Chemicals may affect the weight, strength, color, dimensions, flexibility, and surface appearance of labware. The basic models of interaction that cause these changes are: (1) chemical attack on the polymer chain, with resultant reduction in physical properties, including oxidation; reaction of functional groups in or on the chain; and depolymerization; (2) physical change, including absorption of solvents, resulting in softening and swelling of the plastic; permeation of solvent through the plastic;

To pump viscous fluids 
- Choose tubing at least two sizes larger than the flow size required.
- Keep motor speed <300 rpm; the slower the motor, the better the flow.
- Use adjustable occlusion pumps: 
 Over-occlude to prime pump;
 reduce occlusion for longer life.

Getting the optimal performance from your pH electrodes is important. Several factors can influence an electrode’s functionality, including drifting readings, slow response times, and environmental influences. Find out how to determine what may be affecting your electrode—and what you can do about it.

DRIFTING READINGS

Drifting readings can occur if you are using a gel-filled electrode under the following conditions: when measuring a relatively large volume of sample, measuring samples at slightly colder temperatures, or testing fairly clean water. For reference, read the following article: http://www.coleparmer.com/techinfo/techinfo.asp?htmlfile=pHPureWater.htm

Introduction

There are two types of calibrations applicable to PRTs—characterization and tolerance testing. The type of calibration to perform is determined by the way in which the UUT is to be used and the accuracy required by the user.

Characterization is the type of calibration in which the unit under test (UUT) resistance is determined at several temperature points and the data are fitted to a mathematical expression.