Determination of morphine in poppy capsules

Sections

Reagents and Solutions used
DESCRIPTION OF THE METHOD
CHECK ON THE METHOD
Summary

Details

Author: Giuseppe Pruner
Pages: 34 to 36
Creation Date: 1958/01/01

Determination of morphine in poppy capsules

Giuseppe Pruner
Biological Laboratory, Istituto Superiore di Sanita, Rome

The method here described is based on the same principle as that described in an earlier note (1) on the determination of the morphine in opium. The results obtained were compared with those given by Wüst & Frey's weighing method (2) performed on the same poppy capsule samples by chemists of the Hoffmann - La Roche Company.

Table 1 summarizes Wüst & Frey's method, which is very time-consuming and requires a large quantity of organic solvents, and the much simpler and quicker cerimetric method. As to accuracy, the results obtained by the cerimetric method compared with the results obtained by the La Roche chemists can be considered satisfactory, as will be apparent from table 2. Although the first sample, No. 58, gave a negative result in Wüst & Frey's analysis, the presence of morphine was detected by the cerimetric method and confirmed by the industrial alkaloid yield.

The dry capsules of Papaver somniferum and of other varieties commercially known as poppy straw (Mohnstroh) are the waste parts - useful only as fuel - of the dry plant after its seeds have been removed for the extraction of an edible oil.

An industrial method for extracting morphine directly from the poppy plant was first evolved by the Hungarian scientist Janos von Kabay in 1933, and was developed in Poland, Germany, Russia and other European countries.

New and cheaper sources of edible oils have now reduced poppy cultivation in Europe to such an extent that the industries using this raw material are in difficulties.

The peasants of the Upper Etsch in Italy have grown poppies from time immemorial just for their seeds, which, when ground and sugared, are used in traditional confectionery such as, for instance, "Mohnstrudel ".

TABLE 1

Wüst & Frey's weighing method

 

Cerimetric method

 
Pulverized poppy capsules, 200 g
 
Pulverized poppy capsule, 5 g
 
1. Hot extraction with acid alcohol
1,000 cc
Extraction with H 2O
170 cc
Washing with alcohol
500 cc
 
 
 
 
Purification phases of the aqueous layer:
 
2. Hot extraction with acid alcohol
1,000 cc
 
 
Washing with alcohol
250 cc
1. Filtration on acid aluminium oxide
20 g
Concentration in vacuo to 120 cc; treatment with CaO,
 
 
 
H 2O q.s. for 400 cc; treatment with Na 2CO 3, HCI and
 
2. Concentration to 20 cc and treatment with Ca(OH) 2
 
Na 2CO 3
 
 
 
 
 
3. Purification with lead acetate
 
3. Extraction with butylbenzene alcohol
750 cc
 
 
 
 
4. Treatment with sulphuric ether
20 cc
4. Extraction with 30 cc of 2 % H 2SO 4.Washing with 30 cc
 
 
 
sulphuric ether
 
Dilution with buffer solution having a pH factor of 10,
 
Precipitation with Na 2CO 3.Washing, drying and weighing
 
addition of potassium ferricyanide solution, and titration
 
of the morphine
 
with N/200 Ce(SO 4) 2, with ferroin as indicator
 

Dry poppy capsules collected at 1,500 m in the Dolomites last summer were found to have a morphine content of 1.29 ‰, a very low value compared with the Hoffmann-La Roche samples.

Opium production in Europe has been the subject of experiments in a number of countries, and a good morphine content was obtained; but efforts to start up large-scale production failed because of high labour costs, since thousands of capsules (about 40,000 per kg of opium) have to be cut, and the opium collected afterwards.

The note (1) previously mentioned described the difficulties found in early efforts to apply the same method as is used to determine morphine in opium to poppy capsules, for have a low morphine content of (on the average) 1 ‰ to 60 ‰, they and contain many other substances which have to be eliminated. Apparently, these difficulties can be overcome by providing an acid A1 2O 3filtration of the aqueous extract of the capsules.

The same note also mentions narcotoline, which was thought to be present only in poppy capsules, but was recently found by Pfeifer (3) to be a constituent of opium too.

Porphyroxine meconidine, on the other hand, which is present in opium in amounts depending upon the source country, is apparently not present in poppy capsules, as was found in an origin study based on the determination of the alkaloid pattern (4).

