利用分叉微通道提高夹切进样微流控芯片电泳可靠性的探索

Improvement of Reliability for Microchip Electrophoresis with Pinched Sample Injection Through Branched Microchannels

微流控芯片电泳在众多领域都有广阔的应用前景,但该技术的实际应用仍不多见,成功的微流控芯片电泳分析通常需要精确调控各储液池的液面高度、电极的位置等细节,对操作者的技术要求高。该研究在传统电泳芯片的进样通道和分离通道末端引入分叉结构,增加额外的储液池,利用液面差实现进样通道末端和分离通道末端溶液的持续更新,并以有机磷除草剂为模型分析物考察了设计的适用性。结果表明,在夹切进样条件下,利用该芯片可有效缩短连续多次进样分析时的进样时间,避免基线异常抬升,显著提高了分析结果的重现性。在选定的条件下,连续测定120次未发现分离性能的变化,峰高的相对标准偏差(RSD)可达0.56%。通过调整进样时间还可避免样品基体进入分离通道,简化分离谱图。

Microchip electrophoresis has shown its potential of application in many fields,but its utilization in real world is still limited.To achieve a successful separation on a microchip through electrophoresis,many details have to be carefully taken into account,such as the liquid levels of each reservoir,the exact location of each electrode etc.,skillful operation is therefore required.In this paper,branched microchannels were introduced at the inlet end of the sampling channel and the outlet of the separation channel of traditional microchips for electrophoresis with a cross configuration.Additional reservoirs were made,and the liquid levels of these two reservoirs were lower than that of the sample reservoir and the buffer waste reservoir,maintaining continuous refreshing at the branched points through siphoning.With 2 fluorescein isothiocyanate labeled organophosphorus herbicides,i.e.glyphosate and glufosinate,and a degradation product,(aminomethyl )phosphonic acid,the applicability of the proposed microchip was investigated.Results showed that with this kind of microchips,several improvements could be achieved.Firstly,the injection time for the consecutive analysis with pinched injection could be shortened due to its effectiveness to prevent the dilution of the sample in the sampling channel by the buffer during the separation periods.Secondly,the baseline drift due to the entrance of separation waste back to the detection point during the injection periods could be effectively eliminated.Thirdly,the repeatability of the consecutive analysis was therefore significantly improved,120 times of consecutive injection gave a relative standard deviation (RSD ) of peak height as low as 0.56 %(calculated for (aminomethyl )phosphonic acid ) with replenishing of the buffer and sample every 40 injections.More importantly,by using the proposed microchip,a pre-separation could be performed by controlling the injection time.Components migrating slower in the sample could be excluded from the injection into the separation channel,making it possible to get rid of most of sample matrix by tuning the separation condition to make analytes migrate faster than the matrix components.This kind of pre-separation could simplify the electropherogram and avoid possible contamination of the separation microchannel,which is also beneficial to the reliability of microchip electrophoresis.