ChromiSense: A colourimetric lab-on-a-disc sensor for chromium speciation in water.

The development of a centrifugal device for quantitative analysis of both chromium (III) and (VI) species in water is reported. ChromiSense is a colourimetric sensor system that has been applied to the measurement of chromium in spiked river water samples. For analysis, the sample is loaded into a reservoir on the disposable microfluidic disc, along with reagents. A centrifugal force is created by spinning the disc to pump liquids through microchannels, causing them to mix and react to form a coloured product. The coloured product is then presented to a low-cost optical detection system, where absorbance measurements can be recorded. The optical detection system consists of a light emitting diode (LED) and photodiode (PD) couple. Chromium (III) was measured using 2,6-pyridine dicarboxylic acid as a ligand, forming a complex that was measured at 535nm and at 335nm. While measuring at 535nm allowed for the use of a low cost LED, the sensitivity was improved 2.5 times by measuring at 335nm. However, 335nm also yielded a diminished linear range with little improvement in limit of deteciton (LOD), and required a lengthier manufacturing process due to the need for a UV-transparent material. Chromium (VI) was detected using 1,5-diphenyl carbazide (DPC). This standard analysis method was simplified for automation on-disc, and optimised to achieve a low LOD. The LOD for trivalent and hexavalent chromium using this device were 21mgL-1 and 4μgL-1, respectively. The linear range for quantitative analysis was found to be 69-1000mgL-1 for Cr(III) and 14-1000μgL-1 for Cr (VI). While this range is high for Cr(III), incorporation of an off-disc pre-concentration method would make this technology suitable for environmental sample analysis. The device is simple to use, low in cost, and could provide rapid on-site measurements, with results comparable to those obtained using a benchtop spectrophotometer.

[1]  A. E. Greenberg,et al.  Standard methods for the examination of water and wastewater : supplement to the sixteenth edition , 1988 .

[2]  N. Blaton,et al.  The interaction of chromium(VI), chromium(III) and chromium(II) with diphenylcarbazide, diphenylcarbazone and diphenylcarbadiazone , 1977 .

[3]  G. Meyer,et al.  Two New Chromium(III) Complexes with the Pincer-type Pyridine-2,6-dicarboxylate Ligand , 2011 .

[4]  M. P. Callao,et al.  Chromium determination and speciation since 2000 , 2006 .

[5]  K. Girish Kumar,et al.  Spectrophotometric determination of chromium(III) with 2-hydroxybenzaldiminoglycine , 2006 .

[6]  Keng-Chang Hsu,et al.  An on-line microfluidic device coupled with inductively coupled plasma mass spectrometry for chromium speciation , 2013 .

[7]  J. Caruso,et al.  Chromium speciation by anion-exchange high-performance liquid chromatography with both inductively coupled plasma atomic emission spectroscopic and inductively coupled plasma mass spectrometric detection. , 1995, Journal of chromatography. A.

[8]  M. Demange,et al.  Sampling and analysis considerations for the determination of hexavalent chromium in workplace air. , 2003, Journal of environmental monitoring : JEM.

[9]  E. Salin,et al.  Speciation of chromium by high-performance thin-layer chromatography with direct determination by laser ablation inductively coupled plasma mass spectrometry. , 2008, Analytical chemistry.

[10]  R. Świetlik.  Speciation analysis of chromium in waters , 1998 .

[11]  K. Sano,et al.  Simultaneous Determination of Chromium(VI) and Chromium(III) by Capillary Electrophoresis , 1998 .

[12]  Jens Ducrée,et al.  PhosphaSense: A fully integrated, portable lab-on-a-disc device for phosphate determination in water , 2017 .

[13]  Jintae Kim,et al.  Centrifugal microfluidics for biomedical applications. , 2010, Lab on a chip.

[14]  Eric D. Salin,et al.  Pre-concentration of trace metals on centrifugal microfluidic discs with direct determination by laser ablation inductively coupled plasma mass spectrometry , 2009 .

[15]  D. Wallschläger,et al.  Determination of chromium(III) and chromium(VI) using suppressed ion chromatography inductively coupled plasma mass spectrometry , 2001 .

[16]  J. Ducrée,et al.  New strategies for stationary phase integration within centrifugal microfluidic platforms for applications in sample preparation and pre-concentration , 2017 .

[17]  R. Pflaum,et al.  The Chromium-Diphenylcarbazide Reaction1 , 1956 .

[18]  J. Dugas,et al.  Refractive-index variations with temperature of PMMA and polycarbonate. , 1986, Applied optics.

[19]  Matthew C. Mowlem,et al.  Reduction of surface roughness for optical quality microfluidic devices in PMMA and COC , 2010 .

[20]  B. Paull,et al.  Centrifugally-driven sample extraction, preconcentration and purification in microfluidic compact discs , 2011 .

[21]  Frank J. Millero,et al.  Viscosity of water at various temperatures , 1969 .

[22]  R. Naidu,et al.  Separation of chromium (III) and chromium (VI) by capillary electrophoresis using 2,6-pyridinedicarboxylic acid as a pre-column complexation agent. , 2001, Journal of chromatography. A.

[23]  A centrifugal microanalysis system for the determination of nitrite and hexavalent chromium. , 2009, Talanta.

[24]  Mehmet Toner,et al.  Microfluidic proportional flow controller , 2010, Journal of micromechanics and microengineering : structures, devices, and systems.