the invention is reagents and procedures for determining an amount of cations present in a sample , the reagent including one or more chromogenic cryptand compounds of formula i ## str1 ## wherein k and j , either same or different , are equal to 1 to about 5 ; m and n , either same or different , are equal to 0 to about 4 ; a and e , either same or different , are equal to 0 to about 2 ; b and d , either same or different , are equal to 0 to about 5 ; r , either same or different , is hydrogen , lower alkyl , lower alkylidene , lower alkenyl , allyl , or aryl ; and ## str2 ## wherein x is ch , n or coh ; and y includes ## str3 ## except that when q is ## str4 ## wherein y is p - nitrophenylazo , 3 - phenylisothiazolyl - 5 - azo , isothiazolyl - 5 - azo , thiazolyl - 5 - azo , 2 , 4 , 6 - trinitrophenylazo , p - nitrostyryl , p - benzoquinonemonoimino or bis - hydroxymethyl , then the following condition cannot be present : that simultaneously b is equal to 0 or 1 , d is equal to 0 or 1 , j is equal to 1 , n is equal to 1 or 2 , a is equal to 1 , e is equal to 1 , k is equal to 1 and m is equal to 2 .