Purified Water

(Ph. Eur. monograph 0008)

H₂O 18.02

Ph Eur

DEFINITION

Water for the preparation of medicines other than those that are required to be both sterile and apyrogenic, unless otherwise justified and authorised.

Purified water in bulk

PRODUCTION

Purified water in bulk is prepared by distillation, by ion exchange, by reverse osmosis or by any other suitable method from water that complies with the regulations on water intended for human consumption laid down by the competent authority.

Purified water in bulk is stored and distributed in conditions designed to prevent growth of micro-organisms and to avoid any other contamination.

Microbiological monitoring

During production and subsequent storage, appropriate measures are taken to ensure that the microbial count is adequately controlled and monitored. Appropriate alert and action levels are set so as to detect adverse trends. Under normal conditions, an appropriate action level is a microbial count of 100 CFU/mL, determined by filtration through a membrane with a nominal pore size not greater than 0.45 µm, using R2A agar and incubating at 30-35 °C for not less than 5 days. The size of the sample is to be chosen in relation to the expected result.

R2A agar

Adjust the pH so that after sterilisation it is 7.2 ± 0.2. Sterilise by heating in an autoclave at 121 °C for 15 min.

Growth promotion of R2A agar

— Preparation of test strains. Use standardised stable suspensions of test strains or prepare them as stated in Table 0008.-1. Seed lot culture maintenance techniques (seed-lot systems) are used so that the viable micro-organisms used for inoculation are not more than 5 passages removed from the original master seed-lot. Grow each of the bacterial strains separately as described in Table 0008.-1. Use buffered sodium chloride-peptone solution pH 7.0 or phosphate buffer solution pH 7.2 to make test suspensions. Use the suspensions within 2 h, or within 24 h if stored at 2-8 °C. As an alternative to preparing and then diluting a fresh suspension of vegetative cells of Bacillus subtilis, a stable spore suspension is prepared and then an appropriate volume of the spore suspension is used for test inoculation. The stable spore suspension may be maintained at 2-8 °C for a validated period of time.

— Growth promotion. Test each batch of ready-prepared medium and each batch of medium, prepared either from dehydrated medium or from the ingredients described. Inoculate plates of R2A agar separately with a small number (not more than 100 CFU) of the micro-organisms indicated in Table 0008.-1. Incubate under the conditions described in the table. Growth obtained must not differ by a factor greater than 2 from the calculated value for a standardised inoculum. For a freshly prepared inoculum, growth of the micro-organisms must be comparable to that obtained with a previously tested and approved batch of medium.

Total organic carbon or oxidisable substances

Carry out the test for total organic carbon (2.2.44) with a limit of 0.5 mg/L or alternatively the following test for oxidisable substances: to 100 mL add 10 mL of dilute sulfuric acid R and 0.1 mL of 0.02 M potassium permanganate and boil for 5 min; the solution remains faintly pink.

Conductivity

Determine the conductivity off-line or in-line under the following conditions.

Equipment

Conductivity cell:

— electrodes of a suitable material such as stainless steel;

— cell constant: the cell constant is generally certified by the supplier and is subsequently verified at suitable intervals using a certified reference solution with a conductivity less than 1500 µS⋅cm^-¹ or by comparison with a cell having a certified cell constant; the cell constant is confirmed if the value found is within 2 per cent of the certified value, otherwise re-calibration must be performed.

Conductometer Accuracy of 0.1 µS⋅cm^-¹ or better at the lowest range.

System calibration (conductivity cell and conductometer):

— against one or more suitable certified reference solutions;

— accuracy: within 3 per cent of the measured conductivity plus 0.1 µS⋅cm^-¹.

Conductometer calibration Calibration is carried out for each range of measurement to be used, after disconnection of the conductivity cell, using certified precision resistors or equivalent devices with an uncertainty not greater than 0.1 per cent of the certified value.

If in-line conductivity cells cannot be dismantled, system calibration may be performed against a calibrated conductivity-measuring instrument with a conductivity cell placed close to the cell to be calibrated in the water flow.

Temperature measurement Tolerance ± 2 °C.

PROCEDURE

Measure the conductivity without temperature compensation, recording simultaneously the temperature. Temperature-compensated measurement may be performed after suitable validation.

The water to be examined meets the requirements if the measured conductivity at the recorded temperature is not greater than the value in Table 0008.-2.

For temperatures not listed in Table 0008.-2, calculate the maximal permitted conductivity by interpolation between the next lower and next higher data points in the table.

