Determining Trace Metal Concentrations in White Wines
Andrea Barger*, Alex Havlik, Jamesa Hogges, Danielle Montanari and Siatta Adams
Mercer University Department of Chemistry
Lab Report by: Andrea Barger
Abstract
White wines have been shown to contain certain unsafe amounts of trace metals
such as cadmium and lead; these elements could be absorbed by the body and do harm to the
body’s cells. In this study, two brands of white wine from two different regions of the world
were analyzed for trace metal content, along with the urine samples from two participants who
drank the wine each day for three weeks using an acid digestion and an inductively coupled
plasma instrument (ICP). The study found that wine from the United States contained
approximately 1716.88 ppm Fe, negligible amounts of cadmium and lead, 0.0028 ppm Mg, and
0.0840 ppm V, and wine from Italy contained 268.18 ppm Fe, negligible amounts of cadmium,
lead, magnesium, and 0.0831 ppm V. There also may be a correlation between these vanadium
concentrations in wine and the amount in participants’ urine.
White wine is a popular beverage for many adults of twenty one years of age or older in
the United States. Based on a study done by Gallup.com, about 67% of adults drink alcohol in
the United States, 48% of women and 17% of men say wine is their preferred beverage.1 Several
studies have also been done on the health benefits of wine for human bodies. In general, alcohol
in healthy moderation has been shown to elevate levels of good cholesterol and keep blood
thinner.2 Specifically, wine has been shown to reduce the risk of getting Alzheimer’s disease,
types of cancers, and heart disease. Wine has phytochemicals that act as antioxidants to oxidize
free radicals and prevent them from harming the body’s cells.2
While it has been shown that several adults drink wine, some studies show that wine may
contain trace metals that could be harmful to a person’s health. Trace metals such as lead can be
present in wine from a phenomenon called “atmospheric fallout” where dust containing metals
could settle on the grapes or from metal containing pesticides used in grape growing.3 The
concentration of these metals could increase even more after bottling if the cork and bottling
equipment aren’t clean during use.3 Elements such as lead and cadmium have been shown to be
present in wines.4
From past studies on different types of wines, the researchers of this project determined
five heavy metals that are likely to be found in wine, and these are lead, iron, cadmium,
vanadium, copper, and magnesium. In the right concentrations, these metals can be harmful to
the body. When ingested, a percentage of these metals in absorbed into the body and the kidney
filters out the remaining harmful concentrations through the urine. Metal concentrations in urine
can be indicative of the amount in the body. The unhealthy concentration levels in urine of the
five metals listed above are found in table 1.
Table 1. Metals analyzed and unsafe levels of metals in urine and water.
Metal
Lead (Pb)
Unhealthy Amount of Metal in
Urine
0.20 ppm
Allowable/Recommended Limit of
Metal
0.01 ppm Pb9
Nephrotoxicants
Iron (Fe)
0.05 ppm
30 mg Fe / kg person10
Hepatotoxins
Cadmium (Cd)
0.05 ppm
0.005 ppm Cd11
Nephrotoxicants
Magnesium (Mg)
> 240 ppm
1000 mg / day for average adult12
Hepatotoxins
Vanadium (V)
0.01 – 0.03 ppm
1.0 – 1.2 ppb V in drinking water13
Respiratory
Target Cell
When these metals are absorbed by the body, they can harm several parts of the body.
The body’s kidneys act as a filter for all toxic substances, and even though the kidneys only
comprise 0.5% of total body mass, they receive 20 – 25% of the resting cardiac output.
Therefore, chemicals in different body systems are delivered to the kidneys in relatively high
amounts, and if toxic metals are in the blood at low, harmless concentrations, they can quickly
reach unsafe concentrations in the kidneys. Iron, magnesium, and copper are hepatotoxins and
can harm the liver and iron and copper cause hepatocyte death. Magnesium can cause a disease
called canalicular cholestasis, which impairs the production of bile in the liver and causes
jaundice. Cadmium and lead are nephrotoxicants, which are toxicants that can directly interfere
with kidney function. Even in low doses, cadmium can affect several cellular pathways.
