Zaznavanje amoniaka na osnovi sol-gel senzorskih nanosov

magistrsko delo

Katja Tement (Author), Aleksandra Lobnik (Mentor)

Abstract

V magistrskem delu je predstavljena metoda optičnega zaznavanja raztopljenega amonijaka, in sicer neionizirane oblike amonijaka. Kljub temu, da se amonijak (NH3) v vodnih raztopinah nahaja v kemijskem ravnotežju z amonijem (NH4+), pa vendarle predstavlja NH3 veliko bolj toksično obliko, ki ob preveliki koncentraciji lahko povzroči smrt vodnih organizmov, najpogosteje rib. Z obstoječimi metodami trenutno ni mogoče določati NH3 neposredno, ampak se le-ta poda na podlagi izračunov iz drugih dušikovih spojin (celotni amonijev dušik), katerih koncentracije se določujejo na osnovi nekontinuiranih metod laboratorijskih analiz, ki zahtevajo strokovno usposobljeno osebje. Zaradi navedenega je potreba po razvoju alternativnih metod zaznavanja neionizirane oblike amonijaka, ki bi omogočala hitro in kontinuirano podajanje koncentracij želenega analita na kraju samem, zelo upravičena in bi prinesla velik doprinos in dodano vrednost na področju razvoja alternativnih analiznih metod. Za pripravo senzorskih nanosov, občutljivih na amonijak smo izbrali dve indikatorski barvili bromokrezol zeleno (BCG) in bromofenol modro (BPB), ki smo ju imobilizirali v sol-gel polimerno osnovo po kislo- in bazično-kataliziranem sol-gel postopku. Pri tem so bile uporabljene kombinacije sol-gel prekurzorjev tetrametoksisilana (TMOS) s feniltrimetoksisilanom (Ph-TriMOS) oz. propiltrimetoksisilanom (p-TriMOS) v množinskih razmerjih med TMOS in ormosilnim prekurzorjem 1:1 in 1:2. Izkazalo se je, da senzorski nanosi, pripravljeni po bazično-kataliziranem sol-gel postopku, niso primerni za meritve, saj se je indikatorsko barvilo iz njih izpralo. Za zaznavanje raztopljenega amonijaka so se izkazali primernejši senzorski nanosi, pripravljeni po kislo-kataliziranem sol-gel postopku. Senzorski nanosi z imobiliziranim barvilom bromofenol modro so omogočali zaznavanje NH3 v območju med 0,1 in 97 mg/L, medtem ko so bili senzorski nanosi z imobliziranim bromokrezol zeleno manj občutljivi in so omogočali zaznavanje NH3 med 1 in 97 mg/L NH3. Potrjeno je bilo tudi, da se lahko tovrstni senzorski nanosi uporabljajo za zaznavanje amonijaka v plinski fazi.

Keywords

amoniak;absorpcija;optični-kemijski senzor;sol-gel senzorski nanosi;magistrske naloge;

Data

Language:	Slovenian
Year of publishing:	2016
Typology:	2.09 - Master's Thesis
Organization:	UM FS - Faculty of Mechanical Engineering
Publisher:	[K. Tement]
UDC:	544.022.822:543.31(043.2)
COBISS:	20179990
Views:	2071
Downloads:	93
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Detection of ammonia based on sol-gel sensor layers
Secondary abstract:	The thesis describes a method for the optical determination of dissolved ammonia, namely the non-ionised form of ammonia. Despite the fact that the ammonia (NH3) in the aqueous solution is in chemical equilibrium with the ammonium ion (NH4+), is on the other hand a much more toxic form, which in elevated concentrations may cause death of aquatic organisms (e.g. fishes). Existing methods currently do not allow to determine NH3 directly, but NH3 shall be determined based on calculations from other nitrogen compounds (e.g. total ammonia nitrogen), which are determined by the qualified personnel using discontinuous laboratory analyzes. Hence, the need to develop alternative methods for the determination of non-ionised form of ammonia, which would allow rapid and continuous monitoring of the analyte, is justified and would therefore represent a significant contribution and added value on the filed of alternative analytical methods. For the preparation of sensor layers that are sensitive to non-ionized dissolved ammonia we selected two indicator dyes, bromocresol green (BCG) and bromophenol blue (BPB), which were immobilized into sol-gel polymer via the acid- base and base-catalyzed sol-gel processes. Combinations of sol-gel precursors tetramethoxysilane (TMOS) with phenyltrimetoxysilane (Ph-TRIMOS) and propyltrimetoxisilane (p-TRIMOS) were used for this purpose, respectively. The molar ratios between the TMOS and ormosil precursor were 1:1 and 1:2. It has been shown that the sensor layers prepared via the base-catalyzed sol-gel process were not suitable for measurements, because the indicator dye was leaching out from them. For the detection of dissolved ammonia sensor layers prepared via the acid-catalyzed sol-gel process proved to be suitable. The sensor layers with immobilized indicator dye bromophenol blue enabled the detection of dissolved NH3 in the concentration range between 0.1 and 67 mg/L, while the sensor layers with immobilized bromocresol green were less sensitive and enabled the determination between 1 and 97 mg/L of NH3. It was also confirmed that this kind of sensor layers can also be suitable for the detection of ammonia in the gaseous phase.
Secondary keywords:	ammonia;absorption;optical-chemical sensor;sol-gel layers;
URN:	URN:SI:UM:
Type (COBISS):	Master's thesis
Thesis comment:	Univ. v Mariboru, Fak. za strojništvo
Pages:	VIII, 76 f.
ID:	9156566