**10. Conclusion**

126 Advanced Aspects of Spectroscopy

salinity 8.78mS/cm.

**9. Comparison of results** 

us to characterize the results:

 It should be mentioned that the embodiment of the vast majority of measurements for suspension was made with the HP4192A impedance analyzer, considering the structure and existing coil system, the utilization ratio of the impedance analyzer is because the probes used to interconnect arrangement coils are constructed on purpose, greatly decreasing the

**Figure 25.** Impedance Representation of Biological Suspension, comparatively to the coil system.

After 35 minutes, the yeast was deposited at the bottom of the container; we proceeded to extract 350ml of water and recovered the same amount of water (350ml), but now with a

The interesting thing in this experiment as shown in Figure 25, having increased conductivity, as a result of water replaced without electrolytes, with water with electrolytes (8.78mS/cm) decreased by 6% the impedance of the suspension by the lower proportion of

Measurements of saline cell and a biological suspension with HP impedance analyzer, allow

yeast and major salinity, Zlev = 384.37Ω, Zlev + NaCl = 361.87Ω, ΔΩ = 22.5

amount of error attributable to the length of the coaxial cables.

The presentation of results, by their very short nature, could be interpreted as an activity which is not time consuming, but the opposite is true, because from the moment of preparation of the experiments, there are always a number of imponderables, such as materials or materials that are needed to carry out the measurements do not have them, at least, operating conditions, climate, lighting, etc..

For the characterization of substances, suspensions and / or solutions must take into account, and in a very particular, maintain the same amounts, and make measurements in a repetitive manner, so as to place on record its findings to conditions geometric, physical and mechanical properties, different and contrast with conditions similar to those obtained. The measurements carried out with the Network Analyzer, which was mostly used equipment, are quite contrasting with measurements made with the HP impedance analyzer. As we can see with the first, which strongly influences the distance at which measurements were made, not with the impedance analyzer as it had a "fixture" on purpose.

Speaking of the actual material used and specific the experiment with saline cell, it was found that one of the factors that influence in the admittance at low frequencies is the electrical permittivity of water. The values depend on the frequency of measurements, and the frequency sweep, this due to the response of the dielectric constant of the solution, which varies considerably with frequency.

Using a saline solution with a high degree of salinity, more than 9 g / l of salt, we see that in the graphs of the results if ε'' / ε '<2, the ε" accuracy degrades. This may be because the impedance of solutions with high salt is essentially resistive. In an opposite manner with a "window" at 999 KHz frequency on average, before the resonance frequency of the coil circuit, the impedance of the solution is essentially reactive, and since this type of impedance measurements of reflection / transmission were performed mainly with the network analyzer is a significant higher level of uncertainty in measuring the smaller capacitive component where ε" is derived.

The HP impedance analyzer measurements, both saline solutions and suspensions, allowed us to compare results, specifically ε" values. In the suspensions could be evaluated especially an increase in the impedance, over time, possibly due to increased cell growth, hence an increase in the capacitive reactance of the suspension.

Considering the results obtained, we can consider the approach to the characterization as reasonably good since the relative permittivity is much greater than unity for the dielectric (both saline solutions and biological suspensions).

One of the properties of biological tissue, such as conductivity, is well reflected by the frequency dependence, particularly in the range of 10 KHz-10MHz (β dispersion range). The conductivity at low frequencies denotes the volume of extracellular fluid essence, the additional contribution of intracellular fluid volume with a significant increase in the applied frequency causes a significant increase in conductivity.

And finally and considering the substantial increase in interest in the development of magnetic induction spectroscopy (MIS) as a valid option for obtaining the conductivity of the human body without the need for direct contact with tissue (Korzhenevskii and Cherepenin 1997 Griffiths et al. 1999, Korjenevsky et al. 2000); In addition to other passive electrical properties of biological tissues (Hermann Scharfetter, Casañas Roberto and Javier Rosell, 2003).

Since MIS is based on measurements of small changes in magnetic fields, typically of the order of 1% or less at frequencies up to 10 MHz, and also because of their physical limitations is not recommended at frequencies below 10 kHz, this also represents a great challenge in electronic design, possibly one of its greatest disadvantages.