Vanadium can also cause problems with respiration, such as airway irritation, overproduction of
mucus, and chronic bronchitis. Generally, even low concentrations of metals in the body can
cause harm.
Because of these harmful effects caused by metals in the body, there are several
recommended limits for the consumption of these metals. The consumption limits are listed in
table 1. The FDA regulates the amounts of lead and cadmium in drinking water, which can be
compared to the amounts of these metals in wine. There is also a small amount of vanadium in
drinking water which can also be considered a safe amount. If the concentrations of these metals
exceed these standards in wine, the wine could be harmful to the body. Also, if these metals are
absorbed into the body through the consumption of wine, they would appear in the urine in
smaller concentrations. These limits set forth by the FDA are allowable for the United States;
however, wines from other countries could have different, little, to no standards on how much
heavy metals can be present in food and drink of that country.
Table 2. Information about wines used in this experiment.
Wine Brand
Region of the World
Barefoot Wine
California, United States
Cavit Wine
Year
Flavor
2010 White Moscato
Lombardy’s Provine of Pavia, Italy 2009
Moscato
Store Purchased
Publix, Macon, GA
Kroger, Macon, GA
No conclusive studies have been performed on metal content in wines and the body’s
absorption of these metals from drinking the wine; this study incorporates all three of those
components. In this experiment, two white Moscato wines from two different regions of the
world were selected to be studied. Information about these wines is listed above in table 2. The
wines were analyzed for the five metals listed in table 1 using an acid digestion and inductively
coupled plasma – optical emission spectra (ICP-OES). Finally, two participants were asked to
drink eight ounces of wine each night for three weeks to determine the amount of metals
absorbed by the body. Urine samples were taken before wine consumption commenced and each
week for three weeks afterwards. These urine samples were analyzed using an acid digestion and
ICP-OES as well.
Using acid digestion, a sample of each substance was acid digested and inductively
coupled plasma – optical emission spectra (ICP-OES) was used to quantify metal levels. The
acid digestion of the sample is essential for sample preparation because ICP must have an
aqueous sample in order to nebulize the sample. Acid digestion is especially useful for getting
the trace metals of the wine samples into an aqueous solution with a regulated pH. This
experiment is designed to give accurate results on the trace metal levels in the substances
analyzed. The ICP-OES will calculate the parts per billion of each metal per sample, and from
the metal per sample, we can determine the metal per substance by a back calculation. We must
calculate the amount of metal actually in the value returned by the ICP. We multiply the
concentration by the amount of sample put into the system, and then divide that number by the
total volume before heating to determine the actual concentration in the analyte of interest.
General Methods. White wines are commercially available and were purchased at a
local store in Macon, Georgia. Wines were decanted off Mercer’s campus and brought into the
laboratory in appropriate containers. All glassware used was washed in a 10% HNO3 bath to
remove traces of metal. Calibration solutions were made from serial dilutions using techniques in
Methods for Preparation of Standard Solutions of Metals.8
Sample Preparation of Wine. A 25 mL sample of each wine was taken and diluted to
100 mL with ultrapure water in a volumetric flask. The pH of each diluted wine sample was
measured to ensure the acidic nature of the wine. A method blank was also prepared, using
ultrapure water. The pH of the method blank was adjusted to be in the range of the wine samples.
(pH 1.00 – pH 1.70).
Sample Preparation of Urine. Urine samples were collected each week in appropriate
disposable collection vessels. From these samples, a 5 mL sample of each week of each
participant was taken and mixed with 2.0 mL concentrated HNO3 and 1.0 mL 30 wt%
concentrated H2O2. Samples were heated for one hour and volumes were recorded before and
after heating. After heating, each sample was diluted to 50.0 mL with ultrapure water and filtered
by gravity filtration with Whatman 41 filter paper. Then, the pH of the samples were tested and
adjusted accordingly with concentrated HNO3 to standardize the pH to be in the range of 1.0 to
1.7, similar to wine.
