A light detection cell to be used in a micro analysis system for ammonia

• Published in: Talanta (Oxford) Vol. 56; no. 2; pp. 331 - 339
• Main Authors: Tiggelaar, R.M, Veenstra, T.T, Sanders, R.G.P, Gardeniers, J.G.E, Elwenspoek, M.C, van den Berg, A
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 11-02-2002
• Subjects: Ammonia detection; Berthelot; KOH/IPA etching; Light detection cell; KOH/IPA etching; Light detection cell; Berthelot; Ammonia detection
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/S0039-9140(01)00599-9

This paper describes the design, realization and characterization of a micromachined light detection cell. This light detection cell is designed to meet the specifications needed for a micro total analysis system in which ammonia is converted to indophenol blue. The concentration of indophenol blue is measured in a light detection cell. The light detection cell was created using KOH/IPA etching of silicon. The KOH/IPA etchant was a 31 wt.% potassium hydroxide (KOH) solution with 250 ml isopropyl alcohol (IPA) per 1000 ml H
2O added to it. The temperature of the solution was 50
°C. Etching with KOH/IPA results in 45° sidewalls ({110} planes) which can be used for the in- and outcoupling of the light. The internal volume of the realized light detection cell is smaller than 1 μl, enabling measurements on samples in the order of only 1 μl. Measurements were performed on indophenol blue samples in the range of 0.02 to 50 μM. In this range the measurements showed good reproducibility.