Bestimmung eines niedrigen Nitrit-Niveaus ohne vorherige Extraktion

Walters, C. L.; Downes, Malcolm J.; Hart, Robert J.; Perse, Simon; Smith, Penny

doi:10.1007/bf01135592

Cited by 17 publications

(7 citation statements)

References 10 publications

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“…Without tartaric acid present, no signal greater than background was generated. Walters et al (4) and Cox (7) used acetic acid for acidification, which required the use of alkali traps to remove the volatile acid before passing the nitric oxide gas through the detector. In order to eliminate the traps, we selected tartaric acid since it is nonvolatile and has an appropriate pK, (2.96).…”

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confidence: 99%

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Determination of nitrite in cured meats by chemiluminescence detection

Doerr¹,

Fox²,

Lakritz³

et al. 1981

Anal. Chem.

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analysis of this data set produced a line having a slope of (5.40 f 0.07) X lo4 pA/rpm, an intercept of 0.0874 PA, and a correlation coefficient of 0.9991.These data emphasize the importance of controlling the stirring during the analysis and justify the use of the stepper motor. A change in the stirring rate of more than 2% in the analysis of the 57 ppb Zn ion solution would have produced an error larger than the standard deviation of the measured current at that concentration. The large intercept represents the peak current produced when no stirring occum during the deposition period. The straight line produced by the data indicates that the concentration of metal deposited in the mercury drop is a linear function of the stirring rate. The data show that the control device was useful in obtaining reproducible results at a cost considerably less than similar commercially available devices or microprocessor controlled instruments.This device may be adapted to other electroanalytical instruments that perform direct current, pulse, or differential pulse anodic stripping voltammetry provided the following voltages and signals are available on the instrument for utilization by the device. The working electrode voltage vs. the reference voltage is connected to pin 3 of the MC14433 in Figure 4. The scan control line of the electroanalytical instrument is connected to pin 3 of the MC1488 IC in Figure 6. Control of the scan on the PAR Model 174A instrument is accomplished by the application of either a +15 V signal (commence scan) or a -15 V signal (stop scan) to the appropriate pin on the back of the instrument. A different instrument may require an adjustment of the magnitude or sign of the voltage that controls the scan. The cell working electrode connection is connected to one side of the STAND-BYIANALYZE switch in Figure 6. The other side of the switch is connected to the working electrode input on the electroanalytical instrument.Pin 12 of IC MC14433 in Figure 4 requires a negative voltage between -2.8 and -11 V. The typical current is 0.8 mA. The PAR instrument supplies -15 V, and this is decreased to -9 V by the zener diode in Figure 4. If the instrument the device is being adapted to supplies a negative voltage between -2.8 and -11 V, the zener diode is not needed.A ground line connection is needed to connect the ground of the instrument to the ground of the device. This ground should be a good ground connection such as one that might run to a water pipe. Figure 6 shows two lines that control the recorder. The line labeled "TO RECORDER PEN CONTROL" is +5 V when the pen is disabled and at ground potential when it should respond to the electroanalytical instrument. The line labeled "TO RECORDER CHART CONTROL" is at ground potential when no data needs to be recorded and at +5 V when the scan starts.It should be noted that sensitivity achieved in this work would not be obtainable with the direct current or pulse anodic stripping voltammetry techniques. The device would however improve the precision of any of the te...

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confidence: 99%

“…Walten et al (4) and Cox (7) swept the reaction flask with an inert gas in order to measure the total amount of nitric oxide produced. We chose to measure the evolved nitric oxide by injecting small portions into the chemiluminescence detector by means of an evacuated sample loop and gas sampling valve.…”

mentioning

confidence: 99%

Determination of nitrite in cured meats by chemiluminescence detection

Doerr¹,

Fox²,

Lakritz³

et al. 1981

Anal. Chem.

