The most common cause of error in pH measurements is temperature. The slope of a pH electrode is highly dependent on temperature and pH buffer values and sample values change with temperature. For the most accurate results an ATC probe is always recommended. The epoxy body Thermo Scientific® Orion™ ATC probes (PH4341-1/-3) are not recommended for use in organic solvents, but may be used on an intermittent basis in methanol or ethanol. Glass body Orion ATC probes (PH4341-4/-7) are preferred for use in solutions containing organic solvents or at temperatures over 80°C. The Orion Stainless Steel ATC probe (PH4341-8) is ideal for in-plant and food applications. The Orion Stainless Steel Body Micro ATC Probe (PH4341-12) is recommended for use in small sample containers, test tubes or microtiter plates.