ICUMSA News n°17 – 1993

Message from the President

The Constitution and By-Laws for our Commission is a living document which sets out the objectives of the organisation and the rules under which we operate. It is amended from time to time to reflect changes we find necessary in the light of the new circumstances. Unfortunately, we do not make all the amendments necessary to reflect these changed circumstances, so many parts of our Constitution are quite out of step with what is practised. Your President, in collaboration with John Oldfield t (UK), is working up revisions which it is proposed will be presented at the 21st Session for final approval.

The revisions fall into three classes:

I. A number of changes which by virtue of long-standing practice will be readily accepted by our membership.

Some examples of the changes proposed here are: Our Proceedings have only ever been produced in the English language, yet the By-Laws call for their production in English, French and German. We propose to formalise the production in English only. There is confusion in the wording concerning the election of honorary members. It is proposed that one or more honorary presidents, vice-presidents and general secretaries may be elected.

2. A few substantial changes which already have the membership’s agreement in principle:

An example would be the fomalising of the requirement that Official methods be collaboratively tested according to the IUPAC protocols.

3. A number of changes which have not yet been extensively debated but which are considered desirable for the effective working of the Commission.

In this category it is proposed that the rules for voting be extensively revised. On one hand the words in the present Constitution and By-Laws are ambiguous in that majorities are sometimes expressed in terms “of the members voting” and at other times in terms “of the votes of the members”. We believe that all majorities should be expressed according to the latter term.

It is further proposed that it be made easier to satisfy the requirements of adopting an Official recommendation by letter ballot. The present requirement for unanimity is in practice very difficult to achieve, since some National Committees are very slow to respond to requests to cast their ballots. A new requirement of three-fourths of the votes cast is being sought. This is the same majority that is called for if the vote were held in plenary session.

Any members wishing to study the details of these revisions should keep in touch with their Chairman of National Committees or request a copy of the proposals from the General Secretary.

General Subject 4

Analytical methods for molasses and laboratory accreditation

by Clive Shelton, Referee

Much effort has been taken over the last few decades to develop new repeatable and precise methods of molasses analysis and to find the relationship between results obtained by different methods. This Session, however, a target should be to progress the core methods to completion for the next Conference and to have started by drafting the traditional copper reduction methods into the ISO format. The drafts are presently under discussion with Associate Referees and it is hoped to have received all their comments by December 1992.

Those who criticise the use of non-specific methods of analysis for molasses should understand that for contractual purposes these methods are the most suitable. They give good agreement between laboratories and do not therefore cause as many problems between seller and buyer as would other methods.

The work which ICUMSA is undertaking to rewrite the Methods Book mirrors what is happening across Europe at the present time. The completion of the internal market in January 1993, with no technical barriers to trade, means that testing and inspection procedures are having to be agreed between scientists in different member states. Thus, the new volume will be welcomed by those prescribing official methods for the EEC. Of course, it will be up to individual laboratories to prove that they can apply the new methods correctly and in Europe the subject of Analytical Quality Assurance is not far from any laboratory manager’s mind. (Editor’s note: ICUMSA News n° 14 contained an article on “Laboratory Proficiency”).

The methods in preparation are as follows:

1) Reducing Sugars – Lane-Eynon – Cane and Beet Molasses

2) Reducing Sugars after hydrolysis – Lane-Eynon – Cane and Beet Molasses

3) Sucrose content – Clerget

4) Dry Substance – vacuum oven on sand

5) Dry Substance – hydrometric

6) Dry Substance – refractometric

7) Ash

Comments on any of the methods would be welcomed. The methods are taken from current ICUMSA publications and incorporate amendments made during recent ICUMSA Sessions.

On a more personal note, I have been involved with the UK laboratory accreditation process for a number of years and the molasses analysis in my own laboratory is accredited by the UK National Measurement Accreditation Service (NAMAS).

