Feasibility of DLLME for the Extraction and Preconcentration of As and Cd in Sugar for Further Determination by ICP-MS

Abstract

A method for determining low levels of As and Cd by dispersive liquid-liquid microextraction (DLLME) and inductively coupled plasma mass spectrometry (ICP-MS) was proposed. The following parameters that affect extraction efficiency were investigated: type and volume of extraction solvent (1000 µL acetone), type and volume of dispersive solvent (75 µL carbon tetrachloride), amount of ammonium pyrrolidinedithiocarbamate and sodium diethyldithiocarbamate as chelating agents, sample mass (0.5 g in 10 mL ultrapure water), pH of sample solution (2.0) and number of washing steps (one). Accuracy was evaluated by analytes determination in sugar samples by ICP-MS after digestion by microwave-induced combustion (MIC). No significant difference was observed between results of the proposed DLLME method and MIC in the case of both analytes. Instrument calibration was performed by the standard addition method and good linearity was achieved. Limits of quantification (LOQs) were 0.7 and 0.2 ng g -1 for As and Cd, respectively. The main advantages of this method are relatively high sample mass, low dilution, suitable preconcentration factors and significantly low LOQs (ng g -1 range). When the proposed method was used for determining As and Cd in four sugar samples, their concentrations ranged from 1.13 to 2.95 ng g -1 and from 0.31 to 0.43 ng g -1 , respectively.Keywords: dispersive liquid-liquid microextraction, sugar, arsenic, cadmium, inductively coupled plasma mass spectrometry IntroductionSugar has been widely consumed around the world by people of all ages, since it is an important ingredient found in several products, such as sweets, softdrinks and bread. 1,2 Similarly to other food, it is prone to contamination by toxic elements throughout its production and manufacturing processes.3 Some elements can be classified into essential or toxic, depending on the role they play in the metabolism of living organisms. Ca, Cu and Zn are essential for life whereas As, Cd and others do not have any known biological function and may be toxic, depending on their concentrations, thus posing potential risks to human health. [4][5][6][7] Arsenic may cause several health problems with mutagenic, carcinogenic and teratogenic effects. In humans, it can affect neurological, cardiovascular and respiratory systems, besides causing hypertension. [7][8][9] Cadmium is the most toxic element to humans, since it leads to renal failure, hypertension, emphysema and carcinogenic hazards, mainly in the kidney and prostate. 8,9 Therefore, As and Cd must be considered toxic even at low concentrations and must be monitored in the environment, food and beverages.Several techniques have been developed for simultaneous element determination at ultratrace levels in food samples. Inductively coupled plasma optical emission spectrometry (ICP-OES) 10 and inductively coupled plasma mass spectrometry (ICP-MS) 11 are the most successful examples. Regarding these techniques, the latter, which is the most sensitive, versatile and suitable one for routine applicati...

Comparison Studies on Several Ligands Used in Determination of Cd(II) in Rice by Flame Atomic Absorption Spectrometry after Ultrasound-Assisted Dispersive Liquid–Liquid Microextraction

“…At present, the trace amounts of cadmium is mainly analyzed by flame atomic absorption spectrometry (FAAS) [ 2 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ], graphite furnace atomic absorption spectrometry (GFAAS) [ 19 , 20 , 21 , 22 , 23 ], inductively coupled plasma atomic emission spectrometry (ICP–OES) [ 24 ], and inductively coupled plasma mass spectrometry (ICP-MS) [ 25 , 26 , 27 , 28 ]. Compared with costly analysis technique, such as ICP-OES and ICPMS, FAAS is a conventional technique that has been widely applied in metals analysis because it is a less expensive and simpler alternative technique [ 29 , 30 ].…”

“…Dispersive liquid–liquid microextraction (DLLME) is an attractive method that has been used widely in the field of sample preparation since its innovation in 2006 [ 31 , 32 ]. The conventional and modified DLLME methods have been successfully applied to determine the trace amounts of cadmium in various matrices [ 15 , 16 , 17 , 18 , 19 , 22 , 23 , 24 , 25 , 26 , 27 ]. Generally, the pre-concentration of cadmium ions requires suitable complexing agents to form metal complexes and obtain high partition coefficients of cadmium between the aqueous phase and organic extraction solvents.…”

“…The use of complexing agents that selectively react with cadmium and subsequent extraction of the obtained metal complex has been widely applied in analysis. For instance, cadmium has been complexed with 8-hydroxyquinoline (8-HQ) [ 2 ], 1-(2-thiazolylazo)-p cresol (TAC) [ 10 ], ammonium pyrrolidine dithiocarbamate(APDC) [ 12 , 20 , 22 , 24 , 25 ], 1-(2-pyridylazo)-2-naphthol (PAN) [ 13 , 27 ], 4,4-dimethyl2,2-bipyridine [ 15 ], diphenylcarbazone [ 16 ], sodium diethyldithiocarbamate (DDTC) [ 17 , 23 , 25 ], 1,3-dihydroxybenzene [ 18 ], L-Cysteine [ 19 ], tricaprylmethylammonium chloride(Aliquat ® 336) [ 26 ], sodium O,O-diethyl dithiophosphate (DEDTP) [ 33 ], N,N′-bis(salicylidene)ethylenediamine (BSE) [ 34 ], the obtained cadmium complexes extracted by ultrasound-assisted emulsification microextraction with the solidification of floating organic droplet [ 10 ], supramolecular solvent based liquid–liquid microextraction [ 12 ], solidified floating organic drop microextraction [ 13 ], vortex-assisted room temperature ionic liquid dispersive liquid–liquid microextraction [ 12 , 18 ], green solvent-based ultrasonic assisted dispersive liquid–liquid microextraction [ 19 ], switchable hydrophilicity solvent based liquid phase microextraction [ 20 ], ultrasound-assisted magnetic retrieval-linked ionic liquid dispersive liquid-liquid microextraction [ 22 ], lab-in-syringe magnetic stirring-assisted dispersive liquid-liquid microextraction [ 24 ], liquid phase microextraction [ 28 ], co-precipitation method [ 33 ], magnetic solid-phase extraction [ 34 ], and DLLME [ 2 , 15 , 16 , 17 , 23 , 25 ...…”

“…The presence of an appropriate complexing agent for extraction of Cd(II) is necessary in the mentioned DLLMEs [ 2 , 12 , 15 , 16 , 17 , 18 , 19 , 22 , 23 , 24 , 25 , 26 , 27 ], however, there are rare discussions about the effect of different kinds of ligand in DLLMEs. Most previous researchers demonstrated that the types of extraction solvent and disperser solvent were important in the DLLMEs technique.…”