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Routine monitoring of inorganic arsenic in groundwater using sensitive, reliable, easy-to-use and affordable analytical methods is integral to identifying sources, and delivering appropriate remediation solutions, to the widespread global issue of arsenic pollution. Voltammetry has many advantages over other analytical techniques, but the low electroactivity of arsenic(V) requires the use of either reducing agents or relatively strong acidic conditions, which both complicate the analytical procedures, and require more complex material handling by skilled operators. Here, we present the voltammetric determination of total inorganic arsenic in conditions of near-neutral pH using a new commercially available 25 µm diameter gold microwire (called the Gold Wirebond), which is described here for the first time. The method is based on the addition of low concentrations of permanganate (10 µM MnO4-) which fulfils two roles: (1) to ensure that all inorganic arsenic is present as arsenate by chemically oxidising arsenite to arsenate and, (2) to provide a source of manganese allowing the sensitive detection of arsenate by anodic stripping voltammetry at a gold electrode. Tests were carried out in synthetic solutions of various pH (ranging from 4.7 to 9) in presence/absence of chloride. The best response was obtained in 0.25 M chloride-containing acetate buffer resulting in analytical parameters (limit of detection of 0.28 µg L-1 for 10 s deposition time, linear range up to 20 µg L-1 and a sensitivity of 63.5 nA ppb-1. s-1) better than those obtained in acidic conditions. We used this new method to measure arsenic concentrations in contrasting groundwaters: the reducing, arsenite-rich groundwaters of India (West Bengal and Bihar regions) and the oxidising, arsenate-rich groundwaters of Mexico (Guanajuato region). Very good agreement was obtained in all groundwaters with arsenic concentrations measured by inductively coupled plasma-mass spectrometry (slope = +1.029, R2 = 0.99). The voltammetric method is sensitive, faster than other voltammetric techniques for detection of arsenic (typically 10 min per sample including triplicate measurements and 2 standard additions), easier to implement than previous methods (no acidic conditions, no chemical reduction required, reproducible sensor, can be used by non-voltammetric experts) and could enable cheaper groundwater surveying campaigns with in-the-field analysis for quick data reporting, even in remote communities.

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OBJECTIVE: To test, in a newborn screening (NBS) laboratory, the performance of liquid chromatography-tandem mass spectrometry (LC-MS/MS) to assay 5 enzymatic activities in dried blood spots (DBS) for NBS of 5 lysosomal storage diseases (mucopolysaccharidosis [MPS]-II, MPS-IIIB, MPS-IVA, MPS-VI, and MPS-VII). STUDY DESIGN: Three mm punches from de-identified DBS were obtained from the Washington NBS laboratory and submitted to the 5-plex LC-MS/MS assay. Screen cut-offs were established by analyzing the enzymatic activity in patients confirmed to have the MPS disorder. DNA sequencing of the relevant gene was performed on a second DBS punch for all samples with enzyme activity below 10% of the mean daily activity. RESULTS: (1) For MPS-II, 18 below cut-off samples, 1 pathogenic genotype, and 2 "high risk" genotypes; (2) For MPS-IIIB, no below cut-off samples; (3) For MPS-IVA, 8 below cut-off samples, 4 non-pathogenic genotypes, 4 genotypes unobtainable; (4) For MPS-VI, 4 below cut-off samples and no high-risk genotypes; (5) For MPS-VII, 1 below cut-off sample confirmed by genotype and clinical report to be affected. CONCLUSIONS: These results establish that the number of initial screen positive samples is low and manageable. Thus, population newborn screening for these conditions is feasible in a state newborn screening laboratory.

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OBJECTIVE: To evaluate the initial cutoff values, rates of screen positives, and genotypes for the large-scale newborn screening program for multiple mucopolysaccharidoses (MPS) in Taiwan. STUDY DESIGN: More than 100 000 dried blood spots were collected consecutively as part of the national Taiwan newborn screening programs. Enzyme activities were measured by tandem mass spectrometry from dried blood spot punches. Genotypes were obtained when a second newborn screening specimen again had a decreased enzyme activity. Additional clinical evaluation was then initiated based on enzyme activity and/or genotype. RESULTS: Molecular genetic analysis for cases with low enzyme activity revealed 5 newborns with pathogenic alpha-L-iduronidase mutations, 3 newborns with pathogenic iduronate-2-sulfatase mutations, and 1 newborn was a carrier of an arylsulfatase B mutation. Several variants of unknown pathogenic significance were also identified, most likely causing pseudodeficiency. CONCLUSIONS: The highly robust tandem mass spectrometry-based enzyme assays for MPS-I, MPS-II, and MPS-VI allow for high-throughput newborn screening for these lysosomal storage disorders. Optimized cutoff values combined with second tier testing could largely eliminate false-positive results. Accordingly, newborn screening for these lysosomal storage disorders is possible.

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