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1.
Spectrochim Acta A Mol Biomol Spectrosc ; 283: 121737, 2022 Dec 15.
Article in English | MEDLINE | ID: mdl-35964351

ABSTRACT

Raman spectroscopy (RS) was used to identify and quantify different nitrogen species in fertilizers. This is a fast and inexpensive method that requires no extensive sample preparation. Urea and nitrate were determined at 1000 and 1045 cm-1, respectively. Calibration plots obtained for these analytes showed adequate linearity, with regression coefficients (r) of 0.9989 and 0.9976, respectively. Ammonium was determined by difference after total N determination by high-resolution continuum source flame molecular absorption spectrometry (HR-CS FMAS), which provided a calibration plot with r = 0.9960. The inline coupling of RS and HR-CS FMAS allowed for a fast sequential determination of ammonium, nitrate, and urea, with limits of detection of 0.03 mg/L ammonium, 0.03 mg/L nitrate, and 0.01 mg/L urea. Relative standard deviations were ≤ 11 %, and the external standard calibration method provided accurate results for all analytes determined in certified reference materials, raw materials, and commercial samples of fertilizers. For comparison purposes, all samples were also analyzed by traditional Kjeldahl method. The RS HR-CS FMAS method was further validated by addition and recovery experiments, which provided recoveries in the 93 - 113 % range.


Subject(s)
Ammonium Compounds , Fertilizers , Fertilizers/analysis , Nitrates , Nitrogen/analysis , Organic Chemicals , Spectrophotometry, Atomic/methods , Spectrum Analysis, Raman , Urea
2.
Spectrochim Acta A Mol Biomol Spectrosc ; 246: 119025, 2021 Feb 05.
Article in English | MEDLINE | ID: mdl-33049472

ABSTRACT

Raman spectroscopy is emerging and powerful technique for identifying oxyanions of phosphorus, but it still is not straightforward applied to identify and quantify simultaneously phosphite and phosphate species in solution. Herein, simultaneous determination of phosphate (PO4) and phosphite (PO3) in fertilizer were evaluated by Raman spectroscopy. The influence of pH on Raman spectra of species was evaluated at various solution pH values, and the results showed accurate and selective analysis for phosphate and phosphite by using pH = 10.0 and bands located at 874 cm-1 and 2321 cm-1, respectively. Linear working range in the 0.15%-6.20% (w/v) P concentration was consistently obtained with regression coefficients (r) of 0.9953 (PO4) and 0.9945 (PO3). The limits of detection were 0.10% (w/v) P (PO4) and 0.05% (w/v) P (PO3). Relative standard deviations were lower than 6% for samples containing 10% P2O5 (PO4) and 31% P2O5 (PO3). Commercial fertilizers were analyzed by the proposed method using external calibration and found concentrations of P were in agreement with those obtained by the comparative spectrophotometric method at the 95% confidence level (paired t-test). Recoveries of spiked samples were in the 92-110% range.

3.
Anal Chim Acta ; 982: 31-36, 2017 Aug 22.
Article in English | MEDLINE | ID: mdl-28734363

ABSTRACT

Multi-energy calibration (MEC) is a novel strategy that explores the capacity of several analytes of generating analytical signals at many different wavelengths (transition energies). Contrasting with traditional methods, which employ a fixed transition energy and different analyte concentrations to build a calibration plot, MEC uses a fixed analyte concentration and multiple transition energies for calibration. Only two calibration solutions are required in combination with the MEC method. Solution 1 is composed of 50% v v-1 sample and 50% v v-1 of a standard solution containing the analytes. Solution 2 has 50% v v-1 sample and 50% v v-1 blank. Calibration is performed by running each solution separately and monitoring the instrument response at several wavelengths for each analyte. Analytical signals from solutions 1 and 2 are plotted on the x-axis and y-axis, respectively, and the analyte concentration in the sample is calculated from the slope of the resulting calibration curve. The method has been applied to three different atomic spectrometric techniques (ICP OES, MIP OES and HR-CS FAAS). Six analytes were determined in complex samples (e.g. green tea, cola soft drink, cough medicine, soy sauce, and red wine), and the results were comparable with, and in several cases more accurate than, values obtained using the traditional external calibration, internal standardization, and standard additions methods. MEC is a simple, fast and efficient matrix-matching calibration method. It may be applied to any technique capable of simultaneous or fast sequential monitoring of multiple analytical signals.


