Picogram-level quantification of some growth hormones in bovine urine using mixed-solvent bubble-in-drop single drop micro-extraction.

Growth hormones are important biologically active compounds. However, they can cause deleterious effects if not used with care and their use in farmed animals is banned in the European Union. This study presents the development and application of a mixed-solvent "bubble-in-drop single drop micro-extraction" (BID-SDME) method for enrichment of stilbene hormones in bovine urine samples. The hormones are quantified using GC-MS showing good linearity with the coefficient of determination (R(2)) of 0.999 and 0.999 for hexestrol and diethylstilbestrol, respectively, in the concentration range 0.05-10 ng mL(-1). Excellent precision (RSD<10%) and accuracy (using a bovine urine certified reference material) were obtained. The observed detection capability (CCα, or LOD) values were 0.01 ng mL(-1) (hexestrol), 0.03 ng mL(-1) (cis-diethylstilbestrol) and 0.02 ng mL(-1) (trans-diethylstilbestrol), respectively, while the decision limit (CCß, or LOQ) values were 0.03 ng mL(-1), 0.08 ng mL(-1) and 0.07 ng mL(-1), which are comparable to or better than those reported in literature. Importantly, sample handling is significantly simplified by our method and enrichment values are greatly enhanced. The results show that a 3:1 chloroform/toluene mixture gave the highest extraction efficiency with a drop-bubble ratio of 2:1. We highlight the importance of solvent density on the success of the BID-SDME method.

Solvent-assisted headspace sampling using solid phase microextraction for the analysis of phenols in water.

Headspace analysis is used widely and relies on volatilization of analytes into the headspace above the matrix. We detail the dramatic influence that added solvent can have on headspace analysis of phenols, without the requirement for specialized headspace vials. The use of water-immiscible solvents is key and leads to a 1-3 orders of magnitude enhancement in the volatilization of these analytes and shorter fiber exposure times than are otherwise required.

Rapid detection of atrazine and metolachlor in farm soils: gas chromatography-mass spectrometry-based analysis using the bubble-in-drop single drop microextraction enrichment method.

Tracking of metolachlor and atrazine herbicides in agricultural soils, from spraying through to harvest, was conducted using our recently reported "bubble-in-drop single-drop microextraction" method. The method showed good linearity (R(2) = 0.999 and 0.999) in the concentration range of 0.01-1.0 ng/mL with LOD values of 0.01 and 0.02 ng/mL for atrazine and metolachlor, respectively. Sonication methods were poor at releasing these herbicides from the soil matrixes, while hot water extraction readily liberated them, providing an efficient accessible alternative to sonication techniques. Good recoveries of 97% and 105% were shown for atrazine and metolachlor, respectively, from the soil. The spiking protocol was also investigated, resulting in a traceless spiking method. We demonstrate a very sensitive technique by which to assess, for example, the length of residence of pesticides in given soils and thus risk of exposure.

Pre-concentration of trace elements in short chain alcohols using different commercial cation exchange resins prior to inductively coupled plasma-optical emission spectrometric detection.

Chelex-100, Dowex 50W-x8 and Dowex MAC-3 exchange resins were investigated for separation and pre-concentration of trace amounts of Cd, Cr, Cu, Fe, Mn, Pb, Ti and Zn in alcohols with respect to retention and desorption characteristics. Dowex 50W-x8 was found to be the best sorbent with percentages recoveries >95%. In addition, Chelex-100 appeared to be suitable for the pre-concentration of Cu, Fe and Zn, whereas Dowex MAC-3 was selective for Cu and Fe. Therefore, Dowex 50W-x8 was used for further investigations. The relative standard deviations <4% (n=20), limits of detection and quantification were 0.1-1.2 µg L(-1) and 0.3-1.5 µg L(-1), respectively. The SPE method was validated against a certified reference material and the results were in agreement with certified values. The accuracy of the optimized method was verified by the recovery test in the spiked alcohol samples. The accuracy and spike recovery test for different metal ions were in the range 98-102% and 95-105%, respectively. The optimized method was applied to the separation and pre-concentration of metal ions in different commercial alcohol samples.

Bubbles in solvent microextraction: the influence of intentionally introduced bubbles on extraction efficiency.

Significant improvements to microdrop extractions of triazine pesticides are realized by the intentional incorporation of an air bubble into the solvent microdroplet used in this microextraction technique. The increase is attributed partly to greater droplet surface area resulting from the air bubble being incorporated into the solvent droplet as opposed to it sitting thereon and partly to thin film phenomena. The method is useful at nanogram/liter levels (LOD 0.002-0.012 µg/L, LOQ 0.007-0.039 µg/L), is precise (7-12% at 10 µg/L concentration level), and is validated against certified reference materials containing 0.5 and 5.0 µg/L analyte. It tolerates water and fruit juice as matrixes without serious matrix effects. This new development brings a simple, inexpensive, and efficient preconcentration technique to bear which rivals solid phase microextraction methods.

Use of a simplified generalized standard additions method for the analysis of cement, gypsum and basic slag by slurry nebulization ICP-OES.

The simplified generalized standard additions method (GSAM) was investigated as an alternative method for the ICP-OES analysis of solid materials, introduced into the plasma in the form of slurries. The method is an expansion of the conventional standard additions method. It is based on the principle of varying both the sample mass and the amount of standard solution added. The relationship between the sample mass, standard solution added and signal intensity is assumed to be linear. Concentration of the analyte can be found either geometrically from the slope of the two-dimensional response plane in a three-dimensional space or mathematically from the ratio of the parameters estimated by multiple linear regression. The analysis of a series of certified reference materials (CRMs) (cement CRM-BCS No 353, gypsum CRM-Gyp A and basic slag CRM No 382/I) introduced into the plasma in the form of slurry is described. The slurries contained glycerol and hydrochloric acid and were placed in an ultrasonic bath to ensure good dispersion. "Table curve 3D" software was used to fit the data. Results obtained showed that the method could be successfully applied to the analysis of cement, gypsum and slag samples, without the need to dissolve them. In this way, we could avoid the use of hazardous chemicals (concentrated acids), incomplete dissolution and loss of some volatiles. The application of the simplified GSAM for the analysis did not require a CRM with similar chemical and mineralogical properties for the calibration of the instrument.

Slurry nebulization for the analysis of gypsum and cement by inductively coupled plasma spectrometry.

The usual form of presentation for a sample to be analyzed by an inductively coupled plasma-optical emission spectrometer is in the form of a liquid. For the analysis of solids, this involves a dissolution step and in the case of complex matrices this may be long and difficult. Should it be possible to analyse the sample without prior dissolution, then the problems associated with obtaining a solution would be resolved. A method for analyzing samples is to make use of slurry nebulization. Samples with complex matrices, such as cement and gypsum were selected and analysed as in the form of a slurry. Using different concentrations of a certified reference materials, calibration curves were obtained, from which the unknown samples could be determined directly. Use of aqueous solutions for calibration was also investigated. The method was evaluated using other reference materials or results obtained by an independent laboratory using different technique for the analysis. The slurry method was found to be accurate and precise.