Editor: Rud Frik Madsen
Message from the President
The activity of the Presidency in these first months after the Berlin session has been rather full and demanding, due to the considerable changes which followed our last meeting.
The change of the Presidency and Secretariat represents, as such, a busy time for the new administration. However, I must acknowledge with gratitude the help I have received from our past President, Dr. Murray Player, during the handing over of duties. This assistance has been most valuable. Dr. Player passed on to me all the information he had collected, as well as leading and advising me in this first period of my Presidential activity. Special thanks must also be given to Mr John Dutton who, although resigning as Chairman of the Publications Committee, has helped, and goes on helping me, in the reorganisation and management of ICUMSA publications. This was indeed one of the most important questions to be faced after many years of continuous service by British Sugar and later by Mr. Dutton, on behalf of our Commission. The solution of this problem, as well as of the others we mention below, has been chosen with the aim of streamlining as much as possible the activities of ICUMSA from both the organisational and economic points of view. As part of this reorganisation future sales of publications have been entrusted to International Media Ltd, publisher of the International Sugar Journal, and it was indeed a demanding job to convey to Port Talbot the various ICUMSA publications stored at several different locations in England. From now on International Media Ltd will store all the publications and they will be responsible for receiving orders and mailing the relevant material.
The change in the format of the Proceedings which was agreed upon in Berlin on economic grounds, has called for the evaluation of different options. The new Chairman of the Publications Committee, Eng. Philip Atherton, will prepare in Australia the camera-ready copy of the Proceedings which will be printed, this coming spring, by CPL Scientific Ltd in England, who produced the 1994 ICUMSA Proceedings.
We have also committed ourselves to following the suggestions given in Berlin for easier and more rational arrangement of the Methods Book. In particular, we have carried through Dr. Pollach’s proposal of adopting thin card page dividers and these are now in the press. Such page dividers, which will obviously be included in the new edition of the 1998 Methods Book, can even be provided to owners of the old edition. They may be obtained asking us via fax or e-mail at our address in Ferrara (fax: +39 0532 291 168; e-mail: firstname.lastname@example.org).
In Berlin, the need to have a site on the Internet containing all the information on our Commission, to give easy acces to both the knowledge to its aims and to contacts (National Committees, Referees and Associate Refereees) was emphasised. Thanks to the free-of-charge facilities of the University of Ferrara, a web page is now ready, and this can be found at the address “http://www.unife.it/icumsa”. Such a page, which will be updated every 4 months to coincide with the publication of “ICUMSA News”, may, of course, be modified and suggestions for the future content of this page will be wellcomed.
The question of creating a General Secretariat, as suggested in Berlin, has been discussed with the past-president Dr Player. A proposal has been drawn up which we believe must first be discussed with the Associate Referees of Subject 1 – “Constitution andby-laws”, before being considered by National Committees. We are waiting for the complete list of the Associate Referees before taking the next step.
During the last months we have tried to reallocate the different Subjects and appoint the relevant Referees. The list of Referees so far appointed is as follows:
|GENERAL SUBJECT||PROPOSED REFEREE|
|1. Raw sugar||R. M. Urquhart (Australia)|
|2. White sugar||G. Parkin (United Kingdom)|
|3. Specialty Sugars||M. Burge (United Kingdom)|
|6. Beet||M. Kunz (Germany)|
|7. Cane Sugar Processing||O. L. Crees (Australia)|
|8. Beet Sugar Processing||J.-P. Lescure (France)|
|9. Starch Derived Sweeteners||D. Spruyt (Belgium)|
|1. Constitution and By-Laws||G. Vaccari (Italy)|
|2. Oligosaccharides and Polysaccharides||K. Thielecke (Germany)|
|3. Method Format, Collaborative Testing and Statistical Treatment of Data||M. A. Godshall (United States)|
|4. Density, Optical Rotation and Refractive Index||J. Keitel (Germany)|
|5. Dry Substance||………………………………………….|
|6. Indirect methods of analysis||J. Leblebici (Turkey)|
|7. Colour, Turbidity and Reflectance Measurements||………………………………………….|
|8. Chromatographic Techniques for Sugars||K. J. Schäffler (South Africa)|
|9. Chromatographic Techniques for Non-Sugars||P. Bourlet (France)|
|10. Enzymatic and Immunological Methods||S. J. Clarke (United States)|
|11. Rheology||R. Broadfoot (Australia)|
|12. Microbiology||E. Stoppok (Germany)|
|13. Reducing Sugars||………………………………………….|
|14. Ash||J.-P. Ducatillon (France)|
Nominations for the five vacant Refereeships are being sought urgently by means of a circular letter.
