Dalton unit

Resolution Quadrupole instruments are not capable of achieving the high resolution that is common with double-focusing magnetic-sector instruments. In GC/MS analyses, a compromise is struck between sensitivity (ion transmission) and mass resolution. In the quadrupole instrument, the resolution is set to the lowest possible value commensurate with resolving peaks differing by 1 Dalton (unit resolution). 

The molecular mass has units termed daltons (Da), after the famous English chemist John Dalton (1766-1848). Eor example, the molecular mass of insulin might be said to be about 6000 daltons. However, this designation does not add much to understanding the concept of molecular size and we shall delete the dalton unit in all that follows. 

Dextran, pyrogen-free average mol wt 100,000-200,000 Dalton (United States Biochemical Corp., Cleveland, OH). 

Nanofiltration membranes are commercially available, e.g. with a retention capacity of 400 Da. The dalton unit serves as a measure of the separation ability... 

Dalton Unit of relative molecular mass, symbol Da. 

Most iihrafiltratinn membranes are made fiom PVDF or polysuJplione and are asymmetric. However, two common inorganic UF membranes are made firom a conq>osite of carbon (support) widi mconia (skin) at molecular wmght cut-off (MWCO) of 20 000-50 000, and an ahnnina con o e widi alpha (support) and gamma (skin) at 40 nm. Instead of MWCO the Dalton unit is now in common use (1 Dalton is equal to 1 on a molecular weight scale). 

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