Optima 8300 icp oes

Total carbon and nitrogen (C_t and N_t) were determined by dry combustion using the elemental analyzer (UNICUBE^® Elementar Analysensysteme GmbH, Langenselbold, Germany). For measurements of algae-dominated biocrusts containing a high amount of associated sand grains, 100 mg was used. For thicker, biomass-rich biocrusts, 50 mg per sample was sufficient. Total phosphorus (P_t) was extracted from 500 mg of air-dried material by microwave-assisted digestion using aqua regia solution (3:1 hydrochloric acid—nitric acid). The concentration in the extract was measured by inductively coupled plasma optical emission spectroscopy at a 214 mm wavelength (ICP-OES Optima 8300, PerkinElmer, Inc. 710 Bridgeport Avenue Shelton, CT 06484-4794, USA).

The degree of metal accumulation in BSF larvae fed with chicken feed containing 0 to 50% (w/w) mackerel by-products was analyzed. Heavy metals such as arsenic (As), cadmium (Cd), and lead (Pb) were measured according to the method mentioned in the Food Code [34 ] using inductively coupled plasma optical emission spectroscopy—ICP OES Optima 8300 (PerkinElmer Inc., Billerica, MA, USA). The total mercury (Hg) content was analyzed using the EPA 7473 method [35 (link)] with a Hydra IIc Mercury Analyzer (Teledyne Leeman Labs, Mason, OH, USA). In addition, the heavy metal reduction percentage (MR%) in BSF larvae was calculated using Equation (6).
$$\mathrm{MR} \left(\%\right)=\left(\frac{\left({\mathrm{M}}_{\mathrm{BSFL}}-{\mathrm{M}}_{\mathrm{SBSFL}}\right)}{\left({\mathrm{M}}_{\mathrm{BSFL}}-{\mathrm{M}}_{\mathrm{SBSFL}}\right)+\left({\mathrm{M}}_{\mathrm{TF}}-{\mathrm{M}}_{\mathrm{BSFLD}}\right)}\right)\times 100$$
where M_BSFL means the heavy metals in BSF larvae that consumed chicken feed containing 0 to 50% (w/w) mackerel head, fasted, and with feces removed; M_SBSFL indicates heavy metals in BSF larvae before starting the feeding experiments; M_TF indicates heavy metals in chicken feed supplemented with 0 to 50% (w/w) mackerel head; M_BSFLD means heavy metals in the feces of BSF larvae.

The biosorption capability of bacterial isolates was assayed as above; the biosorption of metal ions was measured by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES optima 8300, Perkin Elmer, Massachusetts, USA). The ICP-OES was calibrated with standard working metal solutions and blank as above to set limits of detection (10–1000 ppm). The emission lines used for the analysis were 327.393 nm, 228.802 nm, and 340.458 nm for copper, cadmium, and lead, respectively, under Argon plasma with the concentric nebulizer. The residual metal concentration was deduced from internal standard curve produced from standardisation before running the samples and culture free control [21 (link)].

The samples were air dried in the darkness for 72 h and subsequently homogenized and again sieved with a metallic mesh (2 mm) and stored. pH, and electrical conductivity (EC) were determined in air dried samples following standard protocols based on Sparks et al. [31 ]. Soil pH and EC were measured in saturation extracts.
For elemental characterization soil samples were grounded to pass through a 0.180 mm sieve. Total C (TC) and N (TN) were determined with a 2400 Series II CHNS Elemental Analyzer (PerkinElmer) calibrated with the LECO CNS 2000 standard. Organic C (OC) was determined in sample aliquots after removal of carbonates using 5 N HCl. Metals such as Cd, Co, Cu, Ni, Pb, and Zn were measured in HNO₃-digested soil samples (Anton Paar Multiwave 3000 for 10 min) by ICP-OES (Perkin Elmer ICP-OES Optima 8300) [32 (link)].

Pulverized dental specimen (0.2 g) (Primary teeth: 49; Permanent teeth: 49) was taken with the help of precision scales, and placed in plastic tubes (Total: 98 tubes). Firstly 3 ml of H2O2 (hydrogen peroxide), and then 2 ml of HNO3 (nitrite oxide) were added to the each tube. After that, the solution was subjected to dissolution. The samples were prepared to be ready for reading by adding distilled water until the total volume was 25 ml. The solution samples prepared for the analysis were read at different wavelengths for each element (Sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), and phosphate (P)) in ICP-OES device (Perkin-Elmer, ICP/OES Optima 8300). The data were recorded in ppm.

Soil samples (12 subsamples of the composite sample) were collected with the aid of a hand steel auger, in the 0–0.20 m soil layer, across the experimental area in 2009, and in each plot in 2017. Soil samples were air-dried and ground until reaching particles smaller than 2 mm, before analyses [47 ]: pH in 1:1 soil-to-water volumetric ratio; clay by densimetry; Mehlich-1 ex-traction for P, K, Cu, Zn and Fe; KCl extraction for Mn; and hot water extraction for B. Elements were quantified through plasma-emission spectroscopy (ICP-OES—Optima^® 8300, Perkin Elmer, Waltham, MA, USA). Total carbon was quantified through dichromate oxidation (Walkley–Black) and multiplied by 1.724 in order to assess organic matter content [48 ].
Soil acidity was corrected with dolomitic limestone in order to raise pH to 6.0 three months before seedlings’ planting in April 2009. Phosphorus (P) and K levels in the soil were corrected to reach high level of both nutrients, according to [45 ]. Limestone, triple superphosphate and potassium chloride were broadcast applied and incorporated into the 0–0.30 m soil layer after a whole sequence of subsoiling, plowing and harrowing. Soil analyses at experiment onset and at the end of it are shown in Table 1.