Analytical Chem istry - DePauw University

394 Analytical Chemistry 2.0Example 8.8A 200.0-mL sample of water was filtered through a pre-weighed glass fiberfilter. After drying to constant weight at 105 o C, the filter was foundto have increased in mass by 48.2 mg. Determine the sample’s total suspendedsolids.So l u t i o nA ppm is equivalent to a mg of analyte per liter of solution; thus, the totalsuspended solids for the sample is48.2 mg solids= 241 ppm solids0.2000 Lsample8D.3 Evaluating Particulate GravimetryThe scale of operation and detection limit for particulate gravimetrycan be extended beyond that of other gravimetric methods by increasingthe size of the sample taken for analysis. This is usually impracticable forother gravimetric methods because of the difficulty of manipulating a largersample through the individual steps of the analysis. With particulate gravimetry,however, the part of the sample that is not analyte is removedwhen filtering or extracting. Consequently, particulate gravimetry is easilyextended to the analysis of trace-level analytes.Except for methods relying on a quartz crystal microbalance, particulategravimetry uses the same balances as other gravimetric methods, andis capable of achieving similar levels of accuracy and precision. Since particulategravimetry is defined in terms of the mass of the particle itself, thesensitivity of the analysis is given by the balance’s sensitivity. Selectivity, onthe other hand, is determined either by the filter’s pore size, or by the propertiesof the extracting phase. Because it requires a single step, particulategravimetric methods based on filtration generally require less time, laborand capital than other gravimetric methods.As you review this chapter, try to define akey term in your own words. Check youranswer by clicking on the key term, whichwill take you to the page where it was firstintroduced. Clicking on the key termthere, will bring you back to this page sothat you can continue with another keyterm.8E Key Termscoagulation conservation of mass coprecipitatedefinitive technique digestion direct analysiselectrogravimetry gravimetry homogeneous precipitationignition inclusion indirect analysisocclusion particulate gravimetry peptizationprecipitant precipitation gravimetry quartz crystal microbalancerelative supersaturation reprecipitation supernatantsurface adsorbate thermogram thermogravimetryvolatilization gravimetry