HPLC in a World Without Acetonitrile

Raw acetonitrile is a by-product of the manufacture of acrylonitrile. It is co-polymerised with butadiene and styrene to make ABS, a plastic used in cars etc, and the market for it has collapsed over the last six months. Hence so has the production of acetonitrile. There are no manufacturing plants to make acetonitrile (unlike THF or methanol) and there is little prospect of one being built. Stocks are now depleted, and hence those distilling it for use in HPLC can no longer get enough supplies. Acetonitrile is now being offered at extortionate prices. In the short term, this means that we will all have less, if any, acetonitrile available to us, and when it does come back on stream, it could be a lot more expensive. Many HPLC methods use acetonitrile as part of the mobile phase. It is an excellent eluent. It has low viscosity, good selectivity, 100% miscibility with water, reasonable buffer solubility, and is almost transparent to UV light. HPLC methods are usually validated (checked thoroughly to ensure that correct results are obtained even if small changes to the operating conditions apply) and are sometimes registered. Validation can take up to three months, registration can take much longer, and both are expensive. So once a method is set in concrete, it is almost impossible to change. However... if the acetonitrile specified in the method ceases to be available, it is necessary at some point to bite the bullet, and make the decision to change the method. There are two approaches. The first is to do the absolute minimum necessary to get the separation to work with another solvent, and re-register as fast as possible. This has obvious attractions in the short term, in terms of time, cost, and ease of re-registration. The alternative is to use this as a once in a lifetime opportunity to redevelop the method using modern columns etc, and to check again that the most appropriate temperature, pH, buffer concentration is being used. It takes longer, but in time to come, with the benefit of hindsight, this can seem a much wiser approach.