Heavy metals

If purified water in bulk complies with the requirement for conductivity prescribed for Water for injections (0169) in bulk, it is not necessary to carry out the test for heavy metals prescribed below.

CHARACTERS

Appearance

Clear and colourless liquid.

TESTS

Nitrates

Maximum 0.2 ppm.

Place 5 mL in a test-tube immersed in iced water, add 0.4 mL of a 100 g/L solution of potassium chloride R, 0.1 mL of diphenylamine solution R and, dropwise with shaking, 5 mL of nitrogen-free sulfuric acid R. Transfer the tube to a water-bath at 50 °C. After 15 min, any blue colour in the solution is not more intense than that in a reference solution prepared at the same time in the same manner using a mixture of 4.5 mL of nitrate-free water R and 0.5 mL of nitrate standard solution (2 ppm NO₃) R.

Aluminium (2.4.17)

Maximum 10 ppb, if intended for use in the manufacture of dialysis solutions.

Prescribed solution To 400 mL of the water to be examined add 10 mL of acetate buffer solution pH 6.0 R and 100 mL of distilled water R.

Reference solution Mix 2 mL of aluminium standard solution (2 ppm Al) R, 10 mL of acetate buffer solution pH 6.0 R and 98 mL of distilled water R.

Blank solution Mix 10 mL of acetate buffer solution pH 6.0 R and 100 mL of distilled water R.

Heavy metals (2.4.8)

Maximum 0.1 ppm.

To 200 mL add 0.15 mL of 0.1 M nitric acid and heat in a glass evaporating dish on a water-bath until the volume is reduced to 20 mL. 12 mL of the concentrated solution complies with test A. Prepare the reference solution using 10 mL of lead standard solution (1 ppm Pb) R and adding 0.075 mL of 0.1 M nitric acid. Prepare the blank solution adding 0.075 mL of 0.1 M nitric acid.

Bacterial endotoxins (2.6.14)

Less than 0.25 IU/mL, if intended for use in the manufacture of dialysis solutions without a further appropriate procedure for removal of bacterial endotoxins.

LABELLING

The label states, where applicable, that the substance is suitable for use in the manufacture of dialysis solutions.

Purified water in containers

DEFINITION

Purified water in bulk that has been filled and stored in conditions designed to assure the required microbiological quality. It is free from any added substances.

CHARACTERS

Appearance

Clear and colourless liquid.

TESTS

It complies with the tests prescribed in the section on Purified water in bulk and with the following additional tests.

Acidity or alkalinity

To 10 mL, freshly boiled and cooled in a borosilicate glass flask, add 0.05 mL of methyl red solution R. The solution is not coloured red.

To 10 mL add 0.1 mL of bromothymol blue solution R1. The solution is not coloured blue.

Oxidisable substances

To 100 mL add 10 mL of dilute sulfuric acid R and 0.1 mL of 0.02 M potassium permanganate and boil for 5 min. The solution remains faintly pink.

Chlorides

To 10 mL add 1 mL of dilute nitric acid R and 0.2 mL of silver nitrate solution R2. The solution shows no change in appearance for at least 15 min.

Sulfates

To 10 mL add 0.1 mL of dilute hydrochloric acid R and 0.1 mL of barium chloride solution R1. The solution shows no change in appearance for at least 1 h.

Ammonium

Maximum 0.2 ppm.

To 20 mL add 1 mL of alkaline potassium tetraiodomercurate solution R. After 5 min, examine the solution down the vertical axis of the tube. The solution is not more intensely coloured than a standard prepared at the same time by adding 1 mL of alkaline potassium tetraiodomercurate solution R to a mixture of 4 mL of ammonium standard solution (1 ppm NH₄) R and 16 mL of ammonium-free water R.

Calcium and magnesium

To 100 mL add 2 mL of ammonium chloride buffer solution pH 10.0 R, 50 mg of mordant black 11 triturate R and 0.5 mL of 0.01 M sodium edetate. A pure blue colour is produced.

Residue on evaporation

Maximum 0.001 per cent.

Evaporate 100 mL to dryness on a water-bath and dry in an oven at 100-105 °C. The residue weighs a maximum of 1 mg.

Microbial contamination

TAMC: acceptance criterion 10² CFU/mL (2.6.12). Use casein soya bean digest agar.

LABELLING

The label states, where applicable, that the substance is suitable for use in the manufacture of dialysis solutions.

Ph Eur