Miguel de la Guardia

A portable and low cost equipment for flow injection chemiluminescence measurements

A compact, reliable and low cost flow injection chemiluminescence system is described. The flow system consists of a set of solenoid micro-pumps that can dispense reproductive micro-volumes of solutions. The luminometer was based on a coiled cell constructed from polyethylene tubing that was sandwiched between two large area photodiodes. The whole equipment costs about US

A validated and fast procedure for FTIR determination of Cypermethrin and Chlorpyrifos.

750 and weights ca. 3 kg. Equipment performance was evaluated by measuring low concentrations of hydrogen peroxide by oxidation of luminol and for the determination of ammonium, based on its inhibition of the luminescence provided by the reaction of luminol and sodium hypochlorite. Linear responses were achieved within 1.0-80 micromol L(-1) H(2)O(2) and 0.6-60 micromol L(-1) NH(4)(+) with detection limits estimated as 400 nmol L(-1) H(2)O(2) and 60 nmol L(-1) NH(4)(+) at the 99.7% confidence level. Coefficients of variation were 1.0 and 1.8%, estimated for 20 micromol L(-1) H(2)O(2) and 15 micromol L(-1) NH(4)(+) (n=20), respectively. Reagent consumption of 55 microg luminol, effluent volume of 950 microL per determination and sampling rate of 120 samples per hour were also achieved.

Automated Fourier transform near infrared determination of buprofezin in pesticide formulations

A FTIR methodology has been developed for the simultaneous determination of Cypermethrin and Chlorpyrifos in pesticide commercially available formulations. The method involves the extraction of both active principles with CHCl(3) and direct measurement of the peak area values between 1747 and 1737cm(-1) corrected with a baseline defined at 2000cm(-1) for Cypermethrin and peak height values established at 1549cm(-1) corrected using a baseline situated at 1650cm(-1) for Chlorpyrifos. The limits of detection achieved were of the order of 0.7 and 0.4% (w/w), and the relative standard deviation 0.4 and 0.2% for Cypermethrin and Chlorpyrifos, respectively. The developed procedure provided statistically comparable results with those obtained by HPLC, for a series of commercial samples, which validated the FTIR method. The procedure developed reduces organic solvent consumption, per sample preparation, from 51ml CH(3)CN required for HPLC to 2.5ml CHCl(3), and reduces waste generation also increasing the sample measurement frequency, from 3 to 30 samples/h, as compared with the HPLC-UV reference method.

A fast method for apatite selective leaching from granitic rocks followed through rare earth elements and phosphorus determination by inductively coupled plasma optical emission spectrometry.

An automated procedure has been developed for Fourier transform near infrared (FT-NIR) determination of buprofezin in pesticide formulations. This methodology is based on on-line pesticide extraction with acetonitrile from solid samples and its determination by using peak area absorbance measurements between 2147 and 2132 nm, corrected with a horizontal baseline established at 2091 nm. The repeatability, as a relative standard deviation of five independent analyses of 18.9 mg g−1 of buprofezin, was 0.06% and the limit of detection 5 mg L−1. The reagent consumption was clearly reduced compared with a chromatographic reference procedure from 40.4 mL acetonitrile per sample, required by high performance liquid chromatography (HPLC), to 2 mL acetonitrile consumed for FT-NIR. The sample measurement throughput obtained by the FT-NIR methodology was 30 h−1, five times higher than that obtained by HPLC (6 h−1). It can be concluded that the proposed vibrational spectroscopic method is appropriate for the quality control of commercial pesticide formulations. The on-line sample treatment avoids contact by the operator with toxic products and this method is an environmentally friendly alternative to the measurement in the mid infrared which requires the use of CHCl3.

Solid sampling Fourier transform infrared determination of Mancozeb in pesticide formulations

Rare earth elements (REE) and phosphorus (P) in apatite were determined using inductively coupled plasma optical emission spectrometry (ICP-OES) after partial dissolution of the granitic rocks and pure apatite. The dissolution was performed with nitric acid in an open system and the matrix elements were separated by a cation exchange procedure. Samples of pure apatite from granitic rocks were dissolved with, 0.14 mol L(-1) nitric acid. The results showed that the release of REE is due to apatite leaching because it could be assessed by comparing the chondrite-normalised pattern corresponding to the rocks and the pure apatite. Similar results were found for absolute REE abundance from the partial dissolution of the rocks and pure apatite. This simple and rapid method can be applied for the determination of REE in apatite as an indicator for mineral exploration, although its use in petrology could be possible.

Vibrational Spectrometry Strategies for Quality Control of Procymidone in Pesticide Formulations

A series of approaches have been assayed for FTIR determination of Mancozeb in several solid commercial fungicides using different calibration strategies. The simplest procedure was based on the use of the ratio between the absorbance of a characteristic band of Mancozeb and that of a KSCN internal standard measured in the FTIR spectra obtained from KBr pellets. It was employed the quotient between peak height absorbance values at 1525cm(-1) for Mancozeb and 2070cm(-1) for KSCN. In these conditions a precision as relative standard deviation (RSD) of 0.6% and a relative accuracy error of 0.8% (w/w) were found. For complex formulations, containing other compounds with characteristic absorption bands at different wavenumbers than Mancozeb, one of them was used as internal reference being employed the standard addition approach. In this case, the Mancozeb bands at 1525cm(-1) or at 1289cm(-1) were employed, being used the ferrocyanide band at 2075cm(-1) as internal reference. RSD values between 0.7-1.4% and a relative accuracy error of 3% (w/w) were found. A third strategy was based on the use of partial least squares (PLS) calibration. A reference set was prepared mixing Mancozeb, Kaolin, Cymoxanil and KBr, being predicted the Mancozeb concentration in pesticide formulations by using the quotient between absorbance bands of Mancozeb and those of Cymoxanil. In these conditions a relative accuracy error of 0.6% (w/w) and a relative standard deviation of 1.3% were found.

Determination of pyrethroid insecticide residues in vegetable oils by using combined solid-phases extraction and tandem mass spectrometry detection

Abstract Two vibrational spectrometry–based methodologies were developed for procymidone determination in wettable powdered pesticide formulations. The Fourier‐transform infrared (FTIR) procedure was based on the selective extraction of procymidone by chloroform and determination by peak area measurement between 1451 and 1441xa0cm−1, using a baseline correction established between 1490 and 1410xa0cm−1, and a precision of 0.4% and a limit of detection of 0.01% w/w procymidone for a sample mass of 25xa0mg were obtained. For FT‐Raman determination, the selected conditions were peak area measurement between 1005 and 995xa0cm−1 Raman shift, with a baseline correction fixed between 1030 and 947xa0cm−1, and a relative standard deviation of 1% and a limit of detection of 0.8% procymidone in the original sample were obtained. The sample frequency for FTIR determination was 30xa0hr−1, lower than that for Raman with 40xa0hr−1. FT‐Raman reduces to the minimum the reagent consumption and waste generation, also avoiding the sample h...