Q2. What was the effect of the voltage between electrode tips on the emission intensity of the plasma?
At distances greater than 4mmmore collisionswere favored in the electron path between electrodes, which reduced the energy of electrons so that they were less efficient in exciting/ionizing the species present in the plasma.
Q3. What are the strategies to enhance sensitivity of phosphate fertilizers?
Among other strategies to enhance sensitivity are the use of CCD detector and high fluence [8], intensified CCD detector [5,6], resonance LIBS [29], laser-induced fluorescence LIBS [32].
Q4. What software was used for data (peak intensities) treatment?
After spectral baseline correction performed by a Whittaker filter on MATLAB® (R2010a) and PLS Toolbox, a softwareMicrosoft Excel® (2016)was used for data (peak intensities) treatment.
Q5. What is the common method of phosphate breakdown spectroscopy?
In the last years, laser-induced breakdown spectroscopy (LIBS) has been employed for P determination in phosphate ores [5,6] mineral fertilizers [7,8] and organicmineral fertilizers [9,10].
Q6. What was the main circuit of the electronic circuit?
The homemade high-voltage electronic circuit consisted of simple components, i.e. a primary circuit of the transformer, a secondary circuit and a voltage divider.
Q7. Why was the data processing performed using an external software?
In particular, due to limitations of the low energy LIBS system employed in this work, the data processing associated to the spectral sumwasperformed using an external software (Microsoft office excel 2016).
Q8. How did the voltage increase the emission intensity?
The emission intensity increased linearly with increasing the voltage up to 4.5 kV (Fig. 4), with a typical RSD ≤7%, which could be ascribed to the increase of plasma temperature caused by the reheating electric pulse [11,23,27,29].
Q9. What is the way to determine the presence of Fe in fertilizers?
As Cu and Zn might be present at low concentration in some phosphate fertilizer formulations [35], the P (I) line at 213.6 nm might be interfered by these elements, thus this line should also be excluded from the P analysis.
Q10. How did the spectra of the San Joaquin Soil Standard compare?
the concentrations of Fe previously determined by HR-CS FAAS in all samples examined fell in the range from 0.14 to 1.08% (m/ m), i.e. they were about 2–3 times lower than that in the SRM 2709a standard.
Q11. Why were some lines of Fe present in the samples?
someemission lines of Fe (II) at 253.4, 253.9 and 254.2 nm [34] were present due to Fe naturally present in the samples.