2007 Workshop on chemical reference materials in ocean science

Survey

Improving the inter-comparability of nutrient measurements in seawater
Dear Fellow Marine Chemist

Please hit the reply button now! then read on and then replace my example answers to the questions I am asking with your answers when you get to them.

Attached is a brief report on a discussion meeting between various European marine chemists and Michio Aoyamma and Hidekazu Ota from Japan .
As follow up I would like to conduct a simple survey of what marine chemists around the world feel is the need for internationally recognised inter-comparison (tracer) materials, and what you do now to calibrate your system.
My plan is to include the anonymous results of this survey in a talk at the Eleventh International Symposium on Biological and Environmental Reference Materials, BERM 11, Tsukuba , Japan , October 29 - November 2, 2007
I would be very grateful if you would take few minutes to read on and then reply to my questions.

Many thanks for your time - which I hope will contribute to a much-needed advance in improving the way we make our measurements.


Best regards
David Hydes


The consensus of the meeting at NOC was that a reference materials were needed and that these should: - (A) be available in sufficiently large batch sizes to be "internationally certifiable" (B) be available in sufficient quantities and at low enough price to encourage the extensive take up of these materials (C) have sufficiently long shelf life (3+ years) to allow comparison between cruises that may be few years apart.(D) be available in range of concentrations to cover the ranges of concentration needed in shelf sea, Atlantic Ocean and Pacific Ocean work. (E) be based on a "real seawater" - a salinity of 35 was considered to be the most appropriate matrix. (F) have a homogeneity of 0.1% or better.
 "Certification" of the solutions could be provided in two stages.
Firstly the manufacturer would provide a number for each batch, an initial analysis and a webpage password.
The second stage would be that, using the password, the users would report their analysis of each bottle to the webpage. Software coupled to the page would automatically update the statistics for that batch. The user would then get back from the webpage information on:-
(1) Offset between their measurements and reported values for the batch (data from registered participants who agreed to report during a set time period) and weighted by the performance of the participants in previous inter-calibrations.
(2) Statistics for the homogeneity of the batch (on a yearly basis).
(3) Statistics for the stability of the batch over time (on a yearly basis).

Question 1 Do you agree with all or only some of the above statements?
Question 2 If not all which ones don't you agree with?
Question 3 Please tell me any comments you have?
6 more questions about how you currently standardise your nutrient measurements
Question 4
Do you use (A) standard solution prepared by yourselves (B) standard solutions prepared by an external organisation (C) both ?
Question 5
How many standards do use to calibrate each auto-analyser run ?
Question 6
How do you check for contamination of your auto-analyser "wash solution"
Question 7
Do you regularly participate in inter-laboratory performance studies such as QUASIMEME (www.quasimeme.org/) ?
Question 8
Do you already use an externally produced reference material such as the Canadian MOOS-1?
Question 9
Do you use an internal tracer solution to check for variations between auto-analyser runs.

Samples answers for my group at NOC

Question 1 Do you agree with all or only some of the above statements?
YES
Question 2 If not all which ones?


Question 3 Please provide tell me with any comments you have?


(1) UNESCO and IOC published reports in the early 1990s highlighting the need for nutrient reference materials but little progress has been made. I think the comparability of our measurements could be improved if a reliable reference martial was available.

(2) I think collecting information on and therefore knowing the stability of the batches of tracer solutions over time will be an important step forward in improving the comparability of data from one cruise to the next.

6 more questions about how you currently standardise your nutrient measurements
Question 4
Do you use (A) standard solution prepared yourselves (B) standard solutions prepared by an external organisation (C) both ?
We prepare standards from dry salts and do a comparison with standard prepared with OSI nutrient solution on each AA run. (www.oceanscientific.com/web/osil/osil.nsf/a/7C458D9FFB2538C880256D04004068A9!opendocument)
Question 5
How many standards do use to calibrate each auto-analyser run ?
We run 3 different concentrations in duplicate at the start of the AA run. Made up in the "wash" solution 40g/L Sodium Chloride. In a "V" formation to check for peak overlap. The set up of the instrument has been adjusted to give a linear output over the range of concentration being used.
The data is forced through the origin when the calibration is calculated so that " Wash "solution is the zero standard.
Question 6
How do you check for contamination of your auto-analyser "wash solution"
New batches of "wash" solution are compared to the previous batch. A sample of OSI "Low nutrient seawater" is also measured on each AA run to check for changes in the blank.
Question 7
Do you regularly participate in inter-laboratory performance studies such as QUASIMEME (www.quasimeme.org/) ?
We have participated in QUASIMEME but feel that a material that can be used to check every run would be useful
Question 8
Do you already use externally produced reference material such as the Canadian MOOS-1?
We did try using the Sagami standards but found that the homogeneity was poor.
Question 9
Do you use an internal tracer solution to check for variations between auto-analyser runs.
On deep sea cruises we include a tracer sample (from a bulk seawater sample) on each AA run. The data from these samples is included in the data report. But we have not back corrected our data to for variation in the measurement of this sample.