The NAMAS Standard follows the requirements of the EN45000 series of standards which are the harmonised standards for laboratories within the EEC. Laboratory accreditation according to the scheme involves full documentation of administrative and testing procedures, full traceability of calibrations to national standards and comprehensive analytical quality control procedures. Laboratories are assessed for compliance with the NAMAS requirements by technical experts as well as officers of the NAMAS executive. Reassessment occurs every 12 months and a laboratory’s accreditation relies upon any non-compliance with the standard being rectified.

The new ICUMSA Methods Book will greatly reduce the work needed for laboratories to achieve accreditation in Europe and the rest of the world and it is certain that the methods included in the volume will be ranked highly within accrediting organisations.

Subject 10

Enzvmatic and immunological methods

by Stephen J. Clarke (Audubon Sugar Institute, USA)

Analytical systems involving biochemical reagents are now dealt with by Subject 10. The scope of the methods includes any which involve enzymes or immunological reagents, particularly those which do not fit within any other Subject. A role of the scientific Subjects is to study the feasibility of such new procedures for application in the General Subject areas. The logic of putting enzymatic and immunological procedures together is that both employ the unique specificity of biochemical systems, thereby making possible the estimation of individual components within complex mixtures, often with the component of interest at very low concentrations. A second potential advantage of these procedures is their rapidity, especially when they are made automatic, but this can lead to high instrument cost.

Specialized techniques are involved which are often quite different from those familiar to the regular sugar laboratory analyst, though not necessarily more difficult. This situation makes research very diverse with individual laboratories pursuing their own interests. Recommendations made at the 20th Session of ICUMSA in Colorado Springs in 1990 were that a series of criteria be established for the standardisation of both enzymatic reagents and immunological reagents. Discussion of these criteria continue, including such factors as the specificity and purity of the reagents. With the more accepted enzymatic procedures, there is growing consensus about these factors, but many problems remain with immunological reagents.

Enzymatic procedures are the more established and are becoming a valuable component of the sugar analyst’s set of methods. Problems continue in the areas of standardization and reproducibility, even when the systems are automated, a necessity if the methods are to become routine. For example, a recent evaluation by several laboratories of an automated sucrose (and glucose) analyser (Sarkar and Day, 1992) confirmed that the system is of value in process control and estimation of sugars in effluents, but is unsuitable when quality control and/or payment systems become involved. Given the inherent inaccuracies in handling small liquid volumes, electrode responses, etc., it is doubtful whether the reproducibility of methods such as Pol determination can be achieved. It may be necessary to establish a distinct set of criteria for data evaluation as well as for reagents.

At present there are no commercially available antibody (immunological) reagents suitable for use in areas of interest to sugar producers. Most of the interest to-date has been in determination of dextran, with each research group producing its own material, either polyclonal or monoclonal, and also developing their own techniques, e.g. ELISA, turbidimetric, etc. Useful methods can only evolve by collaboration, especially on sources of reagents. The reliability of the source and reproducibility of reagent quality must be looked at carefully. This has been a problem for the Referee’s laboratory in Louisiana, where a simple turbidimetric procedure is used by several mills to determine dextran levels in delivered cane. High reagent costs reduce the quantity that can be used for each analysis, thereby reducing their accuracy. The method is very good for indicating the quality of the cane but reproducibility at present is too poor (± 20%) for a serious collaborative test. This type of problem will remain with immunological systems until a reliable commercial source of reagents is developed.

One of the roles of ICUMSA is to determine what should be the qualities of such reagents. Work is continuing in this area and the Associate Referees are being circulated for their opinions on reagent and method specifications.


Sarkar, D. Day. D. F. (1992): Analysis of Molasses and Sugar by YSI 2700 Select. An Interlaboratory Study. Report to US National Committee.

Editor: Dr. R. Pieck, Donystraat 85, B-3300 Tienen, Belgium -Telephone +32 16 823 096- Fax: +32 16 820 826-Telex: 27105