Inductively Coupled Plasma. ICP instrument was warmed up for two hours before
sample analysis. A water blank, a method blank, urine samples in solution, wine samples in
solution were placed into the ICP after digestion. The ICP calculations were done on the
computer and converted using WinLab32™ ICP software from Optima™.
The ICP-OES gave data at several different wavelengths for all five metals. Calibration
curves were not constructed by the WinLab32™ ICP software because the software did not read
the concentrations of the standards correctly. Calibration curves were constructed by Excel and
can be found in Appendix 1. Only one particular wavelength was chosen to examine from each
metal and the calibration curve was constructed from that data set. From the calibration curve, an
equation was determined and the intensities given by the ICP were converted into concentrations
using the equation. Data was taken on both Moscato wines and weeks one and three of urine
samples. The urine samples from week zero before the wine consuming began did not give
usable data because the instrument was clogged. The urine sample from week two for one of the
participants had to be thrown out because she became ill and took antibiotics for a week and
could not ingest wine.
In iron, the wavelength chosen was 259.939 nm. This wavelength was chosen because it
had the highest signal to noise ratio of all the wavelengths and returned a calibration curve with
an R2 value of 0.9974. The concentrations of iron in each of the samples are listed in table 3.
Table 3. Concentrations for iron in wine and urine.
Sample
Participant 1, week 1
Particiant 2, week 1
Participant 1, week 3
Concentration from ICP in sample, ppm Concentration of Fe in substance, ppm
Not detectable
1.16 ppm Fe
Not detectable
Not detectable
0.23 ppm Fe
Not detectable
Participant 2, week 3
Barefoot Moscato
Cavit Moscato
Method Blank
Not detectable
42921.92 ppm Fe
6704.42 ppm Fe
Not detectable
Not detectable
1716.88 ppm Fe
268.18 ppm Fe
Not detectable
The numbers above show that only the wine has a significant concentration of iron in it,
and the wine from Italy actually has less iron than the wine from the United States. It is possible
that this iron could come from pesticides used in the United States that are not used in Italy.
Participant 2 had a small amount of iron in her urine during week 1; however, this is below the
allowable limit and is considered safe. Participant 2 is a pescatarian; her larger amount of iron
could be due to the amount of fish consumed, relative to Participant 1 who is an omnivore.
In vanadium, the wavelength chosen for analysis was 310.23 nm. Again, this wavelength
had the highest signal to noise ration and the calibration curve of these data points returned an R2
value of 0.9919. However, there is an iron peak at 309.278 nm that is overlapping with this
vanadium peak, and it appears that the vanadium is contaminated with iron. This is possible if
the machine were clogged or if the standards were made in close proximity to each other.
Nonetheless, this wavelength’s data points returned workable, positive data, which is listed in the
following table 4.
Table 4. Concentrations for vanadium in wine and urine.
Sample
Participant 1, week 1
Particiant 2, week 1
Concentration from ICP in sample, ppm Concentration of V in substance, ppm
0.221 ppm V
0.454 ppm V
0.0442 ppm V
0.0908 ppm V
Participant 1, week 3
Participant 2, week 3
Barefoot Moscato
Cavit Moscato
Method Blank
0.456 ppm V
0.455 ppm V
0.452 ppm V
2.101 ppm V
2.078 ppm V
0.0912 ppm V
0.0910 ppm V
0.0904 ppm V
0.0840 ppm V
0.0831 ppm V
The urine concentrations of vanadium are higher than what is considered to be safe for
vanadium levels in urine. However, because of the iron peak that overlaps with this vanadium
wavelength, some of the iron’s fluorescence could be influencing the intensities of the vanadium
concentrations in the samples. It is very possible that these concentrations are much lower than
actually listed and quite reasonable. The vanadium levels in wine are below the reasonable limit
for drinking water, which is much safer. However, these concentrations could be high as well.
Vanadium is not usually found in high concentrations in the environment, and it is more
reasonable to think that a negligible amount of the vanadium would be found in urine samples
and wine samples.
