For Seronorm urine analysis, the standard and blank were prepared in synthetic urine solution. Synthetic urine solution2 contains 14.1 g NaCl, 2.8 g KCl, 17.3 g urea, 1.9 mL of 25% v/v ammonia solution, 0.6 g CaCl2 and 0.43 g MgSO4, made up to 1 L with 0.02 M HCl solution.
For seawater analysis, the standard and blank were prepared in artificial seawater solution. Artificial seawater solution3 contains 25.4 g NaCl, 5.083 g MgCl2, 1.104 g CaCl2, 0.722 g KCl, 0.026 g H3BO3 and 0.203 g SrCl2, made up to 1 L with distilled de-ionized water.
1. Long term stability
Long term stability was evaluated by performing a calibration on a multi-element standard and a blank, both being made up in 1% w/v NaCl solution. The standard was then measured as a sample continuously for a period of an hour. After an hour, the reproducibility ranged between 0.8 to 2 %RSD for the measurements plotted in figure 1.
An additional stability test was performed on a seawater solution, as shown in figure 2. The reproducibility over an hour ranged from 2 to 5 %RSD. It was noted that after continuously aspirating the seawater solution for over an hour, the injector tube gradually showed signs of blockage due to salt deposition. Further experimentation confirmed that rinsing between samples is desirable to minimize any potential clogging of the tube and improve the long term stability of the analysis.
2. Urine analysis
Urine samples can be analyzed directly by ultrasonic nebulization. Analysis was performed on a Seronorm urine sample. The standard and blank were prepared in a synthetic urine solution. The results of the ana