Rapid Determination of Alkalinity (Ammonia Content) in Para Rubber Latex Using Portable and Fourier Transform-Near Infrared Spectrometers

Abstract

Ammonia (NH 3) is the main preservative that is added to field and concentrated latices to prevent the deterioration of properties and, in serious cases, coagulation of latex. Almost all factories monitor NH 3 content or alkalinity during processing, as it is an important parameter for trading purposes. Alkalinity is determined by the standard analytical method, acid-based titration, as detailed in ISO 125:2011(E) Natural Rubber Latex Concentrate-Determination of Alkalinity. This method requires a skilled analyst and also the use of chemicals. In addition, the titration involves the subjective determination of the end-point, which may vary with each analyst. Near infrared (NIR) spectroscopy, a rapid, non-chemical and repeatable method, was used in this work. Calibration equations for predicting alkalinity were constructed from the relationship between the absorbance spectra of latex (measured using a portable NIR and a Fourier transform (FT)-NIR spectrometer) and the alkalinity content of the latex. It was found that the best equation obtained using the portable and the FT-NIR spectrometer could be used to predict alkalinity in latex with a coefficient of determination, standard error of prediction and ratio of standard error of validation to the standard deviation of 0.63, 0.101% and 1.62, and 0.97, 0.027% and 6.07, respectively. From the statistics testing for performance measurement as detailed in ISO12099:2010, NIR-predicted values were no different from actual values at the 95% confident interval. Moreover, the best equation obtained from the more reliable calibration achieved using the FT-NIR spectrometer is attributed to the longer wavelength range.

Evaluation of prevulcanisate relaxed modulus of prevulcanised natural rubber latex using Fourier transform near infrared spectroscopy

“…The clear rubber latex absorption bands were similar to the natural rubber reported by Narongwongwattana et al. 10 and Sirisomboon et al. 11 , where they also found the peaks of water and CH 3 structure of Para rubber.…”

Preliminary Study on the Determination of ppm-Level Concentration of Histamine in Tuna Fish Using a Dry Extract System for Infrared Coupled with Near-Infrared Spectroscopy

“…According to the results of experiment 2, the performance of selected calibration equation was evaluated using the validation set according to the procedure described in ISO 12099 (2017) for animal feeding stuffs, cereals, and milled cereals products: Guidelines for the near-infrared spectrometry based on statistical parameters, bias, SEP, and slope. 24 The significance of the bias is determined by a t -test as per the following formula;where T b is the bias confidence limit, α is the probability of making a type I error, t is the appropriate Student’s t value for a two-tailed test with degrees of freedom associated with SEP and the selected probability of a type I error, and n is the number of independent samples.…”

Near infrared spectroscopy as an alternative method for rapid evaluation of toluene swell of natural rubber latex and its products

“…Raw PV latex, thin film and thick film spectra obtained from FT-NIR are shown in Figure 2(a) to (c), respectively, where the wavenumber between 5840 and 5620 cm −1 (1712–1780 nm) clearly corresponded to the functional group of C–H methyl first overtone of CH 3 . 13,14 They are components of the isoprene unit of rubber. 9,11 Based on the established data from Workman and Weyer, 17 the obvious peaks at about 5823 cm −1 (1717 nm) was due to functional group C–H methylene for hydrocarbons, 5230 cm −1 (1912 nm) due to P–OH phosphate (.P–OH) for phosphate, 4613 cm −1 (2168 nm) due to CONH 2 for proteins and 4335 cm −1 (2307 nm) due to C–H methylene associated with linear aliphatic hydrocarbon.…”

“…Sirisomboon et al 9 and Hock and Sirisomboon 10 used this technique to evaluate the dry rubber content of latex. Narongwongwattana et al, 11 Sirisomboon et al 12 and Narongwongwattana et al 13 were equally successful in using NIR spectroscopy to determine the volatile fatty acid number, apparent viscosity and alkalinity of latices, respectively. TS or equilibrium swelling of a vulcanized rubber in a solvent is dependent on the density of the crosslinks, the nature of the solvent and the rubber.…”