Sensor Principle
The principle of operation of Membrapor sensors is explained.
Accuracy
Accuracy is a term that is often used, but is not generally well understood. This article explains it.
All you need to know about pH
The classical first year chemistry definition of “pH” refers back to Danish biochemist Søren Sørenson, who originated the term, alluding to the “potential of hydrogen ion.” Specifically, pH is the negative logarithm of the molar concentration of the hydrogen ion (H+) in the particular solution. This is usually expressed as a formula… pH = -log[H+]…
Biological monitoring and biological exposure indices
According to the American Conference of Governmental Industrial Hygienists… “Biological monitoring provides one of the means to assess the exposure and health risk to workers. It entails the measurement of the concentration of a chemical determinant in the biological media of those exposed and is an indicator of the uptake of a substance. Biological Exposure…
Continuous Monitoring vs. Stream-Switching Monitoring
First, let’s define the terms: “Continuous” monitoring means that each sampling point is being monitored all the time, and in most cases, the concentration displayed reflects what is truly happening at the point in real time. There are certain exceptions to this involving instrument techniques that run batch analysis, but that is beyond the scope…
Data Logging and Data Acquisition in Gas Detection
Virtually every industrial facility has some kind of gas detection in place: Millions of portable units are in service, and at least a million points of continuous gas detection have been deployed. However, what is being done with all the data? The first and most vital use of this data, of course, is to provide…
Detector Tubes And When To Use Them
A detector tube is a graduated glass tube filled with a chemical reagent that will produce a color change, when exposed to the gas in question. It is used with a hand pump that will draw a sample into the tube. The tubes are generally supplied in packages of ten, and are sealed at both…
Determining the Dew Point of a Gas Sample
“Dew Point” is defined as the temperature to which a given volume of air must be cooled at constant pressure and constant water vapor content in order for saturation to occur. If the air is cooled further, some of the moisture will condense. The notion of “Saturated Vapor Pressure” can be understood by considering the…
Estimation of carboxyhemoglobin levels by breath sampling
There has long been interest in measuring the amount of carboxyhemoglobin in the blood of workers who might be exposed to carbon monoxide. CO-induced hypoxia is a real consequence. However, such measurements—when done in the conventional manner—are invasive and cumbersome. It was first demonstrated in 1948, by Torgny Sjöstrand, that COHb saturation could be estimated…
Ethylene And Fruit Ripening
How about a little peak into the secret life of plants? Fruit ripening is a form of senescence and signifies the final stage in fruit development. Ripening, of course, eventually leads to spoilage, so there are important commercial reasons to increase and control post-harvest longevity. Complicating matters, post-harvest longevity varies naturally. Strawberries, for example, last…