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<h2 style="none"><span style="font-size: font-family:仿宋_GB2312;"> 1</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、方法原理</span></h2>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;">在酸性条件下，正磷酸盐与钼酸铵、酒石酸锑氧钾反应，生成磷钼杂多酸，被还原剂抗坏血酸还原，则变成蓝色络合物，通常即称磷钼蓝。</span></p>
<h2 style="none"><span style="font-size: font-family:仿宋_GB2312;"><span> </span>2</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、干扰及消除</span></h2>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;">砷含量大于<span>2mg/L</span>有干扰，可用硫代硫酸钠去除。硫化物含量大于<span>2mg/L</span>有干扰，在酸性条件下通氮气可以去除。六价铬大于<span>50mg/L</span>有干扰，用亚硫酸钠去除。亚硝酸盐大于<span>1mg/L</span>有干扰，用氧化消解或加氨磺酸均可以去除。铁浓度为<span>20mg/L</span>，使结果偏低<span>5%</span>；铜浓度达<span>10mg/L</span>不干扰；氟化物小于<span>70mg/L</span>是允许的。海水中大多数离子对显色的影响可以忽略。</span></p>
<h2 style="none"><span style="font-size: font-family:仿宋_GB2312;"><span> </span>3</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、方法的适用范围</span></h2>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;">本方法最低检出浓度为<span>0.01mg/L</span>（吸光度<span>A=0.01</span>时所对应的浓度）；测定上限为<span>0.6mg/L</span>。</span></p>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;">可适用于测定地面水、生活污水及日化、磷肥、机加工金属表面磷化处理、农药、钢铁、焦化等行业的工业废不澡的正磷酸盐分析。</span></p>
<h2 style="text-indent:21.0pt;"><span style="font-size:14.0pt;">4、仪器</span></h2>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;">分光光度计。</span></p>
<h2 style="text-indent:21.0pt;"><span style="font-size:14.0pt;">5、试剂</span></h2>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;font-family:仿宋_GB2312;">1</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、<span>1+1</span>硫酸。</span></p>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;font-family:仿宋_GB2312;">2</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、<span>10%</span>（<span>m/V</span>）抗坏血酸溶液：溶解<span>10g</span>抗坏血酸于水中，并稀释至<span>100ml</span>。该溶液贮存在棕色玻璃瓶中，在冷处可稳定几周。如颜色变黄，则弃去重配。</span></p>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;font-family:仿宋_GB2312;">3</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、钼酸盐溶液：溶解<span>13g</span>钼酸铵<span>[</span>（<span>NH4</span>）<span>3</span><span>Mo7O24</span>·<span>4H2O]</span>于<span>100ml</span>水中。溶解<span>0.35g</span>酒石酸锑氧钾<span>[K</span>（<span>SbO</span>）<span>C4H4O6</span>·<span>1/2H2O]</span>于<span>100ml</span>水中。</span></p>
<p style="none"><span style="font-size:14.0pt;font-family: 仿宋_GB2312"><span> </span></span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">在不断搅拌下，将钼酸铵溶液徐徐加到<span>300ml</span>（<span>1+1</span>）硫酸中，加酒石酸锑氧钾溶液并且混合均匀。</span></p>
<p style="none"><span style="font-size:14.0pt;font-family: 仿宋_GB2312"><span> </span>4</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、浊度<span>-</span>色度补偿液：混合两份体积的（<span>1+1</span>）硫酸和一份体积的<span>10%</span>（<span>m/V</span>）抗坏血酸溶液。此溶液当天配制。</span></p>
<p style="none"><span style="font-size:14.0pt;font-family: 仿宋_GB2312"><span> </span>5</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、磷酸盐贮备溶液：将磷酸二氢钾（<span>KH2PO4</span>）于<span>100</span>℃干燥<span>2</span>小时，在干燥器中放冷。取<span>0.217g</span>溶于水，移入<span>1000ml</span>容量瓶中。加（<span>1+1</span>）硫酸<span>5ml</span>，用水稀释至标线。此溶液每毫升含<span>50.0</span>μ<span>g</span>磷（以<span>P</span>计）。</span></p>
<p style="none"><span style="font-size:14.0pt;font-family: 仿宋_GB2312"><span> </span>6</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、磷酸盐标准溶液：吸取<span>10.00ml</span>磷酸盐贮备液于<span>250ml</span>容量瓶中，用水稀释至标线，此溶液每毫升含<span>2.00</span>μ<span>g</span>磷。临用时现配。</span></p>
<h2 style="text-indent:21.0pt;"><span style="font-size:14.0pt;">6、步骤</span></h2>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;font-family:仿宋_GB2312;">1</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、校准曲线的绘制</span></p>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;">取数支<span>50ml</span>具塞比色管，分别加入磷酸盐标准溶液<span>0</span>、<span>0.50</span>、<span>1.00</span>、<span>3.00</span>、<span>5.00</span>、<span>10.0</span>、<span>15.0ml</span>，加水至<span>50ml</span>。</span></p>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;">⑴<span><span> </span></span>显色：向比色管中加入<span>1ml10%(m/V)</span>抗坏血酸溶液混匀，<span>30s</span>后加<span>2ml</span>钼酸盐溶液充分混匀，放置<span>15min</span>。</span></p>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;">⑵<span><span> </span></span>测量：用<span>10mm</span>或<span>30mm</span>比色皿，于<span>700nm</span>波长处，以零浓度溶液为参比，测量吸光度。</span></p>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;font-family:仿宋_GB2312;">2</span><span style="font-size:14.0pt;font-family:仿宋_GB2312;">、样品测定</span></p>
<p style="text-indent:21.0pt;"><span style="font-size:14.0pt;">分取适量水样（使含磷量不超过<span>30</span>μ<span>g</span>）用水稀释至标线。以下按绘制校准曲线的步骤进行显色和测量。减去空白试验的吸光度，并从校准曲线上查出含磷量。</span></p>
<h2 style="text-indent:21.0pt;"><span style="font-size:14.0pt;">7、计算</span></h2>
<p align="center" style="text-align:center;"><span style="font-size:14.0pt;font-family:仿宋_GB2312;"><span>
</span></span></p>
<span style="font-size:14.0pt;font-family:仿宋_GB2312;">式中，<span>m</span>——由校准曲线查得的磷量（μ<span>g</span>）；<span>V</span>——水样体积（<span>ml</span>）。</span>
