Solute detection

Nylander s solution (detection of glucose) dissolve 40 g of rochelle salt and 20 g of bismuth subnitrate in 1000 mL of an 8% NaOH solution. 

Nowadays all over the world considerable attention is focused on development of chemical sensors for the detection of various organic compounds in solutions and gas phase. One of the possible sensor types for organic compounds in solutions detection is optochemotronic sensor - device of liquid-phase optoelectronics that utilize effect of electrogenerated chemiluminescence. In order to enhance selectivity and broaden the range of detected substances the modification of working electrode of optochemotronic cell with organic films is used. Composition and deposition technique of modifying films considerably influence on electrochemical and physical processes in the sensor. 

Alkaloids, e.g. cocaine, ecgonine, benzoylecgonine, ecgonine methyl ester 280 °C, 8 min or 260°C, 10-30 min Pale blue induced fluorescence (Xn > 390 nm, cut off filter), fluorescence amplification by a factor of 2 on dipping in liquid paraffin solution detection limits <10 ng. [13]... 

Xn > 390 nm, cut off filter), fluorescence amplification by a factor of 2 on dipping in liquid paraffin solution detection limits <10 ng. 

Miller and Hawthorne [416] have developed a chromatographic method that allows subcritical (hot/liquid) water to be used as a mobile phase for packed-column RPLC with solute detection by FID, UV or F also PHWE-LC-GC-FTD couplings are used. Before LC elution the extract is dried in a solid-phase trap to remove the water. In analogy to SFE-SFC, on-line coupled superheated water extraction-superheated water chromatography (SWE-SWC) has been proposed [417]. On-line sample extraction, clean-up and fractionation increases sensitivity, avoids contamination and minimises sources of error. 

Also, subcritical (hot/liquid) water can be used as a mobile phase for packed-column RPLC with solute detection by means of FID [942]. In the multidimensional on-line PHWE-LC-GC-FTD/MS scheme, the solid sample is extracted with hot pressurised water (without the need for sample pretreatment), and the analytes are trapped in a solid-phase trap [943]. The trap is eluted with a nitrogen flow, and the analytes are carried on to a LC column for cleanup, and separated on a GC column using the on-column interface. The closed PHWE-LC-GC system is suitable for many kinds of sample matrices and analytes. The main benefit of the system is that the concentration step is highly efficient, so that the sensitivity is about 800 times better than that obtained with traditional methods [944]. Because small sample amounts are required (10 mg), special attention has to be paid to the homogeneity of the sample. The system is... 

It is clear from the Nemst equation that the temperature of the solution affects the response slope (2.303A7//0 of the calibration curve. The electrode voltage changes linearly in relationship to changes in temperature at a given pH therefore, the pH of any solution is a function of its temperature. For example, the electrode response slope increases from 59.2mV/pH at 25°C to 61.5 mV/pH at a body temperature of 37°C. For modem pH sensing systems, a temperature probe is normally combined with the pH electrode. The pH meter with an automatic temperature compensation (ATC) function automatically corrects the pH value based on the temperature of the solution detected with the temperature probe. 

Nilsson KPR, Inganas O (2003) Chip and solution detection of DNA hybridization using a luminescent zwitterionic polythiophene derivative. Nat Mater 2 419 124... 

Other Electrochemical Techniques in Non-Aqueous Solutions Detection and Identification of Radicals... 

Atomic emission spectroscopy can be employed, generally with an inductively coupled plasma for thermal excitation. The sample is introduced into the plasma as a mist of ultrafine droplets, and the monochromator and detector are set to measure the intensity of an atomic emission line characteristic of the element. This technique is powerful, general, sensitive, linear, and able to measure over 70 elements, and, as a result, is widely used. Response is typically linear over four orders of magnitude in concentration with relative standard deviations of 1 to 3%. In low-salt aqueous solutions, detection limits range from 10 to 1000 nanomolar without preconcentration. Significant problems with saline samples remain, but use of Babington nebulizers alleviates these problems somewhat. 

Solution detected Applied potential (vs. AglAgCI) Applied time(s)... 

Sobott F, Wattenberg A, Barth HD, Bmtschy B. 1999. Ionic clathrates from aqueous solutions detected with laser induced liquid beam ionization/desorption mass spectrometry. Int J Mass Spectr 185-7 271-279. 

The spots were located by examination under UV light or spraying with one of following solutions (detection limits in yg) fluorescamine (0.5), ninhydrin (1), NBP followed by heating and treatment with a base (5) [51,63a], and 0.5% iodine in chloroform. Visualization using 4-pyridine-carboxaldehyde 2-benzothiazolyl hydrazone has been described under 5.2.1. 

