Pump- and Valve-Free Flow Injection Capillary Liquid Electrode Discharge Optical Emission Spectrometry Coupled to a Droplet Array Platform

Abstract

A miniature (2.5 cm length × 2.0 cm width × 1.0 cm height), low power (<10 W), and capillary liquid electrode microplasma optical emission spectrometer was developed for rapid determination of metallic species in aqueous solutions. The sample solution can be automatically introduced into the source without a pump owing to the inherent capillary attraction and the force arising from the solution vaporization induced by microplasma. A droplet array was used as a sampling platform to realize flow injection without using any valve and pump, significantly increasing throughput to 90 samples h. Sample volume is controlled through the sampling time and reduced to the nanoliter level. With a sampling time of 10 s (equal to 600 nL), detection limits of 30 μg L (18 pg) and 75 μg L (45 pg) were obtained for Cd and Hg, respectively, comparable to those reported for liquid electrode microplasma optical emission spectrometry. However, sample consumption is reduced more than 100-fold, making the proposed technique more suitable for the analysis of elements such as Cd, Hg, Li, Na, and K when sample volumes may be limited. The utility of this system was demonstrated by the determination of Cd and Hg in blood, real water samples, and Certified Reference Materials (rice powder, GBW07601a, and lobster hepatopancreas, TORT-3).

Integration of Flow Injection Capillary Liquid Electrode Discharge Optical Emission Spectrometry and Microplasma-Induced Vapor Generation: A System for Detection of Ultratrace Hg and Cd in a Single Drop of Human Whole Blood

“…Furthermore, the careful operation of this device is required because it is not easy to absolutely prevent high voltage from travelling to the operation table and causing injury to the operator. In order to overcome these shortcomings, a silver film was deposited on the outer surface of the capillary via silver mirror reaction to allow the high voltage to directly conduct along the outer surface of the capillary to its end, thus eliminating the generation of bubbles in the capillary and improving the stability of the microplasma. Moreover, the silver film on the end of the capillary immersed into the sample solution was scraped off with a knife, which would significantly alleviate the risk of injury from electric shock to the operator.…”

“…Most recently, a pump- and valve-free flow injection capillary liquid electrode microdischarge (CLED) OES system has been developed for elemental analysis. , Owing to the capillary action and sample vaporization in the microplasma, the sample solution could be automatically introduced into the plasma to generate atomic emission lines of analytes. In this system, sample consumption could be accurately controlled by sampling time and reduced to the nanoliter level.…”

Growth of Carbonaceous Nanoparticles on Steel Fiber from Candle Flame for the Long-Term Preservation of Ultratrace Mercury by Solid-Phase Microextraction

“…On the other hand, although the considerable improvements of atomic spectrometry have been achieved and even permit directly reporting the content of toxic metals in natural water, their instrumentation is still too bulky, expensive, and gas- and power-consuming to be used for field analysis. Recently, many studies demonstrated that a miniature microplasma atomic spectrometer retains promising potential for the field analysis of toxic metals. ,− However, the low sensitivities of the microplasma atomic spectrometers limit the scope of elements amenable to detection. Interestingly, the use of SPME for sample introduction means miniaturized point discharge optical emission spectrometry (μPD-OES) could improve the detection limit at least 100-fold for Hg and Pb compared to other sampling techniques .…”

Fabrication of a Microfluidic Flame Atomic Emission Spectrometer: a Flame-on-a-Chip

“…The miniaturization efforts have only barely touched atomic spectrometry. Although a few papers appeared about miniaturized plasmas (inductively coupled plasma (ICP), capacitively coupled plasma (CCP), microwave-induced plasma (MIP), or dielectric barrier discharge (DBD) − ) used for element-selective detection, those did not become widely used. In addition, the graphite furnace or flame techniques have not been transferred to microchip format and only a very few papers appeared about hyphenation of microchips with atomic spectrometers.…”