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Speciated Arsenic Analysis in Wine Using HPLC-ICP-QQQ: Validation of an Extended FDA Elemental Analysis Manual Method

The FDA Elemental Analysis Method (EAM) §4.10 describes arsenic (As) speciation in fruit juice by HPLC-ICP-MS. Validation data supporting extension of the EAM method to include wine is presented.

In 2013, the US Food and Drug Administration (FDA) released Elemental Analysis Manual (EAM) Method §4.10. The method describes the Determination of Four Arsenic Species in Fruit Juice using High-Performance Liquid Chromatography-Inductively Coupled Plasma-Mass Spectrometry. To extend the method to include wine, a multi-laboratory validation (MLV) of the method was carried out with three US-based laboratories sharing their data. The data shown in this application note is supplementary to the published data. In addition to the paper, this note includes long term stability of the method, and extended quantitative analysis of five commercially available wines. The method required separation and analysis of all target species. This approach differs from another Agilent application note, which focused on the development of a fast method for inorganic arsenic (iAs).

The US Environmental Protection Agency (EPA) set a maximum threshold of total As in drinking water of 10 μg/kg. There is no equivalent US regulation for As in wine. Studies have shown that As in wine can be the result of an accumulation of As in the grapes from the environment or introduced during the wine making process.

In this study, EAM §4.10 was modified for the determination of the main organic arsenic species (DMA and MMA) and the more toxic inorganic forms (As(V) and As(III)) in wine using HPLC coupled to a triple quadrupole ICP-MS (ICP-QQQ). The ICP-QQQ was utilized to provide the highest possible sensitivity of all the instruments available in the lab at UC Davis. ICP-QQQ also provides superior resolution of potential spectral interferences, but the potential Cl-based interferences on 75As are resolved chromatographically, so QQQ with MS/MS is not essential. This application could also be done on a single quadrupole ICP-MS such as the Agilent 7800 or 7900.

Samples and sample preparation
Five commercially available wine samples were bought from a local store in Davis, California. The wines were selected to represent the main types (and styles) of wine: red (Cabernet Sauvignon), white (Sauvignon blanc), rosé (Zinfandel), sparkling (sparkling white) and fortified (Port-style). To investigate the range of ethanol content that could be analysed using the method, the alcohol concentrations of the wines selected ranged from 9.5—20% (v/v).

An Agilent 1260 Infinity LC comprising a binary pump, autosampler, and vacuum degasser was coupled to an Agilent 8800 Triple Quadrupole ICP-MS (ICP-QQQ).

Results and Discussion
Method blanks (3% ethanol) spiked with low levels of As(III), DMA, MMA, and As(V) were prepared and analysed for the determination of the detection limits. The limits of detection (LOD) for the As species in wine were calculated as described in the FDA’s Elemental Analysis Manual Section 3.2.

Quantitative results
The five wines included in the MLV were analysed in the lab at UC Davis using LC-ICP-QQQ. The average percent recovery of the sum of the species compared to the total As present in the samples (determined using direct analysis without HPLC separation) was calculated using the mass balance approach. The percent recovery for all samples was between 91–107%. The results were found to be in good agreement with the results obtained from the other laboratories taking part in the MLV study.

The As speciation results obtained using an Agilent 1260 Infinity LC coupled to an Agilent 8800 ICP-QQQ were used as part of an MLV to validate the extension of Elemental Analysis Manual Method §4.10 to include wine. The method was optimized for the analysis of four arsenic species including the toxicologically relevant inorganic forms, As(III) and As(V).

In addition to the data published as part of the MLV, five more wines were analysed. The total As levels of the five wines were between 8.56 and 26.19 μg/L. These levels are below the Canadian and European regulatory limits for total As in wine of 100 and 200 μg/kg, respectively. The average percentage of As found in the form of iAs in the five wine samples was 95%.