Method development for HILIC assays.

In this review, method development for hydrophilic interaction LC (HILIC) is highlighted. HILIC is a chromatographic technique that uses aqueous-organic solvent mobile phases with a high organic-solvent fraction, and a hydrophilic stationary phase. It is mainly applied for the separation of polar and hydrophilic compounds. Method development, in general, can be done uni- or multivariately. In the univariate approach, the factors that are expected to potentially affect the separation of the compounds will be examined sequentially and one-at-a-time. All HILIC methods found in the literature were developed in this way. For these methods, the analytes, the considered factors, the selected responses, and the finally chosen experimental conditions are discussed in this review. Where examined, the method validation and the comparison with other analytical assay methods is also described. For the multivariate method-development approach, which is based on the use of experimental designs, only a possible strategy is presented, because of the lack of relevant publications in the literature.FLWINinfo:eu-repo/semantics/publishe

CHAPTER IN BOOK: Experimental design methodologies in the optimization of chiral CE or CEC separations

info:eu-repo/semantics/publishe

POSTER: Precision optimisation of chiral capillary electrophoretic methods: constant current mode

info:eu-repo/semantics/nonPublishe

ORAL PRES. Precision optimisation of chiral capillary electrophoretic methods: constant current versus constant voltage

info:eu-repo/semantics/nonPublishe

ORAL PRES. Fused-core stationary phases for fingerprint development of Phyllanthus and Mallotus species

info:eu-repo/semantics/nonPublishe

ORAL PRES. Quantitation of opioids in human plasma by means of UPLC-MS: triple quadrupole (QqQ) versus quadrupole-time of flight (Q-tof) mass analyzer,

info:eu-repo/semantics/nonPublishe

Comparison of a triple-quadrupole and a quadrupole time-of-flight mass analyzer to quantify 16 opioids in human plasma

The aim of this work is to study whether a quadrupole time-of-flight (QToF) mass analyzer, coupled to an ultra high performance liquid chromatography (UHPLC) system, can be a valuable alternative for a triple-quadrupole (QqQ) mass analyzer, for quantitative toxicological purposes. The case study considered was the quantification of 16 opioids (6-monoacetylmorphine, buprenorphine, codeine, dihydrocodeine, ethylmorphine, fentanyl, hydrocodone, hydromorphone, morphine, norbuprenorphine, norcodeine, norfentanyl, oxycodone, oxymorphone, pholcodine and tilidine) in human plasma. Both methods were validated in parallel in terms of selectivity, matrix effects, extraction recovery, carry-over, bias, precision and sensitivity. Accuracy-profile methodology was used to determine the optimal calibration model, and to estimate bias, repeatability, intermediate precision and total error. Selectivity was demonstrated for all opioids and deuterated analogues, except for codeine-d3 on the UHPLC-QTOF. For most compounds, extraction recoveries were in the range 60 to 80% on both systems, except for the synthetic analogues, buprenorphine, fentanyl and tilidine, where large variability is observed. Carry-over was negligible on both systems. For different opioids, the optimal calibration model was different between the systems. The accuracy profiles of the majority of the opioids indicated that, over the entire tested concentration range, for more than 5% of the future measurements, total errors are expected to exceed the a priori defined 15% acceptance limit. For some exceptions, however, the measurements even suffer from total errors above 30%, which can be attributed to the solid phase extraction procedure that was applied as sample pretreatment technique. Sensitivity was generally tenfold better on the LC-QToF system, probably due to the difference in ion choice for quantification between both systems. In conclusion, the best performing system seemed to depend on the compound, on the parameter and even on the concentration. Accuracy profiles clearly provided valuable information complementary to that obtained in classical validation tests, and therefore preferably are taken into account when deciding on a method's performance.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Gas Chromatographic Fingerprint Analysis for the Comparison of Seized Cannabis Samples

Cannabis sativa L. is widely used as recreational illegal drugs. Illicit Cannabis profiling, comparing seized samples, is challenging due to natural Cannabis heterogeneity. The aim of this study was to use GC–FID and GC–MS herbal fingerprints for intra (within)- and inter (between)-location variability evaluation. This study focused on finding an acceptable threshold to link seized samples. Through Pearson correlation-coefficient calculations between intra-location samples, ‘linked’ thresholds were derived using 95% and 99% confidence limits. False negative (FN) and false positive (FP) error rate calculations, aiming at obtaining the lowest possible FP value, were performed for different data pre-treatments. Fingerprint-alignment parameters were optimized using Automated Correlation-Optimized Warping (ACOW) or Design of Experiments (DoE), which presented similar results. Hence, ACOW data, as reference, showed 54% and 65% FP values (95 and 99% confidence, respectively). An additional fourth root normalization pre-treatment provided the best results for both the GC–FID and GC–MS datasets. For GC–FID, which showed the best improved FP error rate, 54 and 65% FP for the reference data decreased to 24 and 32%, respectively, after fourth root transformation. Cross-validation showed FP values similar as the entire calibration set, indicating the representativeness of the thresholds. A noteworthy improvement in discrimination between seized Cannabis samples could be concluded