№Determination of Trace Arsenic by Solid Substrate-Room Temperature Phosphorescence Quenching Method Based on the Catalyzed Reaction of H2O2 Oxidizing 9-Hyd roxy-2,3,4,9-tet rahyd ro-1,10-anth raquinone

A new solid substrate-room temperature phosphorescence （SS-RTP） quenching method for the determination of trace As（V） has been developed, based on the facts that 9-hydroxy-2,3,4,9-tetrahydro-1,10-anthraquinone （R） can emit intense and stable SS-RTP on solid substrate, and α,α＇-dipyridyl can activate As（V） catalysis of the reaction of H2O2 oxidizing R to non-phosphorescence compound R＇, which can cause the sharp quenching of SS-RTP. Under the optimum condition, the relationship between the ΔIp of the emitting intensity and 1.60-160 fg·spot^-1 As（V） （corresponding concentration： 0.0040-0.40 ng·mL^-1, sample volume： 0.4 μL·spot^-1） conformed to Beer＇ law. The regression equation of working curve can be expressed as ΔIp= 20.46＋0.5492CAs（v） fig·spot^-1） （r= 0.9995, n = 6）. The limit detection （LD） is 0.27 fg·spot^-1 [As（V） corresponding concentration： 6.8 × 10^-13 g·mL^-1, n=11]. The samples containing 0.0040 and 0.40 ng·mL^-1 As（V） were repeatedly determined for 11 times. RSD are 3.0% and 2.7% respectively. The SS-RTP mechanism was also discussed. R was synthesized in this paper. Meanwhile, the structure was determined by NMR, IR, mass spectra and elemental analysis.     

Strong Luminescence Catalytic Solid Substrate Room Temperature Phosphorescence for the Determination of Trace Copper

Under the conditions of reacting at 100°C for 8 min and irradiating with the infrared light for 15 min, methylene blue (MEB) could emit weak room temperature phosphorescence (RTP) on the cellulose acetate membrane (CAM) using Pb²⁺ as the ion perturber in the NH₃‐NH₄Cl (pH=9.80) solution. MEB was oxidized by H₂O₂, which caused the RTP of the system to enhance. Cu²⁺ could catalyze the reaction of H₂O₂ oxidizing MEB, which caused the RTP of the system to enhance sharply. The ΔI_p (I_p0?I_p, the I_p0 and I_p were RTP intensity of the blank reagent and RTP intensity of the test reagent, respectively) of the catalytic system was 133.6, which was 4.1 times larger than that without infrared light irradiation (33.1). Its ΔI_p was proportional to the content of Cu²⁺. Thus, a new catalytic solid substrate room temperature phosphorimetry (SSRTP) for the determination of trace copper has been established. The limit of quantization (LOQ) of this method was 0.12 ag·spot^?1 (sample volume: 0.40 µL·spot^?1, corresponding concentration: 3.0×10^?16 g·mL^?1), showing high sensitivity. This method not only has been successfully applied to the determination of trace copper in the tobacco, tea and human serum, but also could predict human diseases. The catalytic reaction was first order reaction, whose activation energy (E) was 18.17 kJ·mol^?1 and rate constant (k) was 3.4×10^?4 s^?1. At the same time, the mechanism of catalytic SSRTP for the determination of trace copper was discussed.     

Solid substrate-room temperature phosphorimetry for the determination of residual clenbuterol hydrochloride based on the catalysis of sodium periodate oxidizing eosine Y

Clenbuterol hydrochloride (CLB) could catalyze NaIO₄ oxidation of eosine Y (R), which caused the room temperature phosphorescence (RTP) signal of R to quench sharply. The ΔI_P (=I_P2 − I_P1, I_P2 was RTP intensities of reagent blank and I_P1 was RTP intensities of test solution) of the system was directly proportional to the content of CLB. According to that academic thought, a new solid substrate-room temperature phosphorimetry (SS-RTP) for the determination of trace CLB has been established. This method has high sensitivity (detection limit (LD): 0.021 zg spot⁻¹, corresponding concentration: 5.2 × 10⁻²⁰ g mL⁻¹) and good selectivity (Er = ±5%, interfering species were of no interference). It has been applied to the determination of residual CLB in the practical samples. The results were verified using HPLC and GC/MS methods. The reaction mechanism of catalytic SS-RTP for the determination of residual CLB was also discussed.     

