Editor: Rud Frik Madsen,
Message from the President
I am pleased to inform you that the difficulties we have encountered with the preparation of the Proceedings have now been overcome and the camera ready copy film will be sent by express courier to the printer before the middle of December. Given no hold ups from CPL, the printer, the Proceedings should be available early in the New Year.
As I pointed out in my last message, activity on the various Subjects is already occurring, and I ask both Referees and Associate Referees to accelerate this activity by exchanging information and suggestions, if necessary utilising references available on the internet site www.unife.it/icumsa . Any proposal of improving our web site including updating of information correction of errors or omissions will be welcome.
Owing to the depleted stocks we are arranging reprinting of the ICUMSA Methods Book making the corrections which were noted as under “Errata” in the previous edition. The new volumes will include the page dividers which can also be obtained by the owners of the old edition of the ICUMSA Book on request via e-mail (email@example.com) or fax (+39 0532 291168). In addition, we are arranging the production of the “2000 Supplement” which will include the new methods and the ones revised after the Berlin Session. I would like to take the opportunity once again to thank Mr. John Dutton for his invaluable contribution to the reprinting of the ICUMSA Methods Book and the technical editing of the “2000 Supplement”, as well as his availability for maintaining and improving contacts with other organisations and acting as an intermediary for the setting up of the Proceedings. His wide experience over many years of enthusiastic activity within ICUMSA makes his cooperation not only valuable but essential.
In close cooperation with our Honorary Life President Dr. Murray Player and the Associate Referees of Subject 1 – “Constitution and By-Laws” – , we have prepared a revised text of our Constitution with the aim of considering the possibility of establishing a General Secretariat. This new structure would amalgamate the different facets of our organisation so simplifying all the activities, in particular ICUMSA publications. The final text has been submitted to the National Committees for approval and their vote is expected before the end of December 1999. The result this vote and, if it is favourable, the text of the amendments to be made to our Constitution, will be reported in the next edition of ICUMSA News.
Progress Report for Subject 6: Indirect methods of analysis
Jale Leblebici (Turkey), Referee for Subject 6.
Until May 1998 the title of Subject 6 was ”Spectrophotometry”. At the 22nd Session ICUMSA agreed to replace the Subject of Spectrophotometry by ”Indirect Methods of Analysis” dealing with indirect analytical techniques such as NIR spectroscopy. I was nominated as Referee for the new Subject in December 1998. The scope of the new Subject was made clear in communications to me.
The new Subject 6 covers analytical methods which can be applied by means of an instrument such as a NIR Spectrometer, or an automatic moisture meter, which need calibration by means of a traditional analytical method
Because very simple preparation is needed, NIR spectroscopy has become a popular technique in the world. Many papers on NIR spectroscopy have been written in the sugar industry as well as other industries. However, there are some problems with this technique.
Each scientist has been using his own calibration and his own instrument. It is difficult to use a universal calibration for one kind of sample using different kinds of NIR instrument having different sophistication levels.
For a universal calibration the sample set must have a large range. If the range of samples is larger, the correlation will be less satisfactory. If, on the contrary, the range of the sample set used for calibration used for calibration is close to that of the samples of interest the correlation will be more satisfactory and the results more accurate. That is the dilemma of NIR spectroscopy.
Another problem of NIR spectroscopy is that only a NIR spectroscopic method based on an instrument, which requires calibration with a series of samples, which have already been analysed by traditional methods, can be accepted as an official method. Otherwise it can only be used for routine factory control.
Notwithstanding this conflicting situation, AOAC has accepted NIR methods for fibre and protein in animal feed
In spite of the problems stated above, a collaborative test could be planned. For this purpose, the correct type of sample must first be chosen. Up to now beet, cane, pulp, factory juices, molasses and white sugar have been used as samples for the determination of several parameters, mainly dry matter and polarisation.
Beet, pulp or factory juices are samples that need some preservation in order to transport them from place to place without changing their original composition, Therefore molasses or white sugar could be chosen as samples to be used to carry out a ring test. Since the origin of molasses (beet or cane) may affect the accuracy of the calibration, white sugar should be chosen as the sample for the first ring test.
After that the parameter or parameters to be analysed must be chosen. Then the laboratories that can take part in a collaborative ring test must be specified.
Finally, if a ring test is planned, we need at least 8 laboratories, according to IUPAC protocol. With this in mind, I wrote to all associate referees of this subject to get their opinions and to estimate the number of collaborators available. Up until now, only two responses have been received.
