The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis
Hj. Van Den Top et al., The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis, FOOD ADDIT, 17(6), 2000, pp. 419-433
This paper describes the first part of a project undertaken to develop muss
el reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two
interlaboratory studies were undertaken to investigate the performance of t
he analytical methodology for several PSP toxins, in particular saxitoxin (
STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set
criteria for the acceptance of results to be applied during the second part
of the project: the certification exercise. In the first study, 18 laborat
ories were asked to measure STX and dc-STX in rehydrated lyophilized mussel
material and to identify as many, other PSP toxins as possible with a meth
od of their choice. In the second interlaboratory study, 15 laboratories we
re additionally asked to determine quantitatively STX and dc-STX in rehydra
ted lyophilized mussel and in a saxitoxin-enriched mussel material. The fir
st study revealed that three out of four postcolumn derivatization methods
and one pre-column derivatization method sufficed in principle to determine
STX and dc-STX. Most participants (13 of 18) obtained acceptable calibrati
on curves and recoveries. Saxitoxin was hardly detected in the rehydrated l
yophilized mussels and results obtained for dc-STX yielded a CV of 58% at a
mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified g
onyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study, led
to provisional criteria for linearity, recovery and separation. The second
study revealed that 6 out of 15 laboratories were able to meet these crite
ria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of
3.49 mg/kg. Results obtained for STX in the saxitoxin-enriched material yie
lded a CV of 19% at a mass fraction of 0.34 mg/kg. Saxitoxin could not be d
etected in the PSP-positive material. Hydrolysis was useful to confirm the
identity of GTX-5 and provided indicative information about C1 and C2 toxin
s in the PSP-positive material. The methods used in the second interlaborat
ory study showed sufficiently consistent analysis results to undertake a ce
rtification exercise to assign certified values for STX and dc-STX in lyoph
ilized mussel.