Accurate non-ceruloplasmin bound copper: a new biomarker for the assessment and monitoring of Wilson disease patients using HPLC coupled to ICP-MS/MS.

OBJECTIVES: Assessment of Wilson disease is complicated, with neither ceruloplasmin, nor serum or urine copper, being reliable. Two new indices, accurate non-ceruloplasmin copper (ANCC) and relative ANCC were developed and applied to a cohort of 71 patients, as part of a Wilson Disease Registry Study. METHODS: Elemental copper-protein speciation was developed for holo-ceruloplasmin quantitation using strong anion exchange chromatography coupled to triple quadrupole inductively coupled plasma mass spectrometry. The serum proteins were separated using gradient elution and measured at m/z 63 (63Cu+) and 48 (32S16O+) using oxygen reaction mode and Cu-EDTA as calibration standard. The ANCC was calculated by subtraction of the ceruloplasmin bound copper from the total serum copper and the RelANCC was the percentage of total copper present as the ANCC. RESULTS: The accuracy of the holo-ceruloplasmin measurement was established using two certified reference materials, giving a mean recovery of 94.2 %. Regression analysis between the sum of the copper containing species and total copper concentration in the patient samples was acceptable (slope=0.964, intercept=0, r=0.987) and a difference plot, gave a mean difference for copper of 0.38 µmol/L. Intra-day precision for holo-ceruloplasmin at serum copper concentrations of 0.48 and 3.20 µmol/L were 5.2 and 5.6 % CV and the intermediate precision at concentrations of 0.80 and 5.99 µmol/L were 6.4 and 6.4 % CV, respectively. The limit of detection (LOD) and lower limit of quantification (LLOQ) for holo-ceruloplasmin were 0.08 and 0.27 µmol/L as copper, respectively. CONCLUSIONS: ANCC and Relative ANCC are important new diagnostic and monitoring biomarker indices for Wilson disease (WD).

Biomedical copper speciation in relation to Wilson's disease using strong anion exchange chromatography coupled to triple quadrupole inductively coupled plasma mass spectrometry.

Biomedical analytical methods often rely on indirect measurements, such as immunoassays, which can lack effective metrological traceability. In the nephelometric determination of ceruloplasmin (Cp), an important protein whose circulating level is altered in Wilson's disease (WD), the anti-Cp antibody used is not specific for the biologically active holoprotein so the assay can overestimate the concentration of Cp due to the presence of the apoprotein. By providing quantitation using elemental standards, the use of strong anion exchange chromatography (SAX) coupled to triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS-MS) can overcome the drawbacks of methods for the measurement of metalloproteins reliant on immunoassays. In the current study, a SAX-ICP-MS-MS method for Cp quantification was designed and tested in samples of blood serum of WD patients and healthy controls. Using standards based on a copper-EDTA complex for calibration, the method provides relatively simple quantification of Cp with the limit of detection of 0.1 µg L-1 (limit of quantification 0.4 µg L-1). The method was also used to investigate the copper species separated by using a 30 kDa cut-off ultrafiltration device. The so-called "exchangeable" copper fraction is considered as an alternative clinical biomarker of WD. Using the designed speciation approach, it was shown that the ultrafiltration method can overestimate the "exchangeable" copper fraction due to a removal of copper from Cp. This was confirmed by comparing the enzymatic activity of the fractions. Thus, the specificity of the "exchangeable" copper test can be ensured only under strict maintenance of ultrafiltration conditions.

Time-varying analysis of electrodermal activity during exercise.

The electrodermal activity (EDA) is a useful tool for assessing skin sympathetic nervous activity. Using spectral analysis of EDA data at rest, we have previously found that the spectral band which is the most sensitive to central sympathetic control is largely confined to 0.045 to 0.25 Hz. However, the frequency band associated with sympathetic control in EDA has not been studied for exercise conditions. Establishing the band limits more precisely is important to ensure the accuracy and sensitivity of the technique. As exercise intensity increases, it is intuitive that the frequencies associated with the autonomic dynamics should also increase accordingly. Hence, the aim of this study was to examine the appropriate frequency band associated with the sympathetic nervous system in the EDA signal during exercise. Eighteen healthy subjects underwent a sub-maximal exercise test, including a resting period, walking, and running, until achieving 85% of maximum heart rate. Both EDA and ECG data were measured simultaneously for all subjects. The ECG was used to monitor subjects' instantaneous heart rate, which was used to set the experiment's end point. We found that the upper bound of the frequency band (Fmax) containing the EDA spectral power significantly shifted to higher frequencies when subjects underwent prolonged low-intensity (Fmax ~ 0.28) and vigorous-intensity exercise (Fmax ~ 0.37 Hz) when compared to the resting condition. In summary, we have found shifting of the sympathetic dynamics to higher frequencies in the EDA signal when subjects undergo physical activity.

