ORBECO 942-095, Инструкция по эксплуатации

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7
Preserving or Storing Water Samples
Customary methods for preserving a sample include adjusting its pH, adding chemicals, refrigeration, or
freezing. Some materials may change soon after having been sampled, and applicable instructions for these
are given in the Specific Test Procedure.
For details beyond those specifically noted in Section 7, refer to Part 1060 of the current edition of Standard
Methods. This details:
A. Whether polyethylene or glass containers (or both) may be used
B. Recommends preservation including cooling, chemical addition, or pH adjustments
C. Lists the maximum storing times for water tests to be valid
Two Types of Sample Tubes are Supplied -- Plastic and Glass
Break-resistant No. 975-TP Plastic Tubes are ideal for testing swimming pools, foodstuffs or situations where
broken glass would be hazardous. Scratch-resistant No. 975-TG Glass Tubes are preferred for all other test-
ing applications. The 942’s calibrations are equally accurate for either type of tube. But when making tests,
USE THE SAME TYPE OF TUBE FOR THE BLANK AND SAMPLE; DO NOT INTERMIX PLASTIC TUBES WITH GLASS
TUBES.
Importance of Cleanliness
Use only clean tubes, and hold them by their caps to prevent finger marks on the sides of the tubes. The
containers used to obtain samples and labware used with the instrument should be clean both inside and
out. To avoid inaccurate results, always wash and dry tubes and labware promptly after use. If stubborn
residues have adhered to a tube’s surfaces, soak with non-abrasive lab detergent, flush thoroughly with
deionized water and air dry. Some test procedures have special cleaning instructions. To maintain accuracy
and avoid errors, discard any Sample Tube that is scratched or permanently stained.
Proper Use of Graduated Labware
Certain tests are supplied with graduated labware. For highest test accuracy, it is important to measure
accuracy, it is important to measure liquid volumes precisely. Always hold graduated labware vertically, and
align your eye with graduation line and the BOTTOM of the curved liquid surface.
Always Accurately Fill the Sample Tube to the 10mL Graduation Mark
A lower or higher volume will cause inaccurate results. Cap the tube firmly to avoid its coming loose when
the tube is lifted.
Avoid and Eliminate Bubbles
Pour sample slowly and carefully to avoid bubbles from foaming and clinging to the inside tube walls be-
cause they may cause inaccuracies. If bubbles appear, swirl tube, strike bottom gently to dislodge them or
let tube stand with cover removed until bubbles can be knocked free by gently tapping.