Abstract: This invention relates to novel compounds of the formula: ##STR1## wherein X.sup..sym. is a pharmacologically acceptable cation. The compounds are water soluble and are compounded with pharmaceutical carriers to form compositions which are useful as medical treatment for those conditions for which metronidazole is useful in treating.

Abstract: A high pressure liquid chromatography apparatus having a detachable inline filter connected between the sample injection valve and the liquid chromatography column. The inline filter removes solid impurities from the liquid stream comprised of mobile phase and sample that is fed into the liquid chromatography column. If the inline filter becomes plugged, it can be detached from the sample injection valve and the liquid chromatography column and then cleaned by backwashing. The inline filter has a low dead volume and good filtration geometry so that the sharpness of the peaks of the chromatogram are not adversely affected to a significant degree by the use of the inline filter.