Purification pack system

All chemicals were analytical graded: urea, sodium chloride, sodium hydrogenphosphate, potassium dihydrogenphosphate were purchased from Carlo Erba (Milan, Italy); ammonium hydroxide (25% w/v) was bought from J. T. Baker (Deventer, Holland); lactic acid (90% v/v) from Acros Organics (Geel, Belgium); nitric acid (67-69% v/v) from VWR (Milan, Italy). Reagent grade water was obtained using a Millipore purification pack system (MilliQ water). The physiological solution used as the receptor fluid was prepared by dissolving 2.38 g of Na 2 HPO 4 , 0.19 g of KH 2 PO 4 and 9 g of NaCl into 1 liter of MilliQ water (final pH = 7.35). The synthetic sweat solution used as the donor fluid consisted in 0.5% w/v sodium chloride, 0.1% w/v urea and 0.1% w/v lactic acid in MilliQ water; pH was adjusted with ammonium hydroxide (1 N) to pH 4.5 and 6.5. BrushCAST® Copper Beryllium Casting Alloys (Be 0.35 < 2.85%; Cu 95.3-98.7%).

All chemicals were analytical grade. Urea, disodium hydrogen phosphate, potassium dihydrogen phosphate, hydrogen peroxide (30% v/v) were purchased from Carlo Erba (Milan, Italy); lactic acid (90%) from Acros Organics (Geel, Belgium); sodium chloride, ammonium hydroxide (25% w/v), nitric acid (>69% v/v) from Sigma-Aldrich (Milan, Italy). The povidone-iodine solution (10%) used in the experiments is a stable chemical complex of polyvinylpyrrolidone (povidone, PVP) and elemental iodine (Esoform Jod 75, that contains 10% (7.5 g) of polyvinylpyrrolidone-iodine with 0.75% of active iodine; Esoform S.P.A. Laboratorio Chimico Farmaceutico, Via del Lavoro 10, Rovigo, Italy). Water reagent grade was produced with a Millipore purification pack system (milliQ water). The physiological solution used as receptor fluid was freshly prepared by dissolving 9 g of NaCl, 2.38 g of Na 2 HPO 4 and 0.19 g of KH 2 PO 4 into 1 l of milliQ water (final pH 7.35). The synthetic sweat solution used as donor fluid consisted of 0.5% sodium chloride, 0.1% urea and 0.1% lactic acid in milliQ water; pH 4.5 was adjusted with ammonia.

All the chemicals used of analytical grade were purchased from Sigma-Aldrich Co. (St Louis, MO, USA). Water reagent grade was produced with a Millipore purification pack system (milliQ water).
The physiological solution used as receptor fluid was freshly prepared by dissolving 9.00 g of NaCl,
2.38 g of Na 2 HPO 4 and 0.19 g of KH 2 PO 4 into 1.00 L of milliQ water (final pH 7.35). The concentration of the salts in the receptor fluid was approximately the same as that present in blood.
The two refill liquids for e-cigarettes, used as donor phase, are available in the market. The nominal nicotine concentration of 18 mg ml -1 was confirmed by gaschromatographymass spectrometry (GC-MS). Both refill had pH of 7.9 and pKa of nicotine is 8.0 (Gorrod et al. 1999 ).

We purchased palladium (II) chlorite, ammonium hydroxide (25% w/v), sodium hydroxide, sodium chloride, ethanol, hydrochloric acid (37% v/v), polyvinylpyrrolidone PVP (K30, average Mw 40,000) from Sigma Aldrich (Milan, Italy); lactic acid (90%) from Acros Organics (Geel Belgium); hydrogen peroxide (30% v/v), disodium hydrogen phosphate, potassium dihydrogen phosphate from Carlo Erba (Milan Italy). We prepared synthetic sweat using 0.5% sodium chloride, 0.1% lactic acid, 0.1% urea in milliQ water (using a Millipore purification pack system). pH was adjusted at 4.5 with ammonia. We prepared physiological solution with 9.00 g of NaCl, 2.38 g of Na 2 HPO 4 and 0.19 g of KH 2 PO 4 into 1.00 L of milliQ water to obtain a final pH of 7.35. All reagents used were analytical grade.

All the chemicals used in this study were analytical-grade. Sodium chloride, sodium hydrogen phosphate, potassium dihydrogen phosphate, nitric acid (69% v/v), hydrochloric acid (37% v/v) were purchased from Sigma Aldrich (Milan, Italy), while ammonium hydroxide (25%) was purchased from J.T. Baker (Milan Italy). Water reagent grade was produced with a Millipore purification pack system (milliQ water).
The physiological solution used as receptor fluid was prepared by dissolving 2.38 g of Na 2 HPO 4 , 0.19 g of KH 2 PO 4 and 9 g of NaCl into 1 L of milliQ water (final pH = 7.35).

All chemicals were analytical graded. Magnesium nitrate, urea, sodium chloride, sodium hydrogenphosphate, potassium dihydrogenphosphate, were purchased from Carlo Erba (Milan, Italy); lactic acid (90% v/v) was bought from Acros Organics (Geel, Belgium); nitric acid (69.5% v/v), hydrogen peroxide (30% v/v), hydrochloric acid (36.5e38% v/v), ammonium hydroxide (25% w/v) from Sigma Aldrich (Milan, Italy).
Ni nanopowder (CAS 7440-02-0) came from Sigma Aldrich (Milan, Italy), APS (Average Particle Size) < 100 nm, purity !99.9% trace metals basis).
Water reagent grade was produced with a Millipore purification pack system (milliQ water).