S11. ANALYSIS OF MINERALS IN WINE BY ICP SPECTROSCOPY
PURPOSE
1. To determine the concentration of sodium, potassium, calcium and magnesium in wine
using ICP emission spectroscopy.
2. To examine the independence of the technique to the matrix of the solution
INTRODUCTION
One of the major problems associated with conventional flame emission and absorption
techniques is the influence of the matrix. For most samples, either standard addition or an
internal standard must be used. A recent development is the Inductively Coupled Plasma
emission instrument, which uses a cloud of argon atoms trapped inside a high energy
magnetic field. The result of this is the stripping of all electrons from the argon atoms and the
generation of a plasma at a temperature of about 10,000K. Samples aspirated into the plasma
will atomise totally, and the high density of electrons from the argon means that ionisation of
analyte atoms will be limited. It should be emphasised that the ICP “torch” is only the energy
source, the atoms still absorb and emit the same energies as they do in the normal flame.
PREWORK
You will be required to prepare five 100 mg/L Zn solutions each from a different matrix as
listed below. Calculate the mass of the compound you will need to obtain a 100 mg/L Zn
solution:
Chemical
1. zinc acetate
2. zinc bromide
3. zinc chloride
4. zinc iodide
5. zinc sulfate
Formula
Zn(C2H3O2)2
ZnBr2.2H2O
ZnCl2
ZnI2
ZnSO4.7H2O
Formula mass
mass required / 100mL
PROCEDURE
I. Analysis of wines
1. Using the 1000mg/L standards available, prepare 5, 10 and 100 mg/L mixed standards of
Na, K, Ca and Mg (ie that concentration of each element in the one flask). The blank is
de-ionised water. (If you prepare your standards accurately the instrument will provide the
answer without calculations being required)
2. Dilute the samples of red and white wines by a factor of 10.
3. Filter the wine through millipore to ensure there is no particulate material. Show the
filtrate to you teacher
4. Follow the instructions given by the teacher and the software associated with the ICP to
read your samples and standards recording the intensities
II. Matrix Independence
5. Prepare accurately 100 mg/L solutions of zinc using the masses determined in the
Prework.
6. Record the emission intensities of each solution.
CALCULATIONS
I. Analysis of wines
• if the software has not provided the concentration of each element in the diluted sample
you will need to plot a calibration graph and obtain a value for the wine.
• correct the value for the dilution
II. Matrix Independence
• tabulate the emission intensities for the element in the different chemical forms
• calculate the mean and relative precision of the intensities
DISCUSSION
• Compare this method for the analysis of 4 elements to that of the same 4 elements using
AAS
QUESTIONS
1. Explain what is meant by the term “plasma”
2. Explain why ICP is considered to be a solution to both the matrix problems encountered
in AAS and ionisation problems in flame photometry.
3. Some ICP instruments are able to determine emission intensities from many elements
simultaneously, rather than one at a time. What difference in instrument design must be
involved in the simultaneous instruments?
S11. RESULTS SHEET
Date of analysis
I. Analysis of wines
Solution
Na
K
Emission intensity
Ca
Mg
Blank
5 mg/L
10 mg/L
100 mg/L
White wine
Red wine
II. Matrix independence
Solution
Emission intensity
Zn(C2H3O2)2
ZnBr2.2H2O
ZnCl2
ZnI2
ZnSO4.7H2O
Have you?
Completed the instrument log
Completed the sample register
Completed the standard register
Teachers signature
Date
Signature