Determination of trace mercury by solid substrate room temperature phosphorescence quenching method based on lead carboxymethyl cellulose (Pb(CMC)(2)) particles containing luminescent salicyl fluorones molecules

Luminescent particles of lead carboxymethyl cellulose (Pb(CMC)₂), which contains salicyl fluorones (THBF), Pb(CMC)₂-THBF, were synthesized by sol-gel method. Pb(CMC)₂-THBF can emit intense and stable solid substrate room temperature phosphorescence (SS-RTP) on filter paper. EDTA can chelate the Pb²⁺ in Pb(CMC)₂-THBF, causing it decompose into aqueous soluble components PbY²⁻, CMC⁻ and THBF, and these components can react with Hg²⁺ to form (CMC)₂Hg-THBF, causing decrease of phosphorescence intensity. Based on the facts above, a new method for the determination of trace mercury by SS-RTP quenching method was established. The linear range of this method is 2.0-40.0 fg spot⁻¹ (5.0-100.0 pg ml⁻¹) of Hg²⁺, with a detection limit (LD) of 0.26 fg spot⁻¹, and the regression equation of working curve is (fg spot⁻¹, 0.4 μl spot⁻¹), r = 0.9994. This method has been applied to the determination of trace mercury in water sample with satisfactory results. The mechanism of SS-RTP emission is also discussed.     

Affinity Adsorption Solid Substrate‐Room Temperature Phosphorimetry for the Determination of Alkaline Phosphatase

Abstract

In the presence of Pb(Ac)₂, the silicon dioxide nanoparticle containing rhodamine 6G (R‐SiO₂) can emit strong and stable solid substrate‐room temperature phosphorescence (SS‐RTP) signal on the surface of acetyl cellulose membrane (ACM) at λ_ex/λ_em=482/649 nm. It was found in the research that specific affinity adsorption reaction between triticum vulgare lectin (WGA) (which was labeled with luminescent silicon dioxide nanoparticle) and alkaline phosphatase (AP) can be carried out on the surface of ACM. The product of the reaction can emit stronger SS‐RTP signal. A new method of SS‐RTP for the determination of AP was established, based on an affinity adsorption reaction between AP and WGA labeled with nanoparticles containing rhodanime 6G luminescent molecules. The linear range of this WGA‐AP‐WGA‐R‐SiO₂ method is 1.00–360.00 ag AP spot^?1 (sample volume: 0.40 µL spot^?1, corresponding concentration range: 2.50–900.00 fg mL^?1). The regression equation of working curve is ΔIp=16.24+0.8856 m_AP (ag spot^?1), r=0.9993. Detection limit of this method calculated by 3S_b/k is 0.14 ag spot^?1. After 11‐fold replicate measurements, RSD are 3.9% and 3.1% for the systems containing 1.00 and 360.00 ag AP spot^?1, respectively. Compared with R‐SiO₂‐WGA‐AP method (detection limit: 0.45 ag spot^?1, corresponding concentration range: 2.00–320.00 ag spot^?1), the sensitivity of WGA‐AP‐WGA‐R‐SiO₂ method was obviously improved and the linear range was wider. The sensitivity, accuracy, and precision of this method are high. It has been successfully applied to determine AP in human serum.     

A New Fluorescein Isothiocyanate-Piperidine Self-ordered Ring Phosphorescent Probe for the Determination of Trace Protein