Reagents and Solutions used

  1. N/200 cerium sulphate solution, Ce(SO 4) 2.4H 2O: About 1.10 g of salt are dissolved, in a 500 cc measuring flask, in about 250 cc of water to which 14 cc of concentrated H 2SO 4have been added. After complete solution the mixture is made up to the mark.

  2. N/200 solution of anhydrous K 4Fe(CN) 6: This is used to titrate the cerium sulphate solution, and is prepared freshly for each use, 0.3683 g of salt being carefully weighed out and mixed in 200 cc of water.

    Titration is performed as follows : 8 cc of the solution are acidified with 2 cc of HCl (solution 6) and are titrated, the N/200 Ce(SO 4) 2 solution flowing from a 10-cc semi-microburette in the presence of three drops of ferroin (solution 5), which changes colour very markedly from reddish orange to greenish yellow.

  3. 1% solution of K 3Fe(CN) 6.

  4. Buffer solution:

    Bisodium phosphate dihydrate
    4.138 g
    Anhydrous monopotassium phosphate
    1.415 g
    Anhydrous sodium carbonate
    4.285 g
    Distilled water q.s.
    1,000 cc
  5. M/40 solution of indicator (Ferroin). This is prepared by mixing 0.406 g of o-phenanthroline hydrochloride and 0.179 g of crystalline ferrous sulphate in 25 cc of distilled water. 1 cc is taken from this mother liquid and made up with water to 20 cc, the diluted solution being kept in a dropping bottle.

  6. Hydrochloric acid (50 parts by volume of concentrated HCl and 50 parts of water).

  7. 10% neutral lead acetate solution.

  8. 3.75% anhydrous sodium sulphate solution.

  9. Pure sulphuric ether free from peroxides and aldehydes.

  10. Pulverized hydrated calcium.

  11. Acid aluminium oxide for chromatography (C. Erba).

DESCRIPTION OF THE METHOD

5 g of poppy capsules in powder form are macerated for 15 minutes in a mortar with 50 cc of water; 5 g of acid alumina are added and mixing continued for 2 more minutes, when the contents of the mortar are poured into a centrifuge tube. After centrifuging at 2,000 rpm for 2 minutes, the liquid, together with the floating wood particles, is poured on to an 11 G 3 porous Jena glass filter containing 20 g of acid Al 2O 3and connected to a vacuum flask. The liquid should filter slowly through the layer of Al 2O 3.Using a pestle-like glass rod, the residue in the tube is mixed with 40 cc of water added a little at a time. Centrifuging and filtering are carried out as above. This treatment is repeated twice. The contents of the vacuum flask are poured into a glass capsule and the volume of liquid is reduced to about 20 cc by boiling on a water-bath. The capsule contents are poured into a centrifuge tube, cooled, and centrifuged for 2 minutes. The liquid is then transferred through a filter paper into a 25-cc cylindrical vessel with a ground-glass stopper; the capsule and residue in the tube are washed with sufficient water to make up to the mark.

5 g of Ca(OH) 2 is added to the cylinder, mixing is carried out for 2 minutes and the cylinder contents are then poured into a second centrifuge tube, and centrifuged for 2 minutes. The liquid is then filtered through paper into a second cylindrical vessel, of 50-cc capacity, with a ground-glass stopper. After the 20 cc have been added, 4 cc of lead acetate solution are added, the cylinder closed and its contents mixed. 4 cc of sodium sulphate solution are introduced 5 minutes later to precipitate the excess of lead. 12 cc of buffer solution are poured into the cylinder to bring the volume to 40 cc and mixing is continued for a few minutes. Filtration is then carried out.

10 cc of filtrate are taken up in a pipette and placed in a wide tube of about 50 cc capacity with a ground-glass stopper; 10 cc of sulphuric ether are added and the mixture agitated for 2 minutes, preferably by means of an agitating mechanism. After a few minutes, the layer of ether is taken up by means of a piston pipette, a further 10 cc of ether are added, agitation is continued for 2 minutes, and the layer of ether removed. Should the liquid become cloudy, it can be cleared by slight suction at the water pump.

5 cc of this aqueous liquid are sampled, transferred to a 25-cc flask, diluted with 15 cc of buffer solution, and filtered through paper into a second flask. Using a 5-cc pipette, the filtrate is divided up into 3 25-cc beakers which are placed in a water-bath at 20°C if the room temperature is different. This helps to keep the temperature as well as the time of the reaction constant. Using a 10-cc semi-microburette, 1 cc of potassium ferricyanide solution is introduced rapidly into each beaker. The oxidation reaction is stopped after 10 minutes by introducing 2 cc of HCl (sol. 6) into each beaker. Three drops of ferroin are added to each vessel, and the ferrocyanide formed during the reaction is titrated with N/200 cerium sulphate solution, which is dropped in from a microburette until there is a clear change of colour from reddish-orange to greenish-yellow.

The rotating-field electric agitator can be used advantageously for titration, with 12-mm plastic-covered magnetic rods.

The morphine content of 100 g of poppy capsules tested can be deduced from the formula:

M = Ce .
8 x l00
= Ce. 326
2.454    

where Ce denotes the average cc of cerium sulphate used in 3 or more titrations (less 0.10 cc for the control) multiplied by 326; 2.454 represents cc of N/200 cerium sulphate solution, equivalent to 1 mg of morphine.

CHECK ON THE METHOD

Ten samples of poppy capsules from different sources were used for this purpose. They had been dried at 70°C and pulverized by Hoffmann-La Roche, and were despatched in waxed dark glass bottles. The source of three samples was not shown, since they were mixtures of different batches.

Table 2 gives a comparison of the results obtained using the method described with the results obtained by Wüst & Frey's method, as used by the Hoffmann - La Roche chemists.

It will be noted that the cerimetric method gave lower values than Wüst & Frey's method in the case of the old samples dating from 1953, which would tend to confirm the observation made when analysing old opium samples that morphine oxidizes slowly in the course of time due, according to Abraham & Rae (5), to an oxidizing enzyme, opiase, leading to the formation of pseudomorphine (C 17H 18O 3N) 2 (6).

TABLE 2

   

Method

Difference

No.

Sample

Wüst & Frey

Ceri-metric

Absolute

Percentage

 
 
%
%
 
 
58
Austria (1954)
0.00 2.07
-
-
 
821 - 840 (26/9/56)
2.51 2.48
- 0.03
- 1.20
 
801 - 820 (20/9/56)
2.54 2.48
- 0.06
- 2.36
32
Yugoslavia (1954)
2.81 2.85
+ 0.04
+ 1.40
 
Mixture 1601-1602
3.39 3.45
+ 0.06
+ 1.80
26
Federal Republic of Germany (1955)
3.37 3.53
+ 0.16
+ 4.80
87
Federal Republic of Germany (1953)
3.70 3.62
- 0.08
- 2.20
16
Eastern Zone of Germany (1953)
4.18 3.95
- 0.23
- 5.50
33
Romania (1953)
4.64 4.26
- 0.38
- 8.20
36
Romania (1953)
4.45 4.22
- 0.23
- 5.20
     
Average...
±0.14
±3.63

The behaviour of this alkaloid in more conventional methods of opium analysis is being studied.

The reproducibility of the method is satisfactory, as will be apparent from the three analyses performed on sample 821-840: 2.48; 2.52; 2.45.

Thanks are due to Dr. Saenger, General Director of the Deutsche Hoffmann- La Roche of Grenzach, and particularly to Dr. W. Wasmer for supplying me with the ten samples for carrying out this investigation and with the respective analytical results.

Summary

A known cerimetric method for determining the morphine in opium was applied with suitable modifications to the determination of the morphine in poppy capsules.

The aqueous extract of the drug is filtered through acid alumina, concentrated and purified by consecutive treatment with lime, lead acetate and ethyl ether.

The results of the analyses of ten poppy-capsule samples from different sources are compared with the results obtained when Wüst & Frey's weighing method was applied to the same samples by the chemists of the Deutsche Hoffmann - La Roche.

References

001

PRUNER, G. Rend. 1st. Sup. Sanité, 19, 492 (1956).

002

WÜST, H. M. & FREY, A. J., Festschrift Emil Barell, p. 556, (1936), "Opiate aus Mohnstroh ", Hoffmann- La Roche.

003

PFEIFER, S., Arch. der Pharm., 290/62, 209 (1957).

004

United Nations Secretariat, ST/SOA/SER.K/4, 11/9/1951.

005

ABRAHAM, A. C. & RAE J., Amer. Journ. of Pharm., 99, 570 (1927).

006

BENTLEY, K. W., The Chemistry of the Morphine Alkaloids, Clarendon Press, Oxford, 1954.