Dietary acrylamide exposure estimates for the United Kingdom and Ireland: comparison between semiprobabilistic and probabilistic exposure models.

Since the discovery of acrylamide in foods, there have been many calculations of dietary exposure. Total diet studies have been commonly used to estimate consumer exposure of acrylamide; however, these often fall short in evaluating true exposure levels because of limitations in small occurrence data sets. Dietary exposure to acrylamide can also be estimated by use of modeling packages. The U.K. Food Standards Agency and the Food Safety Authority of Ireland have prepared estimates for dietary acrylamide exposure using semiprobabilistic and probabilistic modeling. Occurrence data were obtained from the European Union acrylamide monitoring database, whereas consumption data were obtained from the relevant U.K. and Irish National Diet and Nutrition Surveys. The mean adult U.K. consumer exposure was estimated as 0.61 microg/kg of body weight (bw)/day and high-level adult consumer exposure (P97.5) as 1.29 microg/kg of bw/day. The mean adult Irish consumer exposure was estimated as 0.59 microg/kg of bw/day and the high-level adult consumer exposure (P97.5) as 1.75 microg/kg of bw/day. Owing to the wide range of acrylamide levels in foods, semiprobabilistic modeling does not always provide an accurate picture of dietary exposure levels and patterns. Therefore, a comparison of semiprobabilistic assessments to probabilistic assessments of U.K. and Irish dietary exposure estimates of certain food groups is provided.

Use of chloroflurocarbons as internal standards for the measurement of atmospheric non-methane volatile organic compounds sampled onto solid adsorbent cartridges.

Solid adsorbents have proven useful for determining the vertical profiles of volatile organic compounds (VOCs) using sampling platforms such as balloons, kites, and light aircraft, and those profiles provide valuable information about the sources, sinks, transformations, and transport of atmospheric VOCs. One of the largest contributions to error in VOC concentrations is the estimation of the volume of air sampled on the adsorbent cartridge. These errors arise from different sources, such as variations in pumping flow rates from changes in ambient temperature and pressure with altitude, and decrease in the sampling pump battery power. Another significant source for sampling rate variations are differences in the flow resistance of individual sampling cartridges. To improve the accuracy and precision of VOC measurements, the use of ambient chlorofluorocarbons (CFCs) as internal standards was investigated. A multibed solid adsorbent, AirToxic (Supelco), was chosen for its wide sampling range (C3-C12). Analysis was accomplished by thermal desorption and dual detection GC/FID/ECD, resulting in sensitive and selective detection of both VOCs and CFCs in the same sample. Long-lived chlorinated compounds (CFC-11, CFC-12, CFC-113, CCl4 and CH3CCl3) banned by the Montreal Protocol and subsequent amendments were studied for their ability to predict sample volumes using both ground-based and vertical profiling platforms through the boundary layer and free troposphere. Of these compounds, CFC-113 and CCl4 were found to yield the greatest accuracy and precision for sampling volume determination. Use of ambient CFC-113 and CCl4 as internal standards resulted in accuracy and precision of generally better than 10% for the prediction of sample volumes in ground-, balloon-, and aircraft-based measurements. Consequently, use of CFCs as reference compounds can yield a significant improvement of accuracy and precision for ambient VOC measurements in situations where accurate flow control is troublesome.

Minimization of water vapor interference in the analysis of non-methane volatile organic compounds by solid adsorbent sampling.

Water vapor can be a significant interference in the analysis of air for non-methane volatile organic compounds (NMVOCs) using solid-adsorbent sampling techniques. The adsorbent materials used in sampling cartridges have different hydrophobic characteristics, and it is therefore necessary to characterize solid-adsorbent cartridges over a wide range of humidity. Controlled humidity experiments were performed to assess the extent of water vapor interference when samples are collected onto AirToxics solid-adsorbent cartridges. It was found that elevating the temperature of the cartridge to 10 degrees C above the temperature of the air sample greatly reduced water vapor adsorption and interferences and resulted in > or = 90% recovery of NMVOCs, biogenic VOCs and chlorofluorocarbons. Similar collection efficiencies were obtained at ambient temperature by reducing the relative humidity to > or = 60% in the sample by dilution with dry, scrubbed ambient air. A procedure also was developed and optimized for dry-purging cartridges prior to analysis. However, under optimized conditions, significant losses of C3-C5 compounds still occurred under highly humid conditions. It was determined that these losses were due to reduced retention during sampling rather than loss during the dry purge procedure. The dry purge method was shown to be adequate at high humidities for sampling NMVOCs with retention indices greater than 500.