A 13.56 MHz plasma jet discharge, called a plasma pencil, was investigated. Rotational and excitation temperatures, and electron number densities for the pencil under and without sample load were calculated using OH band spectra, Ar lines and Hb line, respectively. The rotational temperatures were found to be relatively low at about 800 K, however, excitation temperatures exceeded 4000 K. The plasma was found to be strongly non-isothermal. Some atomic lines of elements were easily observed. Aqueous solution-based aerosols were incorporated into the plasma without desolvation. Standard water solutions of the elements were nebulized into the plasma. The Ar carrier gas and Ar plasma gas flow rates were 0.3 and 4.0 l min À1 , respectively. The forwarded power was 140 W. Intensities of the atomic lines, temperatures and electron number densities along the discharge tube were acquired in different positions from the aerosol entrance and an optimal position providing the best signal-to-noise ratio for each line intensity was established. Calibration dependencies for Ca, Cu, Mg, Zn, Li, Na were measured in the rage of 1-100 mg l À1 . 3-sigma detection limits in the best observation axial position were (mg l À1 ): 27 (Ca), 49 (Cu), 58 (Mg), 40 (Li), 13 (Na) and 180 (Zn).
A two-electrodes capacitively coupled plasma jet discharge operated on a symmetrical sinus frequency carrier wave 13.56 MHz in a continual mode and in a pulsed mode is described in this paper. Internally pulsed mode was realised by the frequency modulation by the symmetrical rectangular frequency 22 kHz with duty cycle of 90 %. The pulsed mode has an effect on the electron number densities ranging from 1×10 14 to 1.2×10 15 in the pulse mode and from 1.7×10 14 to 1.0×10 15 cm -3 in the continuous mode, gas 10 temperatures 670-950 K in the pulse and 630-880 K in the continuous mode, excitation temperatures 3100-4250 K in the pulse and 3500-4280 K in the continuous mode, slopes and intercepts of the calibration lines and limits of detection and a weak effect on the coefficients of determination. All these parameters were measured in three different positions from the sample inlet of the plasma pencil. Most line intensities and the excitation temperature decreased while calcium lines and rotational temperature 15 calculated from OH radicals increased in the pulsed mode. These results indicate a strong interaction between calcium species and OH radicals. Analysis of real low mineralized waters showed almost proximity of the yielded results to those obtained by reference ICP-OES.
Standard Reference Material 927c based on pure bovine albumin is still recommended and used as the primary standard for assays of total protein by colourimetric methods. The albumin calibrator is responsible for a positive bias of approximately 3%-5% in serum total protein assayed by the biuret reaction both in the reference and in current methods. Its substitution by a serum calibrator attested by the Kjeldahl method could solve this drawback. Clin Chem Lab Med 2009;47:91-101.
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