Hou Chun Liu

Geographic determination of coffee beans using multi-element analysis and isotope ratios of boron and strontium

This study aims to evaluate the feasibility of using chemical and isotopic compositions of coffee beans to identify their geographic origins. Twenty-one Coffea arabica beans collected from 14 countries in 3 major coffee-producing regions, Africa, America and Asia, were analysed for multi-element of B, Rb, Sr, Ba, Fe, Mn and Zn, as well as isotopic compositions of B and Sr. Our results demonstrate that the geographic origin of coffee beans could be classified based on concentrations of Rb, Sr and Ba. However, the isotope ratios of B and Sr provide more sensitive information for the growth localities. Combined with literature data, this study indicates that B and Sr isotopes are excellent indicators of the origin of coffee beans.

Distribution and accumulation of heavy metals in carbonate and reducible fractions of marine sediment from offshore mid-western Taiwan

Two marine sediment cores from offshore mid-western Taiwan were subsampled and pre-treated using a sequential extraction procedure to separate carbonate and reducible fractions. Aliquots of these extracts were analyzed to determine their chemical composition to evaluate the geochemical processes responsible for heavy metal distribution and accumulation in the coastal environment. Our data demonstrate that sedimentation rates derived from excess (210)Pb associated with metal fluxes show large increases circa A.D. 1990. A well-synchronized increase in metal flux in both geochemical fractions was found and validated by Pearsons correlation. Principal component analysis revealed the heavy metal fluxes to be highly correlated with the sediment deposition rate, with metal contamination potentially driven by a sole contributor. This study emphasizes the changes in sedimentation rate is potentially caused by activities associated with the inland economic development during this time, rather than by raising heavy metal pollution dominated the accumulation offshore mid-western Taiwan.

Precise determination of seawater calcium using isotope dilution inductively coupled plasma mass spectrometry

We describe a method for rapid, precise and accurate determination of calcium ion (Ca(2+)) concentration in seawater using isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). A 10 μL aliquot of seawater was spiked with an appropriate (43)Ca enriched solution for (44)Ca/(43)Ca ID-ICP-MS analyses, using an Element XR (Thermo Fisher Scientific), operated at low resolution in E-scan acquisition mode. A standard-sample bracketing technique was applied to correct for potential mass discrimination and ratio drift at every 5 samples. A precision of better than 0.05% for within-run and 0.10% for duplicate measurements of the IAPSO seawater standard was achieved using 10 μL solutions with a measuring time less than 3 minutes. Depth profiles of seawater samples collected from the Arctic Ocean basin were processed and compared with results obtained by the classic ethylene glycol tetra-acetic acid (EGTA) titration. Our new ID-ICP-MS data agreed closely with the conventional EGTA data, with the latter consistently displaying 1.5% excess Ca(2+) values, possibly due to a contribution of interference from Mg(2+) and Sr(2+) in the EGTA titration. The newly obtained Sr/Ca profiles reveal sensitive water mass mixing in the upper oceanic column to reflect ice melting in the Arctic region. This novel technique provides a tool for seawater Ca(2+) determination with small sample size, high throughput, excellent internal precision and external reproducibility.