Determination of carbaryl in foods by solid-phase room-temperature phosphorimetry

A phosphorimetric solid phase assay is proposed for the determination of the pesticide carbaryl (CBL) at room temperature. CBL was spotted on filter paper together with Tl(I) as heavy metal, and dried for 3 min, after which the diffuse transmitted phosphorescence was measured using two quartz plates to avoid the quenching effect produced by atmospheric oxygen. The linear dynamic range was 0.5–4.0 μg/mL and the detection and quantification limits were 0.09 and 0.31 μg/mL, respectively. The precision of the method, expressed as relative standard deviation, was 2.3% for a sample containing 2.0 μg/mL of CBL. The method was applied to the determination of CBL residues in cereals, potatoes and waters, obtaining recoveries ranging between 92 and 105%.     

Determination of thiabendazole in foods and waters by solid-phase transmitted room-temperature phosphorescence

A new method for the determination of thiabendazole (TBZ) is proposed, based on enhanced native phosphorescence at room temperature when the pesticide is fixed on paper and using Pb (CH₃-COO)₂ as the enhancer. The sample and enhancer solutions were deposited on a slip of paper (Whatman No. 4), previously humidified with pH 4.0 acetic/acetate buffer solution, after which the paper was dried and placed between two quartz plates. The diffuse transmitted phosphorescence intensity was measured directly at _ex = 303 nm and _em = 472 nm. The applicable concentration range was 160.0–1200.0 ng/ml, with a relative standard deviation of 1.2%. The detection and quantification limits were 47.7 and 158.9 ng/ml, respectively. This simple method was used to measure the levels of this pesticide in potatoes, green beans, lettuce and different types of waters, showing good selectivity in all instances.     

Surface analysis of tablets by room-temperature phosphorimetry

The feasibility of surface analysis of homogeneous tablets by room-temperature phosphorimetry is studied for propranolol, p-aminobenzoic acid and acetylsalicylic acid as model compounds. Potassium iodide is used to provide the heavy atom; starch or carboxymethylcellulose is used as the excipient. The analytically useful ranges were found to be 3 × 10^?5?3 × 10^?4% for p-aminobenzoic acid, 5 × 10^?4?5 × 10^?2% for propranolol, and ? 10% for acetylsallicylic acid (all by weight in tablets).     

Determination of trace amounts of carbaryl in water by solid-phase laser-induced fluorescence

A quick and very sensitive method is proposed for the determination of the insecticide carbaryl, following transformation in 1-naphthol, using solid-phase fluorescence excited by a pulsed nitrogen laser and detected with a charge-coupled device. Carbaryl is hydrolized in an alkaline medium resulting in 1-naphthol. This hydrolysis product is fixed on QAE Sephadex A-25 gel at pH 11.20. The fluorescence of the gel, packed in a 1 mm silica cell, was measured directly using a solid-surface attachment. The detection limit obtained was 1.8 ng. A recovery study was carried out on several types of water samples to check the efficiency of the method. The results obtained are compared with data published in a previous paper where the LS-50 spectrofluorimeter was used. The detection and quantification limits are improved here by an order of magnitude.     

On the improvement of solid-phase extraction room-temperature phosphorimetry for the analysis of polycyclic aromatic hydrocarbons in water samples

This article presents considerable improvements in SPE-RTP methodology for the analysis of polycyclic aromatic hydrocarbons in water samples. Bulky glassware and vacuum pump were removed from the previous extraction procedure [E.D. Hagestuen, A.D. Campiglia, Talanta 49 (1998) 547] by processing 10 ml of sample with syringes and stainless steel filter holders. The oven-drying step was substituted by air sample drying, which employed positive pressure to remove water excess from the extraction membrane. As a result, analysis times from 8 to 10 min per sample were obtained. No costs in levels of detection were observed. Limits of detection at the pg ml(-1) level were estimated for phenanthrene, pyrene, benzo(k)fluoranthene, benzo(a)pyrene, and chrysene. The feasibility of identifying single components in PAH mixtures was investigated. Binary and tertiary mixtures were resolved by appropriate choice of excitation and emission wavelengths. The advantage of using excitation-emission matrix analysis was demonstrated for a six-component mixture.     

