Determinations of phosphorus in fertilizers by spark discharge-assisted laser-induced breakdown spectroscopy

作者：Vieira Alan Lima; Silva Tiago Varao; Inocencio de Sousa Felipe Schiavon; Senesi Giorgio Saverio; Santos Junior Dario; Ferreira Edilene Cristina; Gomes Neto Jose Anchieta

来源：Microchemical Journal, 2018, 139: 322-326.

DOI：10.1016/j.microc.2018.03.011

• Spark discharge
• LIBS
• Fertilizer analysis
• Phosphorus determination

A spark discharge system was coupled to laser-induced breakdown spectroscopy (SD-LIBS) to improve sensitivity in the determination of P in fertilizers. A LIBS system consisting of a Q-switched Nd:YAG laser operating at 1064 nm and emitting pulses at 50 mJ with a fluence of 70 J cm(-2) at the focal point was used. Results of preliminary experiments suggested that the most appropriate wavelength to measure P was the P (1) line at 214.9 nm, which did not show interferences by Fe, Cu and Zn. The electrical discharge was provided by a homemade high-voltage electronic circuit consisting of two cylindrical tungsten electrodes at the optimized output voltage of 4.5 kV, with tips arranged at the optimal distances of 4 mm between them and 2 mm above the sample surface. To minimize the expected matrix effects calibration standards of P2O5 in the range of 4.8 and 33.3% were prepared by mixing various amounts of a phosphate rock reference material (SRM-120c) with a mixture of CaCO3, CaSO4, (NH2)(2)CO and KCl at a 1:1:1:1 mass ratio. The calibration curves obtained at a 4.5 kV SD-LIBS output voltage showed correlation coefficients RSD <= 8% and LOQ5.3% (m/m) P2O5. Data obtained by analyzing commercial samples by the proposed system were in good agreement, at 95% confidence level, with those obtained by using high-resolution continuum-source flame atomic absorption spectroscopy.

• 出版日期2018-6