Methanol concentration as a preceding eliminative marker for the authentication of Scotch Whiskies in Taiwan.

Modern rectified spirit is distilled ethanol (EtOH) containing only a tiny amount of methanol (MeOH), as opposed to former industrial alcohol, and is frequently used by perpetrators to adulterate or counterfeit Scotch whiskies in Taiwan. As a result, MeOH level presents an obvious discrepancy between adulterated whiskies and authentic Scotch whiskies. In this study, 54 authentic single malt Scotch whisky samples and 30 authentic blended Scotch whisky samples were comparatively analyzed. Instead of various analog internal standards often spiked for GC/MS quantitative analyses, the isotope-labeled internal standard 2H3-MeOH was employed for optimizing the Scotch whisky analysis to achieve a limit of quantitation (LOQ) of 5 ppm for MeOH. The resulting data were further analyzed by a distribution fitting method and showed that the distribution of MeOH levels corresponded to a lognormal distribution for both authentic single malt Scotch whiskies and authentic blended Scotch whiskies. Based on the statistical characteristics of the lognormal distribution, 99.7% of the MeOH concentrations would lie between 13.4 and 44.2 ppm for authentic single malt Scotch whiskies and between 7.87 and 74.9 ppm for authentic blended Scotch whiskies, suggesting that the MeOH level might serve as a marker for the authentication of the seized Scotch whiskies in Taiwan.

A novel approach to evaluate the extent and the effect of cross-contribution to the intensity of ions designating the analyte and the internal standard in quantitative GC-MS analysis.

In gas chromatography-mass spectrometry methods of analysis adopting the analyte's isotopic analog as the internal standard (IS), the cross-contribution (CC) phenomenon -- contribution of IS to the intensities of the ions designating the analyte, and vice versa -- has been demonstrated to affect the quantitation data. A novel approach based on the deviations of the empirically observed concentrations of a set of standards was developed to assess the accuracy of the empirically derived CC data. This approach demonstrated that normalization of ion intensities derived from the analyte and the IS generates reliable CC data. It further demonstrated that an ion-pair (designating the analyte and the IS) with approximately 5% or higher CC will result in a very limited linear calibration range.

Concentrations of calcium, copper, iron, magnesium, potassium, sodium and zinc in adult female hair with different body mass indexes in Taiwan.

We investigated concentrations of calcium, copper, iron, magnesium, potassium, sodium and zinc using atomic absorption spectroscopy in the hair of four groups of adult females (n = 392), ranging in age from 20 to 50 years, with different body mass index (BMI): BMI < 18, slim group; BMI 18-25, normal group; BMI 26-35, overweight or obese group; and BMI>35, morbidly obese group. We found that the group with BMI < 18 had the highest ratios for [Ca]/[Mg], [Fe]/[Cu] and [Zn]/[Cu], but the lowest ratio for [K]/[Na] in hair. On the contrary, the group with BMI > 35 had the highest ratio for [K]/[Na], but the lowest for [Fe]/[Cu] and [Zn]/[Cu] in hair. Furthermore, when we compared concentrations of Ca, Cu, Fe, Mg, K, Na and Zn between the groups with BMI < 18 and BMI > 35, we found that there were significant differences (p < 0.05) in zinc concentrations between these two groups. In addition, there were significant differences in Ca, Cu, Mg, K and Na concentrations, with p < 0.01 at least. From this point of view, we suggest that hair concentrations of Ca, Cu, Fe, Mg, K, Na and Zn may be correlated with adult female BMI, but further studies are needed.

Isotopic analogs as internal standards for quantitative GC/MS analysis--molecular abundance and retention time difference as interference factors.

The following analyte/isotope-labeled internal standard (IS) systems are adapted to further study the interference phenomenon previously reported from our laboratory--the intensity ratio of the ion-pair designated for a specific analyte/2H-analog system increases as the solvent used to reconstitute the extraction/derivatization residue is increased: (a) Three analyte/2H-analog pairs with 2H-atoms positioned at allylic sites (butalbital, secobarbital, methohexital); (b) Two analyte/2H-analog pairs without these structural features (pentobarbital, phenobarbital); and (c) Two analyte/13C-analog pairs (butalbital, secobarbital). Major experimental parameters adapted in this study include: (a) Varying reconstitution solvent volume while keeping a constant analyte/IS concentration ratio; (b) Varying analyte/IS concentration ratio; (c) Varying gas chromatograph (GC) injection port temperature; and (d) Varying GC column temperature programming conditions, rendering difference in the degree of overlap of the peaks derived from the analyte and the 2H-analog. This study results in the following observations: (a) Changes in the intensity ratio of the ion-pair designated for a specific analyte/2H-analog system depend on molecular abundance, regardless of whether the 2H-atoms are positioned at active allylic positions or not--thus, ruling out hydrogen/deuterium exchange as the cause of the observed interference phenomenon; (b) Variations in GC injection port temperature do not alter the observed interference phenomenon-thus, ruling out chemical reactions at the injection port as the underlying cause; (c) Variations in peak-overlapping between the analyte and the 2H-analog, facilitated by changing GC column programming conditions, alter the observed interference phenomenon. Abundance of the analyte and the 2H-analog and their overlapping characteristic in the mass spectrometer ion source are believed to be the underlying cause of the observed interference phenomenon. The interference phenomenon observed for a specific analyte/2H-analog system has significant consequences on the linearity of the thereby generated calibration curves. Nonlinear approaches can better describe the calibration data and are needed more in comparison to systems in which 13C-analogs are used as the ISs.