Outline

  • Abstract
  • Keywords
  • 1. Introduction
  • 2. Experimental
  • 2.1. Apparatus
  • 2.2. Reagent
  • 2.3. General Procedure
  • 2.4. Determination of Gold in Ores
  • 2.5. Pretreatment and Determination of Gold in Jewel Samples
  • 3. Results and Discussion
  • 3.1. Absorption Spectra
  • 3.2. Effect of Acidity
  • 3.3. Effect of Surfactants
  • 3.4. Effect of Dchnaq Concentration
  • 3.5. Stability of the Chromogenic System
  • 3.6. Solid Phase Extraction
  • 3.7. Calibration Curve and Sensitivity
  • 3.8. Stoichiometric Ratio
  • 3.9. Interference
  • 3.10. Analytical Applications
  • 4. Conclusions
  • References

رئوس مطالب

  • چکیده
  • کلید واژه ها
  • 1. مقدمه
  • 2. بخش آزمایشگاهی
  • 2.1. دستگاه ها
  • 2.2. واکنشگرها
  • 2.3. روش کلی
  • 2.4. تعیین طلا در سنگ معدن
  • 2.5. پیش عملیات و تعیین طلا در نمونه های سنگ گرانبها
  • 3. نتایج و بحث
  • 3.1. طیف جذبی
  • 3.2 . اثر اسیدیته
  • 3.3. اثر سورفکتانت ها
  • 3.4. اثر غلظت DCHNAQ
  • 3.5. پایداری سیستم رنگزا
  • 3.6. استخراج فاز جامد
  • 3.7. منحنی کالیبراسیون و حساسیت
  • 3.8. نسبت استوکیومتری
  • 3.9. تداخل
  • 3.10. کاربردهای آنالیتیکی
  • 4. نتیجه گیری

Abstract

A highly sensitive, selective and rapid method for the determination μg L−1 level of Au(III) based on the rapid reaction of Au(III) with 2,3-dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) and the solid phase extraction of the colored complex with a reversed phase polymer-based C18 cartridge have been developed. The DCHNAQ reacted with Au(III) to form a violet complex of a molar ratio 3:1 [DCHNAQ to Au(III)] in the presence of 5.0 M of phosphoric acid solution and Triton X-100 medium. This complex was enriched by the solid phase extraction with a polymer-based C18 cartridge. The enrichment factor of 100 was achieved. The molar absorptivity of the complex is 2.73 × 105 l mol−1 cm−1 at 633 nm in the measured solution. The system obeys Beer’s law in the range of 0.02–1.30 μg ml−1, whereas the optimum concentration ranges obtained from Ringbom plot was 0.08–1.24 μg ml−1. The relative standard deviation for ten replicates sample of 0.6 μg ml−1 level is 1.28%. The detection and quantification limits, are 6.1 and 19.5 ng ml−1 in the original sample. This method was applied to the determination of gold in water, jewel and ore samples with good results comparing to the GFAAS method.

Keywords: - - - -

Conclusions

The proposed method has the following characteristics:

(1) DCHNAQ is one of the most easily prepared high purity, sensitive, and selective spectrophotometric reagent for gold determination. Molar absorptivity of the chelate was found to be up to 2.73 × 105 l mol−1 cm−1 at 633 nm in the measured solution. The higher sensitivity of the proposed method is notable, greater even than that of the SPE that used 5-(2- hydroxy-5-nitrophenylazo)thiorhodanine. Also, the proposed method is more sensitive than other methods, based on spectrophotometry.

(2) The detection and quantification limits, are 6.1 and 19.5 ng ml−1 in the original sample.

(3) Most common ions do not interfere with the determination suggesting the highly selectivity of the proposed method.

(4) Successful application of the proposed method to the determination of low levels of gold in water, jewel and ore samples was carried out with good results

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