To order oligos well you need to make four decisions before the sequence goes into the form: how much you need, how pure it must be, which modifications the application requires, and how it should arrive. Each decision is a price line and each default on a vendor's form is set for the vendor's convenience rather than yours. This page walks through the order form choice by choice and points at the comparison of published prices so the vendor is chosen on figures rather than habit.
Scale: order what you will use
Synthesis scale sets the maximum yield. For a PCR primer used a handful of times, the smallest scale is the right one and the cheapest. For a probe or a primer used across a whole project, the next scale up costs a little more and saves reordering. For long oligos, remember that the delivered yield at a small scale can be far below the nominal figure, so choose scale from the expected yield the vendor states for your length, not from the label.
Purification: match the grade to the job
Desalted oligos serve routine PCR and sequencing primers. HPLC purified oligos are for probes, modified oligos, long oligos and anything where truncated failure sequences would interfere. PAGE purification suits long unmodified oligos where length purity matters most. Purification adds cost and time and reduces yield, so it is a choice to make deliberately rather than a box to tick by default.
Modifications, format and turnaround
Fluorophores, quenchers, biotin, phosphate groups and backbone changes each add a line item and often force HPLC purification. Delivery in plates at normalised concentration saves handling for large orders; dry tubes are the default and the cheapest. Turnaround is usually quoted in business days from order confirmation and lengthens with modifications and purification, so a modified probe ordered on a Friday for a Monday experiment is a plan that fails. Every vendor publishes its lead time by product, and the comparison links to it.
Choosing the vendor
The oligo pages on this site record what each synthesis vendor publishes for standard oligos by scale and purification, verified on the vendor's page and dated. Use them to compare the per-base price at the scale and grade you actually order, then check the lead time and the shipping charge, which can outweigh a small per-base difference on a small order. For recurring orders, most vendors offer account pricing that the published figure only hints at.
How to order pcr primers, and how to order primers for pcr in bulk
For a routine amplification the specification is short and the defaults are right: the lowest synthesis scale, desalted purification, and a design checked for self complementarity and for a melting temperature within a degree or two of its partner. What is worth adding is a note of the intended annealing temperature in the order record, because that is the number the next person needs and it is not recoverable from the sequence alone. For a plate of primers the useful change is format rather than chemistry: ordering a normalised plate at a stated concentration removes an afternoon of dilutions and a source of error, and it costs little more than the tubes. Where the same pair will be reordered for years, record the vendor, the scale and the purification alongside the sequence, since a pair remade at a different scale can behave differently in a sensitive assay.
A primer order, and the four lines that matter
Every primer order comes down to four lines: the sequence written five prime to three prime, the synthesis scale, which sets the amount rather than the price per base, the purification, desalted for routine amplification and cartridge or HPLC for anything sensitive or modified, and the modifications with their positions. State the application too, since it tells the supplier which purification the sequence really needs. Keep the order record with the design file, because a primer that stops working is diagnosed from its sequence and lot.
oligo molecular weight and what it is used for
An oligo molecular weight is computed from the sequence and the chemistry rather than measured, and it is needed to convert between mass and moles, which is where most concentration errors begin. A modification changes it, so a dye or a phosphorothioate backbone makes the supplier's figure rather than a calculator's the one to use.
order cdna, and what is actually being ordered
To order cdna may mean a synthesised clone of a coding sequence, a library made from a tissue, or a primer set for reverse transcription, and the three are different products. For a clone, the vector, the codon usage and whether the tag is in frame are what the order has to state rather than the gene name alone.
Questions people ask about order oligos
How do I decide what scale to order oligos at?
From the amount you will consume. Small scale for primers used a few times, larger scale for reagents used across a project, and bulk tiers for anything going into a product.
Do I need to purify oligos for PCR?
Usually not. Desalted primers are fine for routine PCR; purify when the oligo is long, modified or used as a probe.
How long does it take to receive oligos?
Standard desalted oligos usually ship within days; modifications and HPLC purification add time. Each vendor states lead time per product.
Can I order oligos in plates?
Yes; most vendors offer plate formats, normalised to a stated concentration, which suits screens and large primer sets.