How to choose petroleum ether/ethyl acetate from the top ten domestic chemical reagent brands for solvent procurement?

20L per week, with a moderate monthly usage. It is recommended to buy 20L/25L barrels directly, which saves a lot compared to 500ml bottles. After opening the large barrel, it should be quickly divided into brown glass bottles or safety solvent bottles. Petroleum ether and dichloromethane should be prevented from volatilization and peroxide generation, and ethyl acetate should be prevented from absorbing moisture. The delivery time for large barrels depends on the East China warehouse. For spot goods, it usually takes 3-7 days, while for full pallet transfer, it takes 7-14 days. The price will significantly decrease based on the barrel and annual agreement, but it depends on the brand and whether it includes tax and shipping. Suggest consulting at least three companies and clearly stating COA, batch number, and whether stable supply is possible.

It is not recommended to use industrial grade silica gel columns, as industrial grade impurities are abundant and the distillation range is wide, which may bring in high boiling point residues, plasticizers, or unknown pollutants, making it difficult to concentrate and perform NMR/MS. Petroleum ether, ethyl acetate, and dichloromethane should be at least analytically pure; For the critical separation section, analytical pure heavy distillation or direct purchase of distillation grade/environmentally friendly grade can be used. Domestic brands such as Xilong, Guanghua, Kemio, Yonghua, etc. have large packaging, and East China has selected suppliers with hazardous chemical barrel warehouses. It is more cost-effective to purchase large barrels at 20L/25L or 200L, with a lead time of 3-7 days for spot goods and 1-2 weeks for non spot goods.

The impact of solvent impurities on column chromatography is not mysticism. It is advisable to perform a blank concentration verification: rotary-evaporate 1 L of solvent from a large drum to near dryness, and observe the residue appearance and GC impurity peaks. Differences in boiling range among different lots of petroleum ether can change elution strength; residual acid/alcohol in ethyl acetate may cause transesterification or affect pH-sensitive components; for dichloromethane, pay attention to acidity, moisture, and stabilizers. Analytical grade generally meets the needs of coarse separation, but when the target fraction has high requirements, it is advisable to purchase the same lot number, or after arrival, pass it through a molecular sieve/alumina column before use for fine separation. For each new lot number, first run a small column pretest to confirm that the resolution of the target fraction has not changed significantly before using it in batches.

It is recommended to establish a "primary plus backup" solvent supply chain rather than focusing only on price increases and stockouts of a fixed brand. For each candidate brand, first purchase a small quantity in large drums for blank concentration and small-column validation. After passing validation, sign an annual agreement to lock in lot numbers. If the analytical-grade impurities of certain brands still affect fine separation, you may redistill or purify them by column treatment yourself, but do not substitute industrial-grade solvents, as potential contamination is difficult to trace. Agree with suppliers on key specifications such as evaporation residue, moisture, free acid/alkali, and peroxides, and retain samples by lot number upon arrival. In terms of price, large drums are much cheaper than bottled solvents, but transportation and storage must comply with regulations. East China spot supply is generally 3-5 days.