Why the BCA Assay Still Rules Protein Quantification

Forty years after its introduction, the bicinchoninic acid (BCA) protein assay remains a popular technique in life science labs, and a look at recent product reviews on Biocompare bears that out: researchers working in fields as different as neuroscience, immunology, and exosome biology are all still reaching for it to answer the same basic question—how much protein is actually in this sample.

Developed in 1985 as a simpler alternative to the Lowry method, the BCA assay works by having protein reduce Cu²⁺ to Cu¹⁺ in an alkaline environment, after which bicinchoninic acid chelates the reduced copper to form a purple complex that absorbs light at 562 nm—the more protein present, the deeper the color. Compared to the Bradford dye-binding assay, its main rival for total protein quantification, BCA has one major practical advantage: it tolerates ionic and nonionic detergents like SDS and Triton X-100, which show up constantly in cell lysis buffers and would otherwise interfere with a Bradford read. That compatibility, combined with a wide linear range and a readout that only requires a basic spectrophotometer or plate reader, is a big part of why the assay has stuck around across so many different kinds of labs.

BCA isn’t unique in that respect. As explained in a recent Biocompare article, it, along with Lowry and Bradford assays, are colorimetric methods that remain popular for being simple, affordable, and broadly compatible, even though all three depend on a standard curve that can introduce its own accuracy limitations.

What researchers are saying

Biocompare reviews bear out just how routine this assay has become. A postdoctoral researcher at Stanford studying gene signaling pathways said the standard Pierce BCA Protein Assay Kit is “reliable, straightforward, and compatible with many common protein extraction buffers,” and uses it to routinely quantify protein before downstream experiments.

A research scientist at SUNY Buffalo working with primary mouse astrocytes and other brain-derived cell samples relies on the same kit to determine protein concentrations “before Western blotting to ensure consistent protein loading across experimental groups,” and also uses BCA-based measurements to normalize biochemical assay results.

A graduate student at Scripps Research pointed to the assay’s versatility across sample types, noting it “works reliably for a wide range of proteins expressed in both mammalian and bacterial systems” and is compatible with detergent-containing buffers while still providing rapid quantification.

Not every lab needs the standard version, though. A scientist at Houston Methodist working with exosome-derived protein—where total yield is often limited—turned to the Micro BCA variant instead, reporting “reliable and sensitive protein quantification for low-yield samples … with consistent and reproducible results.” The tradeoff: because the low-range protocol calls for more standards and replicates, “the assay can consume a relatively large amount of reagents and laboratory supplies,” and kits can get used up faster than expected.

Cost is a factor too, and it’s opening the door to competition from smaller vendors. A graduate student at National Tsing Hua University uses a dual-range BCA kit from Visual Protein for routine quantification of RIPA lysates and tissue homogenates, calling it “a reliable, cost-effective workhorse”.

Old chemistry, new formats

What keeps a 1985-era assay relevant in 2026 isn’t the core chemistry, which hasn’t really changed, but the growing number of formats built around it. Standard BCA kits still cover a broad 20–2,000 µg/mL range with a roughly 30-minute incubation, but labs working with precious or dilute samples now have Micro BCA formulations that push sensitivity down to 0.5 µg/mL, and labs that just want faster turnaround can use “rapid” formats that cut incubation to five minutes at room temperature instead of a 30-minute warm incubation. Dual-range kits, meanwhile, let a single kit cover both a high-throughput standard range and a more sensitive low-end range without buying two separate products. None of this required reinventing the assay—it just made the existing chemistry more flexible, which is likely why BCA has held its ground against newer, more specialized protein-quantification technologies rather than being displaced by them.

That persistence looks different against the wider field. Another recent Biocompare article described a protein-quantification landscape moving toward higher-specificity tools like mass spectrometry and imaging mass cytometry for complex biomarker work. BCA isn’t really competing with those—it’s covering a simpler, more common need, a quick total-protein number before the next step, which is likely why it hasn’t been displaced so much as left alone to do the job it’s always done.

Comparing some of the kits

For most labs, the choice among these still comes down to what is actually being measured. A standard kit remains the default for routine lysate work; the micro format is worth the extra reagent cost when sample volume or protein concentration is the limiting factor, as with exosomes or small biopsies; a rapid format helps when turnaround time matters more than shaving a few dollars off cost-per-well; and a dual-range or budget-branded kit can be a reasonable way to control costs without giving up accuracy, provided the buffer conditions still fall within its compatibility range. And as the reviews and table show—BCA chemistry is widely licensed and manufactured. Four decades in, the assay itself hasn't needed to change much—it’s the packaging and the supplier list around it that keep evolving to fit how labs actually work.