{"id":5348,"date":"2023-12-04T16:35:36","date_gmt":"2023-12-04T15:35:36","guid":{"rendered":"https:\/\/www.em-grade.com\/product\/paraformaldehyde-pfa-in-aqueous-solution\/"},"modified":"2026-04-24T00:33:57","modified_gmt":"2026-04-23T22:33:57","slug":"paraformaldehyde-pfa-in-aqueous-solution","status":"publish","type":"product","link":"https:\/\/www.em-grade.com\/es\/producto\/paraformaldehyde-pfa-in-aqueous-solution\/","title":{"rendered":"Paraformaldehyde (PFA) in Aqueous Solution"},"content":{"rendered":"<h2>\u2697\ufe0f Why choose EM-Grade Paraformaldehyde aqueous solution?<\/h2>\n<ul>\n<li><strong>Ready-to-use, always fresh<\/strong> \u2014 no overnight prep, no quality drift between experiments. Your results are reproducible from day one, your technicians save time.<\/li>\n<li><strong>Methanol-free formulation<\/strong> \u2014 unlike most PFA solutions on the market, our PFA contains no methanol stabiliser. Critical for immunocytochemistry (no epitope denaturation), membrane lipid preservation, and cryo-EM vitrification protocols.<\/li>\n<li><strong>12 months shelf life \u2014 even opened<\/strong> \u2014 our argon-sealed airless bottle prevents oxidation and polymerisation. An opened bottle lasts as long as a sealed one: 12 months of reliable fixation. <a href=\"https:\/\/www.em-grade.com\/es\/sin-categorizar\/cual-es-la-ventaja-de-la-botella-airless-en-nuestros-productos\/\">Learn more about our airless bottles.<\/a><\/li>\n<li><strong>Six concentrations \u00d7 six volumes<\/strong> \u2014 from 10 mL ampoules for single-use fixation to 1 L bottles for routine histology. You never over-order.<\/li>\n<li><strong>Custom pH on demand<\/strong> \u2014 standard pH is ~4.3 (native acidic pH of formaldehyde in solution). For neutral-pH fixation, our chemists adapt the pH to your protocol (PBS 7.4 \u2014 Sorensen 7.2 \u2014 cacodylate 7.4 \u2014 HEPES \u2014 other). <a href=\"mailto:contact@em-grade.com\">Contact us.<\/a><\/li>\n<li><strong>Made in France, eco-responsible<\/strong> \u2014 formulated and bottled in our lab near Toulouse, traceable batches, recyclable packaging, shorter supply chain than US\/UK alternatives.<\/li>\n<li><strong>Responsive support<\/strong> \u2014 direct line to our chemists Arthur Ferullo and Nacer Benmeradi for any protocol question. Response within 24h.<\/li>\n<\/ul>\n<h2>\ud83d\udccb Technical specifications<\/h2>\n<table>\n<thead>\n<tr>\n<th>Specification<\/th>\n<th>Value<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><strong>Product name<\/strong><\/td>\n<td>Paraformaldehyde (PFA) in Aqueous Solution<\/td>\n<\/tr>\n<tr>\n<td><strong>CAS number<\/strong><\/td>\n<td>50-00-0 (formaldehyde in solution)<\/td>\n<\/tr>\n<tr>\n<td><strong>Concentrations available<\/strong><\/td>\n<td>4%, 8%, 10%, 16%, 20%, 32%<\/td>\n<\/tr>\n<tr>\n<td><strong>Volumes available<\/strong><\/td>\n<td>10 mL \u00d7 10 (ampoules), 30 mL, 100 mL, 250 mL, 500 mL, 1000 mL<\/td>\n<\/tr>\n<tr>\n<td><strong>Packaging<\/strong><\/td>\n<td>Argon-sealed airless bottle (sealed ampoule for 10 mL format)<\/td>\n<\/tr>\n<tr>\n<td><strong>pH<\/strong><\/td>\n<td>~4.3 (acidic native pH) \u2014 custom pH available on request<\/td>\n<\/tr>\n<tr>\n<td><strong>Solvent<\/strong><\/td>\n<td>Distilled water (methanol-free formulation)<\/td>\n<\/tr>\n<tr>\n<td><strong>Methanol content<\/strong><\/td>\n<td>None \u2014 pure PFA, no stabiliser added<\/td>\n<\/tr>\n<tr>\n<td><strong>Storage<\/strong><\/td>\n<td>Room temperature, protected from light<\/td>\n<\/tr>\n<tr>\n<td><strong>Shelf life (sealed)<\/strong><\/td>\n<td>12 months from manufacturing date<\/td>\n<\/tr>\n<tr>\n<td><strong>Shelf life (opened, airless)<\/strong><\/td>\n<td>12 months \u2014 same as sealed, thanks to argon airless system<\/td>\n<\/tr>\n<tr>\n<td><strong>Safety<\/strong><\/td>\n<td>H351 \u2014 suspected of causing cancer. See full SDS below.<\/td>\n<\/tr>\n<tr>\n<td><strong>SDS \/ MSDS<\/strong><\/td>\n<td>See \u00abSEE TECHNICAL FILE\u00bb button above<\/td>\n<\/tr>\n<tr>\n<td><strong>Made in<\/strong><\/td>\n<td>France<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em><strong>Note on pH<\/strong> \u2014 our PFA aqueous solution has an acidic native pH (~4.3), as is standard for unbuffered formaldehyde solutions in water (consistent with references from Agar Scientific and Carl Roth). For fixation protocols requiring a neutral pH (most TEM\/SEM applications), we strongly recommend either (a) ordering the <strong>custom pH version<\/strong> adapted to your buffer of choice, or (b) diluting our standard solution in your working buffer on the bench.<\/em><\/p>\n<h2>\ud83d\udd2c PFA applications in electron microscopy<\/h2>\n<h3>TEM &amp; SEM fixation<\/h3>\n<p>PFA aqueous solution is the first fixative in most double-fixation protocols for transmission and scanning electron microscopy. A <strong>4% PFA solution<\/strong> is the standard for cell monolayer fixation, while <strong>2% PFA + 2.5% glutaraldehyde<\/strong> (Karnovsky-type mix) is the reference for tissue ultrastructure. <a href=\"https:\/\/www.em-grade.com\/es\/fijadores\/fijador-karnovsky\/\">Read our full guide to the Karnovsky fixative.<\/a><\/p>\n<h3>Immunochemistry &amp; cryo-EM<\/h3>\n<p>For immunogold and immunofluorescence applications where antigen preservation is critical, PFA alone (2\u20134%) preserves epitope recognition better than glutaraldehyde-based mixtures. For cryo-EM vitrification workflows, the 16% or 32% concentrations can be diluted in your buffer of choice on the bench.<\/p>\n<h3>Cell biology &amp; histology<\/h3>\n<p>Higher concentrations (8%, 10%) are used for long-term tissue storage before paraffin embedding. The 32% stock is a convenient concentrate for laboratories preparing their own working dilutions.<\/p>\n<h2>\ud83e\uddea How to use \u2014 Protocol &#038; best practices<\/h2>\n<h3>Recommended dilution<\/h3>\n<p>The 32% concentrate is intended to be diluted to your working concentration (typically 4%) in your buffer of choice. For ready-to-fix workflows, order the final concentration directly (4%, 8%).<\/p>\n<h3>Buffer compatibility &amp; pH<\/h3>\n<p>PFA is compatible with PBS, Sorensen phosphate buffer, PHEM, cacodylate, and HEPES. Buffer choice influences cell morphology and antigen preservation \u2014 <a href=\"https:\/\/www.em-grade.com\/buffers\/how-to-choose-the-ph-of-your-buffer-in-fixative-solution-for-electron-microscopy\/\">read our guide on choosing the right pH for your fixative buffer<\/a> and <a href=\"https:\/\/www.em-grade.com\/general\/what-is-the-optimal-osmolality-of-a-fixative-solution\/\">how osmolality affects fixative quality<\/a>.