重金屬毒性是人們最關心的問題。人為誘發因素和自然現像都是造成這些有毒元素在反應狀態下濃度上升的原因，這些有毒元素對生態系統的動植物群是有害的。電鍍行業和製革廠釋放含高鉻的廢水。 Cr(VI)在還原劑存在下被還原為Cr(III)，相較之下較為穩定。水源地區附近的水將會受鉻污染，數量為2-5克/升。衛生組織規定的安全限制在0.05毫克/升以內。這種重金屬的過量消耗將導致生物累積，導致遺傳毒性。 Cr(III)和Cr(VI)已被國際癌症研究機構（癌症研究機構）分別確定為第三類和第一類致癌物。因此，快速的檢驗可以有效確保公民不會受到超出這些致癌物質容忍限度的污染。本文列舉了一種偵測極限低、靈敏度高、回報時間快的便攜式生物傳感器的檢測機、用以有效測定液體樣品中鉻的濃度。該新型生物傳感器採用聚氯乙烯(PVC)基質和特定目標化合物，並採用擴展的柵極結構來製造，由於使用單個FET而使得擾動小，可使流通量高。柵極傳感元件與目標受體功能化。當目標溶液與受體結合時，目標溶液影響電導，從而改變有效柵電壓作為目標離子濃度的函數。隨著目標Cr離子濃度的增加，晶體管漏電流呈上升趨勢。該器件性能不受pH的影響，因此該應用可擴展到廣泛的液體介質，例如河水、地下水、果汁、醃製食品等。響應時間近5分鐘，離子選擇膜場效應管易於使用，便於攜帶，價格便宜；使生物傳感器在監測地下水水質時達到最佳使用。其檢測限與ICP-MS、AAS等現代檢測技術相當。這種基準化實驗室設備昂貴，需要時間，需要訓練有素的人員，使其不適於日常應用。這些缺點被離子選擇性薄膜塗覆的場效應晶體管所克服，該晶體管便於使用且用戶界面簡單，便攜且製造成本低，並可集成到從保健、動態水質監測到食品加工的各種應用中。

Heavy metal toxicity is an issue of prime concern. Both human-induced factors and natural phenomena are responsible for the rising concentrations of these toxic elements in the reactive state which prove detrimental to the flora and fauna of ecosystems. Electroplating industry and tanneries release effluents containing high concentrations of total Chromium. Cr (VI) gets reduced in the presence of reducing agent to Cr (III), which is comparatively more stable. Regions in the vicinity of such sources will have water bodies contaminated with total Chromium in the order of 2 to 5 g/L. Standards set by WHO gives safe limits to be within 0.05 mg/L. Overconsumption of this heavy metal will cause bio-accumulation leading to genotoxicity. Cr (III) and Cr (VI) have been identified as group III and I carcinogen respectively by the International Agency for Research on Cancer (IARC). Hence the need of the hour is to ensure citizens are not exposed beyond tolerable limits to these carcinogens. This report enumerates detection mechanism, calibration, and characterization of a portable biosensor with low detection limit, high sensitivity and fast response time to effectively determine the concentration of total chromium present in a liquid sample. The novel biosensor presented here uses polyvinyl chloride (PVC) matrix with target-specific compound and is fabricated using extended gate configuration which facilitates lesser fluctuation due to use of single FET and higher throughput. The gate sensing element is functionalized with the target receptor. The target solution when dropped binds with receptor influencing the conductance and consequently altering the effective gate voltage as a function of the concentration of target ion. The electrode reveals an increasing trend of transistor drain current with an increase in the target Cr ion concentration. The device performance is not affected by pH and hence the application can be extended to a wide range of liquid media, for instance, river water, groundwater, juices, tanned foods, and so on. The response time being nearly 5 minutes, the Ion Selective Membrane FET is easy to use, portable and affordable; making the bio-sensor optimum for daily use to monitor groundwater quality. The limit of detection is comparable to contemporary detection techniques like ICP-MS and AAS. Such benchtop laboratory equipment are expensive, demand time, and require trained personnel making them unfit for daily application. These drawbacks are overcome by the ion-selective membrane coated field effect transistor which is convenient to use with a simple user interface, portable and cheap to fabricate and can be integrated into a wide variety of application ranging from health care, dynamic water quality monitoring to food processing.

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