Analytical Method: Sensitive measurement of iron in drinking water, mineral water, spring water and groundwater

Method: Photometric determination with a triazine derivative

Materials and reagents:

Reagents
Cat. No. 114761 – Spectroquant® Iron Test
Cat. No. 101262 – Water Ultrapur
Cat. No. 100456 – Nitric Acid 65 % for analysis
Cat. No. 119781 – Iron Standard Solution CertiPur®

Instruments
Cat. No. 173018 – Spectroquant® UV/VIS Spectrophotometer Prove 600

Materials
Cat. No. 174011 – Rectangular cell 100 mm
Cat. No. 114901 – Preparation vessel, flat-bottomed long tubes with screw caps
Cat. No. XX1102012 – Plastic Syringes, 20 mL, Luer slip, polypropylene
Cat. No. SLLGM25NS – Syringe filter holder, Millex-HPF LCR Filter, 0.20 μm, PTFE, with glass fiber prefilter

Pipettes – Pipettes for 20 mL with plastic tips or 20 mL volumetric pipette

Measuring range:

0.0025 – 0.5000 mg/L Fe

Working instructions:

Sample preparation:
Preserve sample immediately after sampling by adding 1 mL nitric acid 65% per L of sample solution. If the water is carbonated, degas using an ultrasonic bath.

Filter the sample into a clean and dry vessel using the above mentioned filter holder.

If another filter is used, it must first be checked for interferences using standard solutions. For this purpose measure an iron standard solution with 0.010 mg/L Fe, filtered and unfiltered, with the Spectroquant® Iron Test 114761 and compare the results. If the result of the filtered solution differs from that of the unfiltered one, the filter produces interferences and may not be used for the analysis.

Measurement procedure:
Determine the Fe content with the above mentioned test kit. For measurement in the 100-mm cell, both the sample volume as well as the quantity of reagent Fe-1 must be quadrupled, i.e. using a sample volume of 20 mL and 12 drops of reagent Fe-1.

The measurement is carried out against a blank, prepared from Ultrapur water and the reagents in an analogous manner.

After measurement, the result can be read off from the instrument.

Measurement results for drinking and mineral water

Comparison of results of the Spectroquant® Iron Test 114761 with ICP-MS reference analysis
 

Mineral water
Concentration [mg/L Fe]
Spectroquant® Iron 114761 ICP-MS
Celtic natural < 0.0025 < 0.0007
Justus Brunnen medium < 0.0025 < 0.0007
Vitrex natural < 0.0025 < 0.0007
Vittel natural < 0.0025 < 0.0007
Volvic natural < 0.0025 < 0.0007


Standard addition with the Spectroqunat® Iron Test 114761
 

Mineral water Addition
[mg/L Fe]
Recovered concentration
[mg/L Fe]
Recovery rate
Celtic
natural
0.0050
0.0100
0.0250
0.0050
0.0089
0.0239
99%
89%
96%
Justus Brunnen
medium
0.0050
0.0100
0.0250
0.0046
0.0091
0.0239
91%
91%
96%
Vitrex
natural
0.0050
0.0100
0.0250
0.0048
0.0093
0.0238
95%
93%
95%
Vittel
natural
0.0050
0.0100
0.0250
0.0046
0.0095
0.0241
91%
95%
97%
Volvic
natural
0.0050
0.0100
0.0250
0.0047
0.0098
0.0244
93%
98%
98%

Materials