<\/p>\n<h3>Fixation protocol (generic)<\/h3>\n<ol>\n<li>Pre-warm the PFA solution to room temperature.<\/li>\n<li>Remove culture medium, rinse with PBS (37 \u00b0C).<\/li>\n<li>Apply 4% PFA for 15 minutes at room temperature (cells) or 2\u20134 hours (thick tissues).<\/li>\n<li>Rinse 3\u00d7 with PBS.<\/li>\n<li>Proceed to post-fixation (glutaraldehyde or osmium tetroxide) or immunostaining.<\/li>\n<\/ol>\n<h2>\u26a0\ufe0f Safety &#038; handling<\/h2>\n<p>Paraformaldehyde is classified <strong>H351 \u2014 suspected of causing cancer<\/strong> (GHS Category 2). Handle under a chemical fume hood with nitrile gloves, lab coat, and safety glasses. Avoid inhalation of vapours and skin contact. Dispose of used solutions as halogen-free organic chemical waste according to your institution&#8217;s policy.<\/p>\n<p>Download the full Safety Data Sheet via the <strong>\u00abSEE TECHNICAL FILE\u00bb<\/strong> button at the top of this page.<\/p>\n<h2>\u2753 Frequently asked questions<\/h2>\n[toggles style=\u00bbminimal\u00bb accordion=\u00bbtrue\u00bb accordion_starting_functionality=\u00bbclosed\u00bb]\n[toggle color=\u00bbDefault\u00bb heading_tag=\u00bbdefault\u00bb heading_tag_functionality=\u00bbdefault\u00bb title=\u00bbWhat is the difference between paraformaldehyde and formaldehyde?\u00bb]\n[vc_column_text]Paraformaldehyde is the polymerised, solid form of formaldehyde. When dissolved in water with gentle heating, it depolymerises into formaldehyde monomer \u2014 the actual fixative agent. Our PFA aqueous solution is already depolymerised and ready to use, so you skip the heating step entirely.[\/vc_column_text]\n[\/toggle]\n[toggle color=\u00bbDefault\u00bb heading_tag=\u00bbdefault\u00bb heading_tag_functionality=\u00bbdefault\u00bb title=\u00bbWhich buffer should I use with PFA?\u00bb]\n[vc_column_text]The most common buffers are PBS (7.4), Sorensen phosphate, PHEM, and cacodylate. PBS is the default for immunofluorescence; cacodylate preserves ultrastructure better for TEM. <a href=\"https:\/\/www.em-grade.com\/buffers\/how-to-choose-the-ph-of-your-buffer-in-fixative-solution-for-electron-microscopy\/\">See our buffer comparison guide.<\/a>[\/vc_column_text]\n[\/toggle]\n[toggle color=\u00bbDefault\u00bb heading_tag=\u00bbdefault\u00bb heading_tag_functionality=\u00bbdefault\u00bb title=\u00bbCan I dilute the 32% stock to 4%?\u00bb]\n[vc_column_text]Yes. Dilute 1 volume of 32% PFA with 7 volumes of your buffer (e.g., 1 mL PFA 32% + 7 mL PBS = 8 mL PFA 4%). The diluted solution is stable for up to 24 hours at 4\u00b0C, but we recommend preparing it just before use.[\/vc_column_text]\n[\/toggle]\n[toggle color=\u00bbDefault\u00bb heading_tag=\u00bbdefault\u00bb heading_tag_functionality=\u00bbdefault\u00bb title=\u00bbIs PFA compatible with immunogold labelling?\u00bb]\n[vc_column_text]Yes \u2014 PFA alone (2\u20134%) preserves most epitopes. If you need ultrastructural preservation, a low-percentage glutaraldehyde (0.1\u20130.5%) can be added, but it will reduce antigenicity for some markers.[\/vc_column_text]\n[\/toggle]\n[toggle color=\u00bbDefault\u00bb heading_tag=\u00bbdefault\u00bb heading_tag_functionality=\u00bbdefault\u00bb title=\u00bbHow long does an opened PFA bottle last?