Absolute contents of aroma-affecting volatiles in cooked rice determined by one-step rice cooking and volatile extraction coupled with standard-addition calibration using HS-SPME/GC-MS

To quantify volatiles in cooked rice, analysis methods for one-step rice cooking and volatile extraction in a single headspace vial, combined with standard addition calibration using solid-phase microextraction and GC-MS were developed and applied to 41 rice varieties with various fragrances and palatability. The newly developed methods significantly improved the qualitative and quantitative recovery of volatiles compared with conventional methods. Among 29 aroma-affecting volatiles, the highest average contents (ng/g) were observed for nonanal (39.30), octanal (13.29), and 1-octen-3-ol (13.18); the total volatile contents of aldehyde, base, and alcohol groups were 4156, 2481, and 1739 ng/g, respectively. Fifteen rice varieties contained 2-acetyl-1-pyrroline in range of 41.37-421.70 ng/g. Although there were no linear correlations among volatiles and the Toyo taste-score, multivariate PLS-DA analysis of the volatile could discriminate between low- and high-palatability rice varieties. The results indicated the accuracy and practicality of the newly developed methods for quantifying volatiles in cooked rice.

Single-point calibration and standard addition assays on calibrant-loaded paper-based analytical devices

This article describes a new, simplified approach for performing quantitative colorimetric assays on paper-based analytical devices that uses calibrant-loaded paper devices to perform external calibration and standard addition calibration using one calibration point. Calibrant-loaded devices consist of sensing areas pre-loaded with a colored product which is produced from the reaction of a standard solution of the analyte with the appropriate colorimetric reagents. When the sample is added into the calibrant-loaded sensing zone the analytical signal (i.e. color intensity) increases proportionally to the concentration of the analyte in the tested sample. The total measured signal corresponds to the sum of the concentration of the analyte in the sample and the standard solution pre-stored in the device and is used to calculate the concentration of the analyte in the sample based on the principles of linear calibration. The applicability of this approach was benchmarked in three colorimetric assays (i.e., for the determination of iron, nickel, and amino acids) that use different reaction chemistries. This work demonstrates a simplified calibration-free approach for assays performed on paper-based analytical devices that requires minimum experimental and computational effort, it can be used for either external or standard addition calibration and can be used to identify and eliminate the presence of interferences in a sample.

Inter-laboratory study for the certification of trace elements in seawater certified reference materials NASS-7 and CASS-6

Certification of trace metals in seawater certified reference materials (CRMs) NASS-7 and CASS-6 is described. At the National Research Council Canada (NRC), column separation was performed to remove the seawater matrix prior to the determination of Cd, Cr, Cu, Fe, Pb, Mn, Mo, Ni, U, V, and Zn, whereas As was directly measured in 10-fold diluted seawater samples, and B was directly measured in 200-fold diluted seawater samples. High-resolution inductively coupled plasma mass spectrometry (HR-ICPMS) was used for elemental analyses, with double isotope dilution for the accurate determination of B, Cd, Cr, Cu, Fe, Pb, Mo, Ni, U, and Zn in seawater NASS-7 and CASS-6, and standard addition calibration for As, Co, Mn, and V. In addition, all analytes were measured using standard addition calibration with triple quadrupole (QQQ)-ICPMS to provide a second set of data at NRC. Expert laboratories worldwide were invited to contribute data to the certification of trace metals in NASS-7 and CASS-6. Various analytical methods were employed by participants including column separation, co-precipitation, and simple dilution coupled to ICPMS detection or flow injection analysis coupled to chemiluminescence detection, with use of double isotope dilution calibration, matrix matching external calibration, and standard addition calibration. Results presented in this study show that majority of laboratories have demonstrated their measurement capabilities for the accurate determination of trace metals in seawater. As a result of this comparison, certified/reference values and associated uncertainties were assigned for 14 elements in seawater CRMs NASS-7 and CASS-6, suitable for the validation of methods used for seawater analysis.