20)nH, where n > 6) are free of admixtures of methanol and formic acid. Depolymerized paraformaldehyde is useful in enzyme histochemistry, when the preservation of the enzyme activity is of crucial importance, but it has no advantage over formalin solutions routinely used in pathology and in immunohistochemistry. 

Paraformaldehyde solution, 4%. Prepare a 50-mL solution by adding three drops of 1M NaOH to 40 mL water in a 50-mL tube. Dissolve 2 g paraformaldehyde (Sigma) by heating the tube to 56° C in a hot water bath. When the paraformaldehyde powder has dissolved completely, add 5 mL of 10x PBS and adjust pH to 7.4. Finally add water to bring the volume to 50 mL and filter the solution through a 0.2-p,m sterile filter to remove any remaining particulate matter. The solution should be used immediately, or stored at -20° C. 

To a 6-101. flask equipped with a stirrer and three dropping funnels add 785 g acetic acid, 13 g acetic anhydride and 17 g of paraformaldehyde keeping the tempetaUue at 44 1 C. Add over 15 min a solution of 101 g of hexamine in 165 g acetic acid, 320 g of acetic anhydride and 180 g of ammonium nitrate nitric acid solution prepared by dissolving 840 g of ammonium nitrate in 900 g of nitric acid (99% concentration). The hexamine ami nitric acid arc added continuously in correct proportions. The mixture is stirred for 15 min. After that are added 320 g of acetic anhydride and 271 g of nitric acid-ammonium nitrate solution in that proportion and then 160 g of acetic anhydride are added in bulk. Tire mixture is stirred for 60 min., 350 g of hot water are added and refluxed for 30 min. The content is cooled to 20 C by adding ice, the precipitate is collected and washed with three portions of cold water. 

For immunostaining formaldehyde should be freshly prepared from paraformaldehyde powder or purchased as an EM grade aqueous paraformaldehyde solution sealed in ampoules under nitrogen. 

Depolymerized paraformaldehyde is prepared in a fume-hood by adding 2 g of paraformaldehyde to 40 mL water, heating to 60°C, adding up to 10 mL O.IM NaOH until the solution clears, and adjusting the final volume to 50 mL with water. The paraformaldehyde solution must be freshly prepared each time (see Note 3). 

Paraformaldehyde solution Dissolve 4 g of paraformaldehyde m 80 mL of 0.0 IM PBS with heat, keeping the temperature below 60°C. Stir the slurry until the powder is completely dissolved, and if necessary add few drops of ION NaOH to clear the solution. Adjust the volume to 100 mL and leave the solution to cool before using. Tbe fixative should be freshly prepared before use... 

Paraformaldehyde is prepared on the day of use by adding 4g paraformaldehyde (BDH/Merk Ltd, Poole, UK)/100mL PBS, heating at 65°C until the paraformaldehyde has dissolved and cooling on ice (aliquots can frozen but only freeze-thaw once). Paraformaldehyde is toxic, handle solutions within a fume cupboard. 

Cells were washed with prewarmed PBS (Fluka Chemicals, Buchs, Switzerland) and fixed in a 4% paraformaldehyde solution (freshly prepared from a 20% stock solution, paraformaldehyde powder from Fluka Chemicals, Buchs, Switzerland). After rinsing with PBS, the cells were penneabilized using 0.5% Triton X-100 (Fluka Chemicals, Buchs, Switzerland). The substrata were incubated with Alexa Fluor 488 phalloidin (1 100 dilution in PBS Invitrogen AG, Basel Switzerland) for 25 min at room temperature and rinsed with PBS. The nucleus was stained with DAPI (1 1000 dilution in PBS Invitrogen, Basel, Switzerland) for 15 min at room temperature. The substrata were rinsed again with PBS and kept in PBS in order not to dry off. 

Paraformaldehyde [30525-89-4] is a mixture of polyoxymethylene glycols, H0(CH20) H, with n from 8 to as much as 100. It is commercially available as a powder (95%) and as flake (91%). The remainder is a mixture of water and methanol. Paraformaldehyde is an unstable polymer that easily regenerates formaldehyde in solution. Under alkaline conditions, the chains depolymerize from the ends, whereas in acid solution the chains are randomly cleaved (17). Paraformaldehyde is often used when the presence of a large amount of water should be avoided as in the preparation of alkylated amino resins for coatings. Formaldehyde may also exist in the form of the cycHc trimer trioxane [110-88-3]. This is a fairly stable compound that does not easily release formaldehyde, hence it is not used as a source of formaldehyde for making amino resins. 