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“…The analytical method used relies on chemical denitrosation using HBr and/or HCl [20][21][22] and NO detection by chemiluminescence [23]. Although this method has been developed and refined for the analysis of NOCs [21,[24][25][26], the chemical denitrosation with HBr can also release NO from other compounds such as nitroso thiols (SNO) [24,27], nitriolic acid [26], O-nitroso compounds and nitrosyl iron (FeNO) [28]. Owing to this lack in specificity, the term ATNC (apparent total N-nitroso compound) is used to describe substances measured by this technique [19].…”

Section: Endogenous Formation Of Nocsmentioning

confidence: 99%

Dietary meat, endogenous nitrosation and colorectal cancer

Kuhnle

Bingham

2007

Biochemical Society Transactions

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Colorectal cancer is the third most common cancer in developed countries such as the U.K., but incidence rates around the world vary approx. 20-fold. Diet is thought to be a key factor determining risk: red and processed meat, but not white meat or fish, are associated with an increased risk of colorectal cancer. The endogenous formation of N-nitroso compounds is a possible explanation because red and processed meat, but not white meat or fish, cause a dose-dependent increase in faecal ATNCs (apparent total N-nitroso compounds) and the formation of nitroso-compound-specific DNA adducts in humans. Red meat is particularly rich in haem which has been found to promote the endogenous formation of ATNC. Nitrosyl haem and nitroso thiols have been identified as major constituents of both faecal and ileal ATNC with a significant increase in the formation of these compounds following a diet rich in red meat. In vitro incubations show that, under simulated gastric conditions, nitroso thiols are the main species of nitroso compound formed, suggesting that acid-catalysed thionitrosation is the initial step in the endogenous formation of nitroso compounds. Nitrosyl haem and other nitroso compounds can then form under the alkaline and reductive conditions of the small and large bowel.

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“…Hence an assay was developed which permitted an estimate of the ''total'' N-nitroso compounds present in a complex matrix. This was termed Apparent Total N-nitroso Compounds (ATNCs) and from its inception, 2 analysts were aware that it was not completely specific for N-nitrosamines. This assay uses HBr to release NO from N-nitrosamines but a small number of other susceptible compounds such as nitrolic acids may also give a positive response.…”

Section: Introductionmentioning

confidence: 99%

Progress towards the characterisation of faecal N-nitroso compounds

et al. 2011

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Intestinal nitrosation produces ATNCs (Apparent Total N-nitroso Compounds) and these have been linked with an increased risk of colon cancer from eating red meat. Modern LC-MS instrumentation makes direct detection of ATNC components in faecal water a possibility. The difficulty is in determining which of the many compounds present are N-nitrosamines before embarking on efforts to characterise them. We have assumed that any in vivo nitrosation of alimentary tract contents will be non-specific and depend on the amount and basicity of amine present, with concentration of nitrosating agent being the limiting factor. By further nitrosating faecal waters (and ileostomy fluids) we can increase the amount of ATNC and readily access these compounds. The amount and the number of nitrosamines generated depend on the concentration of individual amines present. By derivatisation separately using both 14 N and 15 N labelled nitrite, we demonstrated that inspecting chromatograms in parallel for a unit mass difference provides a novel and practicable means for identifying unknown ATNC in faecal and ileostomy samples. MS procedures were linked with the traditional approaches of thermal energy analyser (TEA), preparative HPLC, visualisation of nitrosamines with Griess reagent and degradation of N-nitroso compounds by UV irradiation. We have demonstrated that this approach is repeatable and have used it to identify 30 putative N-nitroso compounds (as protonated parent masses [

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Bestimmung eines niedrigen Nitrit-Niveaus ohne vorherige Extraktion

Cited by 17 publications

References 10 publications

Determination of nitrite in cured meats by chemiluminescence detection

Determination of nitrite in cured meats by chemiluminescence detection

Dietary meat, endogenous nitrosation and colorectal cancer

Progress towards the characterisation of faecal N-nitroso compounds

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