The ? COOH in fluorescein isothiocyanate (FITC) reacted with ? NH? in piperidine (P) to form FITC‐P on the center of indentation of polyamide membrane (PAM) when drying for 2 min at (92±1)°C. Then, the FITC‐P diffused outward from the indentation center and formed the round SOR‐P‐FITC (containing the FITC‐P self‐ordered rings). Thus, multi‐FITC accumulated on SOR‐P‐FITC, leading to the enhancement of RTP signal on bio‐target, whose I_p increased 2.0 times compared with non‐generated SOR. When bovine serum albumin (BSA) was added to the center of SOR‐P‐FITC, ? NCS of FITC in SOR‐P‐FITC reacted with ? NH₂ of BSA to form SOR‐P‐FITC‐BSA, which caused the RTP signal of FITC to enhance sharply. The ΔI_p of the system was 3.4 times higher than that without β‐CD and 4.0 times higher than that without SOR‐P‐FITC formed. Its ΔI_p was linear to the content of BSA. Therefore, a new solid substrate‐room temperature phosphorimetry (SS‐RTP) for the determination of trace protein was established using SOR‐P‐FITC as a phosphorescent probe. Under the optimum condition, the linear range of this method was 0.040–16.0 ag·spot^?1 with a detection limit (LD) of 8.5 zg·spot^?1 (0.40 µL sample solution per spot, the corresponding concentration was 2.1×10^?17 g·mL^?1), and the regression equation of working curve was ΔI_p=3.848+4.240m_BSA (ag·spot^‐1), n=6, correlation coefficient (r) was 0.9993. This method with high sensitivity had been applied to determining the content of trace protein in the water samples, and the results coincided well with those obtained with pyrocatechol violet‐Mo(VI) method (P.V.M.M.). At the same time, the mechanism of SS‐RTP using SOR‐P‐FITC as a phosphorescent probe (SOR‐P‐FITC‐SS‐RTP) was discussed.     

A New 4.0-Generation Dendrimer Phosphorescence Labeling Reagent and Its Application to Determination of Trace Alkaline Phosphatase by Affinity Adsorption Solid Substrate-room Temperature Phosphorimetry

A Triton X-100-4.0G-D （4.0G-D refers to a 4.0-generation dendrimer） was brought forward as a new phosphorescence labeling reagent. Two types of specific affinity adsorption （AA） reactions （direct method and sandwich method） were carried out between the labeling product of Triton X-100-4：0G-D-Wheat germ agglutinin （WGA） and alkaline phosphatase （ALP）, the product of AA reaction preserved the good characteristics of room temperature phosphorescence （RTP） of 4.0G-D and △Ip of the product was proportional to the content of ALP. According to the fact stated above, a new method for the determination of trace ALP by affinity adsorption solid substrate-room temperature phosphorimetry （AA-SS-RTP） was established on the basis of WGA labeled with the Triton X-100-4.0G-D. The detection limits were 0.20 ag·spot^-1 （corresponding concentration： 5.0×10^-16 g·mL^-1, namely 5.0×10^-18 mol·L^-1） for a direct method and 0.14 ag·spot^-1 （corresponding concentration： 3.5×10^-16 g·mL^-1, namely 3.5×10^-18 mol·L^-1） for a sandwich method, respectively. For their high sensitivity, good repeatability and high accuracy, the direct method and sandwich method have been successfully appfied to determine the content of ALP in human serum, and the results were coincided with the clinical detection results of the enzyme-linked immunosorbent assay method by the Zhangzhou Hospital of Traditional Chinese Medicine. Meanwhile, the mechanism for the determination of trace ALP by AA-SS-RTP was discussed.     

Determination of Glucose by Affinity Adsorption Solid Substrate‐room Temperature Phosphorimetry Based on Triticum Vulgare Lectin Labeled with Silicon Dioxide Nanoparticle Containing Fluorescein Isothiocyanate

In the presence of heavy atom perturber Pb2＋, silicon dioxide nanoparticle containing fluorescein isothiocyanate (FITC-SiO2) could emit a strong and stable room temperature phosphorescence (RTP) signal on the surface of acetyl cellulose membrane (ACM). It was found in the research that a quantitative specific affinity adsorption (AA) reaction between triticum vulgare lectin (WGA) labeled with luminescent nanoparticle and glucose (G) could be carried on the surface of ACM. The product (WGA-G-WGA-FITC-SiO2) of the reaction could emit a stronger RTP signal, and the ΔIp had linear correlation to the content of G. According to the facts above, a new method to determine G by affinity adsorption solid substrate room temperature phosphorimetry (AA-SS-RTP) was established, based on WGA labeled with FITC-SiO2. The detection limit (LD) of this method calculated by 3Sb/k was 0.47 pg•spot－1 (corresponding to a concentration value 1.2×10－9 g•mL－1, namely 5.3×10－9 mol•L－1), the sensitivity was high. Meanwhile, the mechanism for the determination of G by AA-SS-RTP was discussed.     

