IPT04
STRONTIUM & WATER IN TOOTHPASTE
Last Revised: May 2015 1. PURPOSE This exercise determines the level of strontium in toothpaste by ICP emission spectroscopy and water by oven drying. 2. REAGENTS & EQUIPMENT 2.1
Toothpaste containing strontium 2.2
1000 mg/L Sr 2.3
5 M nitric acid 3. PROCEDURE 3A. Water content 3.1 In triplicate:  weigh small evaporating basins  transfer a 1.5 cm portion of toothpaste into each basin  smear the toothpaste around the basin with a spatula  reweigh  place in a 105°C oven for 1 hour 3.2 Remove from the oven, allow to cool for 5 minutes and reweigh. 3B. Sample Preparation (ICP) 3.3 Weigh accurately about 0.3‐0.5 g of toothpaste in triplicate into 250 mL beakers, labelled Sample 1, Sample 2 and Recovery Check. 3.4 To the recovery check, add 10 mL of 1000 mg/L Sr. 3.5 Add 50 mL of 5 M nitric acid to each, break up the paste into smaller pieces with a glass stirring rod, and boil gently for 10 minutes. 3.6 Filter through a fast filter paper into 100 mL volumetric flasks, and make up to the mark with water. 3.7 Dilute each solution 5 mL to 100 mL. 3.8 Filter each solution by Millepore. 3B. Standard Preparation 3.9 Prepare a 50 mg/L intermediate Sr standard from the 1000 mg/L Sr 3.10 Pipette 5, 25 and 50 mL of the intermediate standard into 100 mL volumetric flasks and make up to the mark. 3C. Analysis 3.11 Run each solution on the ICP and record the intensities. 3.12 Re‐measure the middle standard after the last sample. Reporting 
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Enter the Sr data into the spreadsheet found on the subject website. Calculate the water content manually. 
Transfer the final results – average %w/w for Sr and water, %drift and % recovery – to your Result Sheet and submit this.