Nitrate-nitrogen – LaMotte DC1600 Colorimeter User Manual

Page 59

NITRATE-NITROGEN

CADMIUM REDUCTION METHOD

CODE 3649

QUANTITY

CONTENTS

CODE

2 x 60 mL

*Mixed Acid Reagent

*V-6278-H

5 g

*Nitrate Reducing Reagent

*V-6279-C

Spoon, 0.1 g, plastic

0699

Dispenser Cap

0692

*WARNING: Reagents marked with a * are considered hazardous substances. Material Safety Data Sheets (MSDS) are supplied for

these reagents. For your safety, read label and accompanying MSDS before using.

Nitrogen is essential for plant growth, but the presence of excessive amounts in water supplies presents a major pollution

problem. Nitrogen compounds may enter water as nitrates or be converted to nitrates from agricultural fertilizers, sewage,

industrial and packing house wastes, drainage from livestock feeding areas, farm manures and legumes. Nitrates in large

amounts can cause “blue babies” (methemoglobinemia) in infants less than six months of age. Nitrate concentration is an

important factor to be considered in livestock products, where, in addition to causing methemoglobinemia, it is responsible

for many other problems. Nitrates in conjunction with phosphate stimulate the growth of algae with all of the related

difficulties associated with excessive algae growth.
U.S. Public Health Service Drinking Water Standards state that 10 ppm nitrate nitrogen should not be exceeded. To the

sanitary and industrial engineer, concentrations of less than 1 ppm are acceptable.

APPLICATION:

This method determines nitrate levels in drinking, surface, saline waters, domestic and

industrial waters.

RANGE:

0 – 3.0 ppm Nitrate Nitrogen (Range can be extended by dilution).

METHOD:

Powdered cadmium is used to reduce nitrate to nitrite. The nitrite that is originally present

plus reduced nitrate is determined by diazotization of sulfanilamide and nitrite followed by

coupling with N-(1 naphthyl)-ethylenediamine dihydrochloride to form a highly colored azo

dye which is measured colorimetrically.

SAMPLE HANDLING

& PRESERVATION:

Analysis should be made as soon as possible. If analysis cannot be made within 24 hours, the

sample should be preserved by refrigeration at 4°C. When samples must be stored for more

than 24 hours, they can be preserved by adding 2 mL of concentrated sulfuric acid per liter of

sample. For best results, the analysis for nitrate should be determined at temperatures between

20°C and 25°C.

INTERFERENCES:

Nitrite interferes at all levels. Use the following equation to compensate for nitrite

interferences: Test result (ppm) - (Nitrite-N(ppm) x 5.5) = true Nitrate-N reading.
Strong oxidizing and reducing substances interfere. Low results might be obtained for samples

that contain high concentrations of iron and copper.