Flow injection chemiluminescence determination of meloxicam using potassium permanganate and formaldehyde system

A simple, rapid and sensitive flow injection chemiluminescence （FI-CL） method has been developed for the determination of meloxicam. The method is based on the CL-emitting reaction between meloxicam and potassium permanganate in a hydrochloric acid medium, enhanced by formaldehyde （HCHO）. Under optimum conditions, calibration curve over the range of 1.0-20.0μg/mL was obtained. The proposed method was successfully applied to the determination of meloxicam in capsules with no evi- dence of interference from common excipients. The detection limit of this method was 25.6 ng/mL. The relative standard deviation was 2.1% for 10.0 μg/mL meloxicam. The sample throughput was found to be 120 samples/h.

SELECTIVE SULFUR DIOXIDE DETERMINATION BY GAS DIFFUSION FLOW INJECTION ANALYSIS WITH CHEMILUMINESCENT DETECTION

Sulfur dioxide has been found to decrease the chemiluminescence of luminol-iodine system.A new determination method for sulfur dioxide in atmosphere is developed by applying this reaction to a flow injection gas diffusion separation system.This permits the determination of sulfur dioxide selectively and rapidly.

Luminol-K_3Fe(CN)_6 chemiluminescence system for the determination of glipizide

A rapid and sensitive flow-injection chemiluminescence（CL） method for the determination of glipizide was developed on the basis of finding that glipizide can enhance the CL intensity of the luminol-K3Fe（CN）6 system.In optimum condition,the increased CL intensity was directly proportional to the concentration of glipizide in the range from 4.0×108 g/mL to 1.0×106 g/mL and the detection limit was 1.0×108 g/mL glipizide.The relative standard deviation（RSD） of the developed method was 2.1% with 11 repeated measurements of 1.0×107 g/mL glipizide.The developed method has been successfully applied to the analysis of glipizide in its pharmaceutical preparations.

Evidence for coupled iron and nitrate reduction in the surface waters of Jiaozhou Bay

Iron and nitrate(NO_(3)^(-))are dominant physiologically required nutrients for phytoplankton growth,and iron may also play a key role in the marine nitrogen cycle.In this study,we investigated the temporal and spatial distributions of dissolved iron(DFe)and Fe(Ⅱ)in the surface waters of Jiaozhou Bay(JZB)from April 2 to July 26,2017.High concentrations of DFe and Fe(Ⅱ)predominantly occurred in nearshore and estuarine stations and concentrations were generally higher in April and May.The highest DFe concentration was observed along the coast of Hongdao(51.55 nmol/L)in May,while the lowest concentration was observed in the western coastal region(2.88 nmol/L)in April.The highest and lowest Fe(Ⅱ)concentrations were observed in the Licun estuary(22.42 nmol/L)and outer bay(0.50 nmol/L)in May,respectively.We calculated the proportions of nitrate,nitrite,and ammonium in dissolved inorganic nitrogen(DIN)as well as the ratio of Fe(Ⅱ)to DFe in all four months.The mean Fe(Ⅱ)/DFe ratio was 0.48 in April,0.43 in May,0.69 in June,and 0.32 in July.The mean ratio of NO_(3)^(-)to DIN was 0.78 in April,0.54 in May,0.20 in June,and 0.62 in July.NO_(3)^(-)/DIN continuously decreased in the first three months,while Fe(Ⅱ)/DFe remained high,which suggests that the reduction of iron and nitrate occurred simultaneously in the surface waters of JZB.