Dear Iwo
Does everybody know that an instrument should be calibrated within its
operational range? I think your assertion is debatable. The standard
solutions recommended in the method are not intended to 'calibrate' the
instrument. They are intended to be used to provide a prediction line for
converting instrument readings to concentration and have been chosen to
represent a range in which most samples will fall. The procedure allows for
dilution of the extract if a sample falls outside of the domain of the
standard solutions.
Peter Howgate
----- Original Message -----
From: "Ko, Iwan Setiyono" <isk025@student.uit.no>
To: <seafood@ucdavis.edu>
Sent: Wednesday, March 15, 2006 12:26 AM
Subject: My inquiry to AOAC [Fwd: Inquiry on AOAC fluorometric method for
histamine content analysis]
Dear listers,
I forwarded my inquiry to AOAC regarding its fluorometric histamine
content analysis, to be more specific on fish and seafood products (found
on pp. 876-877 on their manual - see REFERENCES). Basically, I was asking
the (technical/scientific?) foundation(s) why the AOAC' expert(s) chose
these following three points in the calibration, and I am still waiting
for their response. Anyone checked their 1995-version manual?
If it is merely (pure) example, they should have incorporated further
information on this. I suppose that almost everybody knows that equipments
shall be calibrated within their operation ranges. In this case:
calibrating points chosen within 0 to 50 ppm (or larger) range may be more
representative.
The implication the AOAC manual might cause is that the commercial fish
and seafood industries might interpret the method as it is, i.e. the
"official" method. Tons of fish and seafood processors exporting products
to the US may use the AOAC's histamine fluorometric test as it is
considered as the official method recognized by the US FDA (Rogers and
Staruszkiewicz, 1997**)
---------------------------- Original Message ----------------------------
Subject: Inquiry on AOAC fluorometric method for histamine content
analysis From: "Ko, Iwan Setiyono" <isk025@student.uit.no>
Date: Tue, March 14, 2006 2:26 am
To: rrathbone@aoac.org
--------------------------------------------------------------------------
Dear Dr. Rathbone,
I want to ask you technical questions regarding AOAC's fluorometric
method* for histamine content analysis.
"Histamine std solns.-.... (1) Stock solution 1 mg/mL (1000 ppm; assumming
solution density of 1 kg/L)....(2) Intermediate soln. 10 ug/mL (10
ppm)....(3) Working solns. 0.5; 1.0, and 1.5 ug/5 mL......"
My question is:
--------------------------------
Why in the manual, 0.1; 0.2; and 0.3 ppm are selected as the calibrating
points? Why don't we calibrate in the designated range in which
fluorometer will be used, e.g. from 0 to 60 ppm?
REFERENCES
* AOAC. 1990. Histamine in seafood: fluorometric method. Official Method
of Analysis - AOAC. Vol. 2 Food Composition; Additives; Natural
Contaminants. 15th ed. AOAC, Arlington. 1298 pp. (pp. 876-877).
** Rogers, P.L., and Staruszkiewicz, W. 1997. Gas chromatographic method
for putrescine and cadaverine in canned tuna and mahi mahi and
fluorometric method for histamine (minor modification of AOAC Official
Method 977.13): collaborative study. Journal of AOAC International, 80(3):
591-602.
Thank you for the help.
Best regards,
Ko, Iwan Setiyono (Ko, I.S. - ISK)
MSc Candidate - Int. Fisheries Management
E-mail : isk025@student.uit.no
Phone : +47 77 64 60 00
Fax : +47 77 64 60 20
Mobile : +47 45 00 40 97
Visiting address:
Room A-374
Norwegian College of Fishery Science (NFH)
University of Tromsų - Breivika N-9037 Tromsų
NORWAY
This archive was generated by hypermail 2b29 : Wed Mar 15 2006 - 06:38:11 PST