Micro-spectrophotometer Combined With Liquid-liquid Micro-extraction Techniques

The LLME is a kind of miniaturized sample pretreatment technology. It onlyneed less extraction solvent (μL). It can save costs, reduce the extraction solvent tothe environment and weaken health hazards to analyst. Micro-spectrophotometer issimple structure, small size, low consumption, and simple easy to carry, it can be usedfor field rapid analysis. Therefore, the combination of micro-spectrophotometer andLLME is an ideal solution for field quick analysis. This instrument combined withportable regulated power supply, micro cuvettes, and a miniature fiber opticspectrometers, which can be used to trace the colorimetric (50μL). The performanceof micro-spectrophotometer was validate by national standard method, thedetermination of trace iron–1,10-Phenanthroline spectrophotometric method, thelinear range is0-2.8μg/mL, RSD=1.1%（n=10), Its stability on the determination oforganic solvents was evaluated by carbon tetrachloride extraction spectrophotometricdetermination of iron content, and the linear correlation coefficient was0.999.In order to expand application of the combination technique ofmicro-spectrophotometer and liquid-liquid micro-extraction, a method fordetermination of trace copper with dispersed liquid-liquid micro-extractionspectrophotometry is established. And optimized the corresponding experimentalconditions:5mL30%sodium citrate solution,5mL10%hydroxylaminehydrochloride solution,0.6mL0.008%neocuproine-ethanol solution,200μLchloroform solution, the shaking time is40s, the maximum absorption wavelength is456nm. Compared with the traditional method, this method reduces the amount ofsodium citrate double the amount of sodium citrate to reduce the double, the amountof hydroxylamine hydrochloride to reduce10times, the amount of neocuproine toreduce12.5times, the amount of ethanol to reduce20times, the amount ofchloroform to reduce50times, the colorimetric volume to reduce60times (50μL),The limit of detection (L.O.D) decreased by about5-fold. This paper also uses theneocuproine the neocuproine micro extraction spectrophotometric method accuratelyto determine the content of trace copper in geochemical standard material (streamsediment, soil, and rock). The determination results are consistent with the scope of national recommended value. The range of recovery:101%-108%, the relative error:2.3%-7.8%, R.S.D=2.1%(n=10), and the recoveries for the spiked geologicalcertified samples were in the acceptable range of102%-105%.Speciation analysis of heavy metals is one of the main contents of geochemistryin environment, regiona, investigation. At present, the most commonly usedmorphological analysis method is the European Community Bureau of reference(referred to as BCR) sequential extraction method. The instruments that were usedcombination with the method are inductively coupled plasma mass spectrometry(ICP-MS) and other large equipment. But ICP-MS is not popular in the economicallyunderdeveloped areas, meanwhile, because of its stringent requirements to sampleacidity and total salinity, and the expense cost of maintenance and running. However,micro spectrophotometer is not restricted in acidity, salinity and so on, so the study onit is meaningful. This article combined BCR sequential extraction method withneocuproine micro extraction spectrophotometric method, completed the speciationanalysis of Cu in soil, rock, stream sediment: the recovery of GSS-5, GSS-6, GSR-2,GSR-3, GSD-3a, GSD-21are90%,90%,94%,91%,49%,37%, respectively.In addition, a method for determination of trace vanadium with dispersedliquid-liquid micro-extraction spectrophotometer is established. And optimized thecorresponding experimental conditions:0.5mL0.1%phenylhydroxylamine-ethanolsolution,500μL chloroform solution, the shaking time is40s, the maximumabsorption wavelength is440nm. Compared with the traditional method, the amountof phenylhydroxylamine to reduce the double, the amount of ethanol to reduce4times,the amount of chloroform to reduce16times, the colorimetric volume to reduce60times (50μL). This paper also uses the neocuproine micro extractionspectrophotometric method accurately to determine the content of trace copper ingeochemical standard materials (stream sediment, soil, rock). The determined resultsare consistent with the recommended value. The recovery is from94%to108%, therelative error:1.0-6.1%, R.S.D=2.7%（n=10），and the recoveries range of certifiedsamples were98%-110%.Therefore, the combination technique of micro spectrophotometer andliquid-liquid micro-extraction proposed a new way for the determination of traceelements such as copper, vanadium, and so on in geological samples.