Agriculture Reference
In-Depth Information
parent drugs using HPLC-UV. The issue of Rapid Alerts and the adoption of
protective measures has had enormous effects on these countries (e.g. in the
cases of Thailand and Brazil) in terms of trade restrictions, financial losses
associated with rejected consignments and the cost of major capital investment
in laboratories with LC-MS/MS capabilities and trained staff [56].
The EU has a policy of zero tolerance towards the use of nitrofurans in
food-producing animals. According to the current legislation, any confirmed
concentration of any of the metabolites is a non-compliance. EU Member
States have condemned imported product when very low concentrations of the
nitrofuran metabolites are detected and confirmed, providing that the
competent authorities have had sufficient statistical confidence in the
analytical method.
Over all of the foregoing, the MRPL, established under Commission
Decision 2002/657/EC [87], has cast some confusion. The precise meaning of
this term was originally intended as a laboratory benchmarking tool, if a
method can reliably and repeatedly confirm the presence of banned substances
at concentrations equal to or below, the MRPL it would be deemed "fit for
purpose". If it could not confirm at those concentrations then further
development work would be required to enable it to meet those levels. In
effect it was there to put a "cap" on the worst performing methods to ensure
that a minimum
standard was applied across MS laboratories [56].
MRPL description ruled out the use of unsatisfactory methods which are
incapable of quantifying very low concentrations of nitrofuran metabolites.
However, ―
the MRPL concept did not include any provision for a maximum
standard
(for detection methods used)‖ [15]. Nowhere is it stated that the
lowest concentration of a banned substance requiring effective enforcement
action is X.X µgkg
-1
. If the banned substance can be confirmed using the
required level of statistical confidence (α-error of 1 %) - then the sample is
non-compliant. Thus, the lowest concentration at which enforcement action
could be taken - CCα - had the potential to vary markedly between laboratories
- depending on the range of analytical equipment available. The upper limit
(minimum standard) would be the MRPL but the lower limit (maximum
standard) could be considerably lower than the MRPL [56].
In other words, the method is only required to be able to quantify
concentration values up to 1 μg kg
-1
, but the lowest concentration of analyte,
which should be quantifiable, is not specified. This value is referred to as the
decision limit, CCα (described below), and is determined by many laboratories
using validation guidelines provided by the EU. However, the fluctuation of
CCα between different instrumental methods and laboratories is a