\u00bb]\n[vc_column_text]Thanks to the argon-sealed airless bottle, an opened bottle remains usable for <strong>up to 12 months<\/strong> at room temperature, protected from light \u2014 the same shelf life as a sealed bottle. The dispenser prevents air ingress, which is the primary cause of PFA oxidation and polymer drift. This is a key differentiator versus conventional bottles which degrade within weeks of opening.[\/vc_column_text]\n[\/toggle]\n[toggle color=\u00bbDefault\u00bb heading_tag=\u00bbdefault\u00bb heading_tag_functionality=\u00bbdefault\u00bb title=\u00bbWhat is the pH of your PFA solution? Why is it acidic?\u00bb]\n[vc_column_text]Our standard PFA aqueous solution has a native pH of <strong>~4.3<\/strong>, which is the natural pH of unbuffered formaldehyde in water (formaldehyde slowly oxidises to formic acid, lowering the pH). This is consistent with products from Agar Scientific and Carl Roth. For fixation protocols requiring a neutral pH, you can either (a) order our <strong>custom pH version<\/strong> adapted to your buffer of choice, or (b) dilute in your working buffer on the bench.[\/vc_column_text]\n[\/toggle]\n[toggle color=\u00bbDefault\u00bb heading_tag=\u00bbdefault\u00bb heading_tag_functionality=\u00bbdefault\u00bb title=\u00bbCan you provide PFA with a custom pH?\u00bb]\n[vc_column_text]Yes. Our chemistry team adapts the pH to your protocol (PBS 7.4, Sorensen 7.2, cacodylate, HEPES, or any target between 6.0 and 8.0). Specify your target pH when you order or <a href=\"mailto:contact@em-grade.com\">contact Samia<\/a> for bulk and recurrent orders.[\/vc_column_text]\n[\/toggle]\n[toggle color=\u00bbDefault\u00bb heading_tag=\u00bbdefault\u00bb heading_tag_functionality=\u00bbdefault\u00bb title=\u00bbIs your PFA solution methanol-free?\u00bb]\n[vc_column_text]<strong>Yes \u2014 our PFA solution is 100% methanol-free.<\/strong> Most commercial PFA solutions contain methanol as a stabiliser (typically 10\u201315%), which can denature sensitive epitopes, extract membrane lipids, and interfere with cryo-EM vitrification. Our formulation is pure paraformaldehyde dissolved in distilled water under argon, with no additives. This makes it the preferred choice for immunocytochemistry, lipid-sensitive applications, and cryo-EM workflows.[\/vc_column_text]\n[\/toggle]\n[\/toggles]\n","protected":false},"excerpt":{"rendered":"<p>Ready-to-use PFA solution for electron microscopy, immunochemistry, and cell biology. Open, pipette, fix.<\/p>\n<p>\u26a1 <strong>Ready-to-use &#038; methanol-free<\/strong><\/p>\n<p>\ud83d\udee1\ufe0f <strong>Argon-sealed airless<\/strong> \u2014 12 months shelf life, even opened<\/p>\n<p>\ud83c\udf9a\ufe0f <strong>Custom pH<\/strong> on demand (native pH ~4.3)<\/p>\n<p>\ud83c\uddeb\ud83c\uddf7 <strong>Made in France<\/strong> \u2014 4% to 32%, 10 mL to 1 L<\/p>\n","protected":false},"featured_media":5349,"template":"","meta":{"_acf_changed":false,"_seopress_titles_title":"Paraformaldehyde (PFA) Solution \u2014 Ready-to-use | EM Grade","_seopress_titles_desc":"Ready-to-use PFA aqueous solution for electron microscopy. 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