Basic Knowledge of Laboratory Analysis
Major Test Methods of Laboratory Analysis
There are two major test methods of laboratory analysis (chemistry, biochemistry, and biology): test analysis and instrument analysis. Specifically, test analysis can be divided into the spectrophotometric method, volumetric method, and gravimetric method. Speaking of instrument analysis, the major ones used in the laboratory include a mass spectrometer, gas chromatograph, liquid chromatography, ion chromatography, atomic absorption, atomic fluorescence, etc. Analysis test index can be defined as meaning type (eg. iron ion concentration, total phosphorus concentration, amino nitrogen concentration) and definition type (eg. chemical oxygen demand, biochemical oxygen demand).
Quality Control Methods of Laboratory Analysis
Quality control methods are always reflected by the analytical accuracy of standard samples. The common methods are adding standard recovery and relative error of standard samples. We can make adding standard recovery to blank samples as well as experimental samples. However, in practical analysis, laboratory workers mostly make adding standard recovery to experimental samples. They take two identical samples and add quantitative standard target substance to one of them. Complete test via the same procedures on the two samples and then obtain the result.
The Number of Significant Figures and Rounding Rules
Each specific test result has a certain number of significant figures which depend on accurate recording of original data and correct calculating of numerical value. Laboratory workers have to consider of the accuracy and reading error of measuring instrument when recording the measured value.