# The Preservatives in Food Regulations 1989, Paragraph 3: Reagents


The following reagents shall be used–
(a) 70 per centum (weight/weight) orthophosphoric acid;
(b) silicone-based anti-foaming emulsion;
(c) di-isopentyl ether (analytical reagent grade);
(d) purified cyclohexane: shake 3 times with a 4 per cent (weight/volume) solution of sodium hydroxide, wash 3 times with distilled water;
(e) 4 per centum (weight/volume) sodium hydroxide solution;
(f) buffer solution at pH 10.4: into a 2 litre graduated flask put 6.64 g. of boric acid, 8.00 g. of potassium chloride and 93.1 ml. of N sodium hydroxide solution; mix and bring up to calibration mark with distilled water;
(g) reagent I: dissolve 1.0 g. of 4-aminophenazone (4-amino-2, 3-dimethyl-1-phenyl-5-pyrazolone; 4-aminoantipyrin) in 100 ml. of distilled water;
(h) reagent II: dissolve 2.0 g. of potassium ferricyanide in 100 ml. of distilled water. Reagents I and II must be kept in brown glass flasks and are only stable for approximately 14 days;
(j) silica gel;
(k) standard solution: dissolve 10 mg. of pure 2-hydroxybiphenyl in 1 ml. of 0.1 N NaOH; dilute to 100 ml. with a 0.2 M sodium borate solution (1 ml.=100 μg. 2-hydroxybiphenyl). For the standard curve, dilute 1 ml. to 10 ml. with the buffer solution.

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Source: https://www.legislation.gov.uk/uksi/1989/533/schedule/5/part/III/paragraph/3 (the official version)
Page: https://openlegislation.uk/preservatives-in-food-regulations-1989/schedule-5/part-III/paragraph-3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.