If you have an NIR spectrometer in your laboratory, and if you want to take part in a collaborative test, or if you only have some ideas to share with me, please contact me by fax or mail as soon as possible.
Our President Professor G. Vaccari has given a paper on the “Second International NIR Users Meeting for the Sugar and Alcohol Industries” – August 1st to 3rd, 1999 – in Ribeirao Preto, SP Brazil on the problems and challenges of NIR analysis. We have tried to extract the main points in his interesting paper.
NIR Spectroscopy and the Official Methods of Sugar Analysis
My task is to sum up the ICUMSA point of view on the utilisation of NIR spectroscopy, and this is indeed a difficult task because there are, on this subject, conflicting opinions.
I propose to start my speech by describing, as briefly as possible, the chronicle of the impact of NIR on ICUMSA.
The first reference to the utilisation of NIR as an analytical method in the sugar industry was made in Cannes (France) at the 19th Session of ICUMSA held in 1986. Professor Mantovani, (at that time Referee for Subject 13 – “Dry Substance”), cited our work in Italy and that of Burzawa in France on the utilisation of NIR for the measurement of Brix and Polarisation of various sugar juices. This raised a problem by dividing the audience in two parts: in favour and against.
Among the most critical opinions were the following:
“Should ICUMSA be interested in methods that are based on apparatus which require standardisation with a series of samples which have already been analysed by other methods?”
“Although these methods are rapid, they are imprecise and are more suitable for production control purposes. Therefore, I do not think that it is ICUMSA’s job to carry out comparative tests between these instruments. It is ICUMSA’s task to produce reference methods that enable the value closest to the true value to be obtained.”
“I do not know whether ICUMSA should devote its activities to such a matter or leave it up to the factories to decide on which method to use”.
In favour were the following:
“I think that it is very important for ICUMSA to study the applicability of new methods like NIR”.
“I am glad that some work has been done on the use of near infra-red spectroscopy. We evaluated this technique and because of the simplicity and speed of the test we were very impressed with this technique”.
The discussion on this particular subject was concluded with agreement on the following Recommendation:
“Methods for the determination of water by means of near-infrared spectroscopy should be further studied”.
After this first impact of the NIR technique on ICUMSA, the interest of the sugar world in this new analytical technique became “explosive”. We cannot report all the work done within this subject. However, the conclusions are almost always that individual calibration is needed.
Professor Mantovani, in his Report for Subject 6 – Spectrophotometry”, in 1990 reviewed a long list of literature data relating to utilisation of the NIR technique. During the discussion following the presentation of the Report, Mr. Burzawa confirmed the excellent results obtained using NIR-spectroscopy. He showed slides demonstrating agreement between molasses solids and sugar content determined by this new technique in comparison with traditional methods.”
In my capacity of the Referee for Subject 17 – “Dry Substance” in 1990, I did, in my turn, of course, widely review the NIR technique for the moisture content of various products coming from beet and cane.
As may be seen by examining these various reviews from the 20th ICUMSA Session, there were very many references to the NIR technique but, during the discussions, no more criticisms or unfavourable opinions were raised. It was unanimously accepted that the technique was very favourably considered for the analysis of many sugar products.
At the 21st Session held in Havana, Cuba, in 1994, the NIR technique, as we can see in the following, had become so generalised that the opportunities for its utilisation was no longer a problem to be discussed.
Again, during this Session, many Referees reported on their experiences with the NIR technique.
The Referee for General Subject 6 – “Beet” reported the contribution from Huijbregts and Gijssel who utilised NIR for the evaluation of many parameters (sucrose, dry matter, marc, a-amino nitrogen, and extractability) in beet brei using near infrared reflection. As far as the evaluation of the sucrose content is concerned, these authors concluded as follows:
“This is not accurate enough for payment purposes”. The following Recommendation was also adopted by US National Committee: “The beet industry should continue to evaluate the utility, accuracy and precision of the determination of percent sugar by scanning NIR spectroscopy”. ”
Recommendation consequently adopted under General Subject 6 states:
“The development and examination of alternative routine and standard methods for the determination of sucrose (e.g. HPLC, Enzymatic and NIR spectrometric) should be encouraged in collaboration with the Referee for General Subject 8. In doing so, the individual steps of the methods should also be checked for causes of systematic errors.”
In my 1994 Report on Subject 5 – “Dry Substance” I tried to lay the basis for the definition of a status for the NIR technique proposing as follows:
“…we believe that such a technique could be adopted as an “Accepted method”. In fact, it fits, at least in regard to determination of moisture and dry substance of various products, the requirements of the “Report and Recommendations of the ad hoc Committee on Types of Methods”.”