Preparation for nitrocellulose membrane-poly (vinyl alcohol)-ionic imprinting and its application to determine trace copper by room temperature phosphorimetry

Nitrocellulose membrane-poly (vinyl alcohol)-ionic imprinting (NCM-PVA-I-I) was prepared using Cu²⁺ as template. The cavity in NCM-PVA-I-I matched Cu²⁺ very well and the selectivity was high. Cu²⁺ entered the cavity and then could form ionic association ([Cu²⁺]·[(Fin⁻)₂]) with the anion of fluorescein (Fin⁻) outside the cavity by electrostatic effect. [Cu²⁺]·[(Fin⁻)₂] could emit strong and stable room temperature phosphorescence on NCM-PVA-I-I. Its ΔI_p was proportional to the content of Cu²⁺. Based on the above facts, a new method for the determination of trace copper by solid substrate-room temperature phosphorimetry (NCM-PVA-I-I-SS-RTP, SS-RTP is the abbreviation of solid substrate-room temperature phosphorimetry) using NCM-PVA-I-I technique has been established. The linear range of this method was 2.00-144.00 fg Cu²⁺ spot⁻¹ (sample volume: 0.40 μL spot⁻¹, corresponding concentration: 5.00-360.00 pg mL⁻¹), and the detection limit calculated by 3Sb/k was 0.43 fg Cu²⁺ spot⁻¹ (corresponding concentration: 1.1 × 10⁻¹² g mL⁻¹, n = 11). Samples containing 2.00 and 144.00 fg Cu²⁺spot⁻¹ were measured, respectively, for seven times and R.S.D.s were 3.5% and 4.7%. NCM-PVA-I-I-SS-RTP could combine very well the characteristics of both the high sensitivity of SS-RTP and the high match and selectivity of NCM-PVA-I-I, and it was rapid, accurate, sensitive and with good repeatability. It has been successfully applied to determine trace copper in human hair and tea samples.     

Exploitation of phosphorescent labelling reagent of fullerol-fluorescein isothiocyanate and new method for the determination of trace alkaline phosphatase as well as forecast of human diseases

A new phosphorescent labelling reagent consisting of fullerol, fluorescein isothiocyanate and N,N-dimethylaniline (F-ol-(FITC)_n-DMA) was developed. The mode of action is based on the reactivity of the active -OH group in F-ol with the -COOH group of FITC to form an F-ol-(FITC)_n-DMA complex containing several FITC molecules. F-ol-(FITC)_n-DMA increased the number of luminescent molecules in the biological target of WGA-AP-WGA-F-ol-(FITC)_n-DMA (WGA and AP are wheat germ agglutinin and alkaline phosphatase, respectively) which improved the sensitivity using solid substrate room temperature phosphorimetry (SSRTP) detection. The proposed method provided high sensitivity and strong specificity for WGA-AP. The limit of detection (LD) was 0.15 ag AP spot⁻¹ for F-ol and 0.097 ag AP spot⁻¹ for FITC in F-ol-(FITC)_n-DMA, which was lower than the method using single luminescent molecules of F-ol-DMA and FITC-DMA to label WGA (0.20 ag AP spot⁻¹ for F-ol-DMA and 0.22 ag AP spot⁻¹ for FITC-DMA). Results for the determination of AP in human serum were in good agreement with those obtained by enzyme-linked immunosorbent assay. The mechanism of F-ol-(FITC)_n-DMA labelling of WGA was discussed.     