Sampling and the Choice of Samples for Collaborative Testing
Mary An Godshall, Referee for Subject 3
It goes almost without saying that the choice of samples for a collaborative test is among the most fundamental of issues for a successful outcome, perhaps the most important. Yet, within ICUMSA, we have placed very little emphasis on sampling. In the future, we should consider this important subject in greater detail.
Think about this – within ICUMSA, a collaborative test is planned with the hope for result that the method will become an Official method, and possibly an international regulatory standard. How are the samples chosen for such an important undertaking? Essentially, the answer is, in whatever manner the Referee chooses because he has no guidelines or standards to follow. He may have experience with another organization and follow their guidelines. Because he is probably an excellent analytical chemist, he may instinctively understand the demands of the task and choose good samples. Nevertheless, in actuality, the ICUMSA Referee has no guidelines or standardized procedures to help him.
According to Frederick Garfield, Association of Official Analytical Chemists (AOAC), “Sampling, in particular, and sample preparation for analysis are often the least considered steps in solving analytical problems in spite of the fact that they may be the most significant factors and the largest source of error.” 1
During the last several ICUMSA sessions, some problems with collaborative tests arose because of the samples. In one case, a test failed because a sample was spiked with an analyte, and this changed the sample characteristics to such an extent that the test could not be successfully carried out. In other instances, the concentration range of the analyte in some of the chosen samples was outside the range of capability of the method. Determining the range of a method is another fundamental area of method development, and it is gratifying when a collaborative study confirms this information, but it should only happen if that is the intent,and the other samples should be sufficient to carry the test in the usual manner. Ideally, the Referee chooses samples that encompass the entire range of the method, but none that fall outside the range of the method.
IUPAC (International Union of Pure and Applied Chemistry) defines a sampling plan as a “predetermined procedure for the selection, withdrawal, preservation, transportation and preparation of the portion to be removed from a lot as samples, whereby mathematical treatment of the test values or observations yields an estimate for the concentration of an analyte or for a property determined with a degree of uncertainty as a specific confidence level.” 2
Today, most of the accrediting programs and associations (ISO, IUPAC, Codex Commission, Association of Official Analytical Chemists, American Oil Chemists Society, American National Standards Institute, International Dairy Federation, the International Commission on Microbiological Specifications for Foods, to name just a few) have standard protocols for sampling their products. However, this is a slightly different subject from choosing the samples for conducting a collaborative study. The above sampling protocols assume a method already exists for a specific range of analyte, and the emphasis is on obtaining a statistically representative sample for analysis.
In discussing sampling, a number of points are to be considered: How to obtain a representative sample from a larger sample; how to obtain a homogeneous sample; how to handle the sample once it has been obtained to assure it does not change or deteriorate; how to distribute the sample to collaborators; how to store it and how long can it be stored.
Another troublesome sample-related area is that of conducting tests on unstable materials. In the sugar industry, we are fortunate that most of the samples dealt with are quite stable — crystalline sugars and highly concentrated syrups and molasses. However, there are few reliable guidelines on conducting tests on unstable materials such as cane and beet juices. This issue was discussed at the 20th session in 1990. 3 Again, organizations such as the International Dairy Federation and AOAC require that unstable samples undergo collaborative testing in the usual manner, which means that the sample has to be preserved in some way that retains its essential characteristics.