In both participants, the amount of vanadium in the urine increased from week one to
week three. If these results are accurate, it could be reasonable to assume that the amount of
vanadium in the wine is contributing to the increase in vanadium in the urine. Only about 10% of
a vanadium sample is absorbed into the body, and over three weeks, the vanadium content the
body is filtering out could increase in urine.7 However, the differences between the two
participants’ concentrations of vanadium in their urine are quite different, indicating that there
could be other factors at work such as diet.
For cadmium, the original standard samples used did not return workable data. However,
another set of cadmium standards were created and data was taken using those standards. The
instrument had slightly different settings at this point, and this could alter the relative
interpretations of the data of cadmium, compared to the data of the other metals. The cadmium
wavelength chosen for analysis was 226.000 nm. This wavelength was chosen because it had a
relatively high signal to noise ratio and the calibration curve returned an R2 value of 0.9997.
The wavelength with the highest signal to noise ratio had a high baseline caused by a
severe amount of fluorescence. It appeared that some cadmium standards had vanadium
contamination and this could be a reason for the cause of fluorescence. It could also be that these
standards had another unknown contaminant causing the baseline to move upwards. Nonetheless,
the calibration curve did return an equation that was used to find the concentrations of Cd in the
samples, which is listed below in table 5.
Table 5. Concentrations for cadmium in wine and urine.
Sample
Participant 1, week 1
Particiant 2, week 1
Participant 1, week 3
Participant 2, week 3
Barefoot Moscato
Cavit Moscato
Method Blank
Concentration from ICP in sample, ppm Concentration of Cd in substance, ppm
0.533 ppm Cd
0.971 ppm Cd
Not detected
2.428146 ppm Cd
Not detected
Not detected
Not detected
0.1066 ppm Cd
0.1942 ppm Cd
Not detected
0.486 ppm Cd
Not detected
Not detected
Not detected
According to the data, all of the urine samples have concentrations of Cd above safe
levels. However, the vanadium contamination that appeared to be present in this standard could
be adjusting the intensities of the cadmium standards. It is reasonable to think that the cadmium
levels are much lower than this, especially considering the graphs at other wavelengths.
Cadmium standards had a lot of background noise that could be influencing the data and the
unusual concentrations of cadmium in the urine samples could be caused by the clogged
instrument or the adjusted settings of the instrument.
However, in one urine sample, both wines, and the method blank, cadmium was not
detected at all. This could be well representative data because the wine analyzed could not
contain cadmium. This ideal situation is feasible, especially if the two countries do enforce
regulations on trace metals in wine. There is no evidence to believe they do not enforce these
regulations.
The cadmium in participant two’s urine samples increased from week one to week three.
However, because no cadmium was detected in the wine, it is hard to accredit this to the wine
consumption. Therefore, the data could still be affected by the contamination and this increase is
unfounded by wine consumption.
For magnesium, the wavelength chosen to analyze was 279.553 nm because it was the
only wavelength that data points were taken at. However, it had a high signal to noise ratio and
the calibration curve of these data points gave an R2 value of 0.9974. The magnesium data at this
wavelength is listed below in table 6.
Table 6. Concentrations for magnesium in wine and urine.
Sample
Participant 1, week 1
Particiant 2, week 1
Participant 1, week 3
Participant 2, week 3
Barefoot Moscato
Cavit Moscato
Method Blank
Concentration from ICP in sample, ppm Concentration of Mg in substance, ppm
8.541 ppm Mg
19.97 ppm Mg
16.13 ppm Mg
Not detected
0.0700 ppm Mg
Not detected
20.63 ppm Mg
1.71 ppm Mg
3.994 ppm Mg
3.226 ppm Mg
Not detected
0.0028 ppm Mg
Not detected
0.8252 ppm Mg
The concentrations of magnesium in these samples are reasonable concentrations.