Solid Substrate Room Temperature Phosphorimetry for the Determination of Trace Mercury Based on the Reaction between Alkaline Phosphatase and Mercury Using Triton X-100 as a Sensitizer

A new solid substrate room temperature phosphorimetry (SSRTP) for the determination of trace mercury has been established, using Triton X‐100 as a sensitizer. The regression equation of working curve was ΔI_p=11.40m(Hg²⁺)+1.569 (ag·spot^?1, n=6, ΔI_p=I_p1?I_p2, I_p1 and I_p2 referred to the phosphorescence intensity of the blank reagent and the test solution, respectively), and correlation coefficient (r) was 0.9984. The RSD valus of the determination of 0.016 and 8.0 ag·spot^?1 Hg²⁺ were 4.1% and 1.7% (n=8), respectively, indicating that the method had good repeatability. The limit of detection (LOD) calculated by 3Sb/k was 7.0 zg·spot^?1 Hg²⁺ (corresponding concentration: 1.8×10^?17 g·mL^?1, Sb=0.025, n=11). This method has high sensitivity, selectivity and precision, which was applied to determination of trace mercury in water samples with the result being agreed very well with that of dithizone extraction spectrophotometry.     

Determination of trace arsenic(V) by catalytic solid substrate-room temperature phosphorescence quenching method

In the H2SO4 medium and in the presence of dodecylbenzene sulfonic acid sodiumsalt (DBS), dimethyl yellow (R) could emit strong and stable solid substrate room temperature phosphorescence (RTP) on filter paper. And NaIO4 could oxidize R to cause the RTP quenching. Arsenic(V) could catalyze the reaction of NaIO4 oxidizing R, which caused the RTP sharply quenching. The reducing value of phosphorescence intensity (△Ip) for the system with DBS is 3.3 times higher than that without DBS. Moreover, the△Ip is proportional to the concentration of As(V). Based on the facts above, a new RTP quenching method for the determination of trace As(V) has been established.     

A rapid microwave-assisted acid extraction method based on the use of diluted HNO3-H2O2 followed by ICP-MS analysis for simultaneous determination of trace elements in coal samples

Before coal processing such as pyrolysis, liquefaction, gasification and combustion, it is very crucial to monitor the trace element concentration levels as that determines the coal quality. Therefore, the current study describes the development of microwave-assisted acid extraction (MW-AAE) method for extraction of 15 trace elements in coal samples prior to their determination using inductively coupled plasma-mass spectrometry. Diluted HNO₃-H₂O₂ was used in order to reduce reagents amount used, eliminate matrix interferences caused by concentrated acids and to decrease waste produced in analytical laboratories. The optimisation of the proposed extraction method was carried out by using a full factorial design (2⁴) involving four factors; that is, temperature, extraction time, HNO₃ and H₂O₂ concentrations. The optimum conditions for the MW-AAE procedure were found to be 200°C, 5 min, 5 mol L^?1 and 2 mol L^?1 for temperature, extraction time, HNO₃ and H₂O₂ concentrations, respectively. Under optimum conditions, the accuracy of the MW-AAE method was examined by analysing three coal certified reference materials (SARM 18, 19 and 20) and recoveries of 80–115% were achieved for V, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Sr, Zr, Cs, Ba, Pb and U, except for Ti (10–25%) and Hf (27–70%). In addition, the precision of the proposed method, expressed in terms of relative standard deviation (SD) (n = 15), was within the accepted range (≤3.5%). The method detection limits of 0.001–0.57 µg g^?1 for all trace elements under the investigation were similar to the literature reported work, except for Ti (4.00 µg g^?1).     

Redox Speciation of Inorganic Arsenic in Water and Saline Samples by Adsorptive Cathodic Stripping Voltammetry in the Presence of Sodium Diethyl Dithiocarbamate