Ultimately the following Recommendation was adopted:
“NIR spectroscopy for the determination of moisture should be further studied to decide whether collaborative studies are feasible.”
A large part of the Report from the Referee for Subject 6 – “Spectrophotometry” concerns NIR spectroscopy with 20 citations of papers published between 1990 and 1994. Even so, the Recommendation adopted was as follows:
“Near infrared spectrophotometric methods should be further studied.”
In Berlin in 1998 the Referee for General Subject 5 – “Cane”, reported that:
“In Sao Paulo, Brazil, cane payment laboratories at the Copersucar mills are using NIR for cane juice analysis”
Moreover, the Referee pointed out that Shäffler and De Gaye obtained very good results for both cane juice and shredded cane analysis. The Recommendation was:
“Investigation into the application of near infrared spectrometry to cane and cane juice analysis should be continued.”
Concerning the evaluation of some quality parameters of beet, the Referee for General Subject 6 – “Beet” reported results, obtained by various authors, which were, though only in some cases, better than those discussed in previous Sessions.
Even at this Session, great deal of literature data concerning NIR technique, which is not reported here for the sake of brevity, was cited in the Reports for Subjects 5 – “Dry Substance” and Subject 6 – “Spectrophotometry”.
In particular, in my 1998 Report for Subject 5, in which I pointed out my unsuccessful attempt to organise a ring test for the determination of dry substance using NIR, I quoted some of the most meaningful comments on this subject received from some Associate Referees. In particular, I consider it useful to report here a part of a letter sent to me by Dr. Nguyen:
“We would like to draw your attention to those potential difficulties in considering methods based on NIR spectroscopy to be used for ICUMSA.
If no suitable universal calibration can be found, a comparison of results from different laboratories using the best local calibration may give an indication of how well this method can work in individual laboratories. If such is the case, the method would be dependent on the soundness of the local calibration, which would depend on:
The calibration samples adequately represent population to be analysed.
Accurate reference results are available.
The use of appropriate data processing technique to construct the calibration.
The selection of correct wavelengths.
The use of suitable instruments. We believe that some instruments, because of better sampling accessory design, for example, can achieve better results than others.
I suggest that the first step forward would be to collate all data available from the various sources in the sugar industry to determine what is being done and what is achievable.”
Dr. Madsen the Editor of “ICUMSA News”, commented on my last short report in ICUMSA News No. 31 using these words:
“My personal opinion is that these methods have similar characteristics to RDS and conductivity ash, for example, neither of which give the exact dry substance or the gravimetric ash, respectively. All such methods can be made Official providing they stand up to collaborative testing”.
As a conclusion to my Report presented in Berlin on “Dry Substance” I tried to stimulate the audience to discuss a first attempt at organisation of a ring test:
“It is clear that such new analytical techniques, although presenting advantages compared with the time-consuming oven-drying method, need to be properly calibrated by utilising the Official reference methodology. Such a situation creates problems in order to conduct ring tests, as well establishing the Status to be applied to these techniques.
As far as the realisation of the ring test is concerned, a possible solution, although to be attentively discussed, could be as follows: 1) the person coordinating the ring test should collect a series of samples (i.e. 80) having different origins and compositions and analyse them using the Official methodology; 2) a part of such samples (i.e. 50) should than be carefully sent to the participants so that they can prepare calibration curves using their own spectrophotometer (using the analytical data given by the coordinating person); 3) after having collected all the calibration parameters sent by the participants, the coordinating person (after data evaluation from the statistical point of view) sends the other 30 samples for the validation test.
If the results of the ring test were to be acceptable from the statistical point of view the method could be accepted as Official. The various standardisation parameters or calibration curves set up by the different laboratories included in the ring test could be given to those laboratories which plan to buy new instruments. It should be mentioned that it is now possible to transfer calibration curves set up using a particular NIR instrument to another one even though they are manufactured by different companies.”
In the discussion, Mary An Godshall, Referee for Subject 3 – “Method format, collaborative testing and statistical treatment of data” pointed out that this matter is not to be solved easily and suggested studying the problem in a new Subject.
This new Subject “Indirect Methods of Analysis” has been set up and the Referee is Mrs. J. Leblebici from Turkey.
Now we have to wait for the Report on this Subject at the next Session of ICUMSA, which will be held in India in 2002.