Samples may be preserved by freezing and distributed by express delivery services, a chemical preservative may be added, it may be pasteurized, irradiated, canned or freeze-dried; but in every case, its essential characteristics must be retained. Deciding on how to preserve, store and transport samples is, in many cases, a research projectunto itself. What is the best preservative for cane juice, for example? Will the preservative interfere with the analyte under examination?
At one time, freeze drying of cane juice was advocated as a way to stabilize it for transportation for collaborative studies. It is an interesting concept, but, again, we just don’t know the answer unless the preliminary studies are done to show that it works or does not work. Whatever method is used, a considerable amount of research is required to determine its feasibility.
In lieu of handling difficult samples, ICUMSA has in the past, taken a different approach – that is, to consider molasses, usually a very stable product, as a surrogate for many other types of sugar products. Thus, a method accepted for molasses was sometimes extended to other matrices. This is less and less the practice and has essentially been abandoned.
Three basic types of sampling are recognized 1, 4: Probability sampling (with subtypes including simple random sampling, stratified sampling and systematic sampling), Nonprobability sampling (subtypes include judgement sampling, convenience sampling and restricted sampling) and Bulk sampling. A detailed discussion of each type of sampling is beyond the scope of this presentation, but it is likely that the type of sampling used by most ICUMSA referees is either judgement sampling (the sampler uses personal judgement and experience) or convenience sampling (sample is chosen on the basis of accessibility, expediency, cost or other reasons not directly concerned with statistical sampling procedures). These sampling procedures require a great deal of care (i.e, judgement) on the part of the organizer to choose good samples.
What does ICUMSA have to say about sampling? Subject 2, Weighing, Taring, Sampling, and Classification of Sugar, came into being at the 9th Session (London), 1936, under Frederick Bate’s presidency, and continued until the 19th Session, 1986, as Subject 3, Sampling of Sugar and Related Products. It was dropped as a subject in 1990 when the new format for methods, divided into General Subjects (commodity based) and Technical Subjects (analyte or technique based) was adopted. It is noted that in 1986, there were three subjects dealing in some way with testing procedures: Subject 2, Laboratory Apparatus, Subject 3, Sampling of Sugar and Related Products,and Subject 4, Specifications and Tolerances for Pure Sucrose and Reagents. These subjects are now presumably addressed, as appropriate, within individual General or Technical Subjects.
Recommendation 3, in the 1994 report of Subject 3 (Method Format, Collaborative Testing and Statistical Treatment of Data) addressed some issues related to sample selection in collaborative studies: “In collaborative testing, great care must be taken with sample selection, distribution and handling. There should be only a single preparer of samples, samples should be sent out together at one time, and blind duplicates should be used whenever possible4 “
Another area where one begins to appreciate the importance of good samples is in the case of a proficiency scheme. The sampling scheme can be very complex because (1) a large amount is needed for distribution; (2) issues of stability, transportation and storage have to be addressed and understood for every sample; (3) samples must be representative, homogeneous, etc.; (4) a protocol for how long to keep a particular sample has to be established; (5) decisions on where the samples will come from or who will supply them have to made. The samples are of ultimate importance because the accreditation of a laboratory may depend on the results obtained from the samples in comparison to the results from many other laboratories, and decisions are made within companies depending on the results. One wants to be confident that conclusions are based purely on the analytical results and not on any questionable practices regarding the samples.
If (or perhaps, when) proficiency testing comes to the sugar industry, the choice of samples, again, will be very important. Perhaps it is time for ICUMSA to devise a protocol for selecting samples that are to be used in a collaborative study.
1. Garfield, F. M. Sampling in the analytical scheme. (1989) J. A.O.A.C., 72, 405-411.
2. “Nomenclature of Sampling in Analytical Chemistry” (1987) International Union of Pure and Applied Chemistry.
3. ICUMSA Proceedings, 20th Session,1990, pp. 139-140.
4. Springer, J.A. and McClure, F.D. Statistical sampling approaches. (1988) J. A.O.A.C., 71, 246-250.
5. ICUMSA Proceedings, 21st Session, 1994, p. 229.
Mary An Godshall
Sugar Processing Research Institute Inc.
1100 Robert E. Lee Boulevard
New Orleans, Louisiana 70124, USA