Manual punch versus automated flow-through sample desorption for dried blood spot LC-MS/MS analysis of voriconazole.

Dried blood spot (DBS) sampling is a patient-friendly alternative for plasma sampling for the purpose of therapeutic drug monitoring (TDM). To speed up the analysis time, an automated flow-through desorption method of DBS samples may be beneficial. This article describes the cross-validation of a manual punch DBS method with an automated desorption (DBS autosampler, DBSA) method for the DBS analysis of the antifungal drug voriconazole, followed by cross-validation of both DBS methods with a plasma-based method, and an assessment of agreement between DBS/DBSA and regular plasma concentration measurements (gold standard) in samples from patients on voriconazole treatment. DBS and DBSA LC-MS/MS assays for voriconazole were validated according to the latest guidelines on bioanalytical method validation (FDA, EMA). Additional DBS-specific validation parameters included hematocrit effect and the influence of spot volume. Passing-Bablok regression and Bland-Altman plots were used to cross-validate the punch DBS, DBSA and plasma methods. The assessment of agreement between DBS/DBSA and plasma concentration measurements involved the performance of DBS/DBSA measurements to predict voriconazole plasma concentrations in patient samples. Both DBS methods complied with all validation parameters. Sample pre-processing time was reduced from 1.5 h to 3 min when using the DBSA. Cross-validation of both DBS methods showed a proportional bias and a correction factor was needed to interchange voriconazole concentrations of both DBS methods. Similarly, the punch DBS method required a factor to correct for proportional bias compared to the plasma method, but the DBSA and plasma assays showed no bias. Limits of agreement of the DBS/DBSA and plasma assays in Bland-Altman analysis were relatively wide, i.e. 0.75-1.28 for the DBS punch method versus plasma method and 0.57-1.38 for the DBSA versus plasma assay. Interpretation of DBS, DBSA and plasma samples in terms of concentrations in or outside of the voriconazole therapeutic range agreed in 82-86% of the cases. The variability in paired DBS/DBSA and plasma concentration measurements is considered high for TDM purposes and this limitation should be balanced against the advantages of DBS sampling of voriconazole and the speed of flow through desorption.

Design and Evaluation of Online/offline Interface Based on Double Loop for Two-dimensional Chromatography / 分析化学

By using a double loop technique based on a set of mechanical transmission components and a flow path system,a double function of injection and fraction collection was realized. On the basis of double loop technique,a novel type of online/offline interface for two-dimensional liquid chromatography was designed to construct an efficient separation system coupling two different separation modes with a higher peak capacity, and the functions of the interface were evaluated. By means of connecting the interface to an HPLC system, the multiple functions of injection, fraction collection and injection again were fulfilled for preparation and purity analysis of 4 kinds of aromatic compounds. As for combination of 2 sets of HPLC system,5 kinds of protein samples were separated preliminarily by strong cation exchange chromatography, and the components difficult to separate were collected and injected into reversed phase chromatographic system for further separation. Furthermore, the interface was applied to coupling two chromatographic systems in both strong cation exchange mode and microcolumn reversed-phase mode for the two-dimensional separation of bovine serum albumin enzymatic digest. When 1 mAU was set as the integral threshold,a total number of 292 peaks were identified. With the help of the online/offline interface, the preparation of microscale samples, fine separation of hardly separated samples and two-dimensional separation of complex samples were achieved flexibly. The result indicated that the system was a potent tool for the construction of two-dimensional chromatographic system and separation research.

Development and evaluation of a self-cleaning custom-built auto sampler controlled by a low-cost RaspberryPi microcomputer for online enzymatic activity measurements.

A fully automated on-site device (SAMP-FIL) that enables water sampling with simultaneous filtration and effective cleaning procedures of the device's components was developed and field-tested. The SAMP-FIL was custom-built using commercially available components and was controlled by a RaspberryPi single-board computer operating open-source software. SAMP-FIL was designed for sample pre-treatment with minimal sample alteration to meet the requirements of on-site measurement devices that cannot handle coarse suspended solids within the measurement procedure or cycle. A highly effective cleaning procedure provides a fresh and minimally altered sample for the connected measurement device. The construction and programmed software facilitates the use of SAMP-FIL for different connected measurement devices. The SAMP-FIL sample pretreatment was tested for over one year for rapid and on-site enzymatic activity (beta-d-glucuronidase, GLUC) determination (BACTcontrol) in sediment-laden stream water. The formerly used proprietary sampling set-up was assumed to lead to significant damping of the measurement signal due to its susceptibility to clogging, debris accumulation and bio-film accumulation. The implementation of SAMP-FIL considerably increased the error-free running time and measurement accuracy of BACTcontrol devices. This paper describes how low-cost microcomputers, such as the RaspberryPi, can be used by operators to substantially improve established measuring systems via effective sampling devices. Furthermore, the results of this study highlight the importance of adequate sample pretreatment for the quality of on-site measurements.

Study and Compatible Design of Two Types of Liquid Auto Sampler for Gas Chromatographer / 分析化学

We carried out parallel design and development of two differently structured auto sampler based on a multi-axis and multi-mode high-precision closed-loop servo control system. An integrated embedded control drive module was developed based on the idea of compatibility and inter-changeability, so that DC motor and encoder were standardized into uniform models. Meanwhile, electric and mechanical interfaces were uniformed to a same standard. This allows the direct exchange of above-mentioned components between the two models. A 1-μL manual sample injection syringe was installed on both standard 110-sample and platform 40-sample liquid auto sample injectors connected with gas chromatographer. Approximately 0. 5μL of cetane-isooctyl was sampled for 6 consecutive times at six different positions in the sample bottle. The repeatability RSDs of the injection peak areas of the two systems were 1. 1% and 1. 5%, respectively. A linear correlation coefficient (0. 9947) of peak area with injection volume was achieved based on the gradient sampling volume of 0. 1, 0. 3, 0. 5, 0. 7 and 0. 9 μL.