Determination of pirimicarb and endosulfan in commercial pesticide formulations by Fourier transform infrared spectrometry

A routine method based on Fourier transform infrared spectrometry was developed for the simultaneous determination of pirimicarb and endosulfan in commercially available pesticide formulations. The method is based on peak area absorbance measurements between 1362 and 1352 cm(-1), corrected with a baseline fixed at 1338 cm(-1), for pirimicarb and peak area absorbance measurements between 919 and 909 cm(-1) with a baseline fixed at 931 cm(-1) for endosulfan; chloroform solutions for analysis were obtained by direct dilution of emulsifiable concentrates or by solvent extraction from solid samples. Various extraction conditions and appropriate band selection were investigated, and interference studies were performed. Under the experimental conditions selected, limits of detection of 13 microg/g for pirimicarb and 150 microg/g for endosulfan were obtained that correspond to 0.13 and 1.6% (w/w), respectively, in commercial samples. Results from analyses of commercial samples by the developed method compared well with those obtained by a liquid chromatography reference method.     

Validated, non-destructive and environmentally friendly determination of cocaine in euro bank notes

A non-destructive, fast and environmentally friendly procedure has been developed for cocaine determination in euro bank notes. Cocaine was extracted with 15 ml methanol by vortex agitation during 5 min. The extract was evaporated and reconstituted in 0.5 ml methanol. GC-MS-MS analysis was performed using as precursor ion m/z 182.2, with an excitation energy voltage of 1.60 eV, being the product ions measured m/z 150.2 and 82.0. A limit of detection of 0.15 ng per note and a repeatability of 6%, established from the relative standard deviation, of a 1 ng ml(-1) level, were achieved. Recoveries of 101+/-2 and 98+/-3% were obtained for samples spiked with 100 and 10 microg respectively. Results show that all the euro bank notes measured (16 samples) were contaminated with cocaine in the range between 1.25 and 889 microg. Two different contamination levels, high level (150-889 microg) and low one (1.25-77 microg) were found and it could be related with the direct or indirect contact with the drug.     

Quality control of Metamitron in agrochemicals using Fourier transform infrared spectroscopy in the middle and near range

Two vibrational spectrometry-based methodologies were developed for Metamitron determination in pesticide formulations. Fourier transform-middle infrared (FT-MIR) procedure was based on the extraction of Metamitron by CHCl₃ and latter determination by peak area measurement between 1556 and 1533 cm⁻¹, corrected with a two points baseline established from 1572 to 1514 cm⁻¹. Fourier transform-near infrared (FT-NIR) determination was made after the extraction of Metamitron in acetonitrile and measuring the peak area between 6434 and 6394 cm⁻¹ corrected using a two points baseline defined between 6555 and 6228 cm⁻¹. Repeatability, as relative standard deviation, of 5 independent measurements at mg g⁻¹ concentration level, of 0.16% and 0.07% for MIR and NIR and a limit of detection of 0.03 and 0.004 mg g⁻¹ were obtained for MIR and NIR, respectively.NIR determination provides a sample frequency of 120 h⁻¹, higher than that found by MIR and liquid chromatographic methods (60 and 15 h⁻¹, respectively). On the other hand, the NIR method reduces the solvent consumption and waste generation, to only 1 ml acetonitrile per sample as compared with 3.4 ml chloroform required for the MIR determination and 60 ml acetonitrile used in the chromatographic reference procedure. So, vibrational procedures can be considered serious alternatives to long and time consuming chromatographic methods usually recommended for quality control of commercially available pesticide formulations.     

Evaluation of nutritional parameters in infant formulas and powdered milk by Raman spectroscopy

It has been made a critical evaluation of the application of near infrared Fourier transform-Raman spectroscopy for the simultaneous determination of the most important nutritional parameters such as energetic value, carbohydrate, protein and fat contents of infant formula and powdered milk samples based on the use of partial least squares (PLS) regression analysis. A highly heterogeneous population of 23 samples, covering a wide range of infant food formula and powdered milk, were obtained from the Spanish market. Raman spectra, obtained by excitation with a Nd:YAG laser at 1064 nm, show no disturbing fluorescence effects; therefore sample spectra can be recorded without any previous preparation step. After correcting the spectra, hierarchical cluster analysis was performed in order to select a representative calibration set and the corresponding validation sample set. Different PLS models and several spectral windows were tested in order to evaluate their prediction capabilities for the validation set. Considering a calibration set comprised of three replicate spectra of 15 samples and a validation data set of eight samples, the procedure developed provided figures of merit which complied with the statutory values declared by the United States Food and Drug Administration (US FDA).     

Specific peptides as alternative to antibody ligands for biomagnetic separation of Clostridium tyrobutyricum spores

Nowadays, the reference method for the detection of Clostridium tyrobutyricum in milk is the most-probable-number method, a very time-consuming and non-specific method. In this work, the suitability of the use of superparamagnetic beads coated with specific antibodies and peptides for bioseparation and concentration of spores of C. tyrobutyricum has been assessed. Peptide or antibody functionalized nanoparticles were able to specifically bind C. tyrobutyricum spores and concentrate them up to detectable levels. Moreover, several factors, such as particle size (200 nm and 1 μm), particle derivatization (aminated and carboxylated beads), coating method, and type of ligand have been studied in order to establish the most appropriate conditions for spore separation. Results show that concentration of spore is favored by a smaller bead size due to the wider surface of interaction in relation to particle volume. Antibody orientation, related to the binding method, is also critical in spore recovery. However, specific peptides seem to be a better ligand than antibodies, not only due to the higher recovery ratio of spores obtained but also due to the prolonged stability over time, allowing an optimal recovery of spores up to 3 weeks after bead coating. These results demonstrate that specific peptides bound to magnetic nanoparticles can be used instead of traditional antibodies to specifically bind C. tyrobutyricum spores being a potential basis for a rapid method to detect this bacterial target.     

Application of an electrochemical detector to the determination of procarbazine hydrochloride by high-performace liquid chromtography

An amperometric flow-through detector with a carbon paste working electrode was utilized as a high-performance liquid chromatographic (HPLC) detector to determine procarbazine hydrochloride, an antineoplastic agent, in both buffer solution and biological fluids. The HPLC system included an amino-cyano stationary phase and an aqueous (pH 7)-methanolic mobile phase which enabled the separation of procarbazine from its only electroactive degradation product, N-isoprophyl-a- (2-methylhydrazono)-p-toluamide. The electrochemical detector, with an approximate limit of detection of 2 ng procarbazine injected, was 20 times more sensitive to procarbazine than a typical UV detector. The low dead volume (I μl) and superior selectivity of the electrochemical detector enabled the HPLC determination of procarbazine in untreated human urine and plasma.