Enzymatic proteolysis and in situ digestion as strategies to determine Cs and Sr in fish by tungsten coil atomic emission spectrometry

Abstract

Papain is employed to pre-digest and homogenize fish slurries which are directly placed on a tungsten coil atomizer and digested in situ with an oxidizing mixture of HNO 3 and H 2 O 2 . Both Cs and Sr are determined in different fish samples by tungsten coil atomic emission spectrometry (WCAES) with limits of detection of 0.07 and 0.15 mg l À1 , respectively. Sample aliquots of 50 ml are dried, digested/ pyrolyzed and atomized using a 400 W miniature solid-state constant current power supply and a Visual Basic temperature control program. The portable WCAES instrumental setup is composed of a small metallic atomization cell, a 2.54 cm diameter fused silica lens and a hand-held charge coupled device-based spectrometer. Tungsten filaments extracted from 24 V, 250 W commercially available light bulbs are used as atomizers. The method accuracy is demonstrated by comparing WCAES results with values obtained by ICP OES. No statistically significant differences are observed between the results from each different method at a 95% confidence level. Recovery tests are also carried out for Cs and values between 100 and 110% are obtained. The method precision is calculated to be 6.8 and 7.3% for 2.5 mg l À1 of Cs and 100 mg l À1 of Sr (n ¼ 10), respectively. The method described is simple, fast and efficient, offering an interesting alternative for applications in food safety control and determinations in the field.

Direct determination of sodium, potassium, chromium and vanadium in biodiesel fuel by tungsten coil atomic emission spectrometry

“…In a recently published work [13], RSDs of 14 and 20% were reported for P and Si determinations in biodiesel by ETV-ICP-MS using a tungsten coil vaporizer. Average repeatabilities for aqueous solution determinations by WCAES are typically in the 5-15% range [14][15][16][17][18][19][20][21][22]. Therefore, considering the accuracies presented in Tables 5 and 6, the low concentrations of these analytes in biodiesel fuel, the complexity of the sample matrix, and the difficulties of determining these elements by other analytical methods, the WCAES procedure described in this work is adequate for biodiesel analyses.…”

“…This method, first described in 2005 [14], has been successfully applied to different analytes and samples, with performances comparable to other traditional analytical methods [15][16][17]. It is especially sensitive for Groups 1 and 2 elements [17][18][19], and instrumentation improvements have allowed effective determinations of more refractory elements such as Cr and V [20][21][22]. In the work described here, 10-L sample aliquots were used and no sample preparation other than simple dilution in methanol or ethanol was required.…”

“…The typical atomization current used in WCAES procedures is 10 A, which corresponds to a gas phase temperature of 1780 K [29]. Despite the lower value adopted in Na and K determinations, the powers of detection calculated for these elements remain relatively high, which may be related to the high sensitivities observed for Groups 1 and 2 elements in WCAES determinations [17][18][19]. The LODs, repeatabilities, and linear dynamic ranges for Na and K presented in Table 3 are suitable for applications following different biodiesel fuel regulations [5][6][7].…”

Determination of Trace Elements in Cow Placenta by Tungsten Coil Atomic Emission Spectrometry

“…The first descriptions of the WCAES system were published in 2005 and 2006 [18,19]. Since then, this simple, potentially portable, and sensitive atomic spectrometric method has been successfully applied to a variety of samples and analytes [20][21][22][23][24][25][26][27]. WCAES may represent an interesting alternative to complex and expensive methods such as inductively coupled plasma with optical or mass spectrometry detection (ICP OES and ICP-MS) for applications in trace element analysis of complex samples such as bovine placenta [28].…”

Direct determination of chromium in empty medicine capsules by tungsten coil atomic emission spectrometry

“…13 First described in 2005, 14,15 WCAES uses a simple tungsten lament extracted from microscope light bulbs as atomization and excitation source to determine trace element levels in liquid samples by atomic emission spectrometry. Using simple optical apparatus and a handheld spectrometer, or a crossed Czerny-Turner spectrograph combined with a chargecoupled device (CCD) detector, WCAES has been successfully employed in elemental determinations at the mg L À1 level for such complex matrices as soil, 16,17 plant and biological material, [18][19][20] beverages, 21 biodiesel, 22 and lubricant oil. 23 In addition to WCAES, recent publications have also demonstrated the applicability of other potentially portable electrothermal AESbased systems for different applications.…”