Absorption photometry of patterned deposits on IMPROVE PTFE filters.

The IMPROVE program (Interagency Monitoring of PROtected Visual Environments) tracks long-term trends in the composition and optics of regional haze aerosols in the United States. The absorptance of red (633-nm) light is monitored by filter photometry of 24 h-integrated samples of fine particulate matter (PM 2.5).

Elemental Characterization of Ambient Particulate Matter for a Globally Distributed Monitoring Network: Methodology and Implications.

Global ground-level measurements of elements in ambient particulate matter (PM) can provide valuable information to understand the distribution of dust and trace elements, assess health impacts, and investigate emission sources. We use X-ray fluorescence spectroscopy to characterize the elemental composition of PM samples collected from 27 globally distributed sites in the Surface PARTiculate mAtter Network (SPARTAN) over 2019-2023. Consistent protocols are applied to collect all samples and analyze them at one central laboratory, which facilitates comparison across different sites.

Evaluating IMPROVE PM element measurements.

The Interagency Monitoring of PROtected Visual Environments (IMPROVE) network has collected airborne particulate matter (PM) samples at locations throughout the United States since 1988 and provided chemical speciation measurements on the samples using several techniques including X-ray fluorescence (XRF). New XRF instruments for measuring PM elemental content of IMPROVE samples were introduced in 2011. To evaluate the performance of these new instruments relative to the old instruments, archived sample from three IMPROVE monitoring sites were retrieved and analyzed on the new instruments.

Analysis of black carbon on filters by image-based reflectance.

Black carbon (BC) is an important contributor to global particulate matter emissions. BC is associated with adverse health effects, and an important short-lived climate pollutant. Here, we describe a low cost method of analysis that utilizes images of PTFE filters taken with a digital camera to estimate BC content on filters.

Accelerator mass spectrometry best practices for accuracy and precision in bioanalytical (14)C measurements.

Accelerator mass spectrometers have an energy acceleration and charge exchange between mass definition stages to destroy molecular isobars and allow single ion counting of long-lived isotopes such as (14)C (t½=5370 years.). 'Low' voltage accelerations to 200 kV allow laboratory-sized accelerator mass spectrometers instruments for bioanalytical quantitation of (14)C to 2-3% precision and accuracy in isolated biochemical fractions.

Early human ADME using microdoses and microtracers: bioanalytical considerations.

Quantitative assessment of metabolites of drug candidates in early-phase clinical development presents an analytical challenge when methods, standards and assays are not yet available. Radioisotopic labeling, principally with radiocarbon ((14)C), is the preferred method for discovering and quantifying the absolute yields of metabolites in the absence of reference material or a priori knowledge of the human metabolism. However, the detection of (14)C is inefficient by decay counting methods and, as a result, high radiological human (14)C-doses had been needed to assure sensitive detection of metabolites over time.

Quantifying exploratory low dose compounds in humans with AMS.

Accelerator Mass Spectrometry is an established technology whose essentiality extends beyond simply a better detector for radiolabeled molecules. Attomole sensitivity reduces radioisotope exposures in clinical subjects to the point that no population need be excluded from clinical study. Insights in human physiochemistry are enabled by the quantitative recovery of simplified AMS processes that provide biological concentrations of all labeled metabolites and total compound related material at non-saturating levels.