Calibration Strategies for FT-IR and Other Isotope Ratio Infrared Spectrometer Instruments for Accurate δC and δO Measurements of CO in Air.

This paper describes calibration strategies in laboratory conditions that can be applied to ensure accurate measurements of the isotopic composition of the CO in ultradry air, expressed as δC and δO on the VPDB scale, with either FT-IR (in this case a Vertex 70 V (Bruker)) or an isotope ratio infrared spectrometer (IRIS) (in this case a Delta Ray (Thermo Fisher Scientific)). In the case of FT-IR a novel methodology using only two standards of CO in air with different mole fractions but identical isotopic composition was demonstrated to be highly accurate for measurements of δC and δO with standard uncertainties of 0.09‰ and 1.

Methane standards made in whole and synthetic air compared by cavity ring down spectroscopy and gas chromatography with flame ionization detection for atmospheric monitoring applications.

There is evidence that the use of whole air versus synthetic air can bias measurement results when analyzing atmospheric samples for methane (CH4) and carbon dioxide (CO2). Gas chromatography with flame ionization detection (GC-FID) and wavelength scanned-cavity ring down spectroscopy (WS-CRDS) were used to compare CH4 standards produced with whole air or synthetic air as the matrix over the mole fraction range of 1600-2100 nmol mol(-1). GC-FID measurements were performed by including ratios to a stable control cylinder, obtaining a typical relative standard measurement uncertainty of 0.

Normal phase-liquid chromatography-tandem mass spectrometry with atmospheric pressure photoionization for the purity assessment of 17β-estradiol.

A normal phase-liquid chromatography-hybrid tandem mass spectrometry (NP-LC-MS/MS) method utilizing atmospheric pressure photoionization (APPI) without dopant has been developed and implemented for the simultaneous determination of several estrogenic steroid hormones. The combination of both NP-LC and APPI-MS/MS tolerates the use of solvents that have the advantages of being self-doping for APPI and, at the same time, inhibit the in situ formation of estrogen dimers as frequently observed for conventional reversed phase (RP)-LC methods. The NP-LC-APPI-MS/MS method has been validated in-house, and its performance characteristics (linearity, repeatability, limits of detection, etc.

Accurate Fourier transform infrared (FT-IR) spectroscopy measurements of nitrogen dioxide (NO2) and nitric acid (HNO3) calibrated with synthetic spectra.

A novel method for determining the accuracy of laboratory-based measurements of nitrogen dioxide (NO2) and nitric acid (HNO3) mole fractions using Fourier transform infrared (FT-IR) spectroscopy 1 cm(-1) resolution instruments calibrated with synthetic spectra has been developed. The traceability of these measurement results is to the reference line strength data contained within the high-resolution transmission molecular absorption (HITRAN) database. Incorporating a proper estimate of the uncertainty of this data into the measurement results will ensure that the SI traceable values are encompassed within the uncertainty of the measurement results.

Mass balance method for the SI value assignment of the purity of organic compounds.

A mass balance method is described for determining the mass fraction of the main component of a high purity organic material. The resulting assigned value is established to be traceable to the SI and can be determined with a small associated measurement uncertainty. Pure organic materials with values and uncertainties determined in this way are necessary as primary calibrators of reference measurement systems in order to underpin the metrological traceability of routine measurement results.

Highly accurate nitrogen dioxide (NO2) in nitrogen standards based on permeation.

The development and operation of a highly accurate primary gas facility for the dynamic production of mixtures of nitrogen dioxide (NO(2)) in nitrogen (N(2)) based on continuous weighing of a permeation tube and accurate impurity quantification and correction of the gas mixtures using Fourier transform infrared spectroscopy (FT-IR) is described. NO(2) gas mixtures in the range of 5 μmol mol(-1) to 15 μmol mol(-1) with a standard relative uncertainty of 0.4% can be produced with this facility.

Simultaneous determination of various cardiac glycosides by liquid chromatography-hybrid mass spectrometry for the purity assessment of the therapeutic monitored drug digoxin.

A high performance liquid chromatography-hybrid tandem mass spectrometry (LC-MS(n)) method utilising electrospray ionisation has been developed and implemented for the simultaneous determination of several cardiac glycosides (CGs) as well as their corresponding aglycones formed by and extracted from herbaceous plants of the genus Digitalis. The method has been validated in-house and its performance characteristics (linearity, repeatability, limits of detection, etc.) were assessed for use in the quantification of CGs and their corresponding aglycones.