A Fast Optical Method for the Determination of Liquid Levels in Microplates
Parallel liquid handling systems are widely used in different applications of life sciences. In order to avoid false positive or negative results which lead to higher costs due to the replication of the experiments it is necessary to monitor the process and success of liquid delivery. An easy method for the determination of the liquid levels in microplates has been developed and evaluated. The optical method bases on the measurement of the liquid level using CCD cameras followed by special algorithms for the evaluation and visualization of the measured data. The proposed method was tested in changing environmental lighting for two different liquids. These tests confirm our approach towards optical liquid level determination for smallest volumes in microplates and also show the challenges regarding environmental lighting and different physical properties of fluids.
On the Level
A “level” is a carpenter’s tool which simply and elegantly compares the orientation of an object to the horizon. The correct term for a measurable quantity of a substance in a specified volume or mass of a specimen is “concentration.” It is common in colloquial speech to discuss the level of an analyte in a specimen (e.g., “Let’s check the acetaminophen level.”); however, when writing about the outcome of the laboratory analysis, authors should use concentration to denote the finite result. Example 1 (incorrect): “The acetaminophen level was 220 mcg/mL.” Example 2 (correct): “The acetaminophen concentration was 220 mcg/mL.” This distinction is analogous to that between “fewer” and “less” (the former referring to a finite, measurable quantity, and the other referring to an indefinite amount) [1]. If authors will use level less often, editors and reviewers will make fewer suggestions to use concentration.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.