Determination of ofloxacin in tablets by room-temperature phosphorimetry on a poly(vinyl alcohol) solid substrate

An easy and sensitive method for the quantitative determination of ofloxacin (OFLX), a new fluoroquinolone antimicrobial agent, in a pharmaceutical formulation, tablet, was developed by using solid-substrate room-temperature phosphorimetry (RTP) on a poly(vinyl alcohol) substrate. The method did not require a dry gas flush during the measurement of phosphorescence. The influence of different conditions such as solution pH and concentrations of heavy atoms, used as the enhancer, were studied. The phosphorescence intensity of OFLX was enhanced using NaOH and KI as enhancers. A linear relationship between concentration and RTP intensity for each standard solution was obtained in the concentration range of 4-18000 ng/ml, and the determination limit was 4 ng/ml. The proposed method was applied to a determination of OFLX in a commercial tablet, and the results were compared with those of fluorescence and UV methods. It was proven that OFLX in a commercial tablet can be accurately measured by this method with a very small amount of sample solution.     

Constant-energy synchronous, time-resolved, room-temperature phosphorimetry

The combination of constant-energy synchronous luminescence spectrometry (CESL) with a pulsed source and gated detection is used to demonstrate the analytical power of time resolution CESL in room-temperature phosphorimetry. The instrumentation is discussed. Two binary mixtures are evaluated to demonstrate the spectral simplification of this technique.     

Identification and quantification of polynuclear aromatic compounds in synthoil by room-temperature phosphorimetry

Room-temperature phosphorimetry (r.t.p.) is used to identify and quantify polynuclear aromatic compounds in a synthetic fuel (Synthoil). Several trace and major components, benzo[a]pyrene, chrysene, fluorenes, fluoranthene, phenanthrene, and pyrene, have been identified and determined at concentrations ranging from tens to thousands of parts-per-million. The selectivity of the r.t.p. analysis is greatly improved by using selective heavy-atom perturbation and synchronous excitation scanning.     

A Becquerel-disc phosphoroscope for the measurement of lifetimes in room-temperature phosphorimetry

A Becquerel-disc phosphoroscope is constructed from a commercially available optical chopper with variable frequency and digital read-out. By use of a continuous source, phosphorescence lifetimes in the range 1-1000 msec can be measured with better than 4% relative standard deviation.     

Comparative evaluation of two substrates for urinary determination of p-aminobenzoic acid by room-temperature phosphorimetry

Filter paper (S & S 903) impregnated with diethylenetriaminopentaacetic acid, and Whatman DE-81 anion-exchange paper are evaluated for quantitation of urinary p-aminobenzoic acid. The two substrates are compared with respect to drying characteristics, pH variations, heavy atom effect, and some other variables. Impregnated S & S 903 paper is superior in terms of drying characteristics and background interferences but DE-81 has several advantages including lower detection limit, wider pH range, and ready availability. Although both substrates seem applicable to clinical application, DE-81 is probably more useful.     

纸基质室温磷光法快速测定中药材中西维因的研究

以快速定量滤纸为基质,用KI作为重原子微扰剂,建立了快速测定中药材中西维因的固体基质室温磷光(SS-RTP)分析法。其最大激发和发射波长分别为284nm与520nm。在优化的实验条件下,西维因在4×10-6~2×10-4mol/L浓度范围内呈现良好的线性关系。在样品体积为10μL时,方法的检出限为0.89ng/斑点。所建立的方法用于中草药中西维因残留量的测定。     

Phosphorescence detection in flowing systems: selective determination of aluminium by flow-injection liquid room-temperature phosphorimetry

The concept of the micelle stabilized liquid room-temperature phosphorescence (MS-LRTP) was applied to the determination of a metal (aluminium) in a flowing system. A three-line flow-injection manifold was developed and various parameters were optimized. A linear calibration graph was obtained for 0–4 μg ml^?1 aluminium. The limit of detection was 50 ng ml^?1 and the relative standard deviations for 0.1 and 1.0 μg ml^?1 aluminium were 2.7 and 1.3% respectively. The proposed procedure is fairly selective. More than 20 common ions studied did not interfere with the determination of aluminium or could be masked by appropriate reagents. The flow-injection method proposed was applied without any preliminary separation to the determination of aluminium in simulated synthetic samples in water and in clinical samples of particular importance in the control of aluminium toxicity in renal failure patients.     

Time-resolved micelle-stabilized room-temperature phosphorimetry for simultaneous determination of gallium and indium

Ga(III) and In(III) react with 7-iodo-hydroxyquinoline-5-sulphonic acid (Ferron) in the presence of CTAB micelles, forming complexes which exhibit analytically useful room-temperature phosphorescence (RTP). The RTP features of the two complexes are similar and the RTP spectra overlap. However, there is sufficient difference between the two phosphorescence decay rates for both metals to be determined by time-resolved room-temperature phosphorimetry.     

