What Are the Advantages of hc-49u-jacket quartz crystal？

Looks like you are not TradeKey.com's Member yet

View Details

Signup now to connect with over 10 Million Importers & Exporters globally.

A rapid, sensitive, low-cost device to detect trimethylamine was presented in this paper. The preparation of water soluble polyaniline was firstly studied. Then the polyaniline was characterized via Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy and scanning electron microscopy (SEM). Based on the water soluble polyaniline film, a quartz crystal microbalance (QCM) sensor for trimethylamine detection was fabricated and its characteristics were examined. The sensor consisted of one quartz crystal oscillator coated with the polyaniline film for sensing and the other one for reference. Pretreated with trimethylamine, the QCM sensor had an excellent linear sensitivity to trimethylamine. Easily recovered by N2 purgation, the response of the sensor exhibited a good repeatability. Responses of the sensor to trimethylamine, ethanol and ethyl acetate were compared, and the results showed that the response was related to the polarity of the analyte vapor. Experimental result also showed that the sensitivity of the sensor was relatively stable within one month. The simple and feasible method to prepare and coat the polyaniline sensing film makes it promising for mass production.

1.&#;Introduction

Biogenic amines are formed by the activity of bacterial amino acid decarboxylase during the degradation processes of proteins, which have a carcinogenic effect on human body and can be used to indicate bacterial contamination. Being one of biogenic volatile amines, trimethylamine is a good target for the detection of biogenic amines to evaluate the quality of meat food products [1-3]. In human body, trimethylamine is derived from diet either directly from the consumption of foods containing trimethlamine, or by the intake of food containing precursors to trimethylamine such as trimethylamine-N-oxide, choline and L-carnitine. Normally, the flavin-containing monooxygenase isoform 3 (FMO3) enzyme converts fishy-smelling trimethylamine into another molecule that has no odor. If the enzyme is deficient or its activity is reduced, trimethylamine is not processed properly and can build up in the body. As excess trimethylamine is released in a person's sweat, urine, and breath, it causes the strong odor characteristic of trimethylaminuria [4]. Trimethylamine is also of clinical interest because of its potential to contribute to neurological toxicity and &#;uraemic breath&#; in patients with end-stage renal disease [5]. Together with triethylamine, trimethylamine is found to be emitted by building materials degraded by microbial growth [6]. Trimethylamine has an unpleasant smell, and is irritant to the skin, eyes, mucous membranes and respiratory tract [7].In a word, a rapid, sensitive, low-cost method to detect trimethylamine is meaningful.

Various analytical methods have been reported in literature to detect trimethylamine [1, 2, 8-11]. However, all these methods (photometry, gas chromatography, colorimetric analysis, high performance liquid chromatography, ion mobility spectrometry, etc.) are relatively cumbersome, time consuming and require experienced operators.

Polyaniline, a kind of conductive conjugated polymer, has been regarded as a good sensing material due to its advantages of gas sensing ability and optimum performance at room temperature. It has been exploited in thin film sensors for several gas molecules as well as volatile organic compounds [12-16]. In spite of the various advantages of polyaniline based gas sensors, some fundamental problems, such as long-time instability and irreversibility and low selectivity, still persist [17]. Usually solubility of polyaniline is a problem to fabrication quality films. We have recently investigated the method to prepare water-soluble polyaniline based on oxidative polymerization. Moreover, the effect of trimethylamine on the conductivity of polyaniline was investigated [18].

Huixun supply professional and honest service.

QCM sensor can be constructed by coating the surface of a quartz crystal electrode with a film capable of interaction with the environment of interest. The operating principle of QCM sensors is based on the interaction between the surface of a quartz crystal coated with the sensing materials and the target materials. The Sauerbrey equation was developed for oscillation in air and only applies to rigid mass attached to the crystal [19]. It gives the change in the oscillation frequency of piezoelectric quartz (Δf) as a function of the mass (Δm) added to the crystal:

Δf=2f02AρqυqΔm

(1)

where Δf is the observed frequency change (Hz), f0 is the fundamental resonant frequency of crystal, A is the active area of the crystal (between electrodes), ρq is the density of quartz and υq is the shear wave velocity in the quartz. Quartz crystal microbalance (QCM) sensors were widely investigated due to their high sensitivity, durability and linearity for mass of the target materials [20-24].

Chemiresistors are the most popular device configuration of gas sensors based on conducting polymer. However, the resistance of chemiresistor is influenced by many ambient factors, and not only determined by the resistance of the conducting polymer sensing film, but also the contact resistance of electrodes. Moreover, other disadvantages for use of chemiresistors are low limit of detection and sensitivity, compared with sensors based on other configurations such as transistors, optic devices and QCMs. For transistor, its preparation and characterization is slightly complicate. The sensitivity of optic sensors is high, but the detecting procedure is complicate. Because QCM is rather sensitive to mass change, adsorbing a very small amount of analyte can be detected through frequency change. Although a number of polymers have been successfully employed in the coating of QCM sensors [20, 24], polyaniline-coated QCM gas sensor has seldom been investigated. Therefore, we attempted to coat a polyaniline film on a quartz crystal surface, to make a low-cost, high-sensitivity and rapid-response QCM trimethlamine gas sensor. The performance of the sensor was investigated.

For more information, please visit hc-49u-jacket quartz crystal.