To preconcentrate the positively charged cocaine and benzoylecgonine from river water, solid phase extraction was carrie

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To preconcentrate the positively charged cocaine
and benzoylecgonine from river water,
solid phase extraction was carried out at pH 2 using a mixed mode cation-exchange resin
which attracts positively charged ions. After passing 500 mL of river water through 60 mg
of resin, the retained analytes were released first with 2 mL of CH30H and then with 5mL
of 2% ammonia solution. If the resin releases 97% of the analytes, what is the preconcentration factor?
ANSWER: 70
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