分散固相萃取-气相色谱-串联质谱法测定动物源性食品中9种N-亚硝胺类化合物

建立了分散固相萃取-同位素稀释-气相色谱-串联质谱同时测定动物源性食品中9种N-亚硝胺的方法。样品用乙腈提取,上清液经分散固相萃取（dSPE）净化后浓缩。选用DB-WAX极性毛细管色谱柱对待测物进行分离,经EI源电离后以多反应监测（MRM）模式采集数据并做定性筛查和定量分析。9种N-亚硝胺在相应的浓度范围内线性关系良好,相关系数均大于0.99,对4类典型的动物源性食品进行3个不同浓度的加标试验,平均回收率为62.5%~118%,RSD为2.11%~25.6%,检出限（LOD,S/N=3）为0.02~0.31 μg/kg。该方法成本低廉、灵敏可靠,适用于同时对动物源性食品中9种N-亚硝胺进行定性和定量测定。     

Determination of trace calcium by solid substrate-room temperature phosphorimetry

A new method for the determination of trace calcium by solid substrate-room temperature phosphorimetry is established. It is based on the fact that chromeazurols azurol S-phenanthroline-NaCMC (CAS-phen-NaCMC) system can emit strong and stable room temperature phosphorescence (RTF) on the solid substrate in the filter paper. Ca2 and phenanthroline can form complex ion Ca(phen)32 , which will form complex [Ca(phen)3(CAS)2] with CAS. In the result, the number of CAS molecules in each spot increased, causing sharp increase of the RTP signal of the CAS-phen-NaCMC system.     

Determination of organochlorine pesticide residues in foods using solid-phase extraction clean-up cartridges

Fourteen organochlorine pesticide residues in fatty foods were determined using a simple and rapid procedure based on solid-phase extraction (SPE) clean-up cartridges with octadecyl (C18)-bonded porous silica, a tandem C18 and Florisil column, Alumina-N and Florisil. A Florisil cartridge eluted with 12 ml petroleum ether-ethyl ether (95 + 5) was the most efficient clean-up procedure capable of eliminating the matrix interference and satisfying the agreed acceptable recovery for the large numbers of organochlorine pesticides in nine kinds of foods having different fat contents. Average recoveries of organochlorine pesticides in shellfish, fish and meats ranged from 77 to 105%, 84 to 98% and 85 to 107%, respectively. In addition, analysis of a certified Standard Reference Material (SRM 1945) verified the satisfactory performance of Florisil clean-up cartridge. This SPE method not only yielded comparable results for nonfatty foods, but also provided a reliable separation and quantification of organochlorine pesticides for analyzing a large number of foods with a wide range of fat content.     

Study of ph and substrate effects on room-temperature phosphorimetry of some indolecarboxylic acids

Room-temperature phosphorescence (RTP) of eight indolecarboxylic acids has been investigated under different pH conditions, and on several ion-exchange filter papers. RTP excitation and emission wavelengths do not change significantly with pH. The largest RTP signals are obtained from neutral solutions adsorbed on DE-81 anion-exchange filter paper, while alkaline (pH approximately 13) solutions on S & S 903 filter paper treated with DTPA (diethylenetriaminepenta-acetic acid) give stronger signals than neutral or acidic (pH approximately 1.6) solutions on the same substrate. The existence of several hydrogen-bonding interactions between the various ionic indolecarboxylic acid species and the substrates is discussed. Heavy-atom enhancement factors ranging between 4 and 550, according to the compound, are obtained with iodide. Absolute limits of detection between 100 and 500 pg demonstrate the usefulness of RTP for determination of indolecarboxylic acids at the trace level.     

Determination of bisphenol-type contaminants from food packaging materials in aqueous foods by solid-phase microextraction-high-performance liquid chromatography

A fast screening method consisting of off-line solid-phase microextraction coupled to HPLC and fluorescence detection, suitable for the analysis of several bisphenol derivatives and their degradation products in aqueous solution, has been developed. Detection limits of 0.7 ng ml(-1) for 2,2-bis[4-(glycidyloxy)phenyl]propane, 0.9 ng ml(-1) for bisphenol A bis(3-chloro-2-hydroxypropyl)ether, 1.1 ng ml(-1) for 2,2-bis(4-hydroxyphenyl)propane and 2.4 ng ml(-1) for bisphenol F diglycidyl ether have been achieved working in the linear range 10-500 ng ml(-1). The good analytical features achieved make the proposed method an interesting option for the direct determination of these compounds in aqueous canned food such as peas, tuna, olives, maize, artichokes or palm hearts. Both the optimization process and the results, including the analysis of real samples, are given and discussed.