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An RNA extraction kit (also sold as an RNA isolation kit or RNA purification kit) is a packaged set of reagents, buffers and consumables that separates RNA from the other contents of a cell or tissue lysate so it can be used in downstream assays such as RT-qPCR or sequencing. Researchers, core-facility staff and lab managers use them to replace a hand-mixed protocol with a standardised one. This page covers what a kit contains, the main formats, how sizes are specified, and how RNA quality is judged afterwards.
What an RNA extraction kit is
A kit bundles the lysis buffer, wash buffers, a separation matrix and elution solution needed to go from sample to purified RNA. The point is repeatability: the reagents are made and quality-checked as a set, so the lab does not prepare each solution itself. For the step-by-step bench method, see the RNA extraction protocol basics guide; this page is about the product class.
What is physically in a kit
Contents differ by maker, but the QIAGEN RNeasy Mini Kit is a representative silica-column example. Its listed contents are 50 RNeasy Mini spin columns, collection tubes (1.5 ml and 2 ml), and RNase-free reagents and buffers. The workflow it describes is: lyse and homogenize the sample, add ethanol, bind RNA to the silica membrane, wash, and elute in RNase-free water. Buffer RLT is the lysis buffer; Buffer RW1 and Buffer RPE are the wash buffers.
What the user still adds
- Ethanol, added to the lysate before binding (and to the RPE wash concentrate as directed in the handbook).
- Beta-mercaptoethanol, added to Buffer RLT before use (QIAGEN states 10 µl per 1 ml of RLT).
- Optionally, an RNase-Free DNase Set (with Buffer RDD) for on-column DNA digestion. Separately, “Plus” kits use Buffer RLT Plus and a gDNA Eliminator column to remove genomic DNA.
Types of RNA isolation kit
Thermo Fisher’s overview groups RNA extraction products into four formats. The right one depends on sample type, throughput, the downstream assay and the equipment available.
| Format | Purity and throughput (per Thermo Fisher) | Key difference |
|---|---|---|
| Organic extraction (phenol / guanidine isothiocyanate, monophasic) | Medium purity, low throughput | Described as suited to high-fat and cartilaginous samples |
| Silica spin column | High purity, medium to high throughput | No special equipment; recovers total RNA including miRNA |
| Magnetic beads | Highest purity, medium to high throughput | No column to clog; easily automated |
| Crude lysate (for example Cells-to-CT) | No RNA isolation step | Intended for RT-qPCR from cultured cells |
Source: Thermo Fisher Scientific, RNA extraction overview, read 2026-11-07.
Sizes and specifications that matter
Within one product line, kits are scaled by how much starting material they handle. The RNeasy family shows how this is specified.
| RNeasy kit | Cells | Tissue | Elution volume |
|---|---|---|---|
| Micro | < 5 × 105 | < 5 mg | 10-14 µl |
| Mini | 10 to 1 × 107 | 0.5-30 mg | 30-100 µl |
| Midi | 5 × 106 to 1 × 108 | 20-250 mg | 300-500 µl |
| Maxi | Up to 5 × 108 | 150 mg-1 g | 800-2400 µl |
| 96-well | 10 to 5 × 105 | – | 45-140 µl |
QIAGEN also lists binding capacities of 100 µg (Mini), 1 mg (Midi) and 6 mg (Maxi). Source: QIAGEN, RNeasy kits product page, read 2026-11-07.
How to choose
The only selection criteria the manufacturer sources above state are these: the sample type, the throughput needed, the downstream assay and the equipment on hand. Practical readings of the tables follow directly from them:
- Match the kit scale to the amount of cells or tissue you have; a Micro-scale kit is specified for under 5 mg of tissue, a Mini-scale kit for 0.5-30 mg.
- Match the format to throughput and equipment: spin columns need no special equipment; magnetic beads are described as easily automated.
- Match to the assay: if the next step is RT-qPCR from cultured cells only, a crude-lysate format skips isolation altogether.
RNA integrity and purity after extraction
A kit’s output is judged by purity and integrity. QIAGEN states an expected A260/280 ratio of 1.9-2.1 for RNA in 10 mM Tris-Cl, pH 7.5. For integrity it names a denaturing agarose gel, the Agilent 2100 Bioanalyzer and the QIAxcel system; on a gel, intact total RNA shows 28S ribosomal RNA at about twice the intensity of 18S. For a related concentration-measurement comparison, see Qubit vs NanoDrop.
Safe use and handling basics
RNA is degraded by RNases, so kits are supplied RNase-free and the eluate is taken up in RNase-free water. Lysis buffers in these kits contain chaotropic salts, and beta-mercaptoethanol is added by the user; read the kit’s safety data sheet and handbook before use and follow your institution’s chemical-hygiene rules. Blood-derived samples have their own collection tubes; see the PAXgene tube guide.
Common mistakes
- Skipping a user-supplied component. The ethanol and beta-mercaptoethanol are not in the Mini kit box, so confirm the handbook’s “reagents to be supplied by user” list before starting.
- Choosing a scale by habit. Input ranges differ by an order of magnitude between Micro and Mini kits; over- or under-loading a column is a mismatch with the specification.
- Assuming a single absorbance ratio proves integrity. QIAGEN lists purity (A260/280) and integrity (gel, Bioanalyzer, QIAxcel) as separate checks.
FAQ
Is an RNA isolation kit the same as an RNA extraction kit?
Manufacturers use “extraction”, “isolation” and “purification” for the same product class: a reagent set that yields purified RNA from a sample.
How is an RNA purification kit different from a DNA purification kit?
Both use binding, wash and elution steps; RNA kits add RNase-free handling and, where needed, a step to remove genomic DNA. See DNA purification methods.
What do I do with the RNA afterwards?
Typical downstream uses are RT-qPCR and sequencing; for one sequencing context, see single-cell RNA sequencing.
Sources
- QIAGEN, RNeasy kits product page: https://www.qiagen.com/us/products/discovery-and-translational-research/dna-rna-purification/rna-purification/total-rna/rneasy-kits (read 2026-11-07)
- Thermo Fisher Scientific, RNA extraction overview: https://www.thermofisher.com/us/en/home/life-science/dna-rna-purification-analysis/rna-extraction.html (read 2026-11-07)
