Determination of heavy metals in leather and fur by microwave plasma-atomic emission spectrometry

doi:10.1016/j.sab.2015.06.017

Spectrochimica Acta Part B: Atomic Spectroscopy

Volume 112, 1 October 2015, Pages 6-9

https://doi.org/10.1016/j.sab.2015.06.017 Get rights and content

Highlights

•
The application of the MP-AES method in leather and fur was demonstrated.
•
MP-AES showed good accuracy and precision by the test of CRM of leather.
•
The performance of MP-AES is comparable to that of traditional ICP-AES technology.

Abstract

A sensitive method for the determination of heavy metals (Cd, Co, Cr, Cu, Hg, Ni and Pb) in leather and fur by microwave plasma-atomic emission spectrometry (MP-AES) based on microwave-assisted acid digestion and a multimode sample introduction system was developed. The leather was subjected to microwave-assisted digestion in a mixed solution of nitric acid and hydrogen peroxide before analysis by MP-AES. Results were compared with those from the standardized method instrument, inductively coupled plasma-atomic emission spectrometry (ICP-AES). Examination of a leather certified reference material (CRM, GSB 16-3087-2013) was used to validate the proposed method by statistical test, with good accuracy and precision shown for all heavy metals analyzed. Under optimum conditions, recoveries of 98.1%–102.6% and relative standard deviations (RSD) of 0.7%–3.0% were achieved, with limits of detection (LOD) ranging from 0.6 mg/kg (Cd) to 5.0 mg/kg (Pb). Furthermore, the MP-AES heavy metals analysis carried out on 23 test leather and fur samples showed an adequate concordance with results obtained from ICP-AES. The benefits of the MP-AES are related to low analysis cost and improved operational safety with nitrogen used for plasma generation. The MP-AES system investigated could offer comparable performance compare to ICP-AES and may be applied as an optional method for routine analysis in leather and fur testing institution.

Introduction

It is well known that the presence of heavy metals (for example, Cd, Co, Cr, Cu, Hg, Ni and Pb) is of considerable concern to human health, and agricultural, livestock and aquatic industries [1]. Heavy metals are usually found in leather and other textile products due to the use of tanning agents, dyes and additives containing metal salts in conditional tanning processes [2]. Therefore, the concentration of heavy metals in leather and leather products is regulated in several countries and it is clear that monitoring of heavy metals in leather is extremely important.

A variety of analytical methods for the determination of heavy metals have been developed and reported, including atomic absorption spectrometry (AAS) [3], [4], inductively coupled plasma-atomic emission spectrometry (ICP-AES) [5], [6], inductively coupled plasma-mass spectrometry (ICP-MS) [7], [8], [9], [10], and others [11], [12], [13]. Among these techniques, ICP-AES is the most widely employed [14], while AAS provides the highest analytical sensitivity particularly when using an electrothermal atomizer for atoms generation, however, this requires elements to be analyzed one by one. Microwave plasma-atomic emission spectrometry (MP-AES) is an alternative spectroscopic analysis technology in which a stable nitrogen plasma is produced using microwave energy [15]. Although microwave plasmas have been in existence for a couple of decades, the main usage has been restricted to specific research groups with very few studies in commercially available analytical instruments.

Recently, the use of nitrogen as a plasma gas has also been studied. In addition, comparisons of microwave and inductively coupled plasma sources suggest that MP performance approaches that of ICP [16]. Therefore the MP-AES, which runs on nitrogen, is of interest for many fields of analytical chemistry, as operating costs are significantly lower than for argon or helium dependent instruments [17], [18]. Studies have reported the successful use of an MP-AES instrument (Agilent Technologies, 4100 MP-AES) for element analysis on agricultural materials [19]. However, there is no study that outlines the performance of the nitrogen MP-AES technique for analysis of leather and fur materials, with even less scientific information available on heavy metals.

The aim of this work is to develop an inexpensive method for the determination of heavy metals in leather and fur. In this work, samples underwent microwave-assisted digestion and detection by MP-AES and ICP-AES. Verification of the proposed method, including accuracy, precision and limit of detection (LOD) data, are discussed in this paper. The method was applied for the analysis of Cd, Co, Cr, Cu, Hg, Ni and Pb in leather and fur samples by MP-AES, and results were compared with the those from ICP-AES.

Section snippets

CRM, reagents and samples

The stock standard solution (1000 mg/L) of Cd, Co, Cr, Cu, Hg, Ni and Pb were certified reference materials (CRM), which were purchased from National Institute of Metrology (China). 65% (w/w) nitric acid (HNO₃), 30% (w/w) hydrogen peroxide solution (H₂O₂), sodium borohydride (NaBH₄), and sodium hydroxide (NaOH) solutions were obtained from Beijing Chemical Works, all of guaranteed reagent (GR) grade. A reductant solution of 2% (w/v) NaBH₄ stabilized with 1% (w/v) NaOH solution was introduced

Limit of detection

The limits of detection (LOD) were calculated as three times the standard deviation of ten blank measurements. The obtained LOD for the MP-AES method and ICP-AES method for each heavy metal element in leather samples were listed in Table 2. As presented by the analysis, the LOD for MP-AES were comparable to that of ICP-AES. And the small difference in the LOD suggested that the performance of the MP-AES would be comparable to that of ICP-AES.

Accuracy and precision

The accuracy and precision of all procedures were

Conclusions

The method of microwave-assisted digestion for the determination of Cd, Co, Cr, Cu, Hg, Ni and Pb in leather and fur with MP-AES was established in this work. 23 leather and fur samples were analyzed by both MP-AES and ICP-AES, and the values obtained in MP-AES were found to be comparable to those gained with ICP-AES, suggesting that the differences between the two methods are acceptable. Due to important advantages of low running costs and high laboratory safety (as no expensive or flammable

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Analytical NoteDetermination of heavy metals in leather and fur by microwave plasma-atomic emission spectrometry

Highlights

Abstract

Introduction

Section snippets

CRM, reagents and samples

Limit of detection

Accuracy and precision

Conclusions

Talanta

Microchem. J.

Talanta

Microchem. J.

Anal. Chim. Acta

Microchem. J.

Microchem. J.

Spectrochim. Acta B

Spectrochim. Acta B

Analytical Note
Determination of heavy metals in leather and fur by microwave plasma-atomic emission spectrometry