ABSTRACT
In this paper, we present the work of designing and fabricating a new generation of microelectromechanical systems (MEMS) based microfluidic preconcentrators (MFP) for volatile organic compounds (VOCs) quantification. The main objective of this work is to quantify the n-pentane impurities using MFP for sample preparation. The MFP was analyzed using Hewlett-Packard 5890 gas chromatography, having a flame ionization detector under isothermal conditions. The proposed MFP system includes two-microfluidic preconcentrators for continuous action and a system of four 3/2 solenoid valves with a control unit. Microfluidic preconcentrators were placed on metal plates and have circular channels filled with Al2O3 (50 µm), n-octane ResSil-C (80/100 mesh) sorbents of one nature and are hyphenated with the Peltier elements to regulate the temperature of sorption and desorption. The n-pentane quantitative determination was carried out using a calibration plot of gas mixtures on a successive dilution with the nitrogen. This study shows that the microfluidic preconcentrator system with Al2O3 and n-Octane ResSil-C sorbent concentrates the n-pentane traces up to 41 to 47 times from the gas mixture with the standard deviation of ≤5%. It has been observed that the n-octane ResSil-C based MFC shows very fast response (<5 min) and stability up to 300 cycles.
ABSTRACT
BACKGROUND: Automatic 24-hour ambulatory blood pressure (BP) monitoring (ABPM) is a basic procedure performed in adults with arterial hypertension, but ABPM monitors have become widely used in pediatric practice only recently. The main problem is the lack of common normative data sets for ABPM in children and the small number of appropriate monitors that can be used for analysis of the 24-hour BP profile in this age group. The aim of this study was to validate the BPLab(®) ABPM monitor according to the 1993 British Hypertension Society (BHS-93) protocol, as well as to work out solutions regarding the feasibility of this device in pediatric practice. METHODS: Our study included 30 children of both sexes and aged 5-15 years, ie, "older" children according to the BHS-93 protocol. Before starting the study, we obtained ethical approval from the regional scientific ethics committee. All participants and their parents signed their written consent for participation in the study. The data were simultaneously obtained by three experts, who had completed a noninvasive BP measurement training course. BP values were measured using the Korotkoff auscultatory method (Phase I for systolic BP and Phase V for diastolic BP). Discrepancies in the systolic and diastolic BP measurements (n=180; 90 for each expert) were analyzed according to the criteria specified in the BHS-93 protocol. RESULTS: The device was graded "A" for both systolic BP and diastolic BP according to the criteria of the BHS-93 protocol. CONCLUSION: The BPLab ABPM device may be recommended for extensive pediatric use.