Relatively, magnesium in higher concentrations is more common in urine than the other metals
analyzed. Therefore, the magnesium concentrations in urine are reasonable. The third week for
participant two contained an undetectable amount of magnesium; this could be normal for a
person’s urine to not contain any magnesium at one specific time. Only the Barefoot Moscato
had a small amount of magnesium detected; this magnesium could come from the pesticides used
in the United States. Magnesium is also contained in tap water in the United States and in rain in
general. The grape plants could soak up this metal and it could transfer to the grapes. Therefore,
these amounts of magnesium in the urine and wine are reasonable amounts.
Participant one, who was consuming the Barefoot Moscato, did experience an increase in
magnesium in urine levels from week one to week three. This increase could be from the small
amount of magnesium in the Barefoot Moscato, and the body could be absorbing the magnesium
from the wine consumed. However, there is a large difference between week one and week three
magnesium concentrations in the urine, so it is feasible that other factors such as diet are going
into this increase in magnesium.
Finally, in lead, the wavelength analyzed was 220.353 nm. This wavelength had the
largest signal to noise ratio of the wavelengths that had data and the calibration curve for this
data returned an R2 value of 0.998. However, these graphs had broad peaks and a large gap
between each line. It also had a small amount of fluorescence that could be contributed to an iron
peak that appears around 220.353 nm. The concentrations of lead in the samples are listed below
in table 7.
Table 7. Concentrations for lead in wine and urine.
Sample
Participant 1, week 1
Particiant 2, week 1
Participant 1, week 3
Participant 2, week 3
Barefoot Moscato
Cavit Moscato
Method Blank
Concentration from ICP in sample, ppm Concentration of Pb in substance, ppm
9.444 ppm Pb
83.28 ppm Pb
47.19 ppm Pb
7.694 ppm Pb
Not detected
Not detected
Not detected
1.89 ppm Pb
16.656 ppm Pb
9.44 ppm Pb
1.54 ppm Pb
Not detected
Not detected
Not detected
The above lead concentrations for urine are all above the safe lead concentration for
urine. Particpant two’s week 1 is also extremely high. Participant one’s lead content in urine
increased over the two weeks; however, participant two’s lead concentration decreased over the
two weeks. It is likely that there is a contaminant in this sample that is once again influencing the
intensities by increasing them dramatically. An iron peak could be interfering with these
samples; it is also possible that the instrument’s settings were not properly controlled to take
accurate readings. These lead concentrations aren’t plausible because they are so high above the
healthy limits that a person would surely know if he or she were suffering from lead poisoning.
The wine samples had undetectable levels of lead in them. These results are plausible
because if countries do regulate the amount of trace metals in wine, it is possible that the iron has
been taken out of wine. This means these lead levels in the wine are at healthy amounts.
However, it is also possible that there was an error with the instrument and these values were
incorrectly recorded.
In conclusion, the data and results from this experiment are not conclusive to the amount
of trace metals contained in these two white Moscato wines. For the first part of the data
analysis, it is suspected that the instrument was clogged. This clog could have altered data for all
the urine samples, and for one set of urine samples, it did not return usable data whatsoever. If
the clog were fixed before the analysis of the samples, better, more reasonable data would have
been obtained and analyzed.
Also in the experiment was the inconvenience of the contamination in the standard
solutions. The contamination influenced intensity values and made the results slightly
unreasonable for the amounts of metals in urine samples and wine. If the standards were made in
a more carefully controlled environment, the intensities would have more accurately reflected the
concentrations of each trace metal in each sample.
Because of the inconsistent data and suspected errors in this experiment, it is
recommended that more trials of this experiment be performed before conclusive data is
determined. Trace elements are likely to be found in wine to some extent and should be filtered
out of the body by the kidneys. However, a longer study would need to be performed to get
conclusive data. Three weeks is a short span of time for metals to build up in the body, and
studies that have successful results usually experiment with people who have been drinking wine
for years. Each participant in this study was no more than two years past the legal drinking age in
the United States.
Finally, the seeming connection between the increase in vanadium content in the urine
from wine consumption should be investigated further before considered conclusive evidence.
Because so many errors occurred and the unlikelihood of a high content of vanadium consisting
in wine, it is suggested that these experiments be run again, with a closer record kept of other
factors that may be influencing these metals, such as diet.
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