Bischloromethyl ether has been prepared by saturation of formalin with dry hydrogen chloride by the reaction of paraformaldehyde with phosphorus trichloride or phosphorus oxychloride, by solution of paraformaldehyde in concentrated sulfuric acid and treatment with ammonium chloride or dry hydrogen chloride, and by suspension of paraformaldehyde in seventy or eighty percent sulfuric acid and treatment with chlorosulfonic acid. It is formed together with the asymmetrical isomer when methyl ether is chlorinated and when paraformaldehyde is treated with chlorosulfonic acid. The present method has been published. ... 

Rentsch and his coworkers prepared 1,3,6,9,12-pentaoxacyclotetradecane (/) in 47% yield by heating tetraethylene glycol and paraformaldehyde in benzene solution. 

Amino-substituted (Mannich base) polymers can be prepared by reacting amide-containing polymers with formaldehyde and a suitable amine. Sugiyama and Kamogawa (16) treated PAM in aqueous solution with excess paraformaldehyde (50°C, lh) followed by excess dimethylamine (50°C, lh). This procedure gave 68% conversion to amine. Schiller and Suen (9) used a similar procedure with monomeric formaldehyde and various amines, but with excess PAM. Muller et al. (17) prepared monomeric amines from... 

Materials. A series of a,to-bis(hydroxyphenyl)PSU oligomers with different molecular weights were synthesized and characterized as was previously reported (12). Two samples of PPO (one from Aldrich and one from General Electric Co.) were both purified by precipitation from chloroform solution into methanol. A commercial sample (Dow Chemical) of an isomeric mixture of chloromethylstyrenes (C1MS, 40% para, 60% meta) was used as received. 1-Chloromethoxy-4-chlorobu-tane (CMCB) was prepared according to a procedure developed by Olah et al. (14) and modified by Daly et al. (15), i.e., from paraformaldehyde, tetrahydrofuran and anhydrous HC1. 

Formaldehyde is a colorless gas that is soluble in water (3). Commercial aqueous preparations of formalin contain 37 0% w/w solubilized gas. They also contain formic acid (<0.05%) and 10-15% methanol, which is added to prevent the polymerization of formaldehyde into paraformaldehyde (3,11). Methanol and formic acid make these solutions an unacceptable fixative for fine structures (9). Paraformaldehyde is a polymerized form of formaldehyde that dissociates at 60°C and neutral pH. Freshly prepared solutions of paraformaldehyde are preferred for most immunochemical procedures because they provide a fixative free of extraneous additives and are usually the conservative fixatives of choice when beginning the development of a fixation protocol (3,5). 

The use of distilled formaldehyde, not formalin, which contains alcohol, is recommended. Freshly prepared paraformaldehyde can also be used, especially if large volumes of fixative are needed for perfusion fixation. To prepare an 8% solution of paraformaldehyde, in a fume hood add 2 g of paraformaldehyde (trioxymethylene) powder to 25 mL of deionized glass-distilled water. With constant stirring, heat solution to 60-70°C. Once the solution has reached the proper temperature, continue to stir for 15 min. The solution will be milky. Add one to two drops of 1 VNaOH, with stirring, until the solution clears. A slight miUdness may persist. Cool and filter through Whatman No. 1 filter paper. This solution should be used the same day that it is prepared. 

A slurry prepared from 100 g (0.67 mol) of p-tert-butylphenol, 35 g (ca. 1.1 mol) of paraformaldehyde (Note 1), and 2.0 mL (0.02 mol) of 10 N sodium hydroxide (Note 2) 1n 600 mL of xylene Is placed in a 2-L, round-bottomed, three-necked flask fitted with a Dean-Stark water collector and a mechanical stirrer. The air in the flask is replaced with nitrogen, and the stirred contents of the flask are heated to reflux by means of a heating mantle. After 30 min a homogeneous solution is obtained, and after 1 hr a white precipitate begins to form. The reaction mixture is refluxed for 4 hr, the heating mantle is removed, the mixture is allowed to cool to room temperature, and the precipitate is removed by filtration. The crude product Is washed, in succession, with 400-mL portions of toluene, ether, acetone, and water and is... 

Aminomethylene derivatives may be prepared by reacting the pyrido [1,2-a]pyrimidines (63 R = H) with aminomethanols in ethereal hydrogen chloride solution or with amines and paraformaldehyde.295... 

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