and organic arsenic compounds. The in- organic arsenic compounds—specifically the toxic 3+ arsenite and the 5+ arsenate ion—are ingested by the animals, enter the meat, and thus make their way into the human food chain.
Another route of arsenic introduction in
the food chain is via feed. Feed based on
seaweed is controlled by legislation and
must not contain more than 2 ppm of
inorganic arsenic. However, seaweed is
rich in arsenic-containing organic
compounds (such as arsenosugars)
that are non-toxic to the animal (and
humans), and these make their way
into the meat and other edible parts of
the animal. As a result, meat derived
from cows who’ve consumed seaweed-containing feed can contain high—but
harmless—levels of arsenic bound up
in the arsenosugars. To put this into
perspective, the inorganic arsenite ( 3+)
ion is toxic (LD50) at a concentration
of 14 mg/kg, whereas a typical organic
arsenosugar (such as arsenobetain) is
toxic at 10,000 mg/kg—that is, at a
concentration 700 times higher than
the inorganic form of arsenic.
mercury or arsenic in a particular sample,
the results may mean little with regard to
food safety. What is needed is speciation
of the sample, meaning the concentrations
of both the toxic and the non-toxic com-
pounds should be determined. Speciation
of heavy metals is a difficult undertaking,
to say the least. “It is very hard to create a
method for speciation,” says Dr. van der
Lee, “if you have an extraction method
that is too hard on your sample; one spe-
cies can interconvert to another, meaning
allows his team of analytical chemists to
determine with a high degree of certainty
whether a particular sample contains
toxic species (such as methyl mercury,
arsenite, and arsenate). This allows the
regulators who submitted the sample to
determine whether it presents a threat to
human or animal health.
Dr. van der Lee and his team at RIKILT
have developed methods for speciating mercury and arsenic in a variety of
food and feed using a Thermo Scientific
high-performance liquid chromatograph (HPLC) and a Thermo Scientific
XSERIES 2 inductively coupled plasma
mass spectrometer (ICP-MS).
Regulatory Implications
The implications for food regulators
around the world are clear. Food safety
would be considerably improved if
regulators set limits based not on
total concentrations of a particular
element, but on the concentrations
only of its toxic forms. In Europe,
regulators are moving in this direc-
tion, with regulation EU2003/100
stipulating that the concentration of
inorganic arsenic ( 3+ and 5+) in ani-
mal feed must be less than 2mg/kg.
When asked why other parts of the
world are not implementing similar
rules, Dr. van der Lee replied, “Not
every laboratory has the equipment
that we have, so they are not able
to analyze all the arsenic [and other
toxic] species.”
Organic vs. Inorganic—The Case for
Speciation
It is here that our discussion of heavy-
metals becomes more complex. As
already noted, mercury is toxic to humans
primarily in its organic form. Whereas
arsenic is toxic in its inorganic form. The
consequence is that inorganic mercury
and organic arsenosugars are considerably
less toxic to animals and humans, and at
low concentrations can border on benign.
As a result, when food is analyzed to
determine the total amount of elemental
the results do not indicate the presence of
the toxic species of interest.”
Dr. van der Lee and his team at RIKILT
have, nonetheless, developed methods for
speciating both mercury and arsenic in a
variety of food and feed using a Thermo
Scientific high-performance liquid
chromatograph (HPLC) and a Thermo
Scientific XSERIES 2 inductively coupled
plasma mass spectrometer (ICP-MS).
He likes this pairing of instrumenta-
tion because, “All my people can work
with it quite, quite easily.” The analysis
The Complexity Continues
So, what other heavy metals would he
like to speciate? Dr. van der Lee thought
a moment, chuckled, and said, “The
chromium species, chromium 3+ and
chromium 6+; these are on my ‘wish
list’ for next year.” While heavy metals
present a complex challenge, Dr. van der
Lee and his team at RIKILT have the
mettle to face them—accurately speciating heavy metals into their toxic and
non-toxic forms.
