3.1.2. Method precision and accuracy
The recovery rate for free formaldehyde was obtained by
spiking formaldehyde into 5 g of sample matrix containing
known formaldehyde concentrations in triplicate for 3 days.
The same sample preparation procedure for free formaldehyde
was followed and detected by GCeMS. The recovery rate
and method precision for free formaldehyde are listed in
Table 3. The mean recovery rates for 9.2 mg/kg and 22.2 mg/kg
of spiked formaldehyde in 3 days were 108.88% and 103.61%,
respectively.
The method precision was determined by spiking two
formaldehyde standard solutions of 9.2 mg/kg and 22.2 mg/kg
in triplicate for 3 days. The results of the precision study
revealed that the intra-day repeatabilities for the two formaldehyde
concentrations were 1.61% and 1.16%, respectively.
The between-day precision values for the two formaldehyde
concentrations were 8.75% and 5.60%, respectively. The results
indicated that the precision and accuracy of the present
method are adequate for the determination of formaldehyde
in squid and squid products.
The recovery rate was also studied for free and reversibly
bound formaldehyde by spiking formaldehyde into a sample
of known formaldehyde concentration. By spiking 22.2 mg/kg
of formaldehyde, the recovery rate was 0% for 3 days. Therefore,
60 mg/kg and 120 mg/kg were used for the recovery
study. The recovery rates were 51.3% and 30%, respectively,
which were quite poor compared to the recovery rate of free
formaldehyde. The between-day precision values for the two
formaldehyde concentrations were 26.97% and 60.97%,