Novel gravimetric measurement technique for quantitative volume calibration in the sub-microliter range

Abstract

We present a novel measurement method based on the gravimetric principles adapted from the ASTM E542 and ISO 4787 standards for quantitative volume determination in the sub-microliter range. Such a method is particularly important for the calibration of non-contact micro dispensers as well as other microfluidic devices. The novel method is based on the linear regression analysis of continuously monitored gravimetric results and therefore is referred to as ‘gravimetric regression method (GRM)’. In this context, the regression analysis is necessary to compensate the mass loss due to evaporation that is significant for very small dispensing volumes. A full assessment of the measurement uncertainty of GRM is presented and results in a standard measurement uncertainty around 6 nl for dosage volumes in the range from 40 nl to 1 µl. The GRM has been experimentally benchmarked with a dual-dye ratiometric photometric method (Artel Inc., Westbrook, ME, USA), which can provide traceability of measurement to the International System of Units (SI) through reference standards maintained by NIST. Good precision (max. CV = 2.8%) and consistency (bias around 7 nl in the volume range from 40 to 400 nl) have been observed comparing the two methods. Based on the ASTM and ISO standards on the one hand and the benchmark with the photometric method on the other hand, two different approaches for establishing traceability for the GRM are discussed.

Single-cell printing based on impedance detection

“…20 Due to the small volume of individual droplets, each measurement was performed on 50 droplets, which have been dispensed into a vial filled with silicone oil, to prevent evaporation. The piezo is driven by a specific electronic drive circuit (R5-Piezoelektronik, BioFluidix GmbH).…”

A Calibration-Free, Noncontact, Disposable Liquid Dispensing Cartridge Featuring an Online Process Control

“…38 We used an XP2U/M micro balance from Mettler Toledo (Columbus, OH), which provides readability down to 0.1 µg, corresponding to a droplet volume of 0.1 nL for water at standard conditions as described in previous publications. [38][39][40] The dispensing performance was evaluated with respect to the volumetric precision and accuracy within a run of 24 consecutive aliquots (Intrarun Coefficient of Variation [CV] and Intrarun Accuracy), among several syringe and tip assemblies (Tip-to-Tip CV and Tip-to-Tip Accuracy) and among several loading procedures of a single syringe and tip assembly (Load-to-Load CV and Load-to-Load Accuracy). Prior to each run, three predispenses were performed to increase precision by allowing the system to adapt to a set target volume.…”

Validación De Un Método Analítico Para Cuantificar Aluminio en Tejidos De Ratas Sprague Dawley Mediante Eaa-Flama Y Eaa-Horno De Grafito

“…El material volumétrico, así como las micropipetas (High Tech Lab) fueron calibrados mediante el método gravimétrico (Batista et al 2009, Lorefice 2009, Liang et al 2013, con una balanza analíti-ca marca Vibra modelo AF-R220E 220/0.0001g (Max/d). Esta balanza previamente fue calibrada con un juego de masas patrón de laboratorio (0.2, 0.5, 1 y 100 g) marca Rice Like, certificadas por la Entidad Mexicana de Acreditación (EMA).…”