Because SEC is a gentle technique, rarely resulting in loss of sample or reaction, it has become a popular choice for the separation of biologically active molecules. Each solute is retained as a relatively narrow band, which facilitates solute detection with detectors of only moderate sensitivity. Examples of analytes that can be analyzed by SEC are listed in Table 2.7. Possible stationary phases and mobile phases are also provided in Table 2.7. 

When using a pneumatic nebulizer, an unheated spray chamber, and a quadrupole mass spectrometer, ICP-MS detection limits are 1 part per trillion or less for 40 to 60 elements (Table 3.4) in clean solutions. Detection limits in the parts per quadrillion range can be obtained for many elements with higher-efficiency sample introduction systems and/or a magnetic sector mass spectrometer used in low-resolution mode. Blank levels, spectral overlaps, and control of sample contamination during preparation, storage, and analysis often prohibit attainment of the ultimate detection limits. 

Determination of the concentration of the acyclic form by physical means is more satisfactory. Measurement of ultraviolet absorption clearly shows that, under normal conditions, the concentration of the free carbonyl form must be low, but that, in strongly alkaline solutions, detectable amounts of carbonyl compounds may be present. ... 

Table 7 Derivatives, pages 597-598) Anhydrides and acid halides will react with water to give acidic solutions, detectable with litmus paper. They easily form benzamides and acetamides. 

Urea is quantitatively the most important solute excreted by the kidney and was the first organic solute detected in the blood of patients with kidney failure [32]. Yet it is a poor marker of uremic illness. Furthermore, the blood urea nitrogen (BUN) is not a... 

For on-capillary and postcapillary derivatization, the reagent must not fluoresce until reacted with the solute. For these purposes, NDA and OPA are the best choices. With on-capillary derivatization, it is possible to use a reagent that fluoresces, but its removal prior to solute detection can be difficult. 

In conclusion, an ELSD with SFC provides a sensitive analytical tool for qualitative and quantitative analysis of solutes. Detection depends only on the solute being less volatile than the least volatile mobile-phase component. Detection is independent of the basicity or presence of a chromophore for a given solute. The detector response is a logarithmic function of the mass of the solute. The SFC-ELSD combination should be considered whenever a universal high-throughput analysis is needed. 

Activity stains are of great importance during the isolation, purification, and characterization of enzymes, since a particular catalytic reaction is involved and the detection of this activity leads to the unequivocal identification of the zone of interest on the electrophoresis gel. Following separation, the gel is removed from the electrophoresis apparatus and is immersed in a minimal volume of a substrate solution. Detection relies on the formation of a colored product by enzyme in the zones containing the enzyme. Examples of activity stains are given in Table 9.2. 

The UV detector is the most widely used detector for LC. It is a solute property detector that is suitable for those solute compounds that absorb radiation in the UV range ( 190-400 nm). Ultraviolet-photometric detectors are relatively insensitive to temperature and flow rate fluctuations. The sensitivity to solute detection is high (noise equivalent concentration 10 °g/ml).f Ultraviolet-photometric detectors are also well suited to applications that use gradient elution, given that many common LC solvents have low UV absorptivities. 

Fig. 2 Elution profile of a racemic mixture of /-BOC-d-tyrosine (first peak) and /-BOC-L-tyrosine (second peak) on a molecularly imprinted polymer made using /-BOC-l-tyrosine as template and A,0-bismethacryloyl ethanolamine as the only monomer. HPLC conditions particle size 45-63 pm mobile-phase 99/1, acetonitrile/acetic acid flow rate 0.1 mL/min injected volume 5 pi of a 2.0 mM racemic solution detection at 2 = 270 nm. (Courtesy of David Spivak, Lousiana State University.) (View this art in color at WWW. dekker. com.)...

Dilution with (NaOH/Na,CO,) buffer dilution with HCOj7H,CO, buffer filtration over 0.45 (im ion chromatography post-column reaction with DPC solution detection by SPEC with DPC for Cr(VI) and ETAAS for total leachable Cr (Lab. 01)... 

Dilution with HCOC/H COj buffer addition of known amount of Cr(III)- Cr(Vl) enriched spike extraction with liquid anion exchange solution (Amberlite LA-2/M1BK) back-extraction of Cr(Vl) with ammonia solution electrodeposition on Pt wire in ammonia solution detection by IDMS of masses 52 and 53 (Lab. 11)... 

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