Microfluidic chip‐capillary electrophoresis for two orders extension of adjustable upper working range for profiling of inorganic and organic anions in urine

Guo, Wei Dong; Lau, Kap Man; Fung, Ying Sing

doi:10.1002/elps.201000297

Cited by 22 publications

(17 citation statements)

References 29 publications

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“…We have successfully developed an alkaline buffer for anion separation [21] at pH 8.4. In the present work, the pH is increased to 10.3 to reduce the run time to 3 min and to increase the stacking efficiency using a high ionic strength running buffer at pH 10.3 in couple with a low-conductivity sample.…”

Section: Optimization Of the Working Conditions Of The Microchip-ce Dmentioning

confidence: 99%

“…We have developed a microchip-CE device capable of 100 times on-chip dilution prior to CE separation for determining anions in urine [21]. Although the device offers a large enhancement factor, its offline active mixing mode requires extra operation time such as 2-5 min for offline mixing prior to CE separation and 1.5 min to wash the mixing vials between sample runs.…”

Section: Introductionmentioning

confidence: 99%

“…The recent rapid advance of microfluidic chip-CE devices [19][20][21] enables onsite determination of clinically important substances due to its high degree of integration, portability, minimal reagent consumption, high separation efficiency and rapid operation. It provides a promising hyphenated technique by combining microfluidic chip for sample pretreatment and CE for high efficient separation to enable onsite determination of nephrolithiasis markers.…”

Section: Introductionmentioning

confidence: 99%

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Microfluidic chip‐capillary electrophoresis with dynamic multi‐segment standard addition for rapidly identifying nephrolithiasis markers in urine

Guo

Fung

2011

Electrophoresis

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A microchip-CE device was fabricated for bed-side monitoring of nephrolithiasis biomarkers in urine by incorporating on-chip continuous passive mixing and standard addition to reduce sample matrix interference, increase sample throughput and eliminate accessories for active mixing. Under optimized conditions with buffer containing 20 mM borate and 0.5 mM CTAB at pH 10.3, sample and standards injected electrokinetically at -350 V for 10 s for online mixing in a Y-merging flow microchannel prior to CE separation and UV detection at 210 nm, both inhibitors (citrate, CA) and promoters (oxalate, OA and uric acid, UA) for nephrolithiasis can be separated and determined in human urine in a single run completed within 10 min after a simple 50-fold sample dilution and filtering. Satisfactory working ranges from 0.13-40, 0.25-40 and 0.025-40 mM, LOD 2.6, 6.1 and 0.7 μM, repeatability (%RSD, n=5) for migration time 1.40, 1.43, 0.47 and peak area 4.46, 6.10, 1.98, respectively, for CA, OA and UA are obtained for urine samples. The use of on-chip standard addition is shown to improve repeatability of the migration time, assist the identification of nephrolithiasis markers from difficult samples with noisy baseline and enlarge the working range for nephrolithiasis marker determination. The device developed can be used for both routine and emergency monitoring to deliver results on demand for bedside monitoring and public health protection. It provides an early detection of nephrolithiasis to enable timely treatments, ease anxiety of parents for neonates consuming suspected contaminated food, and quick results for patients in a critical condition.

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Section: Optimization Of the Working Conditions Of The Microchip-ce Dmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Microfluidic chip‐capillary electrophoresis with dynamic multi‐segment standard addition for rapidly identifying nephrolithiasis markers in urine

Guo

Fung

2011

Electrophoresis

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“…Active micromixers utilizing only magnetic force [47][48][49] are another recently emerging class of mixers for magnetic micro/nano-particles well-dispersed in the working fluids. Regarding the applications of magnetic microparticles, Rida and Gijs [50] presented an original concept of manipulation of magnetic microbeads in a microchannel.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis of a rapid magnetic microfluidic mixer

et al. 2011

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This paper presents a detailed numerical investigation of the novel active microfluidic mixer proposed by Wen et al. (Electrophoresis 2009, 30, 4179-4186). This mixer uses an electromagnet driven by DC or AC power to induce transient interactive flows between a water-based ferrofluid and DI water. Experimental results clearly demonstrate the mixing mechanism. In the presence of the electromagnet's magnetic field, the magnetic nanoparticles create a body force vector that acts on the mixed fluid. Numerical simulations show that this magnetic body force causes the ferrofluid to expand significantly and uniformly toward miscible water. The magnetic force also produces many extremely fine finger structures along the direction of local magnetic field lines at the interface in both upstream and downstream regions of the microchannel when the external steady magnetic strength (DC power actuation) exceeds 30 Oe (critical magnetic Peclet number Pe(m),cr = 2870). This study is the first to analyze these pronounced finger patterns numerically, and the results are in good agreement with the experimental visualization of Wen et al. (Electrophoresis 2009, 30, 4179-4186). The large interfacial area that accompanies these fine finger structures and the dominant diffusion effects occurring around the circumferential regions of fingers significantly enhance the mixing performance. The mixing ratio can be as high as 95% within 2.0 s. at a distance of 3.0 mm from the mixing channel inlet when the applied peak magnetic field supplied by the DC power source exceeds 60 Oe. This study also presents a sample implementation of AC power actuation in a numerical simulation, an experimental benchmark, and a simulation of DC power actuation with the same peak magnetic strength. The simulated flow structures of the AC power actuation agree well with the experimental visualization, and are similar to those produced by DC power. The AC and DC power actuated flow fields exhibited no significant differences. This numerical study suggests approaches to maximize the performance of the proposed rapid magnetic microfluidic mixer, and confirms its exciting potential for use in lab-on-a-chip systems.

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“…Capillary electrophoresis (CE) is considered to be one of the most accurate analytical techniques for urine analysis, offering a number of simple techniques for quantification of inorganic and organic cations and anions in urine. Direct and indirect UVdetection is used most often in CE [4][5][6][7][8][9][10]. Spectrophotometric techniques are applied for calcium, magnesium, phosphate, uric acid and creatinine quantification.…”

Section: Introductionmentioning

confidence: 99%