Subject(s)
Calibration , Spectrophotometry, Atomic , Antitussive Agents/analysis , Carbonated Beverages/analysis , Reference Standards , Soy Foods/analysis , Tea/chemistry , Wine/analysis
4.
Anal Chim Acta ; 831: 24-30, 2014 Jun 11.
Article in English | MEDLINE | ID: mdl-24861968

ABSTRACT

Bismuth was evaluated as internal standard for Pb determination by line source flame atomic absorption spectrometry (LS FAAS), high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) and line source graphite furnace atomic absorption spectrometry (LS GFAAS). Analysis of samples containing different matrices indicated close relationship between Pb and Bi absorbances. Correlation coefficients of calibration curves built up by plotting A(Pb)/A(Bi)versus Pb concentration were higher than 0.9953 (FAAS) and higher than 0.9993 (GFAAS). Recoveries of Pb improved from 52-118% (without IS) to 97-109% (IS, LS FAAS); 74-231% (without IS) to 96-109% (IS, HR-CS FAAS); and 36-125% (without IS) to 96-110% (IS, LS GFAAS). The relative standard deviations (n=12) were reduced from 0.6-9.2% (without IS) to 0.3-4.3% (IS, LS FAAS); 0.7-7.7% (without IS) to 0.1-4.0% (IS, HR-CS FAAS); and 2.1-13% (without IS) to 0.4-5.9% (IS, LS GFAAS).

5.
Talanta ; 100: 21-6, 2012 Oct 15.
Article in English | MEDLINE | ID: mdl-23141306

ABSTRACT

A procedure is proposed for Pb determination in medicinal plants by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) using direct solid sampling. Among Pd(NO(3))(2), Pd/Mg(NO(3))(2), NH(4)H(2)PO(4) and the W-coated platform tested as chemical modifiers, Pd(NO(3))(2) presented the best performance. Calibration plots (10-1000 pg Pb) with regression coefficients better than 0.999 were typically obtained. Accuracy was checked for Pb determination in five plant certified reference materials. Results were in agreement with reference values at a 95% confidence level (paired t-test). Medicinal plant samples were analyzed by the proposed procedure and line-source GF AAS using slurry sampling as a comparative technique. The RSD was 10% (n=3) for a sample containing 0.88 µg g(-1) Pb. The limit of quantification (dry mass) was 0.024 µg g(-1). The contents of Pb in medicinal plant samples varied in the 0.30-1.94 µg g(-1) range.


Subject(s)
Environmental Pollutants/analysis , Environmental Pollutants/chemistry , Graphite/chemistry , Lead/analysis , Lead/chemistry , Plants, Medicinal/chemistry , Spectrophotometry, Atomic/methods , Temperature
6.
J Agric Food Chem ; 59(6): 2197-201, 2011 Mar 23.
Article in English | MEDLINE | ID: mdl-21348434

ABSTRACT

The usefulness of molecular absorption was investigated for the determination of total sulfur (S) in agricultural samples by high-resolution continuum source flame molecular absorption spectrometry. The lines for CS at 257.595, 257.958, and 258.056 nm and for SH at 323.658, 324.064, and 327.990 nm were evaluated. Figures of merit, such as linear dynamic range, sensitivity, linear correlation, characteristic concentration, limit of detection, and precision, were established. For selected CS lines, wavelength-integrated absorbance equivalent to 3 pixels, analytical curves in the 100-2500 mg L(-1) (257.595 nm), 250-2000 mg L(-1) (257.958 nm), and 250-5000 mg L(-1) (258.056 nm) ranges with a linear correlation coefficient better than 0.9980 were obtained. Results were in agreement at a 95% confidence level (paired t test) with those obtained by gravimetry. Recoveries of S in fungicide and fertilizer samples were within the 84-109% range, and the relative standard deviation (n=12) was typically <5%.


Subject(s)
Fertilizers/analysis , Fungicides, Industrial/analysis , Spectrophotometry, Atomic/methods , Sulfur/analysis
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