Icp multi element standard solution 4

Metal analysis was done using ICP-OES. For sample preparation, 0.12 mg and 0.24 mg of catalytic and reductase components, respectively, were dissolved in 0.5 ml of trace metal grade concentrated nitric acid and incubated for 12 h at 25 °C. Subsequently, the samples were boiled for 2 h at 90 °C before they were diluted 17-fold in distilled water. The metal content was analyzed with a 720/725 ICP-OES device (Agilent Technologies) on iron (λ = 238.204 nm), molybdenum (λ = 202.032 nm), nickel (λ = 216.555 nm) and zinc (λ = 213.857 nm). The device was operated with ICP Expert v4.1.0 software (Agilent Technologies). All analyzed metals were quantified using ICP multi-element standard solution IV (Merck) as a standard. The results were plotted using GraphPad Prism v9.

About 0.5 g of a fine powder of each sample was wet-oxidized with 10 mL of ultra-pure HNO₃ (67% v/v) in a closed MARS 6 - Microwave Accelerated Reaction System (Smith Farm Road, Matthews, NC, USA). The analyses were carried out using an ICP-OES system (iCAP™ 7400 Duo ICP-OES Analyzer, Thermo Scientific™, Germany) equipped with Thermo Scientific™ Qtegra™ Intelligent Scientific Data Solution™ (ISDS) software (Thermo Scientific™, Waltham, MA, USA). Quality assurance and quality control were assessed using an ICP multi-element standard solution IV (23 elements, 1000 mg/L) (Merck KGaA, Germany). A Periodic table mix 1 for ICP TraceCERT^® (Merck KGaA, Germany) was employed, 33 elements were used as a standard and results were expressed as mg/Kg of FW.

The determination of Al, As, Ba, B, Ca, Cu, Fe, K, Mg, Mn, Na, P, S, and Zn was carried out by inductively coupled plasma optical emission spectrometry (ICP-OES, IRIS Intrepid II XSP), while the concentration of Li and Sr was determined by microwave plasma atomic emission spectrometry (MP-AES 4100, Agilent Technologies). The certificated material used was ERM-CZ120. The recovery for all elements was under 5 %.
Six-point calibration solution series were diluted from multi-element calibration stock solution of 1,000 mg l⁻¹ (Merck ICP multi-element standard solution IV).

About 20 mg of tissue samples were analyzed by ICP-AES as previously described²¹ . Briefly, frozen samples were pulverized in liquid N₂ and kept immersed in 1.5 mL 60% HNO₃ at room temperature for 16 h. The sample suspension was subsequently subjected to wet ashing under the following conditions: 105 °C for 2 h, 160 °C for 16 h with 0.2 mL of 30% H₂O₂. After cooling down the solution was messed up to 10 g and then filtered. The resultant sample solutions were analyzed using an ICP instrument (Vista-Pro, Seiko Instruments/Varian Instruments, Chiba, Japan). The detection limits of each element were described in Table S1. The concentration of each inorganic metal was quantified using a calibration curve for the standard solution (ICP multi-element standard solution IV, Merck, Darmstadt, Germany). Resultant data were expressed as the mean ± 2 × standard error (2 S.E.)

To determine the transition metal concentrations, nasal samples and culture media were acidified by adding 1% final volume 65% HNO^3- in a final volume of 3 mL. Analyses were performed using a model X series I ICP-MS (Thermo Fisher Scientific) or on the iCAP-RQ ICP-MS (Thermo Fisher Scientific) and Cu²⁺, Co²⁺, Zn²⁺, Fe²⁺, Mg²⁺, Mn²⁺ and Ca²⁺ levels were measured in all samples. ICP-MS calibration was performed using ICP multi-element standard solution IV (Merck) ranging from 1 to 100 ppb. Quality control was run using 100 ppb ICP multi-element standard VIII (Merck) and 500 ppb Scandium was used as internal standard.

In order to determine the major (Na, K, Ca, Mg, Fe, Cu, Zn) and trace element concentrations (Co, Cr, Mn, Ni, Ba, Sr, Rb), an Xpert closed-vessel system (Berghof, Eningen, Germany) was used for sample digestion. Here, 200 mg of sample was digested using 10 mL HNO₃ 65% and 2 mL H₂O₂ 30% in polytetrafluoroethylene digestion vessels, using a four-step digestion program (120 °C and 170 °C—heating; 100 °C and 25 °C—cooling) for a total digestion time of 25 min. After, the vessels were cooled down and the volume was made up with ultrapure water to 20 mL. The resulting solutions were analyzed using an Optima 5300DV inductively coupled plasma optical emission spectrometer (ICP-OES, Perkin Elmer, Norwalk, CT, USA) for the determination of the major elements, and an ELAN DRC II inductively coupled plasma quadrupole mass spectrometer (ICP-MS, Perkin–Elmer, Waltham, MA, USA) for the determination of the minor elements. The calibration standards were prepared from ICP Multi-Element Standard Solution IV (1000 mg/L) (Merck, Darmstadt, Germany) for the ICP-OES and Multi-Element Calibration Standard 3 (10 mg/L) (Perkin Elmer Pure Plus, Waltham, MA, USA) at appropriate dilutions. The detection limits for the ICP-OES and ICP-MS are mentioned in the Supplementary Files, Table S1.

The major and trace elements were determined using an inductively coupled plasma optical emission Perkin Elmer Optima 5300DV (ICP-OES) spectrometer after microwave-assisted digestion using a Berghof Xpert system. An amount of 500 mg of ground tea was digested using 4 mL of HNO₃ at 65% and 6 mL of H₂O₂ at 30% in polytetrafluoroethylene digestion vessels using a four-step digestion program (145, 170, and 190 °C—heating; 50 °C—cooling) for a total digestion time of 40 min. Subsequently, the vessels were cooled down, and the volume was made up to the mark with ultrapure water. Blanks were prepared for each lot of samples. The calibration standards were prepared from Merck ICP multi-element standard solution IV, 1000 mg/L (Na, K, Ca, Mg, Fe, Cu, Mn, and Zn), and a mono-element standard solution, 1000 mg/L P. The accuracy in determining the major and trace element concentrations in tea samples was evaluated via NIST SRM 1515 Apple Leaves, achieving satisfactory recoveries (%) of K, Ca, Mg, Fe, Cu, Zn, and P (85.6–105.3%). The total nitrogen (N) was determined by combustion using a Flash EA 2000 CHNS/O analyzer (Thermo Fisher Scientific, Waltham, MA, USA).