The accuracy and precision of the method was verified by analyzing Standard Reference Material 1589a (SRM 1589a) from the National Institute of Standards and Technology (Gaithersburg, MD), which has certified concentrations or reference concentrations for all compounds analyzed.
Accuracy was confirmed by analysis of a standard reference material for wheat flour (NIST 1567a), which had certified concentrations of 14.1 ± 0.5 mg kg−1 for Fe and 40 ± 2.0 mg kg−1 for Mg, and the concentrations found using proposed method were 13.7 ± 0.3 mg kg−1 for Fe and 40.8 ± 1.5 mg kg−1 for Mg.
Although their identity and concentration are not certified by NIST, we report values for OH-PCBs detected in the SRM (SI Table S6).
Jet milling of soils and sediments with known or certified pollutant concentrations is an attractive alternative for the production of model SPMs for the subsequent preparation of water test materials.
For quality control, we analyzed the reference material CRM No.18 (certified DMA concentration of 36 ± 9 µg/L; National Institute for Environmental Studies, Ibaraki, Japan) along with the collected samples.
The NO gas (AHG, Jeddah, Saudi Arabia) used in this study was certified at a concentration of 800 ppm NO with < 1% contamination by other oxides of nitrogen.
For H2S delivery and analysis, all gases were certified on grade or concentrations.
Since it is still an analytical niche application, there is a lack of appropriate reference materials certified for homogeneity and concentration of various metal(loid)s.
The ratio between the two fragments was 1.005, which closely approximated the value certified by sequencing, and the concentration was found to be 792 copies/ μ L. This method was precise, with an RSD of ~3%.
In the absence of a DNA reference material certified for absolute copy number concentration, results obtained from the ddPCR system were compared with results obtained from a 765-cdPCR platform.