This paper describes a new voltammetric procedure for the inorganic speciation of As(III) and As(V) in water samples. The procedure is based on the chemical reduction of arsenate [As(V)] to arsenite [As(III)] followed by the voltammetric determination of total arsenic as As(III) at the hanging mercury drop electrode (HMDE) by adsorptive cathodic stripping voltammetry (AdCSV) in the presence of sodium diethyl dithiocarbamate (SDDC). The reduction step involved the reaction with a mixture of Na₂S₂O₅ and Na₂S₂O₃ in the concentrations 2.5 and 0.5 mg mL^?1, respectively, and the sample heating at 80 °C for 45 min. The linear range for the determination of total arsenic as As(III) in the presence of SDDC was between 5 and 150 μg L^?1 for a deposition time of 60 s (r=0.992). A detection limit of 1.05 μg L^?1 for total As was calculated for the method in water samples using a deposition time of 60 s. The detection limits of 4.2 μg L^?1 and 15.0 μg L^?1 for total As in seawater and dialysis concentrates, respectively, were calculated using a deposition time of 60 s. The relative standard deviations calculated were 2.5 and 4.0% for five measurements of 20 μg L^?1 As(V) as As(III) in water and dialysis concentrates, respectively, after chemical reduction under optimized conditions. The method was applied for the determination of As(III) and total As in samples of dialysis water, mineral water, seawater and dialysis concentrates. Recovery values between 86.0 and 104.0% for As(III) and As(V) added to the samples prove the satisfactory accuracy and applicability of the procedure for the arsenic monitoring.     

Reactivity of metal-bound peroxides; alkali triperoxovanadate(V) trihydrates,A[V(O2)3]·3H2O (A = Na or K), as oxidants resembling alkali—H2O2 reagent for some organic substrates

The efficacy of the triperoxovanadium(V) complexes, A[V(O₂)₃]·3H₂O (A = Na or K), as potential oxidants with respect to certain organic substrates has been investigated. Aqueous solutions of the complexes are basic (pH ca. 11) in nature. The complexes efficiently oxidise an α,β-unsaturated ketone to the corresponding epoxide and benzonitrile to benzamide. Such reactions are usually accomplished using alkaline-H₂O₂ reagent. The complexes are also capable of bringing about Bayer-Villiger-type oxidation and oxidise benzil to benzoic acid. The peroxo-depleted vanadium product, isolated after the oxidations, has been identified as a diperoxovanadate(V) complex, [VO(O₂)₂(H₂O)]⁻.     

Detection of trace nitrite in waters using a QDs-based chemiluminescence analysis system

In the present work, a novel flow-injection chemiluminescence method based on CdTe quantum dots (QDs) was developed for the determination of nitrite. Weak chemiluminescence (CL) signals were observed from a CdTe QDs–H₂O₂ system under basic conditions. The addition of a trace amount of hemoglobin (Hb) caused the CL from the CdTe QDs–H₂O₂ system to increase substantially. In the presence of nitrite, the ferrous Hb reacted with the nitrate to form ferric Hb and NO. The NO then bound to ferrous Hb to generate iron nitrosyl Hb. As a result, the CL signal from the CdTe QDs–H₂O₂–Hb system was quenched. Thus, a flow-injection CL analytical system for the determination of trace nitrite was established. Under optimum conditions, there was a good linear relationship between CL intensity and the concentration of nitrite in the range 1.0?×?10^?9 to 8.0?×?10^?7 mol L^?1 (R ²?=?0.9957). The limit of detection for nitrite using this system was 3.0?×?10^?10 mol L^?1 (S/N?=?3). This method was successfully applied to detect nitrite in water samples.

Synergetic effect of Prussian blue film with gold nanoparticle graphite–wax composite electrode for the enzyme-free ultrasensitive hydrogen peroxide sensor

Enzyme-free amperometric ultrasensitive determination of hydrogen peroxide (H₂O₂) was investigated using a Prussian blue (PB) film-modified gold nanoparticles (AuNPs) graphite–wax composite electrode. A stable PB film was obtained on graphite surface through 2-aminoethanethiol (AET)-capped AuNPs by a simple approach. Field emission scanning electron microscope studies results in formation of PB nanoparticle in the size range of 60–80 nm. Surface modification of PB film on AET–AuNPs–GW composite electrode was confirmed by Fourier transform infrared attenuated total reflection (FTIR-ATR) spectroscopy studies. Highly sensitive determination of H₂O₂ at a peak potential of ?0.10 V (vs. SCE) in 0.1 M KCl PBS, pH?=?7.0) at a scan rate of 20 mVs^?1 with a sensitivity of 23.58 μA/mM was observed with the modified electrode using cyclic voltammetry. The synergetic effect of PB film with AuNPs has resulted in a linear range of 0.05 to 7,800 μM with a detection limit of 0.015 μM for H₂O₂ detection with the present electrode. Chronoamperometric studies recorded for the successive additions of H₂O₂ with the modified electrode showed an excellent linearity (R ²?=?0.9932) in the range of 4.8?×?10^?8 to 7.4?×?10^?8 M with a limit of detection of 1.4?×?10^?8 M. Selective determination of H₂O₂ in presence of various interferents was successfully demonstrated. Human urine samples and stain remover solutions were also investigated for H₂O₂ content.     

