The following compounds are soluble in water att a concentration of 50 mg/mL: 1.

Question

The following compounds are soluble in water att a concentration of 50 mg/mL:

1. L-methionine sulfoximine (MW =180.23g/mol)

2. Cefotaxime sodium salt (MW 477.5g/mol)

Bacitracin (MW 1422.7g/mol)

Baed on this information, determine whether solutions of each compound can be prepared at 3 different concentrations: 150mM, 50mM and 10mM.

(You have three compounds and are trying to determine if you can make three different solutions (three different concentrations) of each compound. Hint: You may need to perform calculations to determine this.) To receive full credit you must state if it is possible to make each of the three solutions of each compound and discuss the reason(s) why it is possibleor why it is not possible.

Explanation / Answer

1) L-METHIONINE SULFOXIMINE :

The solubility of the compound = 50 mg/L

in mmols = 50 mg / 180.23 g/mol = 0.277 mmol / mL

Therefore, in 1000 mL = (0.277 mmol/mL)*1000 mL = 277 mM

To prepare 150 mM, 500 mL solution, he has to mix the following amount of the substance in 500 mL solution.

Hence the volume of parent solution needed to prepare 150 mM,
V1 = (150 mmol /L)(500 mL) / 277 mM = 270.75 mL (stock solution to be taken = 270.75 mL)

For 50 mM:

(50 mM)(500 mL) = (277 mM)(V2)

V2 = 90.25 mL (to be taken from starting solution to dilute it in to 500 mL)

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For 10 mM:

(10 mM)(500 mL) = (277 mM)(V3)

V3 = 18.0 mL

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2. Cefotaxime sodium salt (MW 477.5g/mol):

In the similar way, we solve for second compound too.

concentration of stock solution = [(50 mg/477.5 g/mol) /mL] * 1000 mL = 104.71 mM

For 150 mM, it is practically not possible to prepare as the resultant concentration is more than the stock.

For 50 mM (500 mL) :   (50 mM)(500 mL) = (104.71 mM)(V2)

                               V2 = 238.75 mL required to dilute it in to 500 mL to get 50 mM concentration.

For 10 mM (500 mL) : (10 mM)(500 mL) = (104.71 mM)(V2)

                               V3 = 47.75 mL required to dilute it in to 500 mL to get 10 mM concentration.

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