A submersible flow injection-based sensor for the determination of total oxidised nitrogen in coastal waters

Sampling, sample treatment and quality assurance issues for the determination of phosphorus species in natural waters and soils

“…storm events) [17,18], which demonstrates the importance of high temporal resolution monitoring during such events. Submersible or field-based instrumentation is desirable for monitoring dissolved phosphorus because it eliminates the need for sample collection and storage and, although such instrumentation is available [19,20], it is not used on a routine basis. Therefore, a comprehensive and effective sampling, sample treatment and analysis protocol must be adopted in order to minimise the physical, chemical and biological processes that can alter the physico-chemical forms of phosphorus during storage.…”

Trends in microfluidic systems for in situ chemical analysis of natural waters

“…[48][49][50] Of these, colorimetry -in which the sample is mixed with an analyte-specific reagent to produce a measurable colour -has proved to be by far the most popular method and has been used for in situ analysis of a range of chemical parameters including nitrate and nitrite, [21,22,24,29,31,34,35,38] phosphate, [27,38] iron, [23,26,28,36,39,[42][43][44] manganese, [25,26,28,37,40] sulfide [32,33,35,39,41] silicate [30,32,33,38] and pH. [51][52][53][54][55] Colorimetry lends itself well to microfluidic in situ analysers as it is chemically robust, offers excellent analytical performance (limits of detection typically in the order of 10 nM [21,25,36]) and requires relatively small, cheap and easily-sourced components.…”

“…Small sized peristaltic pumps are easily commercially sourced, relatively cheap and easy to M a n u s c r i p t use and consequently have proved consistently popular. [25,26,[28][29][30][32][33][34][35]37,[39][40][41][42][43] Nonetheless, peristaltic pumps can suffer from drifting flow rates due to variation in the elasticity and plasticity of the pump tubing with changes in temperatures [35] and, crucially, are relatively power hungry. [56] Consequently, reported deployments of peristaltic pumped sensors have been limited to a day or less, except where power could be externally supplied via cabling.…”

A Simple, Low-Cost Double Beam Spectrophotometer for Colorimetric Detection of Nitrite in Seawater

“…The latter is attractive since it offers specificity, sensitivity, long-term accuracy, and good resolution [8], [9]. The preferred colorimetric method used to measure nitrite in aqueous samples is based on the Griess reaction, in which nitrite is diazotized with sulfanilamide and then reacted with N-(1-naphthyl)-ethylenediamine dihydrochloride (NED) to form a pink-colored Azo dye [10], [11]. The color intensity of the final product (Azo dye) is proportional to the nitrite concentration present in the aqueous sample, and the detailed chemical reaction is shown in Figs. 1 and 2.…”