Our lab wants to purchase BCA protein assay kits in bulk. Does anyone have any recommendations?

For spot supply channels in Shanghai, you can check local warehouses of Beyotime, Yeasen, Epizyme, and Sangon; they usually offer next-day delivery, and both pricing and replacement for damaged goods are easy to negotiate. Within a budget of 500 yuan, imported Pierce small-pack sizes can sometimes be obtained, but large-pack sizes are likely to exceed the budget and have unstable lead times. During procurement, ask clearly whether BSA standards are included and whether a COA can be provided; many domestic kits now also perform lot-to-lot quality control. For 30-40 samples per week, a 500 mL pack may last 1-2 months if calculated by replicate wells. It is recommended to require the supplier to commit to supplying multiple boxes from the same lot to avoid data fluctuations caused by changing lots midway.

Before switching suppliers, it is recommended to run a small-sample validation first rather than stocking up in bulk right away. You can use your existing lysis buffer (containing 1% SDS) as the standard diluent, and set up a no-SDS control group at the same time to check whether the standard curves are parallel. In the low-concentration range, I would focus on whether points are lost between 25-125 μg/mL. If SDS interference is obvious, first dilute the samples to SDS ≤0.5% or uniformly extend the incubation time. Batch-to-batch consistency should rely on internal quality control: keep one tube of cell lysate at -80°C and test it each time you switch to a new kit batch. If the deviation exceeds the acceptable range, then investigate further. Standards are recommended to be aliquoted and frozen to avoid repeated freeze-thaw cycles affecting linearity.

We've also used a domestic kit before; the batch-to-batch variation mainly showed up as absorbance jumps in the low-concentration range. Now we mainly use Beyotime and Yaenzyme; both have local warehouses in Shanghai, and lead times are generally 1–2 days. With your budget of 500 yuan per kit, you can negotiate a multi-kit price. Cell lysate samples contain 1% SDS, which most conventional BCA kits can tolerate, but I won't trust the product name alone—I'll have the sales rep provide an SDS tolerance statement. For low-concentration linearity, I suggest running three replicate wells yourself at 25, 50, 125, and 250 μg/mL, focusing on R² and replicate-well CV. At 30–40 samples per week, bulk packaging is more cost-effective, but be careful to dispense Reagent A and Reagent B separately to avoid contamination.