A method,
system and apparatus for an automated sample introduction
system, utilizing a demountable direct injection high efficiency
nebulizer (d-DIHEN) is provided which incorporates an
inductively coupled plasma optical emission spectrometer (ICP-OES) for the measurement of the
phosphorus content in acid-digested nucleotides and deoxyribonucleic acid (
DNA). The solution
uptake rate and volume are reduced from 170 μL min−1 to 30 μL min−1 and 10 mL to 2.4 mL, respectively, thereby reducing the required
DNA sample mass for solutions containing 3 μg−1 P from 300 μg to 72 μg
DNA, in comparison to previous analyses in our lab using a glass, concentric
nebulizer with cyclonic spray chamber arrangement. The use of direct injection also improves P (I) 213.617 nm sensitivity by a factor of 4 on average. A high performance (HP) methodology in combination with the previous sample introduction
system and ICP-OES provides simultaneous, time-correlated internal
standardization and drift correction resulting in relative expanded uncertainties (% U) for the P
mass fractions in the range of 0.1 to 0.4 (95% confidence level) for most of the
thymidine 5′-monophosphate (TMP), calf thymus DNA (CTDNA), and
plasmid DNA (PLDNA) analyses. The d-DIHEN with HP-ICP-OES methodology allows for the quantification of DNA
mass at P
mass fractions as low as 0.5 μg g−1, further reducing the required DNA mass to 12 μg, with small uncertainty (≦0.4%). The
present method, system and apparatus can aide in the development and certification of
nucleic acid certified reference materials (CRMs), particularly for these samples that are typically limited in volume.