用硝酸根电极快速测定蔬菜中的硝酸盐含量

详细介绍了硝酸根电极测定蔬菜硝酸盐氮的方法。从回收率试验、对比试验和精密度试验结果评价,该方法简便、快捷、准确,可用于蔬菜硝酸盐的快速测定。     

降低蔬菜硝酸盐含量的农业措施

过量的硝酸盐在人体内积累,会对人体产生毒害作用,目前各大城市普查的结果表明,蔬菜中硝酸盐含量超标２－８倍。控制蔬菜酸盐的积累,是一个迫切问题,本文提出了降低蔬菜硝酸盐含量的若干农业措施。     

施肥对蔬菜中硝酸盐含量的影响

通过对山东省蔬菜面积较大的潍坊和青岛市的蔬菜进行了取样分析及有关的试验，结果表明：依据国家标准(GB18406．1-2001)在所测的所有样品中，蔬菜硝酸盐含量均没有超标。而依据FAO／WHO(1973年)规定，瓜果类和根茎类蔬菜硝酸盐含量均不超标，而叶菜类有近30％超标，超标蔬菜达到了生食盐渍不宜，熟食允许的程度；同一种类蔬菜露天栽培比保护地栽培的硝酸盐积累量少；氮磷钾合理配合施用能减少蔬菜硝酸盐积累。本文提出了控制蔬菜硝酸盐积累的施肥措施。     

济南市售蔬菜硝酸盐含量及施肥影响

１９９５年对济南市两个蔬菜市场４８种蔬菜和肥料试验蔬菜样品测定硝酸盐含量，部分样品同时测含钾量，结果表明：（１）不同种类蔬菜硝酸盐量差异很大，其中约１０种蔬菜可食部分硝酸盐含量超过ＷＨＯ／ＦＡＯ１９７３对食品中硝酸盐的限量标准；（２）蔬菜硝酸盐含量与钾含量呈极显著的指数负相关，（３）施钾肥适当降低硝酸盐含量，而偏施氮肥相应提高硝酸盐含量。     

施肥对蔬菜中硝酸盐含量的影响

通过对山东省蔬菜面积较大的潍坊和青岛市的蔬菜进行了取样分析及有关的试验,结果表明:依据国家标准(GB18406 1—2001)在所测的所有样品中,蔬菜硝酸盐含量均没有超标。而依据FAO/WHO(1973年)规定,瓜果类和根茎类蔬菜硝酸盐含量均不超标,而叶菜类有近30%超标,超标蔬菜达到了生食盐渍不宜,熟食允许的程度;同一种类蔬菜露天栽培比保护地栽培的硝酸盐积累量少;氮磷钾合理配合施用能减少蔬菜硝酸盐积累。本文提出了控制蔬菜硝酸盐积累的施肥措施。     

南宁市蔬菜的硝酸盐含量及评价

通过调查和采样分析结果表明,南宁市各类蔬菜硝酸盐平均含量依次为叶菜类(1932 1mg·kg-1)>根菜类(944 1mg·kg-1)>葱蒜类(488 6mg·kg-1)>瓜菜类(183 6mg·kg-1)>茄果类(157 6mg·kg-1)>豆菜类(147 0mg·kg-1)>水生菜类(62 0mg·kg-1)。部分蔬菜受不同程度硝酸盐污染,以叶菜类污染最重(除韭菜),其次是根菜类和葱蒜类,污染指数在1 04～6 60,多数在2 0以上,其它各类蔬菜的污染指数均<1,未受硝酸盐污染。     

浅析施肥对蔬菜硝酸盐含量的影响

（１）蔬菜硝酸盐含量高低与人民健康密切相关。（２）调查结果表明，市场上销售的蔬菜硝酸盐含量超标比较严重。（３）试验证明，过量施用化肥，尤其是化学氮肥，是造成蔬菜硝酸盐含量增加的主要原因；而在施足有肥的基础上，合理配施磷钾肥可以有效降低蔬菜硝酸盐含量，提高蔬菜品质。     

Use of the nitrate electrode for determination of nitrates in soils

Abstract

A procedure for the rapid and accurate determination of water‐extractable soil nitrates is described. Use of this procedure resulted in quantitative recovery of nitrates added to soil. Reproducibility of results was high, with nitrate‐nitrogen in 40 soil samples determined on successive days differing by a maximum of 4 ppm with 33 determinations differing by 2 ppm or less. Comparison with a phenoldisulfonic acid method on 513 soil samples had a maximum difference of 7 ppm with a majority of determinations having a difference of 4 ppm or less.     

Determination of soil nitrate by means of specific ion electrode: Comparison among different extracting solutions

Abstract

Four different soil nitrate extracting solutions were compared. With the exception of the solution suggested by ORION Manual⁸ which gave the worst results, the efficacy of other solutions does not depend on the employed type but the presence or absence of particles in solution during the assay by means of the electrode.     

Rapid field determination of nitrate in natural waters

Abstract

Brucine, an organic reagent used for nitrate determinations, proved stable for at least one year when dissolved in methanol. This makes possible a consistently accurate and rapid method for field determinations of nitrate in clear solutions with a minimum of equipment. The method is also useful in the laboratory for determining nitrate in water or soil extracts. It is quicker and simpler than other colorimetric methods and more sensitive to low concentrations than the nitrate electrode.     

Use of the nitrate specific ion electrode in soil testing

Abstract

The construction, theory and many of the factors such as interfering anions, extracting agents, soil to solution ratio, reference electrodes, accuracy and precision of the nitrate ion selective electrode are discussed in relation to routine soil testing for nitrate nitrogen.     

Nitrate contents in some vegetables in Tunisia

This study reports the nitrate level of 22 vegetables species collected from 40 farms in several locations of an intensive agricultural area in two regions of Tunisia (Sousse and Monastir). Nitrate levels ranged between 57 and 2970 mg kg^?1. The highest and the lowest levels were found in turnip and tomato, respectively. Only five species (potato, field bean, cauliflower, pea and artichoke) had exceeded the norms established by the World Health Organization. Factors influencing nitrate accumulation in some vegetables were analyzed and discussed. It was observed that nitrate contents in vegetables varied depending on the type of vegetables, genetic factor, level of nitrogen fertilization and soil nitrogen content.     

基于离子选择性电极的硝酸盐快速检测系统

介绍了一种用于快速检测溶液中硝酸盐含量的流体控制系统。系统选用自主研发的以聚吡咯聚合物为膜材料的硝酸盐离子选择性电极作为传感单元,通过底层数据采集器编程控制微型泵和微型阀,实现检测溶液的自动传输控制。根据流体控制流程,离子选择性电极的标定溶液浓度选择为10-1、10-3和10-4 mol/L,标定时间可控制在4.5 min以内,每个样品检测时间为90 s。在10-4～10-1 mol/L的硝酸盐浓度范围内,电极的电势响应斜率值相对稳定,系统的硝酸盐含量检测下限约为10-4 mol/L,可基本满足对土壤浸提溶液和生活饮用水硝酸盐含量的快速和低成本检测要求。     

Nitrate reduction during Kjeldahl digestion of water samples by the perchlorate method

Abstract

An Investigation of the possible reduction of nitrate to ammonia during Kjeldahl digestion of soil drainage water samples by the perchlorate (+ V₂O₅ + Kl) method is reported. Non‐quantitative conversion was observed with samples containing 100 ppm or more of sucrose, an easily acid‐decomposible organic compound, and with 1000 ppm propanol, a less readily decomposible compound. No conversion was observed with samples containing either 10 ppm of sucrose or 1000 ppm of phenol.