Determination of Arsenic in Hair by Resonance Rayleigh Scattering Method with Iodine Green–Molybdate System

Abstract

A simple and fast resonance Rayleigh scattering (RRS) method for the determination of arsenic was developed. The method is based on the formation of ion-association complexes {(IG)₃·[As₂(Mo₂O₇)₁₂]H₅}_m of iodine green (IG) and heteropoly acid anion [As₂(Mo₂O₇)₁₂]^14? formed as As (V) reacts with molybdate in H₂SO₄ solution. The ion-association complexes can lead to distinct enhancement of RRS. The enhanced RRS intensity is proportional to the concentration of As (V) in the range of 0.008–0.40 µg ml^?1. The optimum conditions, the influence factors for the reaction, and the effects of coexisting substances have been investigated. The method has high sensitivity and good selectivity; the detection limit for As (V) (3 S ₀/S) is 1.50 ng ml^?1. The method can be applied to the determination of As (V) in hair samples. Furthermore, the mechanism of the reaction and the reasons for RRS enhancement is discussed.     

Determination of traces of bismuth by quenching of solid-substrate room-temperature phosphorescence from morin-labeled silicon dioxide nano-particles

Silicon dioxide nano-particles, diameter 50 nm, containing morin (morin–SiO₂) have been synthesized by the sol–gel method. They emit strong and stable room-temperature phosphorescence (SS-RTP) on filter paper as substrate, and bismuth can quench the intensity of the SS-RTP. On this basis a new morin–SiO₂ solid-substrate room-temperature phosphorescence-quenching method has been established for determination of traces of bismuth. Reduction of phosphorescence intensity (I_p) is directly proportional to the concentration of bismuth in the working range 0.16–14.4 ag spot^–1 (sample volume 0.40 L spot^–1, corresponding to the concentration range 0.40–36.0 fg mL^–1). The regression equation of the working curve is I_p=14.86+5.279×[Bi³⁺] (ag spot^–1) (n=6, r=0.9982). The detection limit of this method is 0.026 ag spot^–1 (corresponding to a concentration of 6.5×10^–17 g mL^–1).This sensitive, reproducible and accurate method has been used for successful analysis of real samples.     

Determination of trace formaldehyde by solid substrate-room temperature phosphorescence quenching method based on the rose bengal-potassium bromate-Tween-80 system

A new method for the determination of trace formaldehyde by solid substrate-room temperature phosphorescence quenching method has been proposed. It is based on the facts that rose bengal (R) can emit intense and stable room temperature phosphorescence on the solid substrate of filter paper (SS-RTP). Potassium bromate (KBrO(3)) can oxidize R, which causes the quenching of RTP. In the presence of HCHO, it can react with KBrO(3) to form Br(2) and Br(2) can oxidize R, which causes smart quenching of RTP. The phosphorescence intensity (DeltaI(p)) is directly proportional to the concentration of HCHO. In the presence of Tween-80, the DeltaI(p) will be increased to 9.1 times higher than that without it. The linear range of this method is 0.016-1.6fgspot(-1) (corresponding concentration: 0.040-4.0 pgml(-1), 0.40 microlspot(-1)) with the detection limit of 4.5agspot(-1) (corresponding concentration: 1.1 x 10(-14) gml(-1)). The regression equation for working curve is DeltaI(p)=136.6+28.28m(HCHO)fgspot(-1) (r=0.9935, n=6). This method is sensitive, simple, rapid and has been applied to the determination of trace formaldehyde in real samples with satisfactory results. The mechanism of determination of trace formaldehyde by SS-RTP quenching method based on the rose bengal-KBrO(3)-Tween-80 system is also discussed.