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IS 14626 (1999): Method for Determination of Total BromideResidues in Grains and Food Commodities Fumigated withMethyl Bromide [FAD 1: Pesticides and Pesticides ResidueAnalysis]

IS 14626 : 1999

Y7mmw

METHOD FOR DETERMINATION OF TOTAL BROMIDE RESIDUES IN GRAINS AND FOOD COMMODITIES FUMIGATED WITH METHYL

BROMIDE

ICS 65.100 ; 67.040

0 BIS 1999

BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002 *

January 1999 Price Group 1

Pesticides Residue Analysis Sectional Committee, FAD 34

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the Pesticides Residue Analysis Sectional Committee had been approved by the Food and Agriculture Division Council.

Methyl bromide IS used as a fumigant either as such or in admixture with other material for control of pests of stored grains/food commodities, such as fresh fruits and vegetables, stored products like flour, dry fruits, etc. Frequent and increased use of methyl bromide often result in harmful effects due to its toxic nature. Careful assessment of residues is, therefore, an important step in safeguarding human health and in the establishment of sound regulatory policy.

This standard will enable the health authorities andothers engaged in the field to follow a uniform test procedure for estimation of total bromide in grains/food commodities fumigated with methyl bromide.

In preparation of this standard due consideration has been given to the limits of total bromide residues which have been laid down under the provisions of Prevention of Food Adulteration Act, 1954 and Rules framed thereunder. The specified test methods are sensitive to the prescribed levels of residue.

In reporting the result of a test or analysis made in accordance with this standard, if the final value, observed or calculated, is to be rounded off, it shall be done in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values (revised)‘.

IS 14626 : 1999

Indian Standard

METHOD FOR DETERMINATION OF TOTAL BROMIDE RESIDUES IN GRAINS AND FOOD COMMODITIES FUMIGATED WITH METHYL

BROMIDE

1 SCOPE IS No.

This standard prescribes the method for determination of total bromide residues in grains and food

1 iiii (part ‘) ’

commodities fumigated with methyl bromide.

2 REFERENCE 3 TESTS

Title

Methods of sampling for the deter- mination of pesticides residue : Part 1 Agricultural and food com- modities

The following Indian Standard contains provisions Tests shall be carried out in accordance with the

which through reference in this text, constitutes method given in Annex A.

provision of this standard. At the time of publication, 4 SAMPLING the editions indicated was valid. Representative samples for the purpose of estimation

of total bromide residues shall be drawn in accordance with IS 11380 (Part 1).

ANNEX A

(Clause 3)

DETERMINATION OF TOTAL BROMIDE RESIDUE

A-l TITRATION METHOD

A-l.1 Procedure

A sample of 5-10 g is treated in a 100 ml nickel crucible with 40 ml of alcoholic KOH (2.5 g in 100 ml of rectified spirit, that is 95 percent alcohol), allowed to stand for an hour and evaporated to dryness on a steam bath. It is then dried for a short time at 110°C and is covered with 10 g of NaOH pellets. The crucible is left for an hour or two on a hot plate until the bubbling or smoking diminishes, after which it is placed in a muffle furnace at 6OO“C. Fusion should be carried without excessive burning or foaming. If the charge becomes ignited the crucible should be removed from the muffle until the flame is extinguished. It is then returned to the muffle and this process is repeated until the volatile gases have been removed. Sodium peroxide is added to the melt a few mg at a time to complete the oxidation of the remaining carbon or organic matter. The peroxide shall be added cautiously while the crucible is removed from the furnance, bromide is lost if the charge burns with a flare when too much peroxide is added.

Complete combustion of the organic matter can be effected best by returning any organic matter that has raised above the NaOH to the bottom of the crucible, when it mixes with the melt and is easily destroyed by addition of peroxide. This is accomplished by carefully rotating the hot crucible to wash down the organic matter and adding 0.5 g more of peroxide. If no burning or bubbling takes place, the oxidation is complete. A few carbon particles which may remain after final addition of peroxide do not affect the accuracy of the results.

The crucible is rotated to allow the melt to solidify on the sides and cooled, the contents are dissolved in 75 ml of water. Solution of the sodium compounds is hastened by placing the crucible on a hot plate for several minutes. The solution is transferred to a 400 ml beaker and partially neutralized with about 50 ml of 6 N HCl. The solution is boiled to destroy peroxides and to reduce the volume to loo-125 ml. Nickel hydroxides and other insoluble hydroxides are removed by filtering through a Whatman No. 2 filter paper collecting the filtrate and washings in 8 500 ml wide mouth erlenmeyer flask.

1

P

IS 14626 : 1999

A-l.2 Extraction

The filtrate is made slightly acid with 6N HCl, then neutralised with NaOH solution, adjusting to the colour change of methyl red. The volume at this point should be approximately 150 ml.

About 2 g of sodium acid phosphate NaH2 Po4.H20 and 5 ml of hypochlorite (1N sodium or potassium hypochlorite in 0.1 N NaOH or KOH) solution are added and the mix heated to boiling. After a minute or so 5 ml of sodium formate solution (50 g/100 ml) are introduced and boiling is continued for 2 minutes. The sample is cooled and treated with a few drops of 1 percent sodium molybdate solution, 0.5 g pure potassium iodide and 25 ml of 6 N sulphuric acid. Titration should be done immediately with standard 0.01 N Na2S203, starch indicator added just before the end point. A blank titration is also carried out, using all reagents.

A-1.2.1 Standardization of Thiosulphate

O.OlN stabilised with 1 g of Na2C03 per litre, standardized against 0.01 N KI03 using 75 ml water, 10 ml 6N H2S04 and 0.5 g pure KI.

A-l.3 Calculation

Total bromide, mg/kg = (’ - @ ’ N ’ 133*2 M x 0.01

where

S = volume of thiosulphate used for sample,

B = volume of thiosulphate used for blank,

N = normality of thiosulphate, and

M = mass of sample in grams taken for the test.

NOTE-To obtain bromide as methyl bromide use factor 158.3 for detection up to 1 ppm.

Bureau of Indian Standards

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Review of Indian Standards #

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewed periodically; a standard along with amendments is reaffirmed when such review indicates that no changes are needed; if the review indicates that changes are needed,,it is taken up for revision. Users of Indian Standards should ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of ‘BIS Handbook’ and ‘Standards Monthly Additions’.

This Indian Standard has been developed from Dot: No. FAD 34 ( 378 ).

Amend No.

Amendments Issued Since Publication

Date of Issue . . Text Affected

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