Hitachi Z8270 Graphite Furnace Atomic Absorbance Spectrophotometer
Overview -
The Hitachi Z8270 Zeeman Atomic Absoance Spectrophotomeer is used to determine the concentration of metals in a liquid sample. Compared to the Flame AA, the GFAA allows much better detection limits, while using a smaller volume of sample, but at a higher cost. For most metals, the detection limits of the ICP-OES will be better than those for the GFAA (there are exceptions to that aver-reaching statement, though). The ICP-MS will provide much better detection limits than the GFAA, but requires a larger sample volume, and is more expensive.
Basic Theory -
The Hitachi 8270 is a graphite furnace atomic absorbance spectrophotometer that takes advantage of the zeeman effect to increase resolution and sensitivity. As with the other atomic absorbance techniques (the flame AA and mercury analyzer) relies on the atomized metals in sample absorbing light passed through the sample compartment.
Methods -
Microwave digestion of media
Microwave digestion of filter paper
Unlike the other atomic absorbance techniques, the analyte in the sample is atomized by electro-thermal heating of a graphite sampleing cuvette.Typically, 20 uL of the smple is placed into the graphite sampling cuvette accross which a low-voltage high-current potential is placed. ThE cuvette and and the sample contained in it are efficiently heated by this current. By varying the amount of current passing through the cuvette, a well defined temperture profile is applied to the sample. Through this electrothermal heating the sample is dried, driving off the solvent, ashed, burning off anyorganinc constitiuents, atomize, which drives the metal into the gas phase for analysis, and then cleaned, driving off any componenets which vaporize at higher temperatures.
During the atomization phase, the metals of interest are driven into the vapor phase. At this point, as with other atomic absorbance techniques, a lamp providing light of a waveength specific to the metal of interes is passed down the axis of the cuvette, through any vaporized metal from the sample. The metal atoms in the cuvette absorb some of the light passing through the tube, so th light subsequently hitting the detector is decreased. The decrese in the ligh intensity is proporional to the amount of metal present in the sample.
Detection Limits -
The detection limits for the GFAA are, in general, much better than those for the flame AA, comparable with those of the ICP-OES, but not as good as for the ICP-MS. While we can provide an esitmate of the detection limits, and linear working ranges, you should be aware the actual values can vary a little depending on the particular instrument, method, or matrix.
Sample Matrix -
The sample must be homoenous liquid. Although the temperature profile applied to the cuvtte will be different, the sample can be in either an aqueous or organic solvent.
Sample Size -
20-30 uL of sample are injected into the sample cuvette for each replicate of the analysis, but approximately 0.5 mL of sample is loaded into the autosampler vial to ensure the sampling tip reaches completely into the sample. If required, the unused portion of the sample may be retained for further testing.
Approximate C0st -
Neglecting the cost of sample preparation, the cost of the instrument is $XX.XX/hour.