Impact of LC-MS/MS quantification methods on analytical results by example of nationwide U.S. environmental samples.

Although different quantification methods are extensively used in environmental chemistry, the impact of the choice of method on the quality and range of analytical results is understudied. This two-part study consists of (a) in-lab evaluation and (b) a traditional meta-analysis (n = 66) of commonly used quantification methods): (i) external calibration; (ii) isotope dilution method with authentic target analogs; (iii) isotope dilution with non-target standards; and (iv) standard addition prior to LC-MS/MS in liquid chromatography tandem mass spectrometry (LC-MS/MS) by example of antibiotics in sewage sludge from across the U.S. Using method (i) as the benchmark quantification method for the antibiotic erythromycin in biosolids, other quantification methods resulted in an overestimation (110-450 %) or an underestimation (10-60 %). Using the method (iv) as the benchmark for other compounds resulted in an overestimation (101-14,700 %) or an underestimation (6-98 %). Matrix effects were also observed and were dependent on the matrix and analyte type. For example, in the case of erythromycin, all sample matrices showed signal suppression. This study showed that in the absence of isotopically labeled analogs, the most accurate alternate quantification method may need to be experimentally determined depending on the analyte. Analysis of published literature on pharmaceuticals in sewage sludge indicated that isotope dilution with authentic target analog is most commonly used, followed by non-target isotope standards, standard addition, and finally external calibration.

U.S. nationwide reconnaissance of ten infrequently monitored antibiotics in municipal biosolids.

Ten infrequently monitored antibiotics in biosolids were examined in archived American sewage sludges (n = 79) collected as part of the 2006/2007 U.S. Environmental Protection Agency (EPA) Targeted National Sewage Sludge Survey. This study inspected the occurrence of amoxicillin, ampicillin, erythromycin, furazolidone [proxy metabolite: 3-(2-nitrobenzylidenamino)-2-oxazolidinone (NP-AOZ)], nalidixic acid, oxolinic acid, oxytetracycline, spiramycin, sulfadimidine, and sulfadimethoxine in sewage sludges after nearly a decade in frozen storage. Six antibiotics were detected at the following average concentrations (ng/g dry weight): amoxicillin (1.0), nalidixic acid (19.1), oxolinic acid (2.7), erythromycin (0.6), oxytetracycline (4.5), and ampicillin (14.8). The remaining four were not detected in any samples (

Mortality and transmissibility patterns of the 1957 influenza pandemic in Maricopa County, Arizona.

BACKGROUND: While prior studies have quantified the mortality burden of the 1957 H2N2 influenza pandemic at broad geographic regions in the United States, little is known about the pandemic impact at a local level. Here we focus on analyzing the transmissibility and mortality burden of this pandemic in Arizona, a setting where the dry climate was promoted as reducing respiratory illness transmission yet tuberculosis prevalence was high. METHODS: Using archival death certificates from 1954 to 1961, we quantified the age-specific seasonal patterns, excess-mortality rates, and transmissibility patterns of the 1957 H2N2 pandemic in Maricopa County, Arizona. By applying cyclical Serfling linear regression models to weekly mortality rates, the excess-mortality rates due to respiratory and all-causes were estimated for each age group during the pandemic period. The reproduction number was quantified from weekly data using a simple growth rate method and assumed generation intervals of 3 and 4 days. Local newspaper articles published during 1957-1958 were also examined. RESULTS: Excess-mortality rates varied between waves, age groups, and causes of death, but overall remained low. From October 1959-June 1960, the most severe wave of the pandemic, the absolute excess-mortality rate based on respiratory deaths per 10,000 population was 16.59 in the elderly (≥65 years). All other age groups exhibit very low excess-mortality and the typical U-shaped age-pattern was absent. However, the standardized mortality ratio was greatest (4.06) among children and young adolescents (5-14 years) from October 1957-March 1958, based on mortality rates of respiratory deaths. Transmissibility was greatest during the same 1957-1958 period, when the mean reproduction number was estimated at 1.08-1.11, assuming 3- or 4-day generation intervals with exponential or fixed distributions. CONCLUSIONS: Maricopa County exhibited very low mortality impact associated with the 1957 influenza pandemic. Understanding the relatively low excess-mortality rates and transmissibility in Maricopa County during this historic pandemic may help public health officials prepare for and